FOR THE PEOPLE FOR EDVCATION FOR SCIENCE LIBRARY OF THE AMERICAN MUSEUM OF NATURAL HISTORY ! CD nj o m CD THE ANATOMY OF VERTEBRATES, VOL. III. LONDON: PRINTED BY SPOTTISWOODE AND CO., NEW-STBEET SQUARE AND PARLIAMENT STREET ON THE -A. ^ ANATOMY OF VERTEBRATES. VOL. III. MAMMAL S. BY RICHAED OWEN, F.R.S. SUPERINTENDENT OP THE NATURAL HISTORY DEPARTMENTS OF THE BRITISH MUSEUM, FOREIGN ASSOCIATE OP THE INSTITUTE OF FRANCE, ETC. LONDON : LONGMANS, GREEN, AND CO. 1868. A c lc CONTENTS, OR SYSTEMATIC INDEX. -OH CHAPTER XXVII. MUSCULAR SYSTEM OF MAMMALIA. SECTION PAGE 192. Diaphragm .......... . 1 193. Muscles of Monotremata 2 194. Muscles of Marsupialia ........ 8 195. Muscles of Lissencephala ......... 16 196. Muscles of Cetacea . 24 197. Muscles of Perissodactyla ......... 26 198. Muscles of Artiodactyla ... ..... 41 199. Muscles of Carnivora ......... 49 200. Muscles of Quadrumana ....... . 52 201. Muscles of Bimana .......... 54 202. Locomotion of Mammals . ....... 63 A. Swimming ........... 65 B. Moving on Land ... .... .66 CHAPTER XXVIII. NERVOUS SYSTEM OF MAMMALIA. 203. Myelon . . .73 204. Encephalon, its primary divisions 79 205. Macromyelon .... . .... 81 206. Cerebellum 88 207. Mesencephalon ...... .... 97 208. Prosencephalon ........... 99 A. Lyencephala . .... ..... 100 S. Lissencephala ... ......108 C. G-yrencephala . . . . . . . . . . 114 D. Archencephala . . . . . . . . . . 127 209. Size of Brain 143 210. Membranes of Brain . . . 145 VI CONTENTS. SECTION 211. Nerves of Mammals 212. Sympathetic System 213. Organs of Touch .... 214. Organ of Taste .... 215. Organ of Smell .... 216. Organ of Hearing 217. Organ of Sight .... A. Eye-ball .... B. Appendages .... C. Parallel between Eve and Ear PAGE 146 181 186 190 204 219 246 246 258 263 CHAPTER XXIX. DENTAL SYSTEM OF MAMMALIA. 218. General Characters of the Teeth .... 219. Teeth of Monophyodonts A. Monotremata ..... T5. Bruta .... C. Cetacea ..... 220. Teeth of (non-ungulate) Diphyodonts . A. Sirenia .... B. Marsupialia ...... C. Rodentia ........ D. Insectivora ........ E. Quadrumana . ....... F. Bimana Gr. Carnivora ........ 221. Teeth of Ungulate Diphyodonts A. Homologies of the Grinding Surface of Molars B. Artiodactyla ........ C. Perissodactyla ... ... D. Proboscidia ...... 222. Homologies of Teeth 265 271 271 272 276 283 283 285 294 301 313 322 327 340 340 343 352 359 366 CHAPTER XXX. ALIMENTARY CANAL AND APPENDAGES OF MAMMALIA. 223. Mouth . . . 224. Salivary Glands .... 225. Alimentary Canal of Lyencephala . 226. Alimentary Canal of Rodentia 227. Alimentary Canal of Insectivora . 228. Alimentary Canal of Cheiroptera . 229. Alimentary Canal of Quadrumana 230. Alimentary Canal of Bimana 231. Alimentary Canal of Carnivora 383 396 410 420 427 428 429 434 442 CONTENTS. Vll SECTION PAGE 232. Alimentary Canal of Bruta 446 233. Alimentary Canal of Cetacea ........ 452 234. Alimentary Canal of Sirenia ......... 454 235. Alimentary Canal of Proboscidia 457 236. Alimentary Canal of Perissodactyla 458 237. Alimentary Canal of Artiodactyla 465 238. Liver of Mammals .......... 478 239. Pancreas of Mammals .......... 492 240. Peritoneum and Appendages of Mammals ...... 500 CHAPTER XXXI. ABSORBENT SYSTEM OF MAMMALIA. 241. Lacteals ............ 504 242. Lymphatics ............ 506 243. Absorbent ganglions .......... 508 244. Disposition of Lymphatics ......... 508 245. Mammalian modifications . . ..... 511 CHAPTER XXXII. CIRCULATING SYSTEM OF MAMMALIA. 246. Blood of Mammals ......... 513 247. Heart of Mammals .......... 516 A. Lyencephala . . . . . . . . . . . 516 B. Lissencephala . . . . . . . . . . 519 C. Cetacea ........... 520 D. Sirenia 521 E. Ungulata ........... 522 F. Carnivora ........... 523 Gr. Quadrumana ........... 525 H. Bimana 525 248. Arteries of Mammals ... 532 249. Veins of Mammals 549 250. Spleen of Mammals .......... 557 251. Thyroid of Mammals . 563 252. Thymus of Mammals 566 253. Adrenals of Mammals . 568 CHAPTER XXXIII. RESPIRATORY SYSTEM OF MAMMALIA. 254. Lungs of Mammals ... . 572 255. Larynx of Mammals ........ . 582 VI 11 CONTENTS. CHAPTER XXXIV. URINARY SYSTEM OF MAMMALIA. SECTION 256. A. Kidneys .... B. Urinary Bladder and Urethra . PAGE 604 609 CHAPTER XXXV. TEGUMENTARY SYSTEM AND APPENDAGES OF MAMMALIA. 257. Derm 610 258. Epiderm and ' rete mucosum ' 613 259. Callosities 616 260. Hair 616 261. Spines ............. 621 262. Scales 622 263. Nails, Claws, and Hoofs . 623 264. Horns ...... .... 624 CHAPTER XXXVI. PECULIAR GLANDS OF MAMMALIA 265. Opening npon the Head 266. Opening upon the Trunk 267. Opening upon the Tail . 268. Opening upon the Limbs 632 634 637 638 CHAPTER XXXVII. GENERATIVE ORGANS OF MAMMALIA. A. Male Organs 269. In Monotremata 270. In Marsupialia 271. In Rodentia 272. In Insectivora 273. In Bruta 274. In Cetacea 275. In Sirenia 276. In Proboscidia 277. In Perissodactyla 278. In Artiodactyla 279. In Carnivora 641 643 645 649 655 657 658 660 660 661 666 668 CONTENTS. IX SECTION 280. In Quadrumana . 281. In Bimana . B. Female Organs 282. In Monotremata . 283. In Marsupial! a 284. In Rodentia 285. In Insectivora 286. In Bruta 287. In Cetacea . 288. In Sirenia . 289. In Proboscidia 290. In Perissodactyla 291. In Artiodactyla . 292. In Carnivora 293. In Quadrumana . 294. In Bimana PAGE 672 673 676 677 680 686 687 689 691 692 692 693 694 698 701 704 CHAPTER XXXVIII. GENERATIVE PRODUCTS AND DEVELOPMENT OF MAMMALIA. 295. Ovulation .... 709 296. Ovipont 711 297. Corpus Luteum 712 298. Impregnation ........... 713 299. Development of Monotremata . . . . . . . . 715 300. Development of Marsupialia ........ 718 3J1. Development of Lissencephala. ........ 723 302. Development of Mutilata 732 303. Development of Ungulata ......... 732 304. Development of Carnivora ......... 742 305. Development of Quadrumana ........ 745 306. Development of Bimana ......... 747 307. Development of Mammalian brain . . . . . . . 751 308. Development of Mammalian skeleton ....... 753 309. Membrana pupillaris ......... 754 310. Foetal Circulation .......... 755 311. Definition of Male and Female Organs 757 312. Descent of Testes. . 758 CHAPTER XXXIX. MAMMARY AND MARSUPIAL ORGANS. 313. In Monotremata 314. In Marsupialia 315. In Lissencephala 316. In Mutilata 317. In Ungulata 760 768 775 777 778 X CONTENTS. SECTION TAGS 318. In Garni vora ........... 780 319. In Qiiadrumana ........... 780 320. In Bimana ....... ... 781 321. Adipose Substances .......... 783 CHAPTER XL. GENERAL CONCLUSIONS. 322. Biological Questions of 1830 786 323. Horaology or Teleology ? 787 324. Succession of Species, broken or linked ?...... 789 325. Extinction of ditto, cataclysmal or regulated? ..... 797 326. How works the Derivative Law? 799 327. Epigenesis or Evolution ? ......... 809 328. Nomogeny or Thaumatogeny ? 814 WORKS REFERRED TO .......... 827 ZOOLOGICAL INDEX . . . . . . . . . . 839 GENERAL INDEX . ........ 859 EEEATA. Page 26, four lines from bottom, premise f 197. Muscles of Perissodactyla.' ,, ,, thirteen lines from bottom, for ' (sterno-humeralis),' read ' (cephalo-huineraht;.' 49, note l for ' vi.,' read ' vi".' 72, note 3 for ' cxxxi'.,' read ' cxxxi.' 81 , note 5 for ' I/'. ,' read ' xxiv".' ,, 100, sixteen lines from top, premise ' A. Lyencephala.' 120, fig. 95, for ' xxxix".,' read ' xxix".' 129, note ' for ' ix'.,' read ' rx" '. ,, 144, note * for ' LVHI'.,' read ' LYin".' ,, 206, to description of fig. 152, add ' Human.' 212, note * for ' xcm.,' read ' xcra".' 251, note 1 for ' cv".,' read ' cix".' 255, below cut 20, for v".,' read ' cv".' 266, note * for ' xxv".,' read ' xxxix".' ,, 368, last line, for ' first true molar,' read ' first lower true molar.' ,, 412, note J for ' cxxn".,' read ' cxxn'.' 424, note 1 for ' cxxn"., xxm.,' read ' cxxn'. vol. xiii.' ,, 427, five lines from top, for ' 327,' read ' 227 ; ' and so on to ' 399, p. 715,' for which read ' 299.' 428, ten lines from top,/or ' fig. 359,' read fig. 389." 450, ' fig. 354,' for ' cxxn'.,' read ' CXXIi".' 460, note J for ' cxxi.,' read ' cxxn'.' 473, note l for ' ccxxn".,' read ' cxxn'. 479, note 2 for ' cxn".,' read ' cxxn'.' ,, 515, note B for ' Ib.,' read ' CLXXIX".' 535, note "for ' xcvrn".,' read ' xcvn'.' 536, note * for ' cxcii",' read ' xxxiv".' 542, note ' for ' cxLm".,' read ' cxxxi".' 536, note 4 for ' cxcn".,' read ' xxxiv".' 622, twelve lines from top, for fig. 489,' read 4 fig. 489, i.' 637, fourteen lines from bottom, for ' glossa,' read ' fossa.' 718, for ' 400,' read ' 300 ; ' and so on to ' 428, p. 813,' for which read ' 328.' ,, 790, nineteen lines from top,/o/- ' Palceotheria,' read ' Spalacotheria.' THE ANATOMY OF VERTEBRATES. CHAPTER XXVII. MUSCULAR SYSTEM OF MAMMALIA. THE muscular tissue in the present as in the preceding Vertebrate classes presents the two conditions of striped and unstriped elemen- tary fibres : the striped kind, comprising all the voluntary muscles with those of the heart, are red : deeper coloured in Cetacea and Carnivora than in Uncjulata : deeper in the pectoral muscles of Cheiroptera than in those of the legs : paler in the pectorals and other muscles of the fore-legs of the Kangaroo than in the ' psoae ' and those of the hind-legs : palest in some Rodentia. 1 92. The Diaphragm.- -The chief characteristic of mammalian myology is the diaphragm, vol. ii., fig. 139, d, which, as such, is not more completely developed in Man than in the Monotreme. It is the partition between the thoracic and abdominal cavities, fig. 1, vaulted and convex toward the thorax, fig. 2, and consists of carneous and tendinous parts, the latter chiefly In the expanded or aponeuro- tic form. The carneous fas- ciculi are divided into the ( costal ' or greater and the ( vertebral ' or smaller mus- cles. The costal portions arise from the ensiform cartilage, and those of the eighth to the twelfth ribs, by fasciculi which inter- digitate with those of the 6 transversalis abdominis ' mUSCle. I hey aSCeild and Human diaphragm ; abdominal surface. expand, arching and con- to be inserted into the external ( ligamentum arcuatum,' B VOL. Til. 2 ANATOMY OF VERTEBRATES. fig. 1, d, and into the aponeurosis called f centrum tcndineum' or 'cordiform tendon,' ib., T. This centre is widely notched toward the spine, and divided anteriorly into three tracts, of which the right is usually the largest. Between the right and middle tracts is the orifice, c, for the inferior vena cava (' postcaval ' of Mam- mals). Behind the tendon, and to the left of the median line, is the orifice, e } for the oesophagus and pneumogastric nerves : the aorta, , passes from the chest to the abdomen be- tween the f crura ' of the "lesser muscle. The right 6 crus ' in Man arises from the three or four upper lum- bar vertebras ; the left crus does not descend so low : both muscular bundles ex- pand as they rise, decus- sate at the ossophageal open- ing, and are inserted into the posterior concavity of the central tendon and in- ternal ligamentum arcua- tum, fig. I,/. The diaphragm is most muscular, longest, and most oblique in Cetacea, in which the central tendon is almost obsolete : by rising so far back, it permits the proportional extension of the lungs, which in the Duo-ono; and Manatee act as air-bladders. In the o ~ perissodactyle Ungulates, in which the moveable ribs are numerous and continued to near the pelvis, the diaphragm is also extensive, and much arched toward the thorax. 193. Muscles of Monotremata. To give an account of the muscular, as fully as that of the osseous, system of the Mammalia, would not be attended with the same advantages, even if a detailed myology comported with the scope and extent of the present work. This part of Mammalian anatomy will therefore be limited to the notice of a few select examples. Fig. 3, from Meckel, 1 shows the more remarkable muscles of the Ornithorhynchus. The animal is dissected from the ventral surface ; the great e panniculus carnosus,' i, is reflected from the right side, and the deeper-seated muscles are shown on the left. The panniculus carnosus, which is remark- able for its thickness, encompasses nearly the whole body, adhering most firmly to the external skin, but separated from the subjacent muscles, especially where it covers the thorax, abdomen, the arm, 1 LXXI-. Human diaphragm. Thoracic surface from behind. MUSCULAR SYSTEM OF MAMMALIA. 3 and the thigh, by a copious and lax cellular tissue ; and in the female, at the abdominal region, by the mammary glands. The fibres are chiefly longitudinal, but at the lower part of the neck become transverse. The obtuse posterior end of the muscle is at- tached by three or four fasciculi to the dorsal aspect of the caudal diapophyses. The legs and the arms protrude through oblique apertures in this muscular tunic ; some of the anterior fasciculi are inserted by a short tendon into the pectoral ridge of the humerus ; and others, still more anterior, are attached to the cranium, the lower jaw, and lower lip. A strip of fibres, which is cut off at i*, is attached to the os hyoides ; another fasciculus (V) spreads over the cheek-pouch, r, and assists in emptying that receptacle of the food. The trapezius, 9, is divided into two muscles ; the posterior por- tion is an oblong slender triangle arising by a broad tendon from the tenth and eleventh vertebrae and ribs, and inserted by a short strong tendon behind the extremity of the spine of the scapula ; the anterior portion arises from the occiput and tendinous raphe con- necting it with its fellow of the opposite side, and is inserted into the spine of the scapula, and into the outer half of the clavicle. The latissimus dorsi, a very long and broad muscle, arises from the spines of all the dorsal and lumbar vertebrae and from the eleven posterior ribs ; it is inserted by a broad and strong tendon into the distal half of the ulnar margin of the humerus, and, with part of the ( panniculus,' into the fascia attached to the olecranon and spreading over the fore-arm. At its anterior part this muscle may be separated into a superficial and deep stratum. The r/wm- boideus is a single muscle, but thick and long, inserted into the narrow base of the scapula. The splenius capitis is united by an intermediate tendon with the opposite muscle, and is inserted into the mastoid process. The biventer cervicis and the complexus are distinct throughout their whole course, which extends from the anterior dorsal and posterior cervical spines to the occiput ; the complexus is the longest and thickest muscle, and divides into an external, shorter, and deeper-seated portion, and an internal, longer and superficial portion. The sacrolumbalis arises from the dorsal extremity of the ilium, is attached to the ribs, over which it passes in its course to its insertion into the transverse processes of the four or five posterior cervical vertebrae : it is continued by the f cervicalis ascendens ' to the atlas. The longissimus dorsi is a much thicker and narrower muscle, B 2 .Muscular system, ventral aspect. Ornithorhynclms paradoaxts, LXXXV MUSCULAR SYSTEM OF MAMMALIA. 5 and extends from the dorsal aspect of the sacrum along the spine to the third or fourth cervical vertebra. It is continued forward by the transversalis cervicis and trachelo-mastoideuSywhicln. are blended into a sino-le oblono; muscle arising; from the anterior dorsal and o o inserted into the transverse processes of the six lower cervical vertebra? and the mastoid process. The sterno-mastoid is a double muscle on both sides, one por- tion being superficial, 8, the other deep-seated ; each arises sepa- rately from the episternum, and is separately inserted into the mastoid. The omo-hyoideus, 10, and mylo-luj 'oideics, 10, have a common insertion into the hyoid. A muscle, i" ', arising from the basi-hyal and expanding to be inserted into the lower lip, serves to retract this part. The sterno-hyoideus, u, joins the liyo- ylossus. The genio-hyoideus, 12, and the stylo -hyoideus, is, have the normal relations : the biventer maxilla, H, is a short thick muscle, inserted near the bend, representing the angle, of the jaw. The caudal muscles are powerfully developed. The oblique fibres of the inferior or deflector muscles are shown at 63 ; they are removed on the other side to expose the anterior caudal nerves, z. The obliquus externus abdominis, 3, 3, arises from all the vertebral ribs, except the first, and from the dilated ex- tremity of the ilium ; it is inserted by a strong tendon into the outer extremity of the marsupial bone, VI, then expands into an aponeurosis which is attached to the internal margin and base of that bone, and into the symphysis pubis, decussating with the tendinous fibres of the opposite muscle : it does not split to form an ( abdominal ring.' The olliquus interims, 6, arises from the anterior part of the ilium, expands, and is inserted into the broad cartilages of the seven posterior ribs, v, v. The transversus abdominis, 7, is a thicker muscle, and arises from both the ilium and the lumbar diapophyses ; its tendon passes behind the recti to blend with that of the opposite muscle, and with the aponeurosis of the obliqui externi, in the linea alba. The pyramidalis, or superficial rectus, 4, is here, as in the ordinary Marsupials, of very large size ; it arises from the whole inner margin of the marsupial bone ; its fibres converge toward and are confluent at the linea alba with those of its fellow, and it gradually terminates in a point opposite the posterior part of the sternum. It depresses the ribs, shortens the abdomen, and pro- tracts the marsupial bone. The rectus abdominis, or posterior rectus, 5, arises from the posterior margin of the marsupial bone, and is inserted into the 6 ANATOMY OF VERTEBRATES. cartilage of the first rib, the manubrium sterni, and the coracoid bone. The diaphragm presents the structure which is characteristic of the true mammiferous animal. The lesser muscle arises from the first lumbar and four last dorsal vertebrae, and expands to be inserted into the central tendon, which chiefly receives the fibres of the greater muscle arising from the cartilages of the eleven inferior pairs of ribs. The pectoralis, 2, is of very striking dimensions ; the origin of the superficial portion extends from the acromion and episternum, along the sternum and linea alba, almost to the pubis ; a deeper- seated portion arises from the six osseous sternal ribs ; the fibres of both portions converge to be inserted into the largely-developed pectoral or anterior crest of the proximal half of the humerus. The pectoralis minor is attached to the coracoid, and the sub- clavius is likewise inserted, as in some other quadrupeds, into this bone, which is no longer a subordinate process of the scapula in the Monotremes. The subscapularis is a narrow muscle, and narrower in reality than at first sight it appears to be, since the supraspinatus, from the inflection of the spine and acromion, arises from the same aspect of the scapula, and appears to form the anterior fasciculus of the sub scapular is ; its distinct insertion into the anterior tubercle of the head of the humerus points out its true nature. The infraspinatus, 20, and the large teres major cover the whole external surface of the scapula. The deltoid is divided into an anterior and a posterior portion. The anterior portion, 19, arises from the anterior extremity of the coracoid, and is inserted into the summit of the deltoid crest of the humerus: the posterior part, 21, arises from the anterior and superior apex of the scapula, and is inserted into the lower half of the deltoid crest. There are also two muscles to which the name coraco-brachialis may be applied, a superior one, 22, and an in- ferior one, 25. The biceps brachii arises by two heads ; one, 23, arises from the sternal extremity of the coracoid, the other, 24, also arises from the coracoid ; the common tendon is inserted into the middle of the radius. The other muscles of the anterior extremity adhere closely to the Mammalian type. The extensor carpi radialis, so, sends three tendons, to be inserted respectively into the second, third, and fourth metacarpal bones. There is a single common flexor diai- torum, as well as extensor diaitorum, 27. The extensor diaiti minimi, 26, the indicator, 28, the extensor MUSCULAR SYSTEM OF MAMMALIA. 7 pollicis, 29, the pronator teres, 32, and the flexor carpi radialis, 33, are all remarkable for their strength in the Ornithorhynchus, and are still more powerfully developed in the Echidna. The most remarkable muscle on the palmar aspect of the fore arm is the flexor carpi ulnaris, which arises by two separate heads, the longer one from the broad olecranon, the shorter one from the internal condyle of the humerus ; the common tendon is attached to the os pisiforme and the rnetacarpals of the fourth and fifth digits. The psoas magna and iliacus interims form a single muscle, having the usual origins, and inserted by a common tendon into the large internal trochanter. The psoas minor is the largest of these muscles. It arises from the sides of five dorsal vertebras, and its strong tendon is implanted in the remarkably developed ilio-pectineal process. It depresses the pelvis, and with it also the tail and the pelvic extremities. The ectoyluteus is larger than is usually the case with qua- drupeds ; its insertion extends to the plantar fascia and the bone which supports the spur. The mesogluteus, entogluteus, pectineus, 45, biceps flexor cruris, gracilis, 34, sartorius, 35, rectus femoris, 36, adductores femoris, 46, semitendinosus, 47, semi-mem- branosus, vastus externus, offer no notable deviations from the usual structure. A strip of fibres, 49, descends from the gracilis to the sphincter cloacce, H. A muscle, called by Meckel ( flexor accessorius a cauda ad tibiam tendens,' 51, arises from the trans- verse processes of the anterior caudal vertebrae, and converges to be inserted into the tibia. Another peculiar adductor of the leg, which might be termed ( intertibialis,' 52, is attached by its ex- tremities to both tibiaa ; its fleshy belly passes across the sphincter cloacaa, H, and is connected with a strip of the panniculus car- nosus, i. The gastrocnemius, 48, derives its largest origin from the pro- duced and expanded head of the fibula, and its smaller belly from the internal femoral condyle ; its tendon is implanted in the cal- caneum. The homotopy between the gastrocnemius and flexor carpi ulnaris is strikingly illustrated in the Ornithorhynchus. The soleus arises from the head of the fibula and from a large pro- portion of the tibia ; it is nowhere blended with the gastrocnemius, but is inserted by a thick and short tendon into the astragalus. The abductors of the outer digits of both the hand and foot are well developed for the purpose of expanding the web which connects the toes. In the fig-ure the following muscles of the les; are shown viz. o o o 37, tibialis anticus, 38, extensor hallucis longus, 39, peroneus longus, 8 ANATOMY OF VERTEBRATES. 40, peroneus brevis, 4i, extensor digitorum profundus, 42, extensor digitorum xiihlunis, 43, a portion of the same muscle corresponding with the indicator of the fore leg, and 44, extensor diyiti quinti accessorius. 194. Muscles of Marsupialia.- -The most common posture of the Kangaroo is often termed the ' erect ; ' yet the conditions of this posture are very different from those in the human subject. The trunk, instead of resting upright on two nearly vertical pillars, is here swung upon the femora as upon two springs, which descend from the knee-joints obliquely backward to their points of attachment at the pelvis ; and the trunk is propped up behind by the long and powerful tail, vol. ii., fig. 211. In Man the massive and expanded muscles which find their attachment in the broad bones of the pelvis, especially at the posterior part, are the chief powers in maintaining the erect posture. But in the Kangaroo the ylutcei offer no corresponding predominance of size ; the narrow prismatic ilia could not, in fact, afford them the requisite extent of fixed attachment. The chief modifications of the muscular system in relation to the erect position of the trunk in the Kangaroo are met with on the anterior part of the base of the spinal column. The psocz parvcB, for example, present proportions the reverse of those that suggested their name in human anatomy. They form two thick, long, rounded masses, which take their origin, fleshy, from the sides of the bodies and base of the diapophyses of the lower dorsal and all the six lumbar vertebra?, and from the extremities of the three last ribs ; the fibres converge pemiiformwise to a strong, round, middle tendon, inserted in the well-marked tubercle or spine of the pubis, already noticed. The abdominal muscles include a pyramidalis as remarkably developed as in the Monotremes. In the Phalanger, fig. 4, the external oblique., besides the usual origin by digitations from the ribs, also arises from the fascia luiiiborum ; it is in- serted fleshy into the summit of the marsupial bone, a, over which its strong inner tendon is spread : the external oblique becomes aponeurotic at a line continued from the marsupial bone outward, with a gentle curve, toward the anterior ex- tremity of the ilium ; and in the opposite direction, or inward, the carneous fibres of the external oblique terminate in an apoueurosis along a line parallel with the oblique outer margin of the pyramidalis ; the fascia continued from the latter boundary of the fleshy fibres passes over, or dermad of, that muscle, and meets its fellow at the linea alba ; it is homologous MUSCULAR SYSTEM OF MAMMALIA. ing Abdominal muscles, 1'iitilauijinta rulpina. with the anterior layer of the sheath of the rectus in ordi- nary Mammalia. It is seen reflected from the pyramidalis, at by fig. 4. The aponeurosis continued from the external and inferior boundary of the carneous fibres divides as usual into two distinct por- tions. One, a, correspond- to the internal or mesial pillar of the abdo- minal ring, spreads its glistening fibres, as above described, over the dermal surface of the marsupial bone, c, to which it closely adheres : the other co- lumn, d, contracts as it descends obliquely in- ward, forms, like ' Pou- part's ligament,' the upper boundary of the space through which the psoas and iliacus muscles and femoral vessels and nerves escape from the pelvis, and is finally inserted, thick and strong, into the outer end of the base of the marsupial bone. This bone is so connected with the pubis that its movements are almost limited to directions forward and backward, or those concerned with the dilatation and diminution of the abdominal space ; the contraction of the abdominal muscles must draw the bones inward so as to compress the contents of the abdomen, and so far as the connections of the bone permit, which is to a very trifling degree, the external oblique may draw it outward toward the ilium. In some Marsupials, as the Koala, the triceps adduc- tor femoris sends a slip of fibres to the external angle of the base of the marsupial bone, and would more directly tend to bend that bone outward. The upper or anterior fibres of the internal oblique have the usual origin ; the lower ones, e, arise fleshy from the outer and anterior spine of the ilium, and for an inch along an aponeurotic chord extended from that process to the upper part of the aceta- bulum : these carneous fibres pass inward and slightly upward, and terminate close to the outer margin of the rectus, where they adhere very strongly to the transversalis, but give off a separate sheet of thin aponeurosis which is lost in the cellular sheath of the posterior rectus. 10 ANATOMY OF VERTEBRATES. The fleshy fibres of the transversalis abdominis, f, are closely connected by dense cellular tissue with those of the internal oblique ; they are arranged in finer fasciculi, and have, as usual, a more transverse direction ; they terminate along the same line as those of the internal oblique in an aponeurosis, g, which is continued along the inner or central surface of the posterior rectus to the median line. The lower boundary of the fleshy fibres of the transversalis is parallel with the line extended transversely between the anterior extremities of the ilia ; a fascia, less compact than an aponeurosis, is continued downward from this margin, and envelopes the cremaster and the constituents of the spermatic chord, as they pass outward and forward beneath the lower edge of the internal oblique. The pyramidalis, h, arises from the whole inner or mesial margin of the marsupial bone, from which the fibres diverge, the lower ones passing transversely across the interspace of the bones, and meeting at a very fine raphe, or linea alba ; while those fibres from the anterior ends of the marsupial bones gradually exchange their transverse direction for one obliquely forward. The breadth of each pyramidalis opposite the upper end of the marsupial bone is more than an inch, the thickness of the muscle one line. The rectus abdominis, i, comes off from the pubis along the inner part of the strong ligamentous union of the broad base of the marsupial bone, and expands as it ascends until it attains the level of the ensiform cartilage, when it diminishes as it is inserted into the sternal extremities of the ribs reaching to the manubrium sterni and first rib in the Dasyures, as in the placental Carnivores. The slight indications of tendinous intersections are confined to the posterior or central superficies of the muscle. The cremaster , k, in the Phalanger and Opossum, is not a fasciculus of fibres simply detached from the lower margin of the internal oblique or transversalis, but arises by a narrow though strong aponeurosis from the ilium, within and a little above the lower boundary of the internal oblique, with the fibres of which the course of the cremaster is not parallel ; it might be considered as a part of the transversalis, but it is separated by the fascia above mentioned from the carneous part of that muscle. Having emerged from beneath the margin of the internal oblique, the cremaster escapes by the large elliptic abdominal ring, /, bends round the marsupial bone near its free extremity, and expands upon the tunica vaginalis testis. In the female it has the same origin, course, and size, but spreads over the mammary glands at MUSCULAR SYSTEM OF MAMMALIA. 11 the back of the pouch. If the anterior fascicles of the div and embracing fibres be dissected from the posterior ones, the appearance of the cremaster dividing into two layers is produced. The principal modifications of the muscles of the pectoral ex- tremity are here described as they exist in the Perameles lagotis. The trapezius has its origin extended from the skull, along the cervical and dorsal spines, to the fascia covering the lumbar por- tion of the latissimus dorsi : its fibres converge to be inserted alono- . the spine of the scapula, the anterior ones being directly continued into the pectoralis major, whereby it becomes an extensor of the humerus and a protractor of the fore extremity. The latissimus dorsi arises chiefly from the broad aponeurosis covering the muscles of the lumbar region of the spine, and from the spines of the six posterior dorsal vertebras ; the fibres gradually converge, the muscle increasing in thickness as it diminishes in breadth, and terminating in a strong flattened tendon one inch before its insertion at the upper third of the humerus. It is con- nected, as in most brutes, up to and including the Gorilla, with an accessory extensor (pmo-anconeus) * of the antibrachium. This ex- tensor takes its principal origin by fleshy fibres from the terminal half inch of the fleshy part of the latissimus dorsi, and continues fleshy, slightly diminishing in size to its insertion at the apex of the olecranon. To remedy the inconvenience of an origin from a yielding and flexible part, a thin aponeurotic slip, in Peramelcs, attaches a part of the base of the superadded muscle and the cor- responding portion of the latissimus dorsi to the sheath of the teres major, and to the inferior costa of the scapula near its posterior angle. The supraspinatus, a strong penniform muscle, exceeds the infraspinatus in breadth by as much as the supra-spinal fossa is broader than the infra-spinal one : it has a broad and strong insertion into the great outer tuberosity of the humerus. The infraspinatus is inserted into the upper and posterior part of that tuberosity. The deltoides is a comparatively small muscle ; it arises from the anterior half of the spine of the scapula and from a fine aponeurosis covering the infraspinatus ; its fibres converge to be inserted in the upper part of the deltoid ridge. A thin small strip of muscle arises from about the middle of the inferior costa of the scapula, beneath the infraspinatus ; its fibres pass forward and join the lower margin of the small del- toid, thus bracing and enclosing the tendon of the infraspinatus. p. 289 (1846): the muscle is termed ' dorso-epitrochlien' by Duvernoy in the Gorilla, i". p. 80 (1855), where it is inserted into the inner condyle of the humerus. 12 ANATOMY OF VERTEBRATES. In claviculate marsupials the deltoid is larger, and consists of three fasciculi. The teres major is a strong sub-compressed muscle arising from near the posterior half of the inferior costa of the scapula, and joining, as before stated, the tendon of the latissimus. The triceps extensor has its long portion arising from the anterior third of the inferior costa of the scapula ; its second head comes from the posterior part of the proximal third of the humerus ; the third portion takes its origin from the whole of the posterior part of the humerus ; in addition to these, the olecranon receives the above-described fourth superadded slip from the latissimus dorsi. The pectoralis major is, as usual in the Marsupial and many higher quadrupeds, a complicated muscle ; it consists of an anterior or superficial and a posterior or deeper portion ; the anterior portion receives the strip of fibres before mentioned from the trapezius, there being no clavicle or clavicular ossicle interposed in the Pe- rameles ; its fibres converge, increasing in thickness as they diminish in breadth, and are inserted into the anterior and outer part of the strongly developed pectoral ridge. The second and main portion of the pectoralis arises from the whole extent of the sternum ; its fibres are twisted obliquely across each other as they converge to be inserted into the inner part of the pectoral ridge ; some of the internal and posterior fibres of this portion of the twisted pectoral pass obliquely upward and behind the anterior fasciculi, and are inserted into the coracoid process, thus repre- senting the pectoralis minor. Beneath this latter portion of the pectoral, a long and slender muscle passes to be inserted into the anterior part of the tuberosity of the humerus ; this may likewise be regarded as a dismemberment of the pectoralis major, but it arises from the fascia of the rectus abdominis, below the car- tilages of the lower ribs. Thus the strong pectoral ridge of the humerus is acted upon by muscles having a range of origin from the occiput and cervical vertebra? along the whole extent of the chest to the beginning of the abdomen. The biceps is a powerful muscle, although its short head from the coracoid process is suppressed. The long head has the usual origin and relation to the shoulder-joint ; its tendon is very thick and short. The fleshy belly joins that of the strong brachialis in- ternus, situated at the external side of the humerus, whence it takes its principal origin from the short deltoid ridge, closely con- nected there with the second portion of the triceps, and deriving some fleshy fibres from the lower and outer third of the humerus. The portion of the biceps arising by the long head soon resolves MUSCULAR SYSTEM OF MAMMALIA. 13 itself into two distinct pemiiform muscles ; the tendon of the outer one joins that of the brachialis, and this conjoined tendon simply bends the fore-arm, while the inner tendon bends and pro- nates ; the latter, which is a direct though partial continuation of the biceps, is inserted into the ordinary tubercle of the radius ; whereas the outer tendon is attached to the fore part of the proxi- mal end of the ulna. The muscles which arise from the internal condyle of the humerus are the pronator teres, which has the usual origin, insertion, and relative proportions, and next a large pal- inaris longus. There are, likewise distinct and strong fasciculi of muscles corresponding to tia&Jlexores carpi ulnaris and radialis, and to thejferor sublimis diyitorum. The strong ridge continued from the olecranon to the posterior and inner part of the ulna gives origin to a great proportion of the oblique fibres of the flexor pro- fundus ; but both this and thejflexor sublimis terminate in a single thick and strong tendon, which after passing the wrist divides into those corresponding with the perforating and perforated tendons concentrated, in Perameles, upon the three long middle fingers. The pronator quadratics runs the whole length of the interosseous space, passing from the radius a little obliquely downward to the ulna. The supinator longus, arising as usual from the upper part of the strongly developed ridge above the outer condyle, sends its tendon across the carpal joint, which tendon divides before it crosses, and is inserted by one of its divisions into the base of one of the metacarpal bones of the index finger, and by the other into the adjoining metacarpal bone. These are the principal muscles of the fore extremity which require notice. Their modifications, in respect of number and strength, relate to the act of digging up the soil, which is habitual in the Bandicoots, as it is for the purpose of obtaining food, and not for shelter. It is for this purpose that the three middle digits of the hand are developed at the expense of the other two, which are rudimental ; the whole power of the deep and superficial flexors is concentrated upon the fossorial and well-armed fingers ; and, by the sinoie common tendon in which the fleshy fibres of j ~ > these muscles terminate, they move them collectively and simul- taneously. Thus variety of application, and especially the pre- hensile faculty, are sacrificed to the acquisition of force for the essential action. In no Marsupial is the hand so cramped as in the Perameles, excepting in the Chceropus, where the functional and fossorial fingers are reduced from three to two. It is in rela- o tion to this condition, doubtless, that the clavicles are wanting in these genera, while all other Marsupials possess them. In these 14 ANATOMY OF VERTEBRATES, the biceps has the usual two origins : the flexor sublimis digitorum is distinct from the flexor profundus in Didelphys. The muscles of the hinder extremity are chiefly remarkable in the Kangaroo for their prodigious strength and unusual number : the accessory muscle of the biceps cruris, e. g., arises from a caudal vertebra, and, with that from the ischium, forms two strong fasciculi, one inserted into the outer femoral condyle, the other into fascia covering the gastrocnemii. The pyriformis is also a double muscle. The sartorius has its insertion so modified that it becomes an extensor instead of a flexor of the tibia : it is chiefly fixed to the tibial side of the gristly patella, and by fascia into the capsular ligament of the knee-joint and the anterior proximal tuberosity of the tibia. In a Dasyure (Das. macrurus ) I found that the sartorius had a similar disposition and office. In this ambulatory carnivorous Marsupial the external and middle glut&i are so disposed as to extend the thigh, while the in- ternal glutceus inflects and rotates it inward. In a Bandicoot (Perameles lagotis) the sartorius ran nearly parallel with and dermad of the rectus, and was inserted into the upper part of the patella. Besides this sesamoid, which is rarely developed in other Marsupials, I found a thick cartilage attached to its upper part and interposed between the common tendon of the recti and vasti, removing that tendon further from the centre of motion, and in- creasing the power of the extensor muscles of the leg. The rec- tus femoris has its two origins very distinct, and its homotypy with the biceps of the upper extremity is obvious. Thegracilis is a very thick and strong muscle. The biceps flexor cruris in the Perameles is a muscle of very great strength ; it terminates in a strong and broad aponeurosis, which extends over the whole anterior part of the tibia, being attached to the rotular tuberosity of that bone, and terminating below in the sheath of the tendo Achillis, whereby this muscle becomes an extensor of the foot. All the equipedal Marsupials, whether burrowers as the Wom- bat, climbers as the Koala, Phalangers, and Opossums, or simply gressorial, as the Dasyurida, have the tibia and fibula so connected together as to allow of a certain degree of rotation upon each other, analogous to the pronatory and supinatory movements of the bones of the antibrachium, and the muscles of the leg present corresponding modifications. None of the analogous carnivorous, pedimanous, or rodent Placentals present this condition of the hind leg. In the Kangaroo, the gastrocnemii almost rival those of Man in the bulk of the fleshy part. In the Dasyurus macrurus, \heplantaris, instead of rising from MUSCULAR SYSTEM OF MAMMALIA. 15 the femur, has its fixed point in the fibula, from the head to half- way down the bone, fleshy ; its tendon passes obliquely inward, and glides behind the inner malleolus to its insertion in the plantar fascia, so that it rotates the tibia inward besides extending the foot. The soleus has an extensive origin from the proximal to near the distal end of the fibula. There are, as usual, three deep- seated muscles at the back of the leg. Of these three the muscle homologous with the tibialis posticus is readily recognised; its tendon glides behind the inner malleolus, and is inserted into the inner or tibial cuneiform bone. The muscle Avhich has the relative position and origins of the flexor longus pollicis., sends its tendon by the usual route to the sole of the foot, where it di- 5 vides and distributes a flexor tendon to all the toes except the rudimental hallux ; it has the same disposition in the Opossums, where the hinder thumb or great toe is fully developed : for this modifica- tion, however, the Compara- tive Anatomist is already pre- pared by meeting with such common office of the muscle in the first step from Man, viz. in the Orang, Gorilla, and Chimpanzee. The third deep-seated mus- cle, being situated internal to the two preceding ones, may be the homologue of \\\Q flexor digitorum communis longus ; it nevertheless sends no ten- don to the toes nor even to the tarsus, but its fibres pass from the tibia obliquely outward and downward be- tween the preceding muscle and the interosseous ligament to the fibula, where they are -, . , . -. Muscles of leg, Phalangista exclusively inserted so as to oppose the plantaris and rotate the foot outward. This muscle closely adheres to the interosseous fascia, and thus resembles in its 16 ANATOMY OF VERTEBRATES. attachments the pronator quadratus of tlic fore limb : it is most developed in the pedimanous climbing Marsupials, where the rotation of the foot is more frequent and extensive. Fig. 5 shows this modification of the muscles of the hind-foot in the Phalangista vulpina ; a, is the expanded tendon of the sartorius ; byffracilis', c, seinitcndinosus ; and d, semimembranosus ; both these muscles are inserted, as in many other quadrupeds, low down the tibia : c, gastrocnemius ; f, plantaris ; g, the homologue of the flexor lone/us pollicis pedis ; h, tibialis posticus ; this muscle divides and is inserted by two tendons, h' and h" , into the internal and middle cuneiform bones ; /, the rotator muscle of the tibia. In the muscles on the anterior part of the leg, the extensor brevis diyitorum has its origin extended into this region, and is attached to the outside of the fibula. There are three peronei\ the external one is inserted into the proximal end of the fifth metatarsal : the tendon of the middle peroneus crosses the sole in a groove of the cuboid like the peroneus longus : the internal peroneus is an extensor of the outer or fifth toe. The Perameles layotis, among the saltatorial Marsupials, presents a different condition of the extensors of the foot from that above described. The yastrocnemii, soleus, and plantaris all arise above the knee- joint, and the tendon of the plantaris, after sheathing the tendo Achillis and traversing the long sole, is finally inserted into the base of the metatarsal bone of the fourth or largest toe ; thus this muscle, which is strongly developed, bends both this toe and the knee, while it extends the foot. In the Kangaroo the flexor of the toes rises from the outer tuberosity of the tibia, its fleshy part covers the back of the leg beneath the soleus, the tendon passes to the sole and divides into a large tendon for the principal toe, fig. 211, iv, a smaller tendon for the outer toe, v 9 and a still smaller tendon which goes to the two slender inner toes. The muscle seems to combine the homo- logues of the flexor liallucis and flexor diyitorum, with, perhaps, also that of the tibialis posticus. 195. Muscles of L,issencephala. -The Rodentia closely re- semble the Marsupialia in their muscular system ; with like modifications according to the absence or presence of clavicles, and to the gradatory, saltatory, scaiisorial, and fossorial move- ments of the species respectively. They have not the marsupial modifications of the cremaster and abdominal muscles, nor the rotatory muscle of the tibia ; but certain Rodents show pecu- liarities of the masseter which will be noticed in connection with the organs of mastication. MUSCULAR SYSTEM OF MAMMALIA. 17 The Insectivora afford examples of special muscular develope- ment in the fore part of the trunk and pectoral limbs of the Mole, fig. 6, and in the muscles which act upon the prickly skin of the Hedgehog, figs. 7 and 8. The dermal muscles are powerful and extensive in all Insec- tivora : in the Mole ( Talpa europcea) 9 fig. 6, the insertion of one of these is seen at a : it assists in retracting the trowel-like Muscles of the fore part and limbs of a Mole (Talpa europcea). XLIII. fore limb ; and, when this is the fixed point, draws forward the pelvis and thigh. The muscles of the scapula are singularly de- veloped and modified : the trapezius operates upon the short base of the elongate bone with great advantage. The anterior portion, d, arising from the occiput, derives further strength from the ossi- fied ' nuchal ligament,' and is inserted at e : the part answering to the posterior fibres of the muscle, f, arises as far back as the lumbar vertebne to be similarly inserted into the base of the sca- pula, antagonising the former. The f splenius capitisj A, derives fibres from the nuchal style, as well as from certain dorsal and cervical vertebra? : it is inserted into the paroccipital region of the cranium. The stemo-mastoid, g, joined by a ( cleido-mastoid ' from the cubical clavicle, is a very powerful muscle which expands to be inserted into the lateral part of the superoccipital and fascia covering the mandibular angle. The deltoid, k, coextensive with VOL. I IT. C 18 ANATOMY OF VERTEBRATES. the scapula, acts through its length with great power upon the well-developed humeral ridge. The s teres major,' /, commencing at the thickened base of the scapula, and deriving fibres from the lower facet of that triedral bone, combines to be inserted into the humerus with part of the latissimus dorsi, m ; a strip from which muscle is extended to the olecranon. The triceps, o, arising from both scapula and humerus, is extremely broad and thick, calling for an extended olecranon for adequate insertion. Part of the powerful flexors of the hand (j#. diyitorum, q, Jl. carpi ulnaris, r), and part of the extensors, t, are shown in this view. The pectoralis consists of five thick fasciculi, four of which rise from the sternum, and one from the clavicle : they converge to be implanted into the great humeral ' crista pectoralis : ' to these is added a fasciculus of which the homologue may be traced in Cetacea and Unyulata, passing transversely from one insertion of the pectoral to the other, and serving to combine both trowels in vigorous fossorial action. Of the muscles of the jaws the ' tem- poralis ' is shown at b 9 and the ( masseter ' at c. The Hedgehog (Erinaceus] manoeuvres its armour of spines by means of powerfully developed and specially arranged cutaneous muscles. By putting any part of the integument on the stretch, the spines are erected, and their points held firm against the assailant : by the same act of stretching the skin, the proportion Dermal muscles of the Hedgehog. XLIII. thereof to which the prickly armour is restricted can be drawn over ihe whole of the exposed surface of the animal, which in this act rolls and squeezes itself into the shape of a ball. In fig. 7, the Hedgehog is dissected as in the ordinary posture, or unrolled. The layer of muscle, , a, a', consists of concentric fasciculi, thin over the middle of the back, , and becoming thicker toward the periphery, ', a' , which is well defined. All the MUSCULAR SYSTEM OF MAMMALIA. 19 fibres are closely attached to the derm, and to the fibrous cap- sules of the roots of the spines. To the circumference of this circular muscle are attached shorter ones at right angles : a pair of these, b, arise from the caudal diapophyses, pass forward and expand to interblend with the posterior periphery : a second pair, d, with attachments to the nasal and premaxillary bones, pass backward over the forehead to the anterior periphery : a third pair, e, arising from the fore part of the sternum, pass for- ward and outward, diverging, and ascending in front of the shoulder to the antero-lateral part of a. A muscle, c, from fascia external to the mandibular angle, ascends between the auditory meatus and the eyeball, and combines with d in operating on the fore part of the great orbicular muscle. TVhen the Hedgehog assumes its offensively defensive position it bends and retracts the head and draws forward the pelvis, curving the back, as in fig. 8 : the converging slips b, c, d, e, pull down the orbicular muscle, which relaxes to slip over the projecting parts: the peripheral part, a', #', having descended below these, contracts, and encloses the head, limbs, and body, in an orbicular form. In resuming the normal position the sphincter relaxes, the head is rotated forward, the pelvis and tail are drawn back, the limbs begin to extend themselves: the orbicularis, ', a', is pushed up beyond the meridian, and then contracts, dispos- ing itself, after full exten- sion of the parts beneath, upon the dorsum of the animal, as in fig. 7. Su- perficial sheets of muscle, extending from the shoulder joint backward, s, and over the abdominal region, g, concur with the above-de- scribed in the motions of rolling and unrolling the animal. One of the lateral muscles of the snout is shown at m, the masseter at c. In the order Bruta the most notable modifications of the mus- cular system are met with in the Anteaters. c 2 8 Orbicularis dermal muscle, Hedgehog, half unrolled. XLIII. 20 ANATOMY OF VERTEBRATES. On reflecting the skin from the under part of the head in Myrmecophaga jubata, there is seen a feeble developement of a panniculus carnosus in the form of thin transverse fasciculi occurring at intervals of from two to three inches, where they underlie the rami of the slender elongated under-jaw. These muscular strips (dermogulares) have their attachments exclusively in the integument, and aid in accommodatino; its movements to O 9 O the alternating expansion and contraction of the great gular dila- tation near the base of the tongue. The transverse fasciculi are crossed by a longitudinal strip of cutaneous muscle (dermo- labialis posticus) on each side of the under part of the head and neck ; the strip emerges from beneath the fore part of the great subpectoral gland ; it diminishes in breadth and increases in thickness as it extends forward, assuming near the mouth the character of a muscle independent of the skin, where, passing beneath the tendon of the retractor anguli oris, it is inserted into, or blends with, the fibres of an accessory portion of the orbi- cularis oris. A shorter longitudinal muscular strip (dermolabialis anticus) arises from the integument below the fore part of the preceding muscle, becomes free as it advances, and is inserted into the proper orbicularis oris. The flattened and slightly separated fasciculi of the dermo- abdominalis arise from the fascia covering the anterior and in- ferior part of the sternum and contiguous sternal ribs ; also from a median raphe of the subcutaneous fascia, attached to the linea alba, and extending two-thirds of the way towards the pubis. The anterior two-thirds of the above muscular sheet are joined by a broad layer of similar flattened fasciculi covering the side of the thorax, and the muscle so formed passes obliquely downward and outward, converging to form a thick fleshy band, about two inches broad, which is continued along the inner and upper part of the thigh, and becomes slightly twisted prior to its attachment to the aponeurosis covering the knee-joint. The posterior portion of the dermo-abdomina.lis consists of thinner and more scattered flattened fasciculi which pass outw T ard and downward, and, as they diverge from the median line, are lost in the subcutaneous fascia covering the tendinous expansion of the obliquus externus abdominis. Between the dermo-abdomi- nalis and the proper abdominal muscles there is a moderately thick layer of elastic cellular tissue. In the dissection of the head -of the Great Anteater, three pairs of long and slender muscles are met with, which relate to the o 7 movements of the head. MUSCULAR SYSTEM OF MAMMALIA. 21 The sternocervicalis arises from the upper and outer angle of the mauubrmm sterni, close to the inner (mesial) side of the sternomaxillaris, by a thin tendon, which soon becomes fleshy, and the slender muscle gradually contracts to be inserted into the fourth cervical vertebra. The sternomastoideus arises from the outer angle of the manu- brium sterni, by a tendon which, at one inch from its origin, becomes a fleshy flat muscle ; this gradually increases in thickness to a rounded form, then contracts, and forms a tendon inserted into the paroccipital. The sternomaxillaris arises from the inner side, near the upper and outer angle of the manubrium sterni, and from the manubrial fascia, central of the clavicular fascia, and of the origins of the sternomastoideus and sternocervicalis. Its origin is by a flat short tendon : an aponeurosis passes from one tendon to that of the fellow muscle. The fleshy part forms a long slender band, which passes forward, and, about four inches from its origin, sends off a slender fleshy strip to the ceratohyoideus. It then advances as a slender round fleshy muscle, which degenerates into a sub- compressed tendon about half an inch in length, opposite the compressor salivaris. Resuming its fleshy structure, it forms an anterior subcompressed belly, ten inches in length, and from four to five lines in diameter. This gradually contracts, and terminates in a slender tendon three inches long, which expands to be in- serted into the outer and under part of the maxillary ramus, six inches in advance of the angle of the jaw. To the action of the pair of muscles so inserted is mainly due that characteristic movement of the head of the Great Anteater when it composes itself to sleep, and draws its head downward and backward between the fore-limbs, in contact with the chest. The mouth is small, and susceptible of so slight an opening as not to require for that action the usual modification of this part of the sterno-cleido-mastoideus muscle. The proper muscles of the jaws consist of the temporalis, the masseter, and the pterygoidei. The chief peculiarities of the muscles in the present species relate to the unusual developement and movements of the tongue. The mylolnjoideus is of unusual extent, and is divisible into different portions : two of these represent the normal mylohyoideus, and extend from the sym- physis mandibulae backward as far as the ascending ramus of the jaw. A third portion arises fleshy from the inner side of that ramus, whence its fasciculi radiate toward the middle line, in a somewhat twisted course, the anterior ones passing beneath the 22 ANATOMY OF VERTEBRATES second or normal part of the mylonyoideus. The fourth portion at its anterior part arises from the angle of the jaw, then from the base of the cranium, and afterward from a strong fascia extended thence backward, between the post-cranial prolon- gations of the nose and month ; the posterior and longest fasci- culi come off more outwardly, and radiate to spread over and blend with the gular fasciculi of the sternoglossi, passing out- ward and downward, and then bending inward to envelope that part of the hyoid apparatus. All the fibres of the fourth portion terminate in a median raphe, which is less marked than in the anterior portion. The fibres of the posterior division of the mylohyoideus, especially those which are attached to the under surface of the posteriorly prolonged nasal canal, form a kind of muscular sheath for the basal part of the muscles of the tongue. The cerato-hyoideus arises from the cerato-hyal : its fibres converge and form a fasciculus which is inserted into the commis- ^ sural tendon of the genio-hyoid, and is connected with a strip from the sternomaxillaris. After mvino; attachment to the fore- o o going two muscles, and to the anterior constrictor of the pharynx, its extremity is attached to the stylo-liyoideus muscle. In most mammals the hyoid arch, by the length of the ossified part of the stylohyal and the extent of the ossification of the ceratohyal is almost restricted to hinge-movements forward and backward upon the proximal joints of the stylohyals as a fixed point ; so that the basihyal with the tongue cannot be very far protruded or retracted. In the Myrmecophaga jubata the usual place of the stylohyal is occupied by a long and slender muscle, the styloliyoideus, which arises from the petromastoid, and after a course of five inches is inserted into the ceratohyal, here the first bone of the hyoid arch. Supposing the stylohyoideus to contract one-third of its length, it would protract the hyoid arch to the same extent : in which act it combines with the geniohyoideus. The retraction of the hyoid arch is provided for by the sterno- thyroidic and their continuations, the thyrohyoidei. ^^geniohyoideus arises by a single tendon from the symphysis of the jaw, runs back beneath the raphe of the anterior mylo- hyoideus, slightly expands beneath the raphe of the middle mylohyoideus, then again contracts and again expands, and at about ten inches from its origin becomes diffused into fleshy fibres, which gradually acquire a breadth of six lines, continue back in close connection with the mylohyoideus to the commissural tendon, and there expand, the lateral borders being attached MUSCULAR SYSTEM OF MAMMALIA. 23 thereto. Here a mid-line of separation appears, and the muscle bifurcates into two flat fasciculi, which are inserted into the angles of the basihyal. The sternothyroidei, fig. 9, /?, p, come off from the sixth, seventh, and eighth sternal bones, and from the seventh and eighth sternal ribs near their articulations therewith. The in- terthoracic extent of these muscles is six inches. Behind the manubrium the left muscle sends off a small fasci- culus of fibres to the right one, and the right reciprocally to the left. Where the decussation takes place there is a tendinous intersection at the fore part of the muscle. In advance of the interchange of fasciculi the ster- nothyroidei diverge and emerge from the chest, beyond which cavity they are fleshy throughout their extent, and are inserted into the lower and fore part of the thyroid cartilage. Sternoglossus, ib. g, /. This remark- able muscle arises fleshy from the lateral border of the dilated xiphoid and last sternal bone, arid from its junction with the last two true ribs. Linear tendinous intersections mark the part of the muscle within the chest. Emerging from beneath the manu- brium, it advances as a flat fleshy mus- cle. Opposite the hyoid it is perforated by a lingual artery, between four and five inches in advance it is perforated by the lingual nerve, h, and here its in- ferior stratum is resolved into flattened fasciculi of fibres which decussate or combine with those of the opposite muscle. About six inches in advance of the basihyal these fasciculi spread over a dilated membranous portion of the buccal cavity, at the lower part a 1 Ili X - y\ of Tongue.. Great Anteater. 24 ANATOMY OF VERTEBRATES. of which the base of the tongue is situated, and here they con- verge and blend with corresponding flattened fasciculi, sent off from the lower part of the genioglossi, as these pass backward to the base of the tongue. The main continuation of the stcrno- glossus, ?, forms a rounded slender muscle, which raises the buccal membrane so as to form the back part of the fnenum lingua?, penetrates the back part of the base of the tongue, and constitutes a great proportion of its substance. The gcnioylossus., ib. m, n, o, has a complex origin, by a middle portion, from the short symphysis mandibulse, and by a flattened penniform series of fibres, form the lower border of the mandi- bular rami for the extent of four inches behind the symphysis. The symphysial origin is round and slender, and belongs more directly to the proper tongue-muscle : the ramal origins seem to be the more special fixed point of the subgular fasciculi. The fibres of the latter origin pass obliquely backward and inward, con- verging to a middle raphe, to which the symphysial origin closely adheres. The two origins of the muscle are blended into one for about three inches beyond the point of attachment, in which extent the muscle forms a moderately thick depressed mass along the middle of the under part of the mouth. It then begins to expand, and to detach from its under surface those subgular fasciculi, which diverge and imite with the corresponding dis- memberments of the sternoglossi. The main part of the genio- glossus enters, as a single muscle, the fore part of the base of the tongue, carrying into the floor of the mouth a fold of buccal membrane forming the fore part of the fraenum linguae. Beneath the insertions of the geniohyoidei, a pair of more slender muscles, epihyoglossi, come off from the median ends of the epihyals. These muscles, after a brief course, expand into a thin layer, resolve themselves into separate fasciculi, and combine an inch in advance of their origin to form a layer about eight lines in breadth below the middle line of the post-lingual part of the mouth, which layer slightly diminishes in size as it approaches the commissure of the sternoglossi, and, with them, penetrates the back part of the fraenum linguas. 196. Muscles of Cetacea. In the Cctacea the muscles of the trunk are chiefly developed : those of the limbs are restricted to the pectoral pair. Swimming is the principal mode of progres- sion in the muticate orders of Gyrencepliala : but the phytophagous Sirenia have the power, in order to feed upon marine or littoral plants, of crawling at the bottom of the sea and shuffling along MUSCULAR SYSTEM OF MAMMALIA. the shore bv means or aid of their anterior members, which in the & true Cetacea are exclusively natatory organs. The head, in these, has so little mobility, that its axis can be but slightly altered, without that of the body altering also. With bones so short, so little mobile, and extensively co-adapted or anchylosed, as the vertebrae of the neck, muscles proportionately reduced should correspond. The cervical muscles are, neverthe- less, much the same in number as in other Mammals ; but their shortness and thinness, principally in those attached to the atlas and the axis, are extreme. The homologue of the ( splenius capitis,' fig. 10, h, is the best developed: it comes off from the anterior dorsal and cervical series of neural spines, and its fibres converge to be inserted into the paroccipital ridge. The muscles of the back present no other important modifica- tions than their great developement, especially where they are prolonged upon the caudal vertebras. Thus the longissimus dor si and the sacro-lumbalis are attached anteriorly to the skull, and posteriorly transmit their tendons, the first to the end of the tail, the second to all the transverse processes of this part of the spine, associating its movements, especially in the vertical direction, with those of the back. The levator caudcs, takes its rise above the five or six dorsal vertebra?, under the longissimus dorsi, and often in this part blends with it ; it then extends freely as far as the ex- tremity of the tail, Avhere the two muscles unite together again by their tendons. They are opposed by a depressor caudce, of great thickness, which proceeds from the thoracic region, attached by tendinous slips to the ribs and the contiguous transverse processes ; it is inserted into the haemal arches of the tail. A muscle passes from the rudimeiital bones of the pelvis to the haamapophyses of the anterior portion of the tail. The great recti abdominis and obliqui ascendentcs muscles are continued backward from the ab- domen, and attach themselves behind to the sides of the anterior caudal vertebrae. By this aggregation of muscles the tail of the Cetacea expands to proportions of the trunk, and acquires the prodigious strength which it possesses for propelling the most gigantic of the species, with ease and swiftness, through the water ; and, by means of the horizontal expansion of the caudal fin, it enables them to readily ascend to the surface to respire and again seek protection in the deep abysses of the ocean. In the great pectoral muscle, part of which is shown in fig. 10, at g, the costal origin is extensive, and the portion which comes off from the short sternum, passing transversely each to its own 26 ANATOMY OF VERTEBRATES. humerus, closely resembles the transverse connecting fasciculus in the Mole. The muscle answering to ' levator scapulae,' b, rises from the paroccipital, as well as from the cervical diapophyses : it ex- pands to be inserted into the fore and upper angle of the scapula 10 Muscles of pectoral fin, Ddphinus. and the fascia covering the s infraspinatus : ' it is a protractor, or forward rotator, of the scapula. The ' rhomboideus,' a, is the raiser of the blade-bone. Two strong muscles attached to the paroccipital and mastoid, pass, one, e, to the sternum (sterno- mastoideus), the other to the humeral tuberosity (sterno-hume- ralis). The ( latissimus dorsi,'/", is short and slender, coming off by a few digitations from the ribs, and inserted into the humerus and by an extended aponeurosis into the olecranon. The ( supra- spinatus ' is small : it is covered by the f deltoid,' i. The ( infra- spinatus/ c, is a broad and thin sheet of muscle. Behind it is a ' teres major,' k, also of broad and flat form ; and a thick and narrow ( teres minor,' /. The ' serratus magnus' does not extend forward beyond the ribs of the dorsal vertebra?. In the Ungulate series the muscular system has been traced out in both Perisso- and Artio-dactyle species, but most com- pletely in the Horse, figs. 11- 13. In this sensitive quadruped the dermal muscles are well developed, enabling it to shake the MUSCULAR SYSTEM OF MAMMALIA. 27 whole skin, rattling the harness which may be attached thereto., and to vibrate particular portions on which an insect or other irritant may have alighted. This ' panniculus carnosus ' is thick upon the neck, whence it passes downward, becoming ( aponeu- rotic ' upon the fore-limb : the sheets upon the sides and fore part of the trunk send a flat tendon to be inserted, with that of the latissimus dorsi, into the humerus : and other fasciculi pass downward over the muscles of the antibrachium, and 11 Myology of the Horse, ii". terminate in a fascia! expansion over the carpo-metacarpal seg- ment. The posterior part of the panniculus spreads over the loins, and, descending, degenerates into an aponeurosis, which forms, in the male, a sheath for the penis: the hinder portion encases the rump and thigh in a strong carneo-aponeurotic covering, which accompanies the fascia lata to the hind leg. On removing the panniculus carnosus, the superficial proper 28 ANATOMY OF VERTEBRATES. muscles of the trunk and limbs are exposed, as in the side view, %. 11. The ' spinalis dorsi ' repeats closely the characters of that muscle in Man. Its continuation, the ' spinalis ccrvicis,' is in the Horse of great strength and importance : its origin commences from the second dorsal spine, which origin is continued for about one-third of the way down that spine toward its root : it arises likewise from the third dorsal spine and the ligamentum nucha? ; from these origins it runs forward to be implanted by strong and distinct ten- dons into the spines of the anterior cervical vertebra?. The ' longissimus dorsi ' is situated immediately external to the spinalis, taking its origin from the common mass of muscle that arises beneath the lumbar fascia, as well as from the spinous pro- cesses of the loins and sacrum, whence it runs forward to be in- serted by a double set of tendons into the transverse processes of the loins and back, and also into the posterior ribs near their angles. Its continuation, the e transversalis colli,' consists of very powerful fasciculi, inserted respectively into the diapophysial parts of the last five cervical vertebrae. The ' sacro-lumbalis ' arises, in conjunction with the latissimus dorsi, from the back of the sacrum, and also by flat tendons from all the ribs, except two or three of the most anterior ; and its slips are inserted by as many distinct tendons into the inferior edge of all the ribs, except two or three of the hindmost, and also into the transverse process of the seventh cervical vertebra. The continua- tion of this muscle, the f cervicalis ascendens,' is chiefly remark- able for the strength of its tendinous insertions into the middle vertebra? of the neck. The ' multifidus spina?,' in the dorsal region, arises by numerous tendons from the metapophyses of the sacral, lumbar, and dorsal vertebra? ; each slip running forward to be inserted into the neural spine of the vertebra in front of that from which it derives its origin, the whole forming a thick mass, which fills up the hollow situated between the spinous and transverse processes. In the neck a similar disposition exists. Besides the ' intertransversarii colli,' there is a series of muscles arising from the prezygapophyses of the first dorsal and five last cervical vertebra?, and inserted, severally, into the side of the centrum in advance : they are called by Stubbs e intervertebrales/ 1 The ( longus colli ' arises from the transverse processes of the third, fourth, fifth, and sixth vertebra? of the neck, from which origins it runs upward to be inserted by distinct tendons into the MUSCULAR SYSTEM OF MAMMALIA. 29 anterior part of the bodies and transverse processes of the vertebrae above them, and into the anterior surface of the atlas. The muscles which raise or straighten the tail are the following : The f sacro-coccygeus superior ' arises from the third and suc- ceeding sacral spines, and from those of the anterior caudal vertebra?. The fleshy mass formed from these origins gives off numerous slender tendons : the first of these is the shortest, and runs inward to be inserted into the base of the first caudal vertebra, in which the articular apophyses are wanting. The second tendon is in- serted in a similar manner into the succeeding vertebra ; the third into the next, and so on to the end of the tail. Each tendon is lodged in a sort of ligamentous canal, which forms a sheath for it o o * throughout its whole course. When these two muscles act in concert the tail is raised. The ' interspinales superiores ' form a continuation of the inter- spinous series of vertebral muscles ; but as the spinous processes of the tail are short, and soon replaced by tubercular rudiments of the neurapophyses, these muscles are here disposed obliquely, being more widely separated posteriorly than they are in front. The muscles which depress the tail all take their origin in the interior of the pelvis, and are prolonged to a greater or less extent along the inferior aspect of the tail. They form four pairs of series of muscles, called the f ileo-coccygei,' and ( sacro-coccygei inferiores ; ' the latter are the more direct antagonists of the sacro- coccygei superiores, and their tendons are received into sheaths resembling those upon the upper surface of the tail, and are inserted successively into the base of each caudal vertebra, begin- ning about the seventh. The muscles adapted to move the tail laterally are arranged in two sets ; the ( ischio-coccygei externi,' a few fibres of which, in the Horse, are connected with the termination of the rectum and the ( intertransver sales.' The muscles derived from the vertebral column which serve im- mediately for the movements of the cranium have nearly the same origins as in the human subject, but are comparatively of much greater strength, owing to the inclined position of the head with respect to that column. They may be divided into such as pro- ceed, 1st, from the atlas ; 2nd, from the axis ; and, 3rd, from the posterior cervical vertebra? and ligamentum nuchre. To the first set belong The s rectus posticus minor,' ( rectus anticus/ ( rectus lateralis/ and c obliquus superior.' 30 ANATOMY OF VERTEBRATES. The muscles derived from the axis are the ( rectus posticus major ' and the ' obliquus inferior.' The ' complexus ' commences from the prezygapophyses of the third cervical vertebra, continues its origin from all those of the neck below that point, as well as from those of the first dorsal : also by a strong tendon from the transverse processes of the second and third dorsal vertebra? : from these origins it runs forward to be inserted by a strong round tendon into the super-occipital close to its fellow of the opposite side : in this course it is connected by numerous tendinous processes with the ligamen- tum nuclia?. The ' trachelo-mastoideus ' arises from the oblique processes of the third, fourth, fifth, sixth, and seventh cervical and first dorsal vertebra?, and from the transverse processes of the second and third vertebra? of the back ; it runs forward external to the last- mentioned muscles to be inserted by a strong tendon into the paroccipital. The above muscles are overlapped by the ( splenius capitis,' which, arising by strong tendinous processes from the spinous processes of the two superior dorsal and two last cervical, and also extensively from the ligamentum nucha?, runs forward to be inserted into the transverse processes of the fifth, fourth, and third cervical vertebra?, and into the transverse ridge of the super- occipital. The muscles of the ribs and sternum present, in the Horse, a disposition little differing from that of the corresponding muscles in Man : they are the ' scaleni,' the ( intercostals,' the ( levatores costarum,' the ' serratus posticus,' d, and ' serratus anticus,' /, and the ( triangularis sterni,' the two latter of which must be regarded as depressors of the ribs, and consequently acting the part of muscles of expiration. The walls of the abdomen are composed of five pairs of muscles, to which the same names are applicable as are bestowed upon them by the anthropotomist ; but the rectus abdominis is much more extensively developed. Arising from the os pubis, it passes forward enclosed in its usual sheath to be inserted into the ensi- form cartilage and into the cartilaginous terminations of the third, fourth, fifth, sixth, seventh, eighth, and ninth ribs, and also into the sternum between the cartilages of the third and fourth ribs. There are even fleshy fibres derived from this muscle prolonged as far forward as the articulation between the first rib and the sternum. Muscles of the anterior extremity. The ( trapezius ' consists MUSCULAR SYSTEM OF MAMMALIA. 31 of that part only which is called the ascending portion in the human subject, and which is inserted into the posterior margin of the spine of the scapula. The ' sterno-mastoid ' is present, but the ( levator anguli scapula?,' the cleido-mastoid, and the clavicular portions of the trapezius and deltoid are all replaced by the muscular expansion which, taking its origin from the par- occipital and from the transverse processes of some of the superior cervical vertebra, passes downward in front of the head of the humerus and descends along the inner surface of the fore-arm, into which it is ultimately inserted. The ( trachelo-acromialis ' arises from the transverse process of the atlas and of the four following cervical vertebra?, descends toward the shoulder-joint, making its appearance externally between the two divisions of the trapezius, which it separates ; it then spreads out over the acromial portion of the scapula, and descends as far as the middle of the humerus. This muscle draws the shoulder upward and forward in the Tapir, and is implanted into the apoueurosis which covers the deltoid : while, in the Horse, it has its insertion into the middle portion of the humerus by two aponeurotic tendons, which embrace the brachialis internus muscle. The ( serratus major anticus ' arises from the transverse pro- cesses of the third, fourth, fifth, and sixth cervical vertebra?, and also from the external surfaces of the six superior ribs : its origins extending as far backward as the insertion of the tendons of the sacro-lumbalis : from this extensive origin it passes backward around the chest to be implanted into the base of the scapula, its insertion occupying nearly half of the internal surface of that bone. It forms, with its fellow on the opposite side, a kind of sling, by which the trunk is suspended. The ' pectoralis minor ' is represented by a muscle, which, arising from the sternum and from the first, second, third, and fourth ribs near their sternal terminations, runs upward and backward to be inserted into the superior costa of the scapula near the base of that bone ; it also contracts tendinous attachments with the aponeurotic covering of the teres minor and other scapular muscles. The ( rhomboideus ' arises entirely from the ligamentum nucha?, and from the spines of the anterior dorsal vertebra?, whence it runs outward to be affixed to the base of the scapula. The ( omo-hyoideus ' is represented by a strong muscular fasci- culus, from the coracoid tubercle. 32 ANATOMY OF VERTEBRATES. The f sterno-mastoideus,' or stcrno-maxillaris, arises from the anterior end of the sternum, and, running forward strong and fleshy, is inserted by a flat tendon into the inferior maxilla underneath the parotid gland, sending, however, another tendon to be im- planted into the root of the paroccipital. Muscles inserted into the humerus. The e pectoralis major,' from the aponeurosis of the external oblique, from the two hinder thirds of the sternum ; and from the fore part of the ster- num. The first of these portions winds round to be inserted into the head of the humerus ; the second ends in a fascia, which descends over the fore-arm, while the third, running in a transverse direction over the inferior portion, is inserted into the humerus along with the ( levator humeri pro- prius' between the biceps and the brachialis inter- nus : a part of the sternal portion joins the corre- sponding portion of the opposite side to form the ( muscle common to both arms,' by the action of which the two fore-legs are made to cross each other. The f latissimus dorsi ' is powerfully assisted in its action by the cutaneous muscle already described, a strong tendon from which is inserted into the humerus along with that of the latis- simus dorsi. Both are intimately connected with the tendon of the teres major, and from this combination of tendons arises one of the heads of the triceps extensor cubiti. The ' supraspinatus,' the t infraspinatus,' the i subscapularis,' the ' teres major,' and the f teres minor/ with similar attachments, Myology of the Horse, ii". MUSCULAR SYSTEM OF MAMMALIA. 33 differ in their proportions from those in the human subject, dependent upon the shape of the scapula. The ' deltoid ' extends forward in nearly the same direction as the infraspinatus, and has been named by hippotomists the 4 abductor lono-us brachii.' The l coraco-brachialis ' takes its o oristin from the tubercular remnant of the coracoid situated C upon the superior costa of the scapula : the biceps has but one origin, with which the coraco-brachialis is in no way con- nected. The s brachialis interims,' fig. 12, w, has the same arrangement as in the human subject: it is the ' short flexor of the fore-arm.' The 'triceps extensor cubiti,' fig. 11, c, consists of three portions similar to those named in the human anatomy the Ions; extensor, the short extensor, and the brachialis ex- c? ternus: there is also a fourth portion, derived from the common tendon of the latissimus dorsi and teres major, by the inter- vention of which it takes its origin from the inferior margin of the scapula. As might be expected from the construction of the bones of the forearm, both the proiiator and supinator muscles are wanting. The ( extensor carpi radialis,' fig. 11, a, b, is here single, arising from the anterior part of the external condyle of the humerus, and from the external surface of that bone for a considerable distance: it forms a strong fleshy belly, terminating in a powerful tendon, which runs to be inserted into the base of the anterior surface of the metacarpal. This muscle seems, from the extent of its origin, to represent the long supinator and the two radial extensors of the wrist combined, and all three thus co-operate in the extension of the wrist. There is but one 'flexor carpi radialis,' fig. 12, p; it arises from the external condyle of the humerus, and is inserted into the posterior surface of the base of the metacarpal, forming the antagonist to the preceding muscle. The ' flexor carpi ulnaris ' arises from the posterior part of the external protuberance of the os humeri, and also by a distinct head from the protuberance situated above the internal condyle ; its tendon is inserted into the pisiform bone and into the base of the rudimentary metacarpal beneath it. The f extensor carpi ulnaris' arises from the posterior part of the external condyle of the humerus, and is inserted, like the preceding, into the os pisiforme, whence it is prolonged beneath the carpus, so as to perform the office of a flexor of the wrist. The e extensor com- munis digitorum,' fig. 11, k, arises from the external condyle of the humerus and from the contiguous fascia, also from VOL. III. D 34 ANATOMY OF VERTEBRATES. the upper and lateral part of the radius ; its fleshy belly is strong, and terminates in a single tendon, which runs over the foot to be inserted into the last phalanx, having previously 13 Ligaments of the fore-limb, Horse, ir 14 28 Deep muscles of the thigh and ligaments of the pelvic limb of the Horse, ii". given off a slip to join the tendon of the extensor minimi digiti. The ( extensor proprius minimi digiti ' is represented by two muscles : one of these, called the ( extensor of the pastern/ fig. MUSCULAR SYSTEM OF MAMMALIA. 35 11, q, is inserted by the intervention of a strong tendon into the side of the first phalanx of the functional toe. The second muscle, placed between the above and the preceding muscle, furnishes a similar tendon, which, after passing in front of the carpus, becomes united at an acute angle with that of the former, the two co-operating with each other in extending the foot. The tendon of the ' abductor longus pollicis ' is implanted into the internal surface of the base of the metacarpal, so that it thus becomes an extensor of the foot : it is the ' oblique extensor of the cannon ' in Hippotomy. The ' flexor digitorum sublimis perforates ' and the f flexor profundus perforans ' arise in com- mon from the internal protuberance of the os humeri, and the two are confounded together for a considerable distance, when the two muscles separate to form two distinct tendons ; of these, that belonging to the flexor sublimis, fig. 12, Z, m, runs beneath the annular ligaments of the carpus, to be inserted into the base of the proximal phalanx, previously dividing to give passage to the tendon of the profundus, i s on its way to be implanted into the last phalanx. The following are the principal ligaments of the fore-limb, fig. 13 ; a, the ' post-scapular,' c, the ( prescapular,' which extend the base of attachment of scapular muscles ; b, the ligamentous band strengthening the fore part of the capsule of the shoulder- joint ; k, similar ligaments strengthening the capsule of the elbow-joint ; e, e, internal lateral ligaments of the successive joints ; d, ' pisiform ' ligament ; c, ligament from the inner splint-bone (metacarpal n) to the sesamoid behind the metacarpo- phalangial joint ; o, ' outer cartilage of the hoof; ' p, inner cartilage of the hoof. Muscles of the hind-limb. The ectogluteus is a comparatively slender muscle, deriving its principal origin from the sacral fascia, but also reinforced by a long slender fasciculus, which descends immediately from the upper portion of the ilium. Its insertion is into the third trochanter and external rough surface o at the upper part of the thigh bone, and also by strong tendinous apoiieuroses into the fascia lata. The ( mesogluteus,' fig. 11, v, is the principal muscle in this region ; it arises extensively from the sacro-iliac aponeurosis, and from the external surface of the ilium ; it is implanted into the outer surface of the great trochanter, and is prolonged, by means of a strong posterior fasciculus, toward the lower extremity of the femur. The other muscles inserted into the great trochanter namely, D 2 3G ANATOMY OF VERTEBRATE 8. the c entogluteus, 5 fig. 12,/, the ' quadratus femoris,' the c obturator extcrnus,' the ' obturator interims,' the 6 gemclli,' and the f pyra- uiidalis '- -present a disposition similar to that which they have in the human body. The muscles passing between the pelvis and the lesser tro- chanter, and also those that arise from the pubis to be implanted into the internal surface of the thigh, are the ' psoas magnus,' the ( iliacus,' the ' pectmseus,' and the ' tri])le adductor,' fig. 12, p. The flexor muscles of the leg are the ' biceps flexor cruris,' the ' semimembranosus,' the ' semitendinosus,' the ' sartorius,' the ' gracilis,' and the ' poplitaeus,' all of which are enclosed by the dense fascia of the thigh, which is kept tense by the action of a 6 tensor vaginae femoris.' The last-named muscle, called also the o 4 musculus fascia? latie,' arises from the anterior portion of the crest of the ilium, whence it descends obliquely downward, en- closed between two layers of the fascia, covering the thigh, into which it is strongly inserted. The extensor muscles of the leg viz., the ' rectus,' fig. 11, A, the ( vastus internus,' fig. 12, 7, the f vastus externus,' fig. 11, n, and the ' cruraeus ' offer in all quadrupeds the same general dis- position as in Man, the three last forming one great common muscle, e trifemoro-rotuleus.' The anterior margin of the thio-h ~ ~ is formed by the ( sartorius,' which here, from its position and office, has been named by hippo tomists the ' long adductor of the thigh.' The ' biceps cruris ' arises by a single origin, which is derived from the ischium, and the neighbouring ligaments and fascial ex- pansions. This muscle covers a large proportion of the outer surface of the thigh : its principal insertion is into the head of the fibula, but it likewise throughout its whole length contracts ex- tensive and important attachments with the fascia lata, so that it also becomes a powerful extensor of the thigh. There is, how- ever, a distinct portion of the biceps derived from the sacro- sciatic aponeurosis, the fibres of which are directed obliquely from before backward, which, meeting the ischiatic portion at an angle, form with it a kind of raphe, which is prolonged for some distance. This muscle is called ( vastus longus ' in Hippotomy. The ' gracilis,' fig. 12, u, is a very considerable muscle; it is called by hippotomists the ( short adductor of the thigh,' whilst they usually give the name ' gracilis ' to the semitendinosus. The ' semimembranosus ' and ( semitendinosus ' have the same origin and general arrangement as in Man ; but both of them are inserted into the tibia by a broad aponeurosis, extending much MUSCULAR SYSTEM OF MAMMALIA. 37 lower down than in the human subject, a circumstance which causes the leg to be permanently kept in a semiflexed condition. The ( gastrocnemius,' fig. 11,6, is relatively less carneous than in Man : the f solaeus ' is slender and feeble : but the ' plantaris,' fig. 12, 13, is remarkably developed ; it arises from the fossa above the external femoral condyle: its tendon, is, is continued down ward, and runs over the extremity of the os calcis, where it is enclosed in a sheath; passing on from this point, it divides, is, to be inserted upon each side of the posterior surface of the proximal phalanx towards its inferior extremity, here giving passage between its two inser- tions to the tendon of the long flexor of the toe, which it serves to bind down closely to the pastern when the fetlock joint is bent, thus seeming to perform the functions both of the ( plantaris ' and of the short flexor of the toes. The 'tibialis anticus,' fig. 12, 37, is implanted into the anterior surface of the base of the metatarsal, so as to be an extensor of that portion of the foot. The ( tibialis posticus ' is seen at 25 and 2t>, fig. 12. The c popliteus,' ib. 23, is a powerful muscle. The three s peronei ' are represented by a single muscle, the tendon of which becomes conjoined with that of the long extensor of the digit, with which, when in action, it co-operates. The flexor muscles are reduced to a state of extreme simplicity ; the short flexor communis is wanting ; the ( plantaris,' as described above, has a double insertion into the base of the great pastern bone, and presents a similar disposition to that of the flexor per- foratus in digitate quadrupeds, while the f flexor communis longus perforans,' fig. 12, 28, here serving a single tendon, 29, appropriated to the solitary toe, passes on as usual to be inserted into the last phalanx, so, 31. The homologue of the ' flexor longus hallucis' exists in the Horse, notwithstanding the absence of the hallux ; but, instead of its usual destination, it here becomes affixed to the tendon of the flexor communis perforans, to which it forms a powerful auxiliary. The ' extensor communis,' fio;. 11, 21, terminates in a single O J O tendon, 25, which is inserted into the dorsum of the last phalanx of the foot : it receives, however, in its course, a few fleshy fibres, w, derived from the metacarpal and representing the * extensor brevis ' of unguiculate quadrupeds. In fio\ 14, showing the chief ligaments of the hind limb, are O O -5 represented the ( iliacus interims/ /, k, I, and the ( epicotyloideus,' <7, a small and peculiar muscle, which arises by a flat tendon, b, from above the origin of the rectus cruris, d, and is inserted at the fore and outer part of the neck of the femur, c, below the head : 38 ANATOMY OF VERTEBRATES. its fibres are attached to the capsular ligament. 21 is the ' rotulo- condylar ligament ; ' 22 the ' rotular ligament ; ' 23 the ' external rotular ligament; ' 10 the e condylo-fibular ligament ; ' 15 the ' ex- ternal semilunar cartilage;' 25 the ' calcaneal ligament ;' 26, 26, the * external lateral ligaments ' of the ankle and succeeding joints ; 27 the ' ant-oblique ligament ; ' 28 the ligament from the outer splint-bone (metatarsal iv) to the sesamoid behind the metacarpo- phalangial joint : ss and 39 are cartilages of the hoof. Muscles of the hyoid arch. The ' sterno-hyoideus ' and the ' sterno-thyroideus ' form a single muscle, Avhich divides to be inserted into both the larynx and os hyoides. The ' omo- hyoideus,' fig. 11, a, is a very strong muscle. The f stylo- hyoideus ' furnishes a sheath to the longer portion of the digas- tricus, and extends from the furcate extremity of the stylohyal to the base of the thyrohyal. There is also a f cerato-hyoideus ' extending between the thyrohyal and the thyroid cartilage. The ' paroccipito-styloideus ' is a short thick muscle, derived from the paroccipital, whence it descends toward the angle of the stylo- hyal, into which it is inserted, above the origin of the stylo- hyoideus. Facial muscles. The ( occipito-frontalis ' has the usual origin from the posterior part of the cranium, whence, running forward, it covers the skull with its tendinous aponeurosis, and, in front, spreads in muscular slips upon the forehead, some of which, fig. 11, 12, extend downward, to spread over those of the orbicu- laris palpebrarum. Situated upon the outer side of the orbit there is another descending slip of muscle derived from the lateral cartilage of the ear, which, by elevating the external canthus of the eye, con- tributes to the expression of that organ. The f levator anguli oris,' fig. 11, n, is inserted into the upper lip and margin of the nostril : it has two origins, derived from the surface of the superior maxillary bone, between which the lateral dilator of the nostril and upper lip passes to its destination. The ' zygomaticus ' is a depressor of the external angle of the eye, as well as an elevator of the corner of the mouth, its fibres being intermixed with those of the orbicularis palpebrarum, as well as of the orbicularis oris. The f long dilator of the nostril, and elevator of the upper lip ' arises at a little distance below the inferior margin of the orbit ; and, passing between the two origins of the levator anguli oris, terminates in a tendon, which becomes connected with that of the opposite side, and then spreads out in front of the upper lip. MUSCULAR SYSTEM OF MAMMALIA. 39 10 Vertical section of the middle or functional digit of the fore- foot of the Horse, ni". From the tendon of the last muscle arises the ' anterior dilator of the nostril/ fig. 11, t, which, acting upon the interior nasal cartilage, powerfully expands the aperture of the nose. The ' orbicularis oris,' fig. 11, o, the 'levator labii superioris,' the ( elevator of the chin,' 15 and the f depressors of the lower lip, and angle of the mouth,' are well developed. The anatomy of the limbs of the Horse would be incomplete without a notice of the structure of the terminal segment of these best of terrestrial locomotive or- gans, in the perfection of which the whole mecha- nical force is concentrated on a single hoof. The longitudinal section of the huge finger that forms the foot or hoof' of the horse, fig. 15, shows the structure of the three phalanges proximal i, middle 2, and distal or ungual 4, with that of the sesamoid, or nut-bone s, adding to the lever-power of the division of the tendon, 7, of the flexor profundus, going to the last phalanx : the insertion of the tendon of the ' flexor sublimis,' 6, and that of the tendon of the common ' extensor,' 5, are also shown. The hoof-box of the ungual phalanx is denser at its periphery, 12, than at its base, 10, but is not continuous over either surface ; the former part is the ( wall,' the latter the ' floor ' of the horny or ' insensible ' hoof. The wall, or f external wall,' has the form of a hollow cone obliquely truncate above, so that it is highest in front, 12, becoming vertical, and lower as it extends backward, losing density, degenerating partly into the elastic tissue, 9, but being mainly inflected inward, toward the centre of the sole, where it tf blends with the horny ( floor,' and forms the ( internal wall : ' this supports the superincumbent softer elastic tissue, and partly that called the ' frog,' fig. 16, 3, for w T hich a triangular space is left between the inflected parts of the ' internal wall.' Thus the posterior part of the periphery and of the floor of the ( hoof is left uncovered by the horny box, which is accordingly free for a certain degree of elastic expansion and contraction, especially posteriorly. The inner surface of the f wall ' is produced into a 40 ANATOMY OF VERTEBRATES. 16 number of subvertical lamella 1 , fig. 17, .3, with which interdigi- tatc corresponding lamella, ib. 17, from the periosteum of the lingual phalanx : the first are called the c horny lamellae/ the second the ' vascular ' or 'sensitive lamellae.' At the interspace between the inflected parts or prongs of the ' wall ' projects the mass of elastic suhcorneous tissue called by the French farriers ' fourchc,' and misnamed by the English ' frog.' In the horizontal section of the hoof, fig. 16, in which a part, 2, is reflected back, the ' frog,' 3, is seen to extend to the centre of the sole : its exposed outer surface is the hardest and most horny ; but this tissue is not so thick as some farriers, misapplying the paring-knife, suppose : it gradually passes into elastic tissue : it is im- pressed at its middle part by the ' cleft of the frog,' and is reflected upon the ( internal wall.' In fig. 16, 2, 6, is the section of the ' wall ;' 3, the upper surface of the ( frog ; ' 4, 4, are the parts of the ' wall ' called the ( heels ; ' 5, parts of the sole called the 'bars;' 7 11 indicate the boundaries of the space lodging the frog ; 12, are the ' vascular Iamella3.' The horny matter of the sole possesses more elasticity than that of the wall : the sole is slightly concave toward 12 the ground, abutting by its lower circumference against the wall : it is cleft to its centre by the triangular / O space through which the frog pro- jects. In fig. 17, i is the skin reflected; 2, soft elastic tissue, with oil, forming a cushion behind the me- tacarpo-phalangial joint ; 3, * wall ' of the hoof turned back, showing the horny Iamella3 ; 4, section of front part of the 'wall; ' 5, 6, ligamentous parts of metacarpo-phalangial joint; 7, tendon of common ' extensor;' 8, 9, 10, those of the deep and superficial flexors ; 15, expansion of the great anterior cartilage of the hoof; IG, the ( coronary frog-band ' reflected ; 17, the ' vascular lamella?; ' 18, elastic portion of the 'frog;' the 'coronary venous plexus' is shown at 10. Transverse section of the Loof of the Horse, in". MUSCULAK SYSTEM OF MAMMALIA. 41 17 19 In the Indian Rhinoceros the panuiciilus carnosus is more discontinuous than in other Perissodactyles, but where it exists is of unusual thickness. One sheet at the side of the thorax sends its fascia into the interstice of the dermal fold in front of the fore limbs. A similar portion be- hind is inserted into the posterior fold of the skin, suggesting that such permanent folds served the pur- pose of affording a firmer insertion to the aponeuroses of the cutaneous muscles than a plane surface could have done. Two sheets of panniculus rise, broad and thick, one on each side of the anterior part of the abdomen from the superficial fascia, and, passing back- ward, terminate in aponeuroses covering knee-joint. As the patelhx) are higher than the line of the abdomen, in the erect position of the animal, the preceding muscles afford additional support to that bulky part, some of the weight thus being trans- ferred to the hind-legs, which, reciprocally, are by these muscles drawn forward in locomotion. 1 198. Muscles of Artiodactyla.--\\\ the Ruminant division of the Artiodactyle Ungulates the ' panniculus carnosus ' is better developed than in the non-ruminant group, e. y. the hog and the hippopotamus. The fixed points from which, in the ox, the Avcll-cleveloped sheets of dermal carneous fibres act on the skin are the scapula, mandible, ilium, pubis, and patella: a 1 V. p. 36. Dissection of the digit forming the Horse's foot. m". 42 ANATOMY OF VERTEBRATES. subjacent layer of fascia allows the play of the tf panniculus' independently of the main masses of the muscular system, fig. 18. To the sheet of carneous fibres spreading from the scapular fascia over the neck the term ' cutaneus colli ' is applied : to a thinner layer extending from the fore part of the neck over the forehead and cheeks to the lips, that of f cutaneus faciei.' The thick layer expanding from the supra-scapular attachment over the shoulder and part of the fore-limb is the ( cutaneus humeri ; ' that which extends from the iliac and pubic fascia lata, and from the patella, forward, expanding upon the abdomen, is the ( cutaneus abdominis : ' the ' musculus preputialis,' in the Bull, is a deriva- tion from the foregoing dermal muscle. The e trapezius,' fig. 18, 10, n, answers to the scapular division of that muscle in Man ; it arises in the Ox from the neural spines of the anterior half of the thorax, and from the f ligamentum nuchse.' In the Giraffe it is in two portions : one arises from the 18 Superficial muscles of the Cow. iv transverse processes of the fifth and sixth cervical vertebrae, its fleshy part is thick and strong but expands as it passes down- ward and backward and finally is lost in a strong fascia over- spreading the shoulder-joint ; the second portion is thin and broad, arises from the ligamentum nuchre, and is inserted into the fascia covering the scapula, 1 The ' masto-humeralis,' fig. 18, 8, 8, may represent the ( cleidal ' part of the trapezius in claviculate Ungulates : it arises by an aponeurosis from the ligamentum nucha3, and, by a tendon, from the paroccipital ; the chief and more superficial portion is inserted into the humerus, the deeper portion into the sternum. The ' latissimus dorsi/ fig. 18, 12, in 1 xcvir. p. 234. MUSCULAR SYSTEM OF MAMMALIA. 43 the Ox, as in the Horse, is a comparatively small muscle, and acts upon both humems and antibrachium. The f rhomboideus,' fig. 19, 9, is not single, as in the Horse and Giraffe, but consists in the Ox of pre- and post-rhomboid portions : the former rises from the nuchal ligament, as far forward as its occipital insertion : the latter from the spines of the two or three anterior dorsals ; both converge to be inserted into the base of the scapula. The ( splenius capitis,' fig. 19, 7, arises from the anterior dorsal and posterior cervical spines ; the fibres diverge to a flat tendon inserted into the paroccipital and the ridge rising therefrom. In the Sheep an insertion of a small fasciculus into the diapophysis of the atlas represents the ' splenius colli.' The ( scaleni ' form three strong muscles in the Camelidce, in the Giraffe four, which rise from the fourth to the seventh cervical vertebra and are inserted into the manubrium sterni and first rib. The s scalenus anticus ' in the Cow is shown at 12, fig. 19. The ( sterno-maxillaris ' arises from the manubrium and divides, at 9, fig. 18, to be inserted into the paroccipital and mandibular angle. 19 Deep muscles of the Cow. iv. The levator anguli scapula?,' fig. 19, 8, arises from the pleur- apophyses of the third and fourth cervical vertebrae, and is inserted into the anterior angle of the scapula : it seems part of the follow- ing muscle. The 'serratus magnus,' fig. 19, 10, has an extensive origin from the pleurapophyses of the anterior half or two-thirds of the dorsal series, forward, to that of the fifth cervical inclusive, by * dentations,' or an angular strip from each : the fibres converge, as- cending beneath the scapula, to be inserted into the cartilaginous suprascapula. Thus, as the fore-part of the trunk is, as it were, slung upon the two great serrate muscles which principally support 44 ANATOMY OF VERTEBRATES. 20 the weight of the deep chest of the Ruminants, the interposition of the elastic cartilages between the upper attachments of the muscles and the capitals of the bony columns of the two fore-legs is attended Avith the same advantage as is obtained by slinging the body of a coach upon elastic springs. The main body of the 'pectoralis major,' fig. 18, is, rises from the sternum and ensiform cartilage, the fibres converging to the O y O O tendon inserted in the outer tuberosity of the humerus : the an- terior derivative from this muscle, effecting the crossing of the fore-limbs, is present in Ruminants as in Solipeds and Cetaceans. Two muscles converge to an insertion answering to that of the f deltoid ; ' one is the superficial portion of the ' masto-humeralis,' fig. 18, 8, fig- 19, 11 ; the other, ib. u, arises from the spine and post-spinal fossa of the scapula : the latter is the proper homologue of the ( deltoid.' The ( supra- or pre-spinatus ' is shown at i, figs. 20 and 21 ; it is inserted by a double ten- don into the fore and inner tuberosities of the humerus : the ' infra- or post-spinatus,' fig. 20, 2, has a single strong insertion into the JD ~ outer tuberosity. The insertion of the ' teres major ' is seen at fig. 20, 3. The subscapularis, fig. 21, 2 and 2 X , con- sists of two chief masses, and corresponds in length and narrowness with the bone from o which it originates ; it consequently produces, like the muscles on the opposite surface of the scapula, more rapid and extensive motion ot the humerus, to the inner tuberosity of which it is attached. The s coraco-brachialis,' fig. 20, 8, arises from the tuberous representative of the coracoid ; its insertion into the humerus ex- tends down to the inner condyle. The ' biceps brachii,' fig. 21, 10, shows an origin from the coracoid as well as the chief one from above the glenoid cavity of the scapula. It is in- serted into the radius, below the usual tuberosity, and also sends a strip of tendon to the antibrachial aponeurosis. In the Camelidce the tendon of origin is double, but approximated, and encloses a sclerous sesamoid as it passes over the head of the humerus. The * brachialis internus ' rises from the neck of the humerus ; its in- IV ?Ju\ 21, is, Muscles of the fore-umb, Cow * . ' from the inner (radial) side. IV". sends its flat and strong tendon behind the cannon-bone, near the lower end of which it divides, and perforates the corresponding divisions of the ' flexor perforatus,' to be inserted into the ungual phalanges of the digits, Hi, iv, fig. 193, Ox, vol. ii. The 'flexor carpi ulnaris internus,' fig. 21, 16, is inserted into the ' pisiforme.' The ectogiuteus, fig. 18, is, arises from the fore part of the ilium and sacral fascia, and is inserted into the lower part of the great 46 ANATOMY OF VERTEBRATES. troclianter ; it is closely connected with the ( tensor fascine femoris.' This muscle, fii>'. 18, ic. arising from behind the outer iliac tube- * O O rosity, expands upon the thigh, and is lost in fascia covering the knee-joint, and attached to the spine of the tibia, whereby the muscle becomes, with the rectus, a flexor of the thigh. There is a 6 sartorius ' crossing obliquely the inner side of the thigh, and in- serted aponeurotically into the inner side of the head of the tibia. The ( mesogluteus,' fig. 19, is, arising from the outer side of the ilium, is inserted into the outer part of the great troclianter. The ' entogluteus,' ib. 19, rises above the acetabulum, and is inserted into the upper part of the great trochanter. The 'biceps femoris,' fig. 18, 17, is, arises from the sacro-sciatic fascia and from the ischial tuberosity ; the fasciculi from both origins unite to form a broad muscle (the ( vastus longus ' of Hippotomy), which is in- serted by a strong aponeurosis into the head of the tibia and fascia of the leg. The 'iliacus interims ' is shown at 17, fig. 19 : 23, 24, and so, ib., are muscles of the tail. The ' vastus externus,' fig. 19, 20, covers the whole of the outer part of the thigh-bone, from the great trochanter ; it is inserted into the patella and head of the tibia ; a small part of the ' rectus femoris ' appears in front of its upper part. The ' gracilis ' is a large broad muscle, arising from the pubic symphysis, and inserted into a long tract of the tibia. The e adductor magnus ' is seen at 27, the e semitendinosus ' at 28, and the ' semimembranosus/ or e adductor tibia? longus,' at 29, fig. 19. The last two muscles are blended in the Hog. The 6 tibialis anticus ' arises from the inner side of the fore part of the head of the tibia by a strong tendon ; the muscular part swells into the chief of those on the fore part of the leg ; the tendon of inser- tion splits to give passage to that of the ' peroneus longus,' and is inserted into the outer side of the head of the metatarsal. There is an extensor of the middle phalanx of each functional toe ; the tendon of the long f extensor digitorum' bifurcates at the end of the metatarsus for insertion into the ungual phalanx of the same toes. The chief peculiarity of the flexors of the digits of the hind-foot in hoofed quadrupeds is the accession of muscles not so applied in most other mammals. Thus the i gastrocnemius.' besides its inser- CJ * tion into the heel-bone, sends a strong tendon along the back of the metatarsal, to the phalanges, where it expands and bifurcates, each division again splitting for the passage of that of the ' flexor perforans,' before being inserted into the middle phalanges. In like manner the homologue of the l tibialis posticus ' combines its ten- don with that of the ' flexor perforans ;' such common tendon MUSCULAR SYSTEM OF MAMMALIA. 47 expanding behind the metatarsal, and splitting to perforate the tendon of the preceding flexor in its way to the last phalanx. Of the abdominal muscles, the f obliquus externus ' is shown in fig. 18, 14; its broad tendon is perforated by the mammary artery and vein, at 19. The ( obliquus interims ' is seen at 16, fig. 19. I found the following conditions of the hyoid muscles in the Giraffe i 1 - -The ' mylo-hyoideus,' thick and strong, arose from the internal surface of the lower jaw, and was inserted into the raphe dividing it from its fellow of the opposite side. It ad- hered firmly to the ( genio-hyoideus :' this arose by a well marked tendon from the symphysis menti, and had the usual insertion. The ( genio-glossus ' arose by a tendon close to the inner side of the tendon of the ( genio-hyoideus ; ' its fleshy belly had a considerable antero-posterior extent, and diminished to a very thin edge at its anterior margin. The ' digastricus ' had the usual origin, and was inserted, broad and thick, into the under side of the lower jaw. The { stylo-hyoid ' was remarkable for the slenderness and length of its carneous part. The most interesting modifications in the muscles of the os hyoides were found in those which retract that bone. The muscle which, as in some other ruminants, combines the offices of the ' sterno-thyroideus ' and ' sterno-hyoideus,' arose by a single long and slender carneous portion from the anterior extremity of the sternum ; this origin was nine inches long, and terminated in a round tendon, six inches long ; the tendon then divided into two, and each division soon became fleshy, and so continued for about sixteen inches ; then each division again became tendinous for the extent of two inches, and ultimately carneous again, when it was inserted into the side of the thyroid cartilage, and thence continued in the form of a fascia to the hyoid. This alternation of contractile with non- contractile tissue gave a striking example of the use of tendon in limiting the length of the contractile part of a muscle to the extent of motion required to be produced in the part to which the muscle is attached. Had the sterno-thyroideus been continued fleshy as usual from its origin through the whole length of the neck to its insertion, a great proportion of the muscular fibres would have been useless ; for as these have the power of shorten- ing themselves by their contractility one-third of their own length, if they had been continued from end to end in the sterno- thyroidei, they would have been able to draw the larynx and hyoid one-third of the way down the neck ; such displacement, however, is neither required nor indeed compatible with the 1 xcvir. p. 232. 48 ANATOMY OF VERTEBRATES. mechanical connections of the parts ; but, by the intervention of long and slender tendons, the quantity of the contractile fibre is duly apportioned to the extent of motion required for the larynx and os hyoides. The ' oino-hyoideus ' was adjusted to its office by a more simple modification ; instead of having a remote origin from the shoulder-blade, its fixed point of attachment was brought for- ward to the nearest bone (the third cervical vertebra) from which it could act upon the hyoid to the due extent. In all Herb Ivor a the muscles more directly worked in masti- cation, c. g. the ( masseter ' and ( pterygoidei,' are proportionally more developed than the biting muscles, e. g. 6 temporales ; ' but there are degrees of difference ; in those Ungulates in which the canines are most developed, as e.g. the Hog and Camel tribes, the temporal muscles are larger. In all Ungulates the chief depressor of the jaw, or opener of the mouth, passing from the paroccipital to the mandibular angle, has a single fleshy belly ; it is, however, the homologue of the ( digastricus ' in Man. One of the muscles proceeding from the neural arches of the dorsal vertebrae to the occiput is tendinous, along a portion of its mid-course, in most unguiculate Mammals : it is called ( biventer cervicis ' in Aiithropotomy. Contiguous muscular fasciculi ex- tending from the neural spines of the anterior dorsals to those of more or less of the cervical series, are termed ' spinalis cervicis.' The pair of fibrous masses with like attachments, but in which the striated fibre is almost wholly reduced to the yellow elastic tissue in Ungulates, is commonly known as the ( ligamentum nuchae.' In the Giraffe this mechanical stay and support of the long neck and head commences from the sacral vertebra?, and receives fresh accessions from each lumbar and dorsal vertebra, as it advances forward ; the spines of the anterior dorsal vertebrae become greatly elongated to afford additional surface for the attachment of new portions of the ligament, which appears to be inserted, on a superficial dissection, in one continuous sheet into the longitudinally extended but not elevated spines of the cer- vical vertebra}, as far as the axis ; the atlas, as usual, is left free for the rotatory movements of the head ; the ligament passes over that vertebra to terminate by an expanded insertion into the occipital crest. It consists throughout of two bilateral moieties. In the specimen I dissected, the nuchal ligament, in situ, measured 9 feet in length : an extent of 6 feet was re- moved, which immediately contracted to 4 feet. In the Camel the ligamentum nucha? arises, broad and thin, from the anterior dorsal spines, but gathers substance as it advances and MUSCULAR SYSTEM OF MAMMALIA. 49 becomes condensed into a pair of cords which receive accessions from the cervical spines, by which the ligaments seem bound down so as to follow the curve of the neck : the insertions are into the superoccipital. Posteriorly a continuation of the ligament may be traced spreading out and losing itself in the base of the single hump of the Dromedary, and as far back as that of the hind hump in the Camel. 1 The relative size and insertions ( cervical, b nuchal) of the ligamentum nuchie of the Elephant are shown in fig. 22. Much of the same kind of yellow elastic tissue is combined with the aponeuroses of the abdominal muscles in the Elephant, Rhino- ceros, 2 and Giraffe, in reference to the capacity and heavy con- tents of parts of the alimentary canal. Lignmontnm nuchae, Elephant. 199. JWuscles of Carnivora.- -The commencement of certain facial muscles that reach their full developement in Man may be discerned in the IJnguiculates. Small detached sheets of muscular fibre, ( cervico-facial ' or ( platysma inyoi'des,' are attached to the skin at the side of the neck, spread upon the lateral inte- guments of the face, and, in the Cat, show a special arrangement or developement by affording a muscular capsule to the bulb of each long hair of the whiskers, upon the chin, lips, cheeks, and eyebrows, to which they give the impressive movements of those sensitive parts. Both the ( occipital ' and ( frontal ' parts of the human ' occipito-frontalis ' are also present in the Cat The muscles of the jaws in Carnivora are chiefly remarkable for the large proportional size of the ( temporalis,' with which the ' masseter,' by the more vertical disposition of its fibres than in Herlrivora, combines in the act of forcibly closing the mouth. The ( pterygoidei ' are small and not very distinct from each 1 vi. 2 v . p. 36. VOL. I IT. E 50 ANATOMY OF VERTEBRATES. other. The ' digastric ' is a powerful muscle and seemingly ' mo- nogastric,' but many tendinous filaments in the middle of the carncous substance indicate the division which is established in higher Gyrcnccphala. In the Lion it arises by a strong tendon from the paroccipital ; and its action may be seen in the effort the animal makes to disengage the mandible from ligamentous O cj O parts of its food. In the Felines the latissimus dorsi has its chief insertion into the tendinous arch, bridging over the biceps, and, with the f dcrmo-humcralis ' similarly inserted, it acts upon the inner side of the upper part of the humerus, but sends a strong aponeurosis between the external and scapular ' heads ' or por- tions of the triceps to be continued upon the antibrachial fascia : in the Dog, a distinct fasciculus of the muscle combines its tendon with that of the s scapular ' portion of the triceps. In the Seal- tribe the retractile action of the latissimus dorsi is extended, by the aponeurotic insertion, to the palmar aspect of the pectoral fin. The homologue of the 6 serratus posticus superior ' is largely developed in the Lion, extending its anterior attachments to the nape. The ' protractor scapulae ' arises in Felines from the diapophyses of the atlas, axis, and third cervical, and is inserted into the spine of the scapula near the acromion. The origins of the f great pectoral muscles ' interblend and cross each other in Felines, so as to seem to form a common adductor muscle of the fore-limbs ; but the mass of the fibres resolves itself into four almost distinct muscles, answering to the t large pectoral ' and grand pectoral of Hippotomists, and including the ( sterno- trachiterien ' and ( pectoantebrachial ' of Straus-Durckheim. The ( pectoralis minor ' in the Dog is inserted into the upper part of the glenoid cavity of the scapula. In unguiculate, and especially claviculate, Gyrencephala, the deltoid conforms by the greater extent of origin and size to the more varied movements of the humerus, as compared with the ungulate order. In the Cat the deltoid consists of an anterior portion arising from the acromion, and a posterior one from the spine, of the scapula : in the Bear only the acromial portion is developed. In noncla- viculate Carnivora the ' masto-humeralis ' is present: in cla- viculate species the ( cleido-cucullaris ' and ' cleido-mastoideus ' are its divisions : the former, in Felines, rises from the paroccipital crest, and from the neural spines of the anterior cervicals, passes back and down to the transverse ligamentous tract in which the clavicular ossicle is developed; the ' cleido-mastoid ' is inserted into two outer thirds of the clavicular bone, Avhence is continued a fleshy belly descending along the fore-part of the brachium, in MUSCULAR SYSTEM OF MAMMALIA. 51 front of the biceps, to be inserted into the tuberosity of the radius : it answers to 8, fig. 18, in Ungulates. The biceps, in Felines, derives its single head from the upper rim of the glenoid cavity, and is inserted into the bicipital tuberosity of the radius. The ' brachialis interims ' is a long muscle on the outer side of the humerus, and is inserted into the lower wall of the sigmoid cavity of the ulna. The ( triceps extensor ' is represented by three or more muscles, distinct in their fleshy part, and remark- able for their volume in Felines : their common tendon incloses the olecranon like a strong capsule. Besides the foregoing there are three shorter extensors, one of which is represented by the human ( anconeus ; ' but all belong to the same system as the tricipital extensor. The ( pronator teres ' is proportionally large : in the Lion its carneous part extends far down the fore-arm : in the Cat it ends in the tendon inserted about half way down the radius. The ' palmaris longus ' is also more developed than in man. The e supinator longus,' on the other hand, has a short and slender fleshy portion ; and this relates to the habitual prone position of the paw in Carnivora. The flexors and extensors of the carpus and manus closely accord with those of Man, but with excess of fleshy fibres in the larger Felines ; and a minor degree of distinction of some muscles, as, e. independent ( indicator ' has not yet come about. The ' flexor sublimis ' is a powerful muscle and the principal bender of the paw in ordinary locomotion ; its origin is restricted to the humerus ; its insertions are extended into all the five digits by the fasciae attached to the sides of the metacarpo-phalangial joints, as well as the ordinary perforated tendons into the sides of the first and second phalanges. The f flexor profundus ' arises by five heads from the antibrachium, which form a common flattened E 2 52 ANATOMY OF VERTEBRATES. tendon, along the carpus ; this first detaches a tendon to the lingual phalanx of the pollex, and, at the metacarpus, divides into the four tendons similarly inserted into the four long digits. In each the insertion, fig. 36, b, is into the lever-like process from the palmar part of the bone of the last phalanx. It is this muscle which overcomes the retractile force of the elastic ligaments, ib. , of the claws, and concentrates the power of all five upon the part seized. There is no separate ' flexor longus pollicis.' In the hind limb of Felines, the psoas and iliacus": are more obviously parts of the same muscle than in Man : a fasciculus of the ' psoas ' sends a tendon to the pubis ; but the mainjbody of the muscle acts upon the inner trochanter. In the Cat a detachment of the small ectogluteus descends to be inserted into the patella. The much longer mesogluteus has five origins from lumbar, sacral and caudal vertebra, and from the crista ilii : its tendon goes to the great trochanter. The ' gracilis ' is relatively large. The muscle at the foremost part of the thigh, in Felines, ansAvers to the f sartorius ' and ' rectus femoris ;' there is also a ' tensor fascia?,' which sends an aponeurosis over the fore part of the knee-joint and a tendon to the inner part of the head of the tibia. The f biceps flexor cruris ' receives a slender' accessory fascicule from an anterior caudal vertebra ; besides its normal in- sertion it is continued by fascia into the e tendo achillis.' In the Lion, a special muscle, ' caudo-femoralis,' from the same vertebrae is inserted by its own long tendon into the outer condyle of the femur. The Bear has not the latter muscle. The largest part of the ' gastrocnemii ' muscles is at or near to their femoral origins : the tendons of each are at first distinct, and finally blend by ex- pansions which spread over the calcaneum. The soleus is small, and rises from the fibula : its tendon unites with that of the gastrocnemius externus. The tendon of the ' plantaris ' combines with that of the l short flexor ' of the toes to augment the power of bending their phalanges : its fleshy part is relatively much greater than in Man. 200. Muscles of Quadrui?iana.--In this series, up to the apes, the panniculus carnosus exists ; but is reduced to a thin sheet of carneous fibres from the dorso-lumbar fascia, spreading over the latissimus dor si, and again degenerating to fascia attached to the inner side of the humerus. The f platysma myoi'des ' begins to be defined, in the Aye-aye, as a pair of broad thin layers, arising from pectoral and clavicular fascia, and ascending over the front and sides of the neck, mandibular rami, and cheeks. In the Grants O and Chimpanzees it supports the large cervico-pectoral air-sac communicating Avith the larynx. MUSCULAR SYSTEM OF MAMMALIA. 53 From the Aye-aye to the Gorilla, 1 with a few exceptions, there is a s cleido-mastoideus ' as well as a ( sterno-cleido-mastoideus ; ' but in some Baboons (Macacus} the distinct fasciculus from the clavicle has not been found. In an Orang I found the cleidal part inserted into the diapophysis of the axis vertebra. The term ( digastricus ' is applicable to that mandibular muscle in all Quadrumana, although the partition by tendon of the ante- rior from the posterior belly is not complete in many. In most, as in the Aye-aye, the anterior portions of the pair occupy the anterior interspace of the mandibular rami. The middle tendi- nous part is attached to the hyoid, except where it is feebly marked, as in Stenops. The intermediate tendon of the omohyoid is not found save in the higher tail-less Apes. In all Quadrumana the power of the arms in drawing up the trunk is increased by the accessory muscle from the ordinary ten- don of the ' latissimus dorsi,' which extends its action from the upper to the lower end of the humerus (interior condyle), and to the olecranon. The ( rhomboidei ' extend to the occiput in Maca- ques, Baboons, and the Orang. The 'protractor scapulae* (' acro- mio-trachelien,' Cuv.) exists in most Quadrumana below the Apes; in these the s levator anguli scapula? ' is distinct from the f serratus nragnus ; but is the fore part of that muscle in Baboons.' In the Gibbons (Hi/lobates) the two portions of the 'biceps flexor cubiti' are more powerful and unite lower down the lumerus than in other Quadrumcma, and the inner portion derives an origin from near the pectoral ridge of the humerus : their common tendon is inserted beneath the radial tubercle, and into the antibrachial fascia. In Stenops the biceps has only its 'long head' or origin : that from the coracoicl process is, at least, not distinct from the coraco-brachialis. The f triceps extensor cubiti ' is complicated in Quadrumana by the accessory fasciculus in connection with the tendon of the latissimus dorsi. The lower portion of the f internal head ' of the triceps has also a distinct origin or fasciculus from the ento- condyloid ridge in Chiromys and Tarsius ; in Stenops it arises more from the back part of the humerus. The deep and superficial flexors of the fingers are distinct, but a remnant of that blending which exists in most lower mammals may be seen in the short connecting tendon which in the Aye-aye 2 passes from the ulnar belly of the s flexor sublimis ' to the division of the ' flexor profundus,' giving off the tendon to the middle finger. The fleshy part of both flexors, but especially of the deeper one, is continued nearer to the hand, in Lemuridce and most other 1 cir. p. 30, pi. xi. fig. 1, 22 d. 2 cir. p. 34, pi. xi. fig. 4, e. 54 ANATOMY OF VERTEBRATES, Quadrumana, than in Man, thus enabling the muscles to continue their action as finger-benders -when the hand itself is flexed. The fasciculus of the f flexor profundus ' which sends the tendon to the last phalanx of the thumb, is more distinctly a * flexor longus pollicis ' in Apes than in lower Quadrumana. In the Aye-aye it adheres to the supplementary carpal and fascia on its way to the thumb, and thus opposes both the last phalanx and the ' pad ' at the base of the thumb in the act of grasping. The ' flexor brevis,' the ( abductor,' the ' adductor,' and * opponens pollicis ' are present in the Chimpanzee and Gorilla, as are like- wise the ' extensor longus ' and ' extensor brevis.' In the Orang these muscles begin to be confounded ; in most lower Quadru- mana they are blended together. The homologue of the 'extensor indicis' of Man bifurcates and sends a tendon to both the index and medius digits; the homologue of the extensor minimi digit! likewise splits and sends a tendon also to the annularis ; so that, while in Man the index and minimus only have two extensor tendons, all four fingers (ii v) have them in most Quadrumana. The hand is thereby the stronger as a suspensor of the body from a bough. The ( ectogluteus ' is feebly developed compared with that in Man : the Gorilla, though receding far in this respect, recedes the least. The homologue of the ( gracilis ' is relatively larger in all Quadrumana than in Man, and its insertion is extended lower down the leg. In Stenops the vastus externus contributes a fasciculus to the rectus femoris ; in Chiromys it is as distinct as in higher Quadrumana. But here the mesogluteus exceeds the ectogluteus in size, although the latter is supplemented in the Gorilla by fleshy fasciculi from the ischial tuberosity, which spread their insertions from that of the ectoglutseus down the femur to the internal condyle, apparently representing the adductor magnus. In both Orang and Chimpanzee a muscle from the outer border of the ilium to near the acetabulum is inserted into the under and outer part of the great trochanter and rotates the thigh inwards. 1 The gastrocnemii have a greater length and minor breadth and Thickness of the fleshy part : the soleus rises from the fibula exclu- sively, and joins the gastrocnemii low down. 201. Muscles of J3imana. - The myologies of Anthropotomy reduce the need of noticing human muscles here to some com- parison with those of highest Apes, bringing out the ordinal characteristics of the limbs, and to the illustration of those si vino; o o expression to the face and reflecting the action of the organ that marks Man's place in Creation as the type of a distinct sub-class. 1 ' Scausorius,' Trail, xxxv . ' luvcrtor femoris,' xxxiv. p. 68. MUSCULAR SYSTEM OF MAMMALIA. 23 10 Figures 23 and 24 give a view of the superficial muscles and tendons of the fore-arm and hand of a full-grown male Gorilla and Man of correct relative size. The portion of the triceps is seen in the Gorilla at 2" ; in Man at 5', in whom the origins of the carneous fibres of that part from behind the inter-muscular septum are continued lower down the humerus. The ( brachialis anticus ' is seen at 4, fig. 23, and 17, fig. 24. This muscle is not so completely differentiated from the deltoid and supinator longus in the Gorilla as in Man, nor so individualised as a single muscle : its two portions being more distinct. The biceps, fig. 23, 3, maintains in Man more of its full fleshy character to the sending off of the tendon, 3', to the rough posterior margin of the tuberosity of the radius, gliding over the anterior smooth surface of that process with an intervening ( bursa.' The aponeurosis, 3", sent off to the fascia of the fore-arm crosses the ' pronator teres.' This muscle, 8, fig. 24, is attached to the outer side of the radius below the middle of the bone in the Gorilla, but rather above it in Man. The double origin, viz. from the inner humeral condyle and the coronoid process of the ulna, is better defined in Man, fig. 23, 6. The ( palmaris longus,' fig. 23, 8, arising as a distinct muscle in Man from the inner humeral condyle, is a fasciculus, 5, of the 'flexor carpi ulnaris ' (3, fig. 24) in the Gorilla ; but, as this muscle is subject to variation, and sometimes absent in Man, it may shoAV analogous inconstancy in the Go- rilla. The flexor carpi ulnaris is inserted into the pisiforme in both Man and Ape, but the Muscles of the fore-arm and hand, fleshy and tendinous parts are better defined, and the latter relatively longer and more slender in Man, fig. 23, 9. The flexor carpi radialis arises in Man, fig. 23, 7, from the inner condyle, from the antibrachial fascia and septa continued there- from between the pronator teres, 6, and palmaris longus, 8 ; but in the Gorilla, fig. 24, 4, it derives a considerable accession of 13- 10 -Ik 12 15- 15. ANATOMY OF VERTE CRATES. 24 fibres directly from the radius, and its tendon is shorter and much thicker than in Man. In both it passes through a pulley pro- vided by the trapezium to its insertion into the base of the metacarpal of the index. The tendon of the supina- tor longus in the Go- rilla, fig. 24, 4', is also shorter and thicker, and is not crossed, as in Man, by the exten- sors of the metacarpal and first phalanx of the pollex (fig. 23, n and 12) before its in- sertion into the styloid process of the radius. Part of the carneous mass of the flexor sub- limis dis;itorum is seen o at is, fig. 23, and o', fig. 24. External to this a greater pro- portion of the flexor profundus appears in the Gorilla, fig. 24, 6, than in Man, fig. 23, 15. The flexor longus pollicis, fig. 23, 14, ex- pends its force in the Gorilla, fig. 24, 20, upon both the pollex and index, furnishing tendons to the distal phalanx of each, but the largest and most direct beino; that to the o index. There are mo- Muscles of the fore-arm and hand, Gorilla, i". dificatioilS of minor importance in the origin of this muscle which tend to give it a MUSCULAR SYSTEM OF MAMMALIA. 57 character of being part of the system of the ' flexor profundus' in the Gorilla. The relations of the tendons of the superficial and deep flexors to each other and to the digits are much alike in Man and Ape, but the tendons are relatively broader, and their restraining and strengthening sheaths and bands stronger GJ o o ^^ in the Gorilla ; those formed by the oblique decussating liga- mentous fasciculi, as in the mid-finger of fig. 23, are more distinctly shown in Man than in the Ape. The muscles acting on the metacarpal and first phalanx of the pollex fig. 24, 22, 'abductor,' ib. 24, flexor brevis, ib. 25, adductor -- are longer and more slender in the Gorilla. The abductor in Man is shown at fig. 23, 17. In the Gorilla the ' abductor minimi digiti ' is shown at fig. 24, 10 ; the ' flexor brevis ' at n ; the tendon of the flexor profundus at 13; that of the e flexor sublimis ' at e'. Two of the ' lumbricales ' are shown at 14 and 28, and one of the interossei at 27, fig. 24. The carneous part of the common extensor of the fingers is continued to the wrist in the Gorilla ; three strong tendons go to the second, third, and fourth digits, and a fourth, less strong, to the fifth digit. This digit also receives the tendon of an extensor minimi digiti, and the index a small ten- don of an 'indicator' which is more completely blended with that of the ordinary extensor, besides being more feeble, than in Man. The extensors of the metacarpal, first and last phalanges of the pollex, are present in the Gorilla, but of smaller size than in Man. In the Gorilla the portion of the biceps cruris derived from the ischiadic tuberosity, and inserted, fig. 25, 4, into the outer part of the head of the tibia, is more distinct than in Man from that, ib. 5, derived from the femoral linea aspera and inserted into the head of the fibula, and which expands, 5', upon the cnemial fascia. The external gastrocnemius, fig. 25, 7, continues longer distinct from the internal, and both present longer but narrower and thinner carneous portions than in Man. The soleus, ib. 8, arises exclusively from the fibula and is much narrower than in Man, where it also derives fibres from the oblique line of the tibia and from the middle third of its internal border. The margins of the tendon of the soleus first unite with those of the gastrocnemius, the middle part continues distinct to near the calcaneum. The plantaris has not been met with in the Gorilla. The peroneus longus, fig. 25. 9, has a longer carneous and shorter but thicker O " & O tendinous part in the Gorilla than in Man : the course and insertion of the tendons are the same. The peroneus brevis, 58 ANATOMY OF VERTEBRATES. 25 ih. iy, very closely repeats the characters of that muscle in Man. The 'tibialis anticus,' fig. 25, 17, commences by a broader and more fleshy origin, but gradually decreases as it descends, not swelling out into the well-marked 'belly/ as in Man: the tendon divides more distinctly and deeply to be inserted into the metatarsal of the hallux and the entocuneiforni bone. The extensor longus digitorum, with the same relations at its origin to the tibialis anticus and peroneus longus as in Man, divides, after pass- ing under the annular ligament, into three, instead of four tendons ; the innermost of which subdivides to sup- ply the second and third toes. The extensor longus hallucis sends its ten- don to the last phalanx of the hallux, as in Man. The short extensor of the toes, ib. 20, also sends off a strong fasci- culus, 2(/, the tendon of which acts upon the proximal phalanx of the hal- lux. Three other fasciculi send ten- dons to the second, third, and fourth toes. The long flexors of the toes are dis- tinguished in the Gorilla, as in lower Quadrumana, by their relative posi- tion at the back of the leg. The one toward the inner or tibial side sends its tendon through a strong liga- mentous synovial sheath behind the inner malleo- lus to the sole, where it divides into three chiel tendons which are con- nected with those of the ' flexor accessorius.' In nV. 26, the divisions of o * the long tibial flexor, i, are cut and reflected ; \a ^^^^ goes to the fifth toe ; 4 is the perforated tendon of the fourth toe, 4', reinforced by carneous 21 20 Muscles of the leg and foot, Gorilla. MUSCULAR SYSTEM OF MAMMALIA, 59 fibres from the deeper surface of the main tendon ; \b is the ten- don to the last phalanx of the second toe. 27 26 IV Muscles of the foot, Gorilla. r - . Muscles of the foot, Man. The long fibular flexor of the toes, arising from the back part, of the fibula and interosseous ligament, grooves by its tendon the posterior part of the tibia, the astragalus and the calcaneum, and divides at the sole, fig. 26, 2, into the perforating tendons of the hallux, 2c, the third, 2Z>, and the fourth, 2#, toes. The portion of the flexor brevis which rises from the calcaneum divides into two tendons which form the perforated ones of the third, 3', and second, 3", toes. The short muscles giving the grasping power to the hind thumb are, s, ' abductor hallucis,' 9, * flexor brevis hallucis,' 10 ' adductor obliquus hallucis,' and n, ' adductor trans- versalis hallucis.' The lumbricales and interossei are powerfully developed. In the Orang the long fibular flexor sends no tendon to the hallux. The ordinal modification of the hind- or lower- limbs for the whole work of sustaining and moving the body, in Bimana, is accompanied by well marked and considerable modifications of the toes, the chief of which are illustrated by comparison of the figure, 26, from the highest ape, with fig. 27. The long 60 ANATOMY OF VERTEBRATES. fihular flexor now becomes the ' flexor longus hallucis,' and con- centrates its force exclusively on the tendon, 2, 2c, which goes to the last phalanx of the hallux, z; this tendon is twice the size of any of the divisions of that of the long flexor on the tibial side. This is limited to the function implied by the name 'flexor longus digitorum pedis,' its tendon, fig. 27, i, sending off successively the perforating tendons to the second, third, fourth, and fifth toes. In fig. 27, are shown the insertion of the 'tibialis posticus,' 15; the 'flexor brevis minimi digiti,' 7 ; the ( flexor brevis pollicis,' inserted into the outer, 9, and inner, 10, sesamoids, the adductor pollicis, 8, and the peculiar ( transversalis pcdis,' 10, arising from the under surface of the distal and of the fifth metatarsal, crossing three of the other metatarsals, to be inserted into the outer side of the proximal phalanx of the hallux, blending there with that of the e adductor pollicis.' The heel being the lever-power by which the whole superincum- bent weight of the body is raised in the peculiar ' walk,' or bipedal gait, of Man, muscles that are distinct in quadrupeds are here, contrary to ordinary rule, blended, or have a common insertion. Not only the outer and inner gastrocnemius, but the soleus, and even the plantaris, might be regarded as so many origins of the same muscle, which combine and concentrate their forces upon the calcaneum. The f panniculus carnosus' of quadrupeds is reduced in Bimana to the f platysma myoides,' fig. 28, p, p, p, which extends from the upper and fore part of the chest upward over the front and side of the neck to the mandible and lower part of the face, where the two muscles meet below the symphysis. The middle fibres are attached to the base of the jaw, and posteriorly ascend to the fascia of the masseter ; the anterior ones ascend with the depressor anguli oris and quadratus mexiti to the lower lip and angle of the mouth. In many instances there is a strip from the parotid fascia which converges to this angle, and constitutes the ( risorius san- torini.' The platysma draws down the lower part of the face, or, by a slighter action, the lower lip : the ' risorial ' slip tends to raise the angle of the mouth. Most of the muscles of the face are attached at one part to bone, at another to skin or to some other muscle. The skin of the human face is remarkable for its tenuity, flexibility, and abundant supply of vessels and nerves; its vascu- larity tinting the cheeks and lips : it is more adherent and the subjacent cellular tissue is denser along the median line than at other parts. The ' orbicularis oris,' fig. 29, o o, has no attachment to bone. MUSCULAR SYSTEM OF MAMMALIA. 61 It consists of two semi- elliptic planes of muscular fibres which surround the mouth and interlace on either side with those of the ( buccinator ' and other dilators of the oral orifice. The ex- ternal or peripheral surface adheres to the skin, the internal or posterior surface is covered by the mucous membrane of the mouth. Acting as a whole it closes the mouth, bringing the lips 28 29 nuiccles of the head and neck. Muscles of the face. in contact and pressing them firmly together, but the upper and lower halves can act separately, or the fibres of one side may contract while the others are quiescent, so that different parts of the lips may be moved by different portions of the muscle, which may be regulated or antagonised by the muscles which con- verge to the mouth. A pair of accessory strips to the orbi- cularis, ' accessorii orbicularis superioris,' rise from the alveolar border of the premaxillary, and arching outward on each side are continuous at the angles of the mouth with the other muscles there inserted. A second pair, ' naso-labiales,' descend from the septum of the nose to the upper lip, but with an interval, cor- responding with the depression on the skin beneath that septum. fi-2 ANATOMY OF VERTEBRATES. The 'Icvator labii superioris/ fig. 29, I, arises from the lower maririn of llie orbit, and descends to be inserted into the orbi- o cularis and the skin of the upper lip. The ' levator anguli oris,' fig. 29, c', arises below the snborbital foramen and descends, inclining outward, to the angle of the mouth, blending its fibres with those of the zygomatici and orbicularis. The f zygomaticus major,' fig. 29, 3, is cylindrical, rising from the malar and de- scending obliquely inward to a similar insertion at the angle of the month. The zygomaticus minor, fig. 29, 3, arises in front of the xyg. major, and passing downward and inward to the angle of the mouth, where it is continuous with the outer margin of the levator labii superioris. The levator menti is a conical fasciculus arising from the incisive fossa of the mandible, external to the symphysis, and expanding as it descends to be inserted into the integument of the skin. The ' depressor labii inferioris,' fig. 30, d, arises from the inner half of the external oblique line of the mandible, and is partly also continued from the platysma : its fibres ascend, inclining inward to be attached to the lip, where they blend with those of the orbicularis oris. The ( depressor anguli oris,' fig. 29, t, arises from the external oblique line of the mandible : its fibres ascend and converge to the angle or commis- sure of the lips, blending with the other insertions at that part. The buccinator, fig. 30, b, arises from both upper and lower jaws and the ptery go-maxillary ligament : its fibres line the cheek and converge toward the angle of the mouth, where some decussate, the lower ones going to the upper segment of the orbicularis, the upper ones to the lower segment, while other fibres are continued forward into the corresponding lip. The buc- cinator acts, in antagonism with the orbicularis, in spirting fluids from the mouth and in playing on wind instruments. In mastication the buccinator presses the food from between the cheek and gums into the cavity of the mouth. It assists also in deglutition when the mouth is closed, by pressing the food back- ward. The ' levator labii superioris alaeque nasi ' arises from the nasal process of the maxillary, descends obliquely outward and divides, a short strip being attached to 30 LOCOMOTION OF MAMMALIA. 63 tlie cartilage of the ala nasi, the outer and longer strip to the skin of the upper lip near the nose, and becoming blended with the orbicularis and levator labii proprius. The ' triangularis nasi/ or ( compressor iiaris,' figs. 29, and 30, n, arises from the maxillary external to the incisive fossa : its fibres proceed upward and inward, expanding to an aponeurosis continuous, over the bridge of the nose, with that of the opposite muscle. The f depressor alre nasi ' is a short flat muscle radiating upward from the myrtiform or incisive fossa of the maxillary ; it sends upper fibres to the septum and back part of the alse nasi and lower ones into the orbicularis oris. The ' orbicularis palpebrarum,' fig. 29, o, surrounds the orbit and eyelids : it arises from the internal angular process of the frontal, from the nasal process of the maxillary, and by a short tendon at the inner angle of the orbit. It rapidly expands to form a broad thin elliptical plane of fibres : the palpebral por- tion is thin and pale : the orbital portion is thicker and of a reddish colour. The action of the muscle is that of a sphincter, the curved fibres in contraction approaching the centre : but as thcv are fixed at the inner side the skin to which the muscle is */ attached is drawn toward the nose, and becomes corrugated into folds which converge toward the inner canthus. The ( comiffator O o snpercilii, is a small triangular muscle placed at the inner end of the eyebrow, arising from the same end of the superciliary ridge : its fibres pass upward and outward to be inserted into the under surface of the orbicularis palpebrarum. It depresses the eye- brow, and, in conjunction with its fellow, throws the integuments into vertical folds as in the act of frowning. The 'occipito- frontalis ' consists of an anterior and posterior carneous expansion united by a broad f epicrauial,' aponeurosis. The anterior muscle, fig. 28, f, consists of two lateral portions, each connected in- feriorly with the integument of the corresponding eyebrow, and slightly overlapped by the ' orbicularis.' The posterior or oc- cipital portion, ib. o, also consists of a pair, attached inferiorly to the upper curved line of the superoccipital, and to the mastoid. The fibres are parallel and nearly vertical. The action of this muscle is most apparent upon the skin of the forehead and the eyebrows : it raises the latter and throws the former into trans- verse wrinkles. 202. Locomotion of Mammals. In the movements of the human frame the three kinds of lever are exemplified. Those of the head upon the atlas are on the principle of the first kind, fig. 31, in which the fulcrum F is between the power p and the resistance w. When the body is raised on tip-toe by the action of the ANATOMY OF VERTEBRATES. muscles on the heel-bone, fig. 37, k, the action is that of the second kind of lever, in which the resistance (of the tibia on the astraga- lus), as in fig. 32, w, is between the fulcrum F (afforded by the ball of the hallux), and the power a (tcndo achillis). 31 A y B l'r'''TI'n;-;iT'iiiiiiiii'ii'iiiiL':'iil'riiiiiii-'ii-;ii-.;niiMiiimiiiiiiiiiiiiiiiii!iii.ijiji'ii.-.!Hii'iiiiu'iiiiinin!T 32 F w Lever of the first kind. Lever of the second kind. In lifting a weight in the hand by motion of the fore-arm only, fig. 33, the elbow-joint is bent ; the power (of the flexors of the fore-arm) being applied (as by the biceps, />) at a, between the fulcrum (elbow-joint)^ and the resistance w or b, according to the third kind of lever exemplified in fig. 34. The mechanism of the pulley is exemplified in the passage of the tendons of the peronei muscles through the groove of the external malleolus of the human ankle-joint, in the tendon of the obturator 33 interims gliding through the groove in the os ischii, in the tendon _ of the circumflexus palati passing through the hamular process ot the sphenoid bone, in the tendon of the obliquus superior gliding through the ring attached to the frontal bone, and -in several other instances where a change of the directions of the limbs results from tendons passing over joints, through grooves in LOCOMOTION OF MAMMALIA. 65 bones, or under ligaments, by which the muscles are capable of producing effects on distant organs without disturbing the sym- metry of the body, an effect which, owing to the limited power of contraction in the muscles, could O 4 be accomplished in no other way. The joints in the mammalian skeleton are chiefly of two kinds, ( ginglymoid ' or hinge-joints, and 6 enarthrodial ' or ball-and-socket r" joints. In Man the former are less definitely fitted for motion on one plane than in most brutes. The Lever of the third kind. arm and fore-arm move in concen- tric planes upon the elbow-joint ; the knee-joint allows a certain rocking motion of the leg upon the thigh ; the ankle-joint has a greater latitude of motion, and the foot may be directed out of the plane of the leg's motion. Atmospheric pressure exercises its influence upon joints. Dr. Arnott estimates the amount of that on the knee-joint at 60 Ibs. ; AVeber of that on the hip-joint at about 26 Ibs. : in the hip-joint of the Megatherium the pressure could not have been less than 150 Ibs. A. Swimming. - - Quadrupeds with inflated lungs are of less specific gravity than water, and swim by alternate extension and flexion of their legs; the effective stroke being the act of extension, when the limb presents a larger area to the water than in flexion : this is seen in the Horse, which strikes the water with the ex- panded and subconcave surface of the hoof, but draws the convex conical part through the water in the bending of the limb pre- paratory to the next effective stroke. In the best water dogs the digits are connected by webs, which are stretched in the back or down-stroke, folded in the return movement. The feet of the Otter are broader, especially the hind ones, and more fully palmated. The Seals and Whales have the limbs fashioned as fins. Man, Avith the chest well expanded, is lighter than water : the presence of mind which counteracts the tendency produced by immersion in a cold and dense medium to expel the air from the lungs is the first safeguard against drowning ; and next, if the art of swimming has not been learnt, to keep the head immersed to the mouth and nose, and to refrain from the misdirected struggles of terror which tend only to hasten on the catastrophe. In swimming, the hands and feet are employed so as to present the greatest surface to the water in the effective stroke, the least in VOL. III. F G6 ANATOMY OF VEKTEBBATES. the preparatory movement ; in this the hands are brought near the mesial plane, with the palmar surfaces parallel to each other ; they arc then thrust forward by the extension of the arm, with the points of the fingers in advance to cut the water with the least resistance ; when the hands have nearly reached their greatest distance from the centre of gravity, they are rotated by pronation, so that the palms are directed at an oblique angle outward and downward ; they are then forced backward by the abduction of the Avhole arm through a large arc of a circle, having the shoulder- joint for its centre, and the length of the arm for its radius ; the fore-arm is then flexed, and carried into its former position pre- paratory to making another stroke. During the extension of the arm, the feet are drawn toward the centre of gravity, with their convex surface directed obliquely backward by the extension of the ankle and flexion of the hip and knee joints, and during the ab- duction of the arm the flat surfaces of the feet are driven forcibly backward and downward by the sudden extension of the leg. From the ratio of the areas of the hands and feet, and the ratio of the difference of their velocities in the two strokes, there results such a preponderance of the force in the vertical direction upward and in the horizontal direction forward as is sufficient to keep the respiratory openings above the surface of the water, and to over- come the resistance which the water opposes to the motion of the body, due to its figure and velocity. B. Moving on J,and. In mammalian quadrupeds the limbs are usually long, and support the trunk horizontally, uplifted from the ground, as on columns expanded at their base. The uppermost long bone is single, the next two form a pair, side by side, and these rest on more numerous ossicles, transferring the weight upon the base of two, three, four, or five diverging piles : the single hoof of the Horse seems an exception, but it, too, ex- pands to its base. The shafts of the long bones are hollow, agreeably with the principle of combining greatest strength with least weight. According to the lightness and speed of the quad- ruped, the limb-bones are inclined to each other's axes at a greater angle. In the colossal Elephant and Megathere they rest on each other almost vertically, in supporting the trunk. The horizontal trunk and produced head and neck of quadrupeds cause the largest proportion of the weight to fall upon the front pair of supporting columns, of which, accordingly, the angles of the joints are less, and the direction more vertical than in the hind pair, as is well exemplified in the hoofed kinds (vol. ii. figs. 307, 309,310). LOCOMOTION OF MAMMALIA. 67 In walking, the Horse, if the right side be in advance, moves first the left hind-leg, second the right fore-leg, third the right hind-leg, fourth the left fore-leg ; propelling the centre of gravity forward over a space equal to the length of the first step. When the left hind-leg is in the act of advancing, the trunk is supported on the other three legs and is balanced on a triangular instead of a parallelogrammical basis. A succession of movements of the four legs, in the above order, constitutes the progression by walking in most quadrupeds ; its rapidity depends on the time occupied in the series of movements by which the limbs effect the step. In a large well-made Horse one foot may move the length of a step in a second of time, when each leg may swing during one quarter and rest on the ground three quarters of a second. Rapid walkers do it in less time, and the interval between putting down one leg and lifting another becomes inappreciable. In quadrupeds with limbs unusually long in proportion to the trunk there is a modifi- cation of the act of walking : the Camel and Giraffe seem to swing along by moving the two right limbs together and alter- nately with the two left limbs. But, though in a quick walk the two legs of the same side seem to be moved forward simul- taneously, and are both off the ground at the same time through the greater part of the step, yet on close inspection the hind-leg is seen to be first lifted from the ground, and after a very brief interval the fore-leg of the same side. 1 In this way of walk the trunk is balanced on a linear basis of support, alternately trans- ferred from one side to the other. In the Giraffe the long neck is then stretched out in a line with the back, giving the animal a stiff and awkward appearance; but this is lost when they commence their graceful undulating amble : 35 the motions of the legs are now peculiar ; the hind-pair are lifted alternately with the fore, and are carried outside of and beyond them by a kind of swinging movement. 2 In the pace of the Horse called the ( trot,' the legs move in pairs diagonally, those marked B, E, fig. 35, e.g. being raised as soon as A, D, strike the ground : the bases of sup- port are alternately in the lines A, D, B, E ; and the undulations from the projection of the trunk are in the vertical, not as when walking 1 xcvir. p. 244. Ib. p. 244. F 2 68 ANATOMY OF VERTEBRATES. in the horizontal, plane. Moreover, in the rapid trot, each leg rests a short time on the ground and swings a longer time. The gallop includes three combinations of movements of the limbs. When the Horse begins the gallop on the right hind-leg, the left one reaches the ground first ; the right hind and left fore- legs next, simultaneously, and the right fore-leg last ; this is termed the gallop of three beats. In the gallop where the four legs strike the ground successively, the left hind-foot reaches the ground first, the right hind-foot second, the left fore-foot third, and the right fore-foot fourth ; this is the ( canter,' or gallop of four beats, but it is not the kind of movement adapted for great speed. The gallop wherein the legs follow the same order as in the trot that is, the left hind and right fore-feet reaching the ground simul- taneously, then the right hind and left fore-feet is the order in which horses move their feet in racing, where the greatest speed is required, and is called the gallop of two beats. In the ' amble,' the two legs on one side rest on the ground and propel the centre of gravity forward, whilst those 011 the opposite side are raised and advanced, and, on taking a new position on the plane of motion, the former pair are raised and advanced in a similar manner : these successive actions are accompanied by considerable lateral motion. This resembles the gallop of the Giraffe, and is a result of special training in the Horse. In the ordinary gallop, the centre of gravity moves in a vertical plane, and describes the path of a projectile. The space passed over on the plane of motion is equal to the horizontal velocity of the centre of gravity multiplied by the time. According to Sambell, the horse Eclipse, when galloping at liberty and with its greatest speed, passed over the space of twenty-five feet at each stride or leap, which he repeated 2J times in a second, being nearly four miles in six minutes and two seconds. Flying Childers was computed to have passed over eighty-two feet and a half in a second, or nearly a mile in a minute. In both these famous racers the muscular system had been allowed to gain its full developement, as at four years, before being exercised for the course : modern impatience strains and spoils the muscles by the chief prizes being allotted to three-year-old horses. In many Marsupials and Rodents the hind-legs are shorter than the fore-legs, the disproportion being greatest in the Kan- garoos and Jerboas. In slow progression the Kangaroo supports the body on the tail and fore-legs, while the hind-legs are simul- taneously moved forward outside and in advance of the fore-legs ; the base of support being here transferred from a triangle to a transverse line. In full speed the tail is rigidly outstretched to LOCOMOTION OF MAMMALIA. 69 afford a firm fulcrum to muscles passing from the caudal vertebrae to the pelvis and hind-limbs : the short fore-limbs are tucked up to the chest so as to offer the smallest surface to the air, and the animal progresses in a series of bounds by simultaneous move- ments of the hind-limbs. The Rabbit, in moving slowly, advances the fore-feet two or C5 / 3 three steps alternately. The body being thus elongated, the hind- legs are suddenly extended and drawn forward simultaneously : it thus, as it were, walks Avith the fore-legs, and leaps with the hind. The Hare is under disadvantage with its long hind-limbs in running down-hill, owing to the great inclination of the axis of the trunk to the plane of motion, and it usually zigzags as it descends ; but it gains proportionally in the ascent, and its speed on level ground, through the size and strength of the chief pro- pelling limbs, is very great. The degree of flexion of the trunk accompanying the movements of these and other quadrupeds is indicated by that in which the neural spines converge toward the single vertical one marking the centre of motion, and it is commonly greatest in the unguiculate quadrupeds. The vertically of the long and narrow tarsus and metatarsus producing the f digitigrade ' character of the type Carnivora, com- bines with the geometrical and physical relations of the other parts of the limbs to give them their superior speed and agility. In the Dogs and Cats the oblique scapula, being unfettered by bony (clavicular) connection with the sternum, enjoys the freedom of rotation which characterises it in the swift Ungulates. The humerus in the Lion (vol. ii. fig. 337) has its axis directed down- ward and backward, forming with that of the scapula an angle of 110. The olecranon projects so far behind the axis of rotation in the elbow-joint as to constitute a powerful lever for the exten- sors of the fore-arm. The hind-limbs are longest, and the bones o are inclined more obliquely to each other than in the fore-limbs, subserviently to elasticity and power in springing. The calca- neum is produced on the same principle as the olecranon, but forms the more powerful lever of the two. The last perfection is given to the limbs of Carnivora by the modifications of the toes of Felines, whereby their tread is noiseless, and the claws exempt from the wear and tear of progressive motion. It is effected by a joint allowing the ungual phalanges to be brought in extension above the middle phalanges, elastic ligaments being adjusted to keep the joint so extended, and by a thick cushion of soft elastic substance beneath the joint or parts of the phalanges transmitting the superincumbent weight to the ground. 70 ANATOMY OF VERTEBRATES. In the toes of the fore-foot the last phalanx is retracted on the ulnar side of the second phalanx. The principal elastic ligament arises from the outer side and distal end of the second phalanx, and is inserted into the upper angle of the last phalanx : a second arises from the outer side and proximal end of the second phalanx, and passes obliquely to be inserted at the inner side of the base of the last phalanx : a third arises from the inner side and proximal end of the second phalanx, and is inserted at the same point as the preceding. The tendon of the s flexor profundus 36 perforans' is the antagonist of these ligaments. The toes of the hind-foot are retracted in a different direction, viz. directly upon, and not by the side of, the second phalanx ; and the elastic ligaments are differently disposed. They are two in number, arise from the sides of the second phalanx, and converge to Elastic ligaments of Liou-s daw. ^e inserted at the superior angle of the last phalanx. In fig. 36, a is the pair of elastic ligaments ; b, the tendon which pulls out and works the claw; c, inelastic ligament continued from the 6 extensor ' tendon, which is mainly inserted into the second phalanx. 1 The main purport of the modifications of the motory system in Quadrumana is to make them climbers. By the developement and direction of the hallux the hind-foot is converted into a hand, with unusual power of prehension, especially in the Gorilla ; the joint of this hand is so modified as to give it a free motion excentric to the axis of the leg, whereby its outer edge is applied to the ground ; the whole hind-limb is shortened, disproportion- ately so in the best climbers (vol. ii. fig. 180), in which also the hind-limb may be unfettered, for its acts of manipulation, by the absence of the ( ligamentum teres ' of the hip-joint (Pithecus). The length of the iliac bones relates to elongation of the muscles for rotating the hind-limb and hand more quickly and through greater spaces. Correlatively, the scapular arch approximates to the condition of the pelvic one by the extension of complete clavicles to the manubrium, and the head of the humerus is re- ceived into a deeper and more secure socket than in Bimana. This is well exemplified in the long-armed Gibbons, which enjoy the peculiar mode of locomotion called ' brachiation.' The body is set into pendulous vibration by the action and reaction of the 1 The dissections of the Lion's foot showing the above-tlescrihed modiiications of the elastic ligaments are Nos. 287A and 288A, Physiol. Series, vol. i. xx. LOCOMOTION OF MAMMALIA. 71 muscles of one arm and of the trunk, the force finally attained and the swing being such as to propel the animal some distance through the air ; a bough is seized by the opposite out-stretched arm, and the momentum is applied in aid of a repetition of the action to gain a longer launch. I have myself witnessed, in the London Zoological Gardens, an aerial leap of upwards of fifteen feet so effected by the long arms of a captive Hylobat. M. Duvaucel, observing them in their native forests, testifies to their passing through a distance of forty feet from bough to bough. Mr. Martin, when curator of the Zoological Society's Museum, watching the same female Hylobates agilis which had been the .subject of my own study of the brachiating mode of motion, states that, ( a live bird being set at liberty in her pre- sence, she marked its night, made a long swing to a distant branch, caught the bird with one hand in her passage, and at- tained the branch with her other hand, her aim both at the bird and the branch being as successful as if one object only had gained her attention.' * In most of the Platyrhine monkeys the tail is prehensile, and becomes, in Ateles more especially, a fifth independent organ of grasping. In ordinary progression on the ground the Quadrumana move as quadrupeds ; but the higher tailless Catarrhines (Apes), in- stead of setting the palm or outer margin of the fore-hands, like the inferior families, to the ground, apply the back of the second phalanges of the flexed fingers, the skin covering which has a broad and thick callosity, whence these apes are sometimes called collectively, f knuckle-walkers.' The longer-armed kinds, in slow movement, support the body upon the knuckles, as upon a pair of crutches, and swing the hind-limbs forward between them. In more rapid movement they sway the trunk and hind-limbs in a sort of sidelong sweep, progressing by a kind of shambling amble. The tracks of the Gorilla show this to be o the habitual mode of progression along the ground. 2 Station or motion on the lower limbs only is shown to be difficult by its awkwardness and the shortness of time during which it can be maintained. The walk is a waddle from side to side, the huge superincumbent body being balanced by swinging movements of the long arms, or by clasping the hands behind the head. When so pursued as to be driven to stand at bay, the Gorilla, like the plantigrade Bear, raises himself on the hind-hands, so as to have his powerful arms and fists free for the combat. 1 XLVIII". - xili". p. 532. 72 ANATOMY OF VERTEBRATES. 37 The Bimana are as expressly adapted to station and movement on the ground as are the Quadru- inana to climbing in the forest. There is no known connecting link between the lowest variety of Man and the highest species of Ape. No animal is served by arms, at once so large and variously flexible and applica- ble as Man ; in none are the termi- nal divisions of the limb so distinct in their power and adaptability. 1 The mechanism of the vertebral column and limbs which makes Man a f plantigrade biped,' and the only one in the Animal Kingdom, is as perfect in the Mincopie, 2 Australian, or Boschisman, as in the most advanced member of the white race. The locomotive frame of any variety would equally serve as the subject of such elaborate analyses of the mechanical condi- tions of ( standing,' ' walking,' ' run- ning,' ( leaping,' &c. as have been given by Borelli, 3 Barthez, 4 Rou- lin, 5 Gerdy, 6 and W. & E. Weber, 7 to whose works, and especially the latter, the reader is referred for this interesting branch of Animal Mechanics. LX1V. 4 XIV. - XXXVII". XV. 6 XVI". 3 cxxxr 7 XII". Figure 37 exemplifies a Man stooping with a load, and sustained in that position by the glutei, f, the quadriceps feraoris, y, and the gastrocnemii, /. If the weight r be 120 Ibs., that of the bearer 150 Ibs., and if the line r s be the direction of the force of gravity cutting the femur and tibia in c and x, the centre of gravity of the Man being at b, and the common centre of gravity of the Man and his load at a, then the weight of the Man from the head to b will be = 'I Ibs. = 75 Ibs., and that of the section b to c, by supposition, = 47 ; therefore the weight of the arc a b c = 75 + 47 = 122, also by supposition the section c v x = 20, and consequently the whole arc a b v x 142 ; the distances of the directions of the muscles from the axes of the joints to the distances of the line of gravity arc, according to Borelli, in the following ratio, ^ the distance/ b is to the distance m b as 1 is to 8 ; ^ o v is to t v as 1 to 6 ; \ k d is to p d as 1 to 3 ; and t v to b m as 3 to 4 ; hence he derived certain proportions, from which he estimated that the extensor muscles of the leg, to sustain this weight, exerted a force = 6032 Ibs., being more then fifty times the weight. MYELON IN MAMMALIA. CHAPTER XXVIII. NERVOUS SYSTEM OF MAMMALIA. 203. Myelon. - The myelon in Mammals, as in Birds, quits, in the course of develope- meiit, the hinder part of the neural canal, mov- ing and concentrating forwards, and leavino- *- J o ' O the concomitaiitly elongated roots of the nerves, between their places of exit at the intervertebral foramina and their places of attachment to the myelon, as an indication of the primitive extent of the nervous axis. It is remarkable that the Monotrematous order, so restricted in its representative genera, should present the two extremes of this deve- Ippemental difference in the length of the myelon. The Ornithorhynchus hardly departs from the condition of the lizard, the myelon extending into the sacrum, and having the intravertebral nerve-roots limited to the short canal of the caudal region ; whilst in the Echid- na, fig. 38, the myelon moves forward to the middle of the dorsal region, d, where it ends in a point, and leaves all the canal behind occupied by the elongated nerve-roots and shrunken emptied myelonal sheath, answering to the ' caucla ecjuina ' and ( filum terminale ' of anthropotomy, but of extraordinary length. In the Ornithorhynchus the myelon fills closely the neural canal : it is thickest at its commencement and at the lower two-thirds of the cervical region ; it is more slender in the back, especially near the loins ; it is slightly enlarged in the lumbar region, and gradually terminates in a point at the end of the sacral canal. The short and thick myelon of the Echidna presents the two usual enlarge- Brain and spinal chord, Echidna, half nat. size. 74 ANATOMY OF VERTEBIIATES. 39 merits, giving origins respectively to the nerves of the pectoral mid pelvic extremities, the slightly contracted intermediate por- tion being extremely short. In the Marsupialia the myelon usually extends to the sacrum, and presents both brachial and pel- vic enlargements which correspond with the relative size and muscu- larity of the extremities to which they furnish the nerves ; the latter enlargement is consequently most marked in the Kangaroo, fig. 39, but does not exhibit the rhomboid al sinus of this part in Birds. The disposition of the layer of grey matter enveloping the central me- dullary tract in each lateral moiety of the chord is shown in the three situations marked i, 2, and 3 ; the superior expansion and com- plexity of the grey matter in the anterior columns of the pelvic en- largement, 3, accords with the pre- dominance of the locomotive over the sensory functions in the long and strong saltatory legs of the Kangaroo. In the Lissencephala we have again examples of the concentra- tive protraction of the myelon into the dorsal region, as e.g. in some Cheiroptera and in the Hedgehog. From the coincidence of the condition of the myelon with the tegumentary covering in Erinaceus and Echidna, we are led to ask, whether the shortness of the solid chord, and the great length of the suc- ceeding nerves within the neural canal, have any physiological relation with the habit, common to both the placental and mono- trematous hedgehogs, of rolling the body into a ball when torpid or asleep, or when the tegumentary armour is employed in self- defence. In the bat it would seem to be concomitant with the reduced size and function of the pelvic limbs : but, in the Noctules ( Vespertilio noctula), the myelon extends to the lumbar vertebra. The anterior enlargement is the chief one in Cheiroptera, and is close Myelencephalon, Macropus. MYELON IN MAMMALIA. 75 to the medulla oblongata, as it is likewise in the Cetacea. In most Rodentia the myelon terminates in the lumbar region, but in the rabbit it extends a little way into the sacrum. In the mouse the relative proportion of the myelon to the brain is as 22 to 100. In the Cetacea and Sirenia, the myelon presents only the anterior enlargement, which is very near the brain, and is remark- able for the close aggregation of the origins of the nerves from that part. The myelon is closely invested by the dura mater, which is directly perforated by the nerves, and the sheath terminates at the pointed end of the myelon, not being continued as such, over the c cauda equina.' The myelon is small in proportion to the size of the body, shows the central canal, and, Hunter remarks, ' is more fibrous than in other animals ; when an attempt is made to break it longitudinally, it tears with a fibrous ap- pearance, but transversely it breaks irregularly.' * In the Elephant the dura mater surrounds the myelon less closely than in the Cetacea, and the roots of the nerves have a longer course within the sheath. In the Giraffe 2 I found the myelon closely invested by the dura mater, which was thinner on the dorsal than on the ventral side : it is chiefly remarkable for the length of the cervical portion, which from the corpora pyra- midalia to the pectoral or brachial enlargement measured four feet three inches. The elongation of this part during foetal de- velopement proceeding by uniform interstitial addition, the roots of the nerves become equally separated from each other ; and, as the lowest filament of one root was not further removed from the hio-hest of the next below, than this from the succeedino; filament O J CD of the same root, such filaments were extended over an unusual space of the myelon ; the root of the third cervical coming from a tract of not less than six inches in length : the contrast between the cervical myelon of the Porpoise and Giraffe in this respect is striking. o With the singular exceptions of the Echidna, Hedgehog, and certain bats, the mass of the myelon bears a direct ratio to that of the body throughout the Mammalian series, and its structure is essentially the same. In the adult human male it a little exceeds an ounce in weight ; its tissue is firmer than that of the O brain. As in all Vertebrates, the ventral and dorsal surfaces are respectively divided into equal moieties by a longitudinal fissure, of which the dorsal is deepest, and, in the Mammalia, closest. In Man, the interfissural plate of pia mater can be shown to be a fold in the ventral (anterior) fissure, fig. 40, a, but is confluent as a 1 xciv. p. 374. 2 xcvn'. 76 ANATOMY OF VERTEBRATES. single delicate layer of vascular tissue in the dorsal (posterior) one, ib. c. A layer of white iieurine accompanies the ventral fold, which, when withdrawn, shows the fissure to be closed by such layer, perforated by numerous holes for capillaries : its fibres are trans- verse and form the ( white myelonal commissure.' The depth of the ventral fissure is greatest at the pectoral enlargement of the myelon, and gradually diminishes towards the ' cauda equina.' The deeper dorsal fissure penetrates fully one-half of the dorso- ventral diameter of the myelon through the greater part of its course, but becomes shallower in the lumbar region : it is bounded by a layer of grey neurine, connecting the same tissue in each lateral moiety of the myelon,, which layer forms the ( grey mye- lonal commissure.' In the developemeiit of the myelon, as of the encephalon, the central part contains a fluid which is reduced by the endogenous grow 7 th of neurine, on ap- proaching maturity ; it re- mains in the myelon, as its e canal,' which is obvious in the cold-blooded Verte- brates, 1 and is exposed, in birds, as the ' ventricle of the pelvic enlargement,' as it is in the ' fourth ventricle ' of all Vertebrates, where it bears the name of ' calamus scriptorius ' in anthropoto- my. The myelonal canal is more obvious in lower mam- ancl fourth cervical nerves. Magnified ten diameters- mals 2 than in Man, aild in Z Transverse section of the human myelon, close to the third XVIII". the foetus than in the adult ; in whom, whilst unobliterated, it is surrounded, like the more obvious myelonal canal in Reptiles, by the grey commissural neurine. The canal is lined by ciliate cells. 3 The lateral columns of this tissue, united by the commissure, are thicker but less peri- pherally extended in the ventral, y, than in the dorsal, h, portions of the myelon. In transverse section the grey neurine resem- bles a comma, the concavity of which is directed outward, the head, fig. 40, g, is surrounded by the peripheral white neurine, and the tail, ib. h, i, is produced to the issue of the dorsal (posterior) nerve-roots, ib. k. The proportions of the grey and 1 vol. i. pp. 272, 296. 2 xx. vol. iii. p. 43, no. 1362. 3 xvni". MYELON IN MAMMALIA. 77 white neurine vary in different parts of the myelon. In fig. 41, i is a section at the fore (upper) part of the pectoral enlargement, the head of the comma is small, the tail narrow : in the middle of the enlargement, section 2. the head is larger, . * i with more distinct processes, the tail is thicker. In the dorsal region, sections 3, the grey matter is more reduced than in the neck. In the lum- bar region, sections 4, it again expands, the head shows the stellar character, is fenced off from the ventral periphery by a smaller extent of white neurine ; the tail is thicker, but here becomes shorter and seems not to reach the dorsal surface. Near the termination of the myelon the comma-shape is lost, and the grey neurine reduced to a subcylindrical tract, slightly notched laterally and surrounded, save at the commissure, by the white neurine. Of this tissue the largest proportion exists in the cervical part of the myelon and its enlarge- ment, where the small columns called ( posterior pyramids ' are continued from the dorsal part of the medulla oblongata, contracting to a point, near the end of the brachial enlargements, and there allowing the proper dorsal (posterior) columns of the myelon to come into contact at the posterior fissure. The difference in the proportions of white and grey neurine in the ventral and dorsal tracts of the myelon coin- cides with the different nervous endowments of the pectoral and pelvic limbs : in the former volition and sensation are greatest ; in the latter reflex actions with diminished sensibility : the exercise of the arms and hands induces more calls upon cerebral action, that of the legs and feet operates more exclusively through physical changes of the lumbar part of the mye- lon itself: hence, therefore, the need of a greater proportion of the reproductive or grey tissue. Numerous multi-caudate vesicles are present in the grey neurine, and linear tracts are continued from the major part of its periphery, as seen in transverse section, towards that of the myelon, accompanied by capillary vessels which enter the pia mater. The proportion of the neural canal to the myelon varies in Transverse sections of the human Myelon. A. Anterior or ' ve ntra\. P. Posterior or ' dorsal.' 78 ANATOMY OF VERTEBRATES. different mammals: it is greatest in the Cetacea, Sirenia and Seal-tribe, the space between the myelon and neural arches being occupied by blood vessels, which, in those aquatic orders, are chiefly arterial plexuses. In land-mammals and Man the veins pre- Communication of the ' perineurar sinus with the veins of vertebral centrum, vii". Transverse section of dorsal vertebra and contents of its neural canal, xix". dominate, having more or less of the character of sinuses, as shown in the section of the lumbar vertebra, fig. 42, where the communi- cation of the f perineural ' veins, d, with those of the tissue of the vertebral centrum, is shown. But the most constant fluid exter- nal to the myelon is that which has been called 6 cerebro-spinal.' In the dorsal region of the neural canal, in Man, the position of this fluid is shown in fig. 43, where c is the myelon, with its pia mater and arachnoid, in the dorsal or posterior septum, n the nerve-roots, and s s the sub- or ent-arachnoid space. The use of the uniform support and defence afforded by the interposition of this fluid between the myelon and the hard walls of the neural canal is obvious. 1 The arachnoid is disposed about the myelon, as about the brain, after the manner of the serous membranes ; it consists of an exterior or ( parietal layer ' reflected upon the myelon to form the internal or ( myelonal ' layer. If a section be made through a pair of nerve-roots, those e.g. of the fifth cervical, fig. 44, the arachnoid is seen to be continued as a loose sheath, about the inter-neural part of the root, n n, and is reflected so as to form small culs-de-sac, at the orifices of emero-eiice. O In Man the myelon is loosely invested by the ' dura mater,' to which it is attached by In which (he effects of the removal of this fluid in the Dog are described. 44 Transverse section of the myelon and its membranes across the roots of the fifth cervical nerves. 1 XIX". ENCEPHALON IN MAMMALIA. 79 46 processes of the arachnoid called f ligamentum denticulatum,' and the nerve-roots. 204. Encephalon, its primary divisions. The encephalon, or brain, of Mammals, like that of lower Vertebrates, Tur- tle, fig. 45 (vol. i., Shark, fig. 187, and Lepidosiren, fig. 186), presents four primary Se "- Brain of a Turtle (Chelone), side view. merits or divisions, indicated by as many superincumbent, origi- nally vesicular, masses, or pairs of masses ; but consisting, not only of those, but of tracts of the myelencephalic columns from which those masses are successively developed. The hindmost division, or 6 epencephalon,' fig. 46, c, con- sists of the enlarging parts of the myelencephalic columns, a, called f medulla oblongata,' of the superincumbent mass, c, originally a pair in the human foetus (fig. 47, c), called ( cere- bellum,' and of a transverse commissure of that body, called 6 tuber annulare ' or ( pons varolii,' p ; the three parts, so named in anthropotomy, are subordinate elements of one and the same pri- mary division of the encephalon. 1 The next division includes the parts of the myelencephalic columns which support, and from which are developed, the optic lobes, o : it is the 'mesen- cephalon,' figs. 45, 46 and 47, o. With the columnar elements v j^^^/ K are the parts Called the ( fillet,' Brain of human foetus, at four months, side view. and ' processus a cerebello ad testes ' in anthropotomy, including the 6 third ventricle ' and its prolongations into the vascular appendages 1 The severance of the 'pons,' and raising it, in association with parts of another segment, to the rank of a distinct primary division as ' mesocephalon,' and the sever- ance of the ' medulla oblongata' from the cerebellum, as a co-equal division, called ' metencephalon,' indicate the warping of the judgment through habitual contem- plation of the characteristically modified and developed parts of the human brain. P Brain of Opossum > side view. 80 ANATOMY OF VERTEBRATES. called ( pineal ' and ( pituitary ' h, glands : a second pair of gangli- onic masses are developed in Mammalia behind the optic lobes, o, and received from the old anthropotomists the name of ( testes,' the more constant and important pair being the f nates,' and the whole, from their arrested condition in Man, forming the ' corpora ( quadrigemina ' or ( bigemina.' The third primary division of the brain includes the ( crura cerebri ' with the reinforcing or recruiting ganglions called ( thalami optici ' and ' corpora striata,' and the superincumbent masses called ( cerebral hemispheres : ' it is the e prosencephalon,' figs. 46 and 47, P. The foremost primary division of the brain includes the anterior termination of the columnar tracts, called ' crura rhinencephali,' and the appended vesicular mass, called ( olfactory lobe ; ' it is the 6 rhinencephalon,' ib. R. The nature and value of this division are masked, in Man, by the arrest of its developement and the contrast of the excessive expansion of the vesicular part of the antecedent division. Accordingly the ( crura rhinencephali ' are termed ( olfactory nerve ' with its ( roots,' and the primary vesicle is the ' bulb of the olfactory nerve,' of anthropotomy. Each primary encephalic division has its cavity or cavities called ' ventricles.' The epencephalic prolongation of the mye- lonal canal is the ( fourth ventricle :' its continuation into the primary vesicle is the ( cerebellar ventricle :' it is persistent in fishes (vol. i. p. 275, fig. 178, c\ reptiles (ib. p. 295, fig. 193), and birds (vol. ii. p. 120, fig, 45), but is obliterated in Mammals where the cerebellum is solid. The ' myelonal canal ' passes for- ward as the ' third ventricle,' and ' iter ' or communicating canal between that and the ' fourth.' Its continuation into the optic lobes, retained in oviparous Vertebrates (vol. i. p. 278, fig. 182, h, b, p. 279, fig. 183, d, p. 295, fig. 193, 3, vol. ii. p. 120, fig. 45, o,) is obliterated by growth of neurine in Mammals ; as is also its ascending canal to the ' pineal appendage ; ' the descending one to the ( hypophysis ' is retained as the ' infundibulum.' Each cerebral hemisphere begins in Mammals, as in lower Vertebrates, as a bladder with a thin wall of brain-substance, the cavity including, potentially, all the anthropotomical 'horns,' ' fore,' 6 aft,' and 'under,' of the 'lateral ventricle,' which are subsequently meted out by endogenous growths of grey and white neurine, in size and shape according to the group or genus. In most Mammals which derive so important a share of their ideas through the olfactory sense, the ' lateral ventricle ' is con- MACROMYELON OF MAMMALIA. 81 tinned into the ' rhinencephalon,' as shown in fig. 46, d. So that all the essential parts of a primary encephalic division, viz. the columnar as ( cms rhinencephali,' the superimposed mass, and the cavity exemplifying the nature of the olfactory bulb as a c primary vesicle ' of the brain, are present. 205. Macromyelon.- -The epencephalon consists of the ma- cromyelon and cerebellum. The term ( macromyelon ' is not exactly the equivalent of the ( medulla oblongata ' of anthropo- tomy, the authorities in that department of anatomy having ap- plied the phrase in different senses. With Willis, 1 it included the part of the brain beneath the cerebellum and cerebral hemispheres, * all that substance,' e.g., which reaches from the cavity of the callous body and conjuncture in the basis of the head to the hole at the hinder part where the same substance, being further con- tinued, ends in the f spinal marrow.' With Vieussens, 2 the ( oblong marrow ' included the columns of the neural axis between the 4 spinal marrow ' and the ' cerebral hemispheres,' with the ( crura cerebri ' and their ganglionic enlargements, called ' optic thalami,' and ' corpora striata.' Winslow 3 defines the ' medulla oblongata ' as the medullary basis common to both cerebrum and cerebellum. Haller 4 restricts the 'medulla oblongata' to the intracranial myelonal columns, as far as the ( pons varolii.' Rolando 5 prefers the older view of its extent. Chaussier, 6 ao*ain, distinguishes 7 O O the portions of the intracranial columns crossed by the transverse commissural fibres of the cerebellum as a primary division of the brain, under the name ' mesocephale ; ' and this term has been extended by Todd 7 to include the f corpora quadrigemina ' with the f processus cerebelli ad testes,' and part of the floor of the fourth ventricle. But the developement of the human brain and its several stages, represented by the conditions at which it is arrested in lower vertebrates, show that the transverse commissural fibres which cross or decussate with the intracranial myelonal columns, whether under the name of ' pons,' or ( trapezoid bodies,' or ' arciform fibres,' are subordinate adjuncts to other parts, chiefly the cere- bellum ; while the distinct and superimposed masses called ( cor- pora quadrigemina ' include the true correlatives of the cerebrum and cerebellum, as primary vesicles of the brain. By ( macromyelon,' therefore, I signify the intracranial prolon- gations of the myelonal columns as far forward as their emergence from the ' pons,' or cerebellar commissure : in this tract they are 1 xxi". p. 5. 2 xxir'. 3 xxiii". 4 xxnii". 3 i.". 6 xxvi". r xxvii". p. 084. VOL. III. G 8-2 ANATOMY OF VERTEBRATES. 48 reinforced by masses of grey neurine, and the transverse commis- sural fibres are so intermixed with the longitudinal ones as to compel their being combined in description as in delineation, figs. 48, 56. But, before quitting the Mammalian class, the reduction of the * pons,' concomitaiitly with that of the side-lobes of the cerebellum, as in figs. 51 and 53, is such as significantly to testify against its title to be regarded as a primary division of the brain ; and in birds a ' tuber annulare ' or ( pons varolii,' ceases to appear upon the under surface of the myelencephalous tract above defined. From this tract the cerebral nerves, from the fifth to the hypoglossal or ninth inclusive, arise. In advancing to the formation of the macromyelon growing central tracts of the myelonal columns come to the peri- phery, and push aside the medial tracts on both the ventral and dorsal surfaces. On the former, fig. 48, they decussate, as they appear, at d, and, with a con- tiguous portion of the anterior myelonal columns, b, expand to form the s prepyramidal bodies,' p. The rest of the anterior columns, b, with the contiguous antero-lateral co- lumn, in their course along the macromyelon, are associated with a mass of grey matter oc- casioning a swelling out of the surface, called the ( olivary bodies,' ib. o. A thin layer of superficial fibres which, in lower Mammals with non-prominent ( olives ' pass outward, as a ' trapezoid layer,' in Man curve round the exterior of the olivary prominences, and constitute the ' arci- form fibres,' ib. A. The transverse fibres defining anteriorly the f prepyramids ' and c olives ' increase in mass, from the lowest Mammals ( Orni- tliorhynchus, fig. 51, c, Didelphys, fig. 53, b), to Man, fig. 48, a. As they arch over the fore part of those macromyelonal tracts they have been called ' pons ;' but their true position is that of an inverted or suspended bridge : their developement is in the ratio of that of the side-lobes of the cerebellum. On the posterior or dorsal surface of the myelon the deep- Macrcmiyelon, anterior or ventral aspect. Man, nat. size. MACROMYELON OF MAMMALIA. 83 49 X Macromyelon, posterior or dorsal aspect, with section of cerebellum. Infant, nat. size. seated tracts become superficial at a greater distance from the skull than on the ventral surface, and do not decussate ; they ex- pand as they enter the macromyelon, and form the ' post-pyra- midal bodies,' fig. 49, Y. The posterior myelonal columns which thev / push aside, diverge as they are continued into the macromyelon, and combine with the con- tiguous lateral columns to form the post-resti- form tracts, x. In ad- vance of the post- pyramids, still deeper columns of the myelon come into view, as the ' teretial tracts,' ib. A, F, bounding the sides of the fissure, called 'calamus scriptorius,' at the floor of the expanded macro - myelonal canal called f fourth ventricle.' This is over-arched by the cerebellum, here bisected, and one half reflected at R ; the pe'duncle or ' crus ' of the opposite half being shown at u. The thin layer roofing the ventricle anterior to the crus is called ( valve of Vieussens,' B. Sections of the macromyelon, as at fig. 50, show the form of the grey matter, called ' corpus dentatum,' of the olives, o o, and the relative position of the en- larging columns. Those on each side the fissure A, are the prepyramids ; those on each side the fissure P, are the post-pyramids ; the lateral or restiform tracts intervene between them and the olivary tracts, o. In the Monotremes the macromyelon is large in proportion to the rest of the brain, but the ' pons ' bears relation to the cerebellum in its smallness. The prepyramids, figs. 51 and 52, , are long, narrow, flat, and contract as they Transverse sections of 1,1 n i i the macromyelon, at the approach the pons, especially in the Ormtho- parts marked x and Y i i ,1 i r> r -i r> /* s\ ? fig. 49. Man, nat. size rhyncnus; the olives, fig. 51, , fig. 52, b, are also long and flat, but expand as they approach the pons, and are crossed, before reaching it, by the ' trapezoid ' homologues of the ( arciform ' fibres in Man. The distinction between the olivary and pre-restiform tracts is less marked. The grey matter G 2 84 ANATOMY OF VERTEBRATES. is small in the olivary tracts, and does not form a 'corpus denta- (11111." The pons is Hat, it forms a narrow transverse band in the Side view and base of brain, Ornithorliynchus. Base of brain, Echidna. 53 Ornithorliynchus, fig. 51, c ; these fibres cover a greater antero- posterior extent of the macromyelon in the Echidna, and give the pons a triangular form. In the Opossum the pons, fig. 53, b, is reduced almost to the proportions of that in the Ornithorliynchus ; the prepyramidal, d, and olivary tracts are similar, and the latter are crossed by as well- marked a trapezoid arrangement of trans- verse fibres, c. The prepyramidal tracts come to the sur- face at a greater distance from the pons, in most Mammals, than in Man, and thus resemble more the postpyramidal tracts ; this character is shown in the Horse, fig. 54, Dolphin, fig. 60, b, and Baboon, fig. 62. In the anthropoid Apes, the proportions of the prepyramids (fig. 112, Orang) approach those in Man, and the arciform disposition of the superficial layer of crossing fibres begins to prevail, and to allow the olives, which are likewise here more prominent, to come into view. Although the olives are less prominent in Delphinus than in the Apes, they are equally uncovered by the trapezoid fibres : and show internally the arrangement B:ise of brain, Didelpliys. MACEOMYELON OF MAMMALIA. 85 of grey matter called ( corpus dentatum.' The pons, fig. 60, 5, c, by its prominence and antero-posterior extent, corresponds with the great lateral developement of the cerebellum, e. When the prepyramids, fig. 55, /?, are divaricated in the human macromyelon, the median fissure, which is wider and shallower than 55 al Base of the Brain, Postpontal part of Macromyelon, anterior or ventral aspect. Man, xxxiti". that, c, below the decussation, shows the same cribriform cha- racter of its f floor,' formed by the penetrating vessels from the fold of pia mater which lined it. A further extent of divarication shows transverse fibres uniting the halves of this part of the macromyelon, and decussating with longitudinal fibres, as in fig. 56. The section of the prepyramid on each side of a, fig. 57, shows its triangular figure and the restriction of grey matter to the ' nuclei,' /*, s ; they are mainly composed of white longi- tudinal fibres which enter the pons above its lower or peripheral transverse fibres, and interlace with the fibres of a higher plane : at the entry each pyramid is constricted, as at fig. 56, p, but soon expands. The proportion of the decussating and non-decussating tracts of the prepyramidal columns is shown in fig. 56, where p is part of the right prepyramid cut across near the pons and reflected to show the decussating fasciculus, d, and the non-decus- sating fasciculus, n, continued through the pons, P: the decus- 86 ANATOMY OF VERTEBRATES. sating fasciculus of the left prepyramid is shown at d f . The fibres of the outer white neurine of the olives are longitudinal, and are continued forward above the pens, as shown at f, fig. 66. The nucleus of grey matter sinks deep into the macromyelon, as shown in the sections, figs. 50, o and 57, y ; its section in any direction presents the undulated course of the white capsule suggesting the anthropotomical term 4 corpus dentatum.' The lateral or restiform columns, diverging, as in fig. 49, x, are mainly continued into the cerebellum, of which they form the hinder or f in- ferior peduncle,' fig. 66, r. Recruit- ing grey neurine is developed in their interior. The post-pyramidal columns, contracting as they diverge and ascend, are closely applied to the restiform tracts, but are continued, as the ( fasciculi graciles,' into the crura cerebri. Stilling l has enriched anatomy following magnified view Dissection of macromyelon, seen obUaiiely from the right side. Man, xxxiii". of a transverse section of the macromyelon, one half of which shows the structures as seen by transmitted light, fig. 57. The anterior or ventral fissure, , is here seen to be much deeper than the opposite one, b, represented by the ( calamus scriptorius.' The septum or raphe, c, of the lateral moieties is a compact white neurine ; d, v, are the prepyramidal columns, of which r is the large nucleus, s s the smaller nuclei ; the roots of the hypo- glossal nerve, /, run along the interspace between the pyramids and olives. Of the latter the nucleus is shown at g^ with its plicated capsule of white neurine ; a small mass of grey substance is situated near the olivary one at u ; x indicates grey matter and % gelatinous matter, near the roots of the vagal nerves, k k. The nucleus of the vagus is h, with the root of which nerve is also connected the white longitudinal fibres, m. Whether g be ex- clusively related to the hypoglossal, or is the place of origin (part of the larger root) of the trigeminal, is undetermined ; n is the f soft column,' o the wedge-like column ; f is the nucleus of the restiform body. The transverse or arciform fibres covering this 1 XVIll". MACROMYELON OF MAMMALIA. 87 w. lateral column are marked p, those continued over the olives, and those over the prepyramids, v ; they form the trapezium in lower Mammals. The nucleus in the trapezium, on each side of the raphe, so closely resembles, at a higher section, the olivary body, that it has 57 \v Transverse section of the macromyelon through the lower third of the olivary hodies. Magnified tea diameter*. been termed the ' upper olive ' ; it makes its appearance near where the lower olives first diminish in size. In the Sheep it appears as a group of large stellate multipolar cells, and these cells are more numerous in the Rodents, and still more so in the Cat. In the Rabbit the upper olivary body is convoluted in three or four turns ; in the Mouse it consists of a wavy mass of large and numerous cells ; its structure is especially distinct in the Cat. The f post-pyramidal ' and ( restiform ' nuclei are present in all Mammals. The olivary bodies consist of lavers of small cells / / penetrated by the arciform filaments, by which they are connected with each other and with the raphe ; they are not absent in the Sheep. The transverse section of the human medulla oblongata in the region of the first cervical nerve is more circular, less 88 ANATOMY OF VERTEBRATES. elliptical, than in the Sheep and most lower Mammals. The restiform and postpyramidal nuclei are relatively larger, but the Quad nim ana and Caruivora approach the human structure in this particular; the Cat, e.g., shows an intermediate condition be- tween those in Ruminantia and Bimana. 1 In comparing the macromyelon of the Mammal (fig. 50) and Fish (vol. i. fig. 172) the usual course of structural differentiation seems to be reversed ; a greater number of longitudinal tracts are definable in that of the Sturgeon or Shark than in that of Man. But the superior character is more seeming than real ; the super- addition of ascending fibres in the higher Vertebrate tends to obliterate the boundary lines and seems to blend tracts the i funicular ' and post-pyramidal, e. g. in the Mammal, which are distinguishable in the Fish. 206. Cerebellum. The posterior and restiform columns, pushed aside by the postpyramidal and teretial tracts in ap- proaching the macromyelon, diverge and expand into a fibrous stem, which, arching over the fourth ventricle, developes the central transversely folded lobe, answering to the cerebellum of the Shark (vol. i. fig. 187, c) and Bird, and expands into lateral lobes 58 Vertical section of the median lobe of Cerebellum and Macromyelon. characteristic of the Mammalian class. The myelonal tracts, which in describing the brain from behind forward may be said to enter into the formation of the cerebellum, fig. 66, r, leave it, after some expenditure and exchange of substance, as ' departing ' 1 The progress of chemistry has lent new and valuable aids to the unravelling of the minute, but physiologically most interesting, structures of the myelon and macro- myelon. A solution of chromic acid is one of the best for preliminary immersion of slices of their tissues for a few weeks ; these, if afterwards put into alcohol, are hardened, but become less brittle than if kept longer in the acid. CEREBELLUM OF MAMMALIA. 89 restiform tracts, ib. t, continued into the basis of the mesence- phalon, forming also those called f processus cerebelli ad testes,' united above by the thin layer of medullary matter called ' valve of Vieussens,' fig. 49, B. The progressive increase of the lateral lobes is attended by corresponding developement of the system of transverse or arciform fibres constituting the ' pons varolii,' which, entering the cerebellum at the ' infero-lateral ' or ' sernilunar fissure,' fig. 64, h, i, interblend with the longitudinal ( entering ' and 'departing' columns, and constitute the commissural part of these lobes. In Anthropotomy the part where the formative and commissural tracts join on entering the cerebellum are collectively called its ' cruSj'the tracts being its constituent ( peduncles ; ' thus the enter- ing or posterior and restiform tracts, which are the ' homotypes ' of the ' crura cerebri,' are termed the ' inferior or posterior peduncles,' or ' processus ad medullam oblongatam,' fig. 66, r ; the emerging restiform tracts, called ' processus ad cerebrum,' and ' processus ad testes,' are the ' superior or anterior peduncles,' ib. t ; whilst the entering fasciculi of the ' pontal or varolian com- missure' are the 'middle peduncles' or 'processus ad pontem,' fig. 64, ?'. 'These latter are porportionally least in the lowest, and largest in the highest, species of Mammals. In all, the formative columns on entering the white axis receive grey or ' recruiting ' matter for the developement of accessory fibres, relating in size and com- plexity to the increase of the cerebellum, and chiefly of its lateral lobes. In the Monotremes, figs. 51 and 52, the 'pontal' or cerebellar commissure is a thin layer of transverse fibres of small antero-posterior extent ; the true character of the real ' crura cerebelli,' or formative fasciculi, is here well exemplified. The cerebellum, fig. 38, b (Echidna), consists mainly of the median lobe, which being transversely folded presents in vertical sec- tion that arrangement of grey and white matter called ' arbor vitas.' In the Marsupial Order, the cerebellum presents close-set, sub- parallel, transverse convolutions ; few in the climbing Koalas and Opossums, fig. 46, c, more numerous in the locomotive Kanga- roos : it is remarkable, as in Monotremes, for the large propor- tional size of the median or vermiform lobe as compared with the lateral lobes, especially in the carnivorous and insectivorous Marsupials, where this condition is associated with a corresponding diminution of their commissural band as shown in the view of the base of the brain of an Opossum, fig. 53, b. In the Kangaroos, ANATOMY OF VERTEBRATES. Perameles, Phalangers, and Koala, the hemispheres or lateral lobes of the cerebellum are characterised by a small subspherical lateral process or appendage, , Didelphys, and fig. 75, B, Pliascolomys, in the Marsupial order ; by fig. 79, Lepus, and fig. 80, 8, 9, Cavia, in the Rodentia ; and by fig. 67, Talpa, in the Insecti- vora. Both Z?/- and Liss-enccphala manifest their inferior posi- tion in the present class, and affinity to oviparous Vertebrates, by the larger proportion of the mesencephalon (fig. 46, o) to the pros- enccphulon, than in Gyrcncephala. In most Marsupials (Dasy- urus, fig. 72 ; Didelphys , fig. 73), in many Rodents (fig. 81, Lepus ; fig. 80, Castor), in all Insectivores (fig. 76, Rliynchocyon), and in Bats, the bigeminal bodies are more or less exposed between the cere- brum and cerebellum. As in Amblyopsis (vol. i. p. 278, fig. 175), so in Talpa, the optic lobes, fig. 67, c, do not show a reduction of bulk commensurate with that of the visual organ ; yet there is a de- gree of such relationship in Mammals. Thus the Ungulates which have large eyes have the optic lobes or nates, fig. 68, a, proportionally larger than they are in a Carnivorous quadruped with a similar-sized brain. In both the ' testes,' ib. b, are broader, but in Felis they also rise higher ; whilst in Un- gulates, and especially Ruminants, the 6 nates ' show the greater vertical developement. 1 In all Carnivores the ( testes' have a minor antero-posterior extent than the ' nates.' The white bands or tracts ( f brachia ' in an- thropotomy ), extending along the outer sides of the bigeminal bodies o to the thalami and com- mencement of the optic tracts, fig. 68, d, are prominent in the higher Quadrumana and in Man. In most Gyren- cephala the white fibres continued from the optic lobes develope an oblong nodule, ib. e, also containing grey matter (' corpus geniculatum ' of anthro- potomy), which in the human brain is divided into an external and internal portion. The f crura ccrebri ' formed by the pre- and post-pyramidal 1 This difference I exemplified in the preparations, nos. 1326 A and 1826B, xx. vol. iii. p. 30. Mcsenceplialon, upper view, Horse. PROSENCEPHALON OF MAMMALS. 99 and ' teretial ' tracts, expand in passing beneath the bigeminal bodies, and receive accessions from grey matter continuous with that of the macromyelon, but so dark as to have received the name ( locus niger ' when exposed in section. They are divided by the third ventricle, and swell out respectively at their upper part, through the superaddition of formative neuriiie, into the bodies called ' thalami optici,' fig. 68, c, figs. 71 and 75, t. The free surface is white, but the grey matter constitutes their chief bulk, and is partially divided by the longitudinal fibres into an outer and an inner portion : from the latter the soft commissure is continued. The optic tracts, fig. 68, d, commencing at the optic lobes and geniculate bodies, bend round the outer and back part of the ( thalami,' from which they derive accessory filaments to form the optic nerve. In connection with the mesencephalon must be noted the tract of white fibres continued from the fornix, on each side the third ventricle anterior to the soft commissure, to a nodule, conspicuous in Gyrencephala behind the infundibulum, and forming a pair (' corpora albicantia' in anthropotomy) in Apes, fig. 112, and Man. 208. Prosencephalon. As the 'crura cerebri' enter the pros- encephalou, they are augmented by further accessions of formative neurine in masses which in the human brain have received the names ' nucleus tremreformis,' ( nucleus lenticularis,' and ( nucleus caudatus.' The latter projects into the prosencephalic ventricle, as the ' corpus striatum,' figs. 70, s, 75, r. But this name extends or applies also to the deeper-seated grey masses, w r hich are so in- terblended with the diverging white fibres as, in section, to give alternate white and grey strias. The accession of white fibres from these formative nidi, diverging to form the basis of the cerebral hemispheres, causes the form expressed by the term 6 fibrous cone,' fig. 66, c. The grey matter again appears as a thin superficial covering or ( cortex ' of the expansion of the white fibres : and this grey matter contains cells similar to those in the corpus striatum. In most Ly- and Liss-encephala, and in a few of the smallest kinds of Gyrcncepliala, the prosencephalic vesicles retain the out- ward uniformity of surface which they have in birds and reptiles : unlike those of the mes- and ep-encephalon, they are so little united together that they are called and seem to form distinct ( hemispheres.' These are connected together in all Mammals as in Birds by the cord-like fasciculus of transverse fibres, figs. 69 and 73, c, called e anterior commissure.' But the main dis- tinction lies in the superaddition to the ( diverging ' or ' crural ' H 2 100 ANATOMY OF VERTEBRATES. fibres of other t commissural ' tracts either ( longitudinal.' con- O * necting parts of the same hemisphere, or ' transverse,' and bringing a greater proportion of the two hemispheres into mutual com- munication. But there are steps in this differentiation. Eacli hemisphere of the cerebrum begins as a vesicle of neurine, the cavity of which receives the growth from the ' crura ' forming the ' corpus striatum.' This, in Birds, mainly fills the ( ven- tricle ' or remnant of the primitive cavity of the sac. But, in Mammals, the w r all of the vesicle is augmented bv folds, of which CJ * the first and most constant is pushed from the mesial or inner side of the ventricle into its cavity, giving rise to the convexity, figs. 70, 71, h, fig. 75, n, representing the part called ( hippo- campus ' in anthropotomy, The ( fissure upon which the hippo- campus is folded ' 1 is numbered 4 in the ' Table of Cerebral Fissures,' p. 136, as in fig. 69, et seq. In Lyencephala it extends from the fore part of the inner sur- face of the hemisphere backward and downward in a curve with the concavity toward the centre or ' nucleus cerebri,' fig. 69, b. It is not, however, a mere doubling of the wall of the hemispheral vesicle ; longitudinal fibres are de- veloped therein for commissural office ; they cause a definite production of the lower part of the fold within the ven- tricular cavity called hippocampal band (t&nia hippocampi}, or, because in Man it is plaited, ' corpus frmbriatum : ' its im,er surface of hemisphere, vertical m f er ior hinder termination is in the section of brain, Ormthorhynchus. ' pes hippocampi ; ' its upper or anterior one becomes the ( posterior pillar ' of the fornix. ( Fornix ' is the anthropotomical term for the anteriorly continued and transversely connected longitudinal fibres of the hippocamp : the ' posterior pillars,' fig. 69, a, one from each hemisphere, converge as they advance, are united by a commissure of their own, ib. o, beyond which some fibres pass forward and radiate upon the inner surface of the fore part of the hemisphere ; while others bend down, as the f anterior pillars ' of the fornix, pass between the anterior commissure, ib. c, and the nucleus cerebri, b, and terminate in the mammillary body already mentioned. Delicate fibres, running on the inner surface of the hemisphere at right angles to the line of the hippocampal fissure, are con- tinued into the ventricle, where they cover the longitudinal fibres 1 So defined in i.xx'. p. 90 (1837) PROSENCEPHALON OF MAMMALS. 101 developed in the hippocampal fold,, and which form the main part of the hippocamp and its anterior extension. 1 This fold and its concomitantly developed longitudinal and transverse or arched fibres, constitute a great and abrupt dis- tinction and rise in structure in the Mammalian brain as com- pared with the Avian one, and indicate that birds are an offshoot from the lower Ovipara, forming a branch apart. 2 In Ornithorhynchus the postero-inferior parts of the hemispheres are brought into connection with the antero-internal parts by the longitudinal fibres, while the antero-internal parts of the hemispheres are connected with each other through the transverse fibres at the approximated anterior ends of the folds, where the stratum connecting those ends together, and radiating the fibres upon the inner surface of the anterior lobes of the hemispheres, and over the inner wall of the ventricle, is thickest. 3 The greater part of the hemispheral cavity or ventricle is overarched in Lyenccphala by the inner leaf of the hippocam- pal fold, and its developements called ' trenia hippocampi ' and 6 fornix.' The transverse fibres connecting the taenia hippo- campi and terminating that body anteriorly in Lyencephala, are carried, in the ascending Mammalian series, by the growth of the hemispheres anterior to them, as it were by a movement of rotation, from before upward and backward, until, in Man, they become the ' psalterial fibres ' which connect the posterior ( genu ' of the corpus callosum with the ( trenia hippocampi,' these being compared to the ' frame ' and the transverse fibres to the 6 strings ' of the harp, by the old anthropotomists. The super- addition of cerebral matter above and anterior to c, figs. 69, 73, is associated with transverse commissural fasciculi, progressively added, from behind forward, and now overarching the lateral ven- tricles, and fulfilling all the functions, relations, and definitions of the anthropotomical 'corpus callosum,' figs. 78, /, and 123, c. Its hind part is embraced by the ( callosal convolution,' ib. o. 4 1 These fibres are shown at x, fig. 4, pi. vii. LXX'., which gives a view of the hippo- campal fold from the ventricular or 'lateral' side, as ' part of a thin stratum of medul- lary fibres arching over the hippocampus major, and continued therefrom into the internal wall of the ventricle,' p. 95. 2 If we could examine the brains of Dinosauria or Dicynodontia, the actual gap in the series of cerebral structures might be better filled. 3 From this point in the lowest (Lyencephalous) mammals, as in the embryo of the highest, the growth of the great supraventricular body of transverse commissural fibres forming the ' corpus callosum ' begins : ' Anterior fibres of the " tasnia hippo- campi v continued into the anterior lobes of the hemispheres.' LXX'. p. 95, pi. vi. figs. 4 and 6, o'; and pi. vii. fig. 4, x. 4 The part marked B in the Echidna has become the part marked N in Man. Pis. xxxvi. and xxxviii. of XLIII". 102 ANATOMY OF VERTEBRATES. 70 Lateral ventricle, Echidna. Such urc the essential characters of the Mammalian ( prosen-- cephalon.' The chief modifications of the Mammalian brain, as above characterised, will next be noticed in the different leading groups of the class. A. Lyencephala. In the Ornithorhynchus, the brain, figs. 52 and 69, is to the weight of the body as 1 to 130 ; the hemispheres arc triangu- lar, depressed, the broader posterior part over- lapping the optic lobes, and reaching to the cerebellum. With the exception of the hippo- campal fissure, fig. 69, 4, and the depression lodging the rhinencephalic crus, the surface is unbroken or smooth, with a few vascular im- pressions diverging from the fore part. The medulla oblongata is broad and depressed ; the corpora pyramidalia, fig. 5 1 , a, are in very low relief ; the corpora olivaria, a, expand as they advance ; they are crossed anteriorly by the ' corpora trapezoidea,' b, which are large ; the ' pons,' c, is narrow : anterior to it is a large ganglionic body, c', from which issues the husje trigeminal nerve, 5. The longitudinal groove be- o o * o o 71 tween the optic lobes is shallow ; it is wanting in the small and IOAV ( testes.' The hippocampus is the chief prominence within the ventricle of the hemisphere ; the corpus striatum is long and narrow. The brain of the Echidna, fig. 71, is relatively larger than in the Ornithorhynchus y and the exposed outer surface of the hemispheres is extended by con- volutions. The cerebral hemi- spheric cavity is mainly occupied in both Monotremes by the ' hip- pocamp,' fig. 70, h, which con- stitutes a great part of its floor as well as inner Avail. This, with much of the hippocamp, is removed in fig. 71, to show the proportions of the 'corpus stria- turn,' 5, and to bring into view the thalami, t ; these are divided from the ' nates,' r, by a linear groove ; the ( testes,' s, are half the size of the f nates,' and the median longitudinal groove, which is shallow between the nates, is not continued further liralu and lateral ventricle, hippocampus removed Echidua. PROSENCEPHALON OF MAMMALS. 103 back. 1 Like the water-shrews, the Ornithorliynchus has a smooth cerebrum; the JEchichia, like the Great Ant-eaters and the Sloths, has a convoluted one. Besides the long and deep ( hip- pocampal fold,' the fore part of the mesial surface shows a beginning of the supercallosal one ; behind which it is also notched vertically by the mesial ends of the upper transverse folds, 2 fig. 71. Of these, three nearly parallel ones extend across the broad posterior part of the upper surface of each hemisphere, their outer ends inclined forward ; anterior to them is a larger convolution bent upon itself so as to form the inner boundary of the anterior half of the upper surface. In the angle of the above are two oblique folds inclining ( mesiad ' toward the contracted fore part of the hemisphere. The base of the brain, fig. 52, shows a few short foldings of the surface of the great natiform protuberances, b'. The principal folds sink about a line's depth into the substance of the cerebrum. The rhineiice- phalon is enormous, ib. R. Some of the fibres of the great anterior commissure bend forward, and are continued into each of its crura. The outer part of the crus, ib. i , continued from that of the prosencephalon, emerges from the fore margin of the natiform protuberance, from which it has a reinforcement of fibres ; the inner division, tumid with added grey neurine, ib. i b, is also very broad. The prosencephalic cavity or ' ventricle ' is con- tinued into the rhinencephalon, and is exposed in fig. 52, by re- moval of the thin floor which rests upon the large 6 cribriform plate.' The ( pineal ' and pituitary (ib. p) appendages of the prosencephalon offer no monotrematous characters. There is not that difference of size between the Ornitho- rliynchus and Echidna which would lead us to connect therewith the convolution of the hemispheres in the latter animal ; what is known of their habits suggests no superiority of psychical power and resource in the land- over the water-monotrematous Insectivore. Increased extent of the walls of the hemisphere in no 1 My observations on this state of the ' corpora quadrigemina ' in Monotremes accord with those of Laurent and Eydoux on the Echidna, and of Meckel on the Ornithorhynchus. ' En comparant les tubercules quadrijumeaux de 1'Echidne a ceux de 1'Ornithorhynque, nous avons facilement constate ce que 1'a deja ete par Meckel pour ce dernier, c'est-a-dire qu'on ne peut pas distinguer les tubercules posterieurs des anterieurs, et que ce que Meckel a remarque chez 1'Ornithorhynque et exprim6 en ces termes : " Eminentia quadrigemina magna, posterior tamen vere percipienda, ut fere bigemina esset," est encore plus prononce dans les tubercules du cerveau de 1'Echidne, qui sont reellement bijumeaux simplement.' LVII". p. 164. - Well given in LVII". pi. ix. fig. 4 : omitted ill the diagram of a similar section in XLIII". pi. xxxvii. fig. 7. 104 ANATOMY OE VERTEBRATES. degree influences the developement of a supraventricular trans- verse commissure ; the seeming small one exposed at o, fig. 7 1 , is hippoc'ampal or psalterial. This low phase of Mammalian brain- growth is essentially related to the common monotrematous con- ditions of generation. The brain bears a small proportion to the body in the Marsupial order; in the Ursine Dasyure, fig. 72, it is as 1 to 520; in the Wombat, as 1 to 614; in the great Kangaroo, as 1 to 800. In smaller Kangaroos the disproportion is less ; thus in the Tree- kangaroo (Dendrolagus inustus) I found it as 1 to 250. The brain is relatively largest in the smaller species of Petaurists and Phalangers. The cerebral hemispheres do not extend over the cerebellum in any of the species, and in some, as the Dasyures and Opossums, they leave the optic lobes exposed. In the Phalangers and Petau- rists, the Opossums, Perameles, the insectivorous Phascogales, and the smaller Dasyures, the exposed surface of the cerebral hemispheres is unconvoluted. In the Dasyurus ur sinus, fig. 72, b, this surface is broken by a few slight indentations, two of which may indicate the beginnings of the ( medi-lateral ' longitudinal folds. In the Wombat an ectorhinal fissure bounds the outer side of 72 the olfactory tract at the base of the brain ; ! from the anterior moiety of this fissure three or four smaller ones curve up- ward upon the sides of the hemispheres, one of which answers to the ' fissura Syl- vii,' 2 but is less defined than in the Kan- garoo. On the upper surface a short transverse fissure marks off the outer part of the anterior lobe of the cerebrum, and behind this each hemisphere exhibits a few detached shallow fissures. The American Opossums show a range in size from that of a mouse to that of a cat, and the Australian Dasyures rise from the same diminutive extreme (Antechinus pusillus] to the size of the wolf ( Tliyla- cinus). But the cerebral hemispheres are as smooth in Didel- pliys Virginiana* as in D. (Philander, Microdelphys) murina\ and the great Ursine Dasyure, fig. 72, shows but a few short and shallow indentations of the exposed cerebral surface. 4 Thylacinus 'd Brain of Dasyurus ursinus. . i.xx' pi. v, fig. 8. 2 Ib. fig. 3. 8 Ib. fig. 6. 1 Ib. fig. 5. PKOSENCEPHALON OF MAMMALS. 105 73 B Didelphys Virginian;!. has the anterior apex of the hemisphere marked off by a deeper transverse fissure, extending to the inner surface. In the Her- bivorous Marsupials the fissures are more definite, deeper, and rather more numerous in the larger (Macropus major, fig. 74) than in -the smaller species (Hypsiprymnus). All Marsupials have the hippocampal fissure, fig. 46, 4, fig. 73, z, coextensive with the antero-posterior range of the prosencephalic cavity, and arching over all the commissural apparatus of the hemispheres. The concomitant extent of the convolution (hippocampus major) is shown in LXX'. pi. vii. figs. 3 (JDidelpliys) and 4 (Macropus), in the exposure of the ventricle from the outer side. In Didelphys, fig. 73, the surface of the hemisphere above the fissure is feebly impressed by blood-vessels ; in Tltylacinus there is a short fissure above the back part of the hippocampal one ; in Phascolomys and Macropus there is also an anterior one which bends or bifurcates at its fore part. 1 These fissures mark the level of the roof of the lateral ventricle ; the surface below forming the thin mesial o wall of the cavity, fig. 75, q, which in the higher Pla- centals is defined, as the ' sep- tum lucidum,' by a corpus callosum from the part above, On the upper surface of the hemisphere, in Macropus ma- jor, a longitudinal part of the fissure, fig. 74, s, marks off a medial convolution, /, at the anterior half, and occasion- ally it is prolonged backward by the fissure, 10, as in the left hemisphere of fig. 74. But there is continued from 8, in both hemispheres, a fissure extending outward, which bounds behind the part of the hemisphere impressed by the ( sylvian fissure,' 5. The 74 1-2 Brain of Macropus major. 1 LXX'. pi. vi. figs. 4 and 6, The Aye-aye agrees with the Lemurs and Aye-aye. all Quadrumaiia in this respect ; the homology of b, fig. Ill, with the basirhinal fold, figs. 52, U ' , 82, k, in Ly- and Liss-encephala, is masked by such interruption of the fissure, 2, in Quadrumana. In Lemur proper the lateral fissure (between I and c/, fig. 116) is shorter than in Chironujs and is not distinct from the supersyl- ..vian : in some species it bends outward more abruptly, in so far marking more plainly the coronal fissure, 12, as in higher Quadru- mana, and indicating a longer anterior lobe than in Chiromys : a frontal fissure, 14"', appears there. In the main we recognise in the cerebrum of Chiromys and Lemur, as in that of Carnivora, the primary division of the upper mass of the hemisphere into sub- parallel folds, medial, /, medilateral or supersylvian, n, and sylvian, e ; but, shorter and more bent as they recede from the middle line ; with indications of a longer anterior lobe or tract. The hippocampal fissure is prolonged into a f post-hippocampal,' fig. 110, 4', as in higher Quadrumana. In the diminutive Platyrhine (Midas, GeofFr., figs. 109, 116) the smoothness of the upper surface of the hemisphere is broken only by the extension thereon of the sylvian fissure, 5. In the next stage ( CaUithrix) a ' postsylvian fissure,' ib. 9, is added, and the hemisphere may also show a longitudinal fissure, fig. 116, 8, 12, curving, like the supersylvian, over the end of the sylvian, n, and postsylvian, 9, fissures ; but which, in relation to tH inter- hemispheral fissure, corresponds rather with the lateral fig. 89, n, of Carnivora : the large anterior tract may show a short frontal fissure, fig. 104, H'". In all the small Platyrhines (Midas, Calli- 1 cir. This has also the character of the ' supcrcallosal,' 7', fig. 117. 126 ANATOMY OF VERTEBEATES. Ill thriz, fig. 109) the sylvian fissure, 5, and fold, e, are directed more obliquely from above and behind, downward and forward, than in the Aye-aye, ib., and most Lemuridaj : this character appears to be due to the preponderating growth of the frontal lobes, and becomes more marked as the Quadrumana rise in the scale. AVe next find that each hemisphere is divided into an anterior, middle, and posterior tract or region by two deep and extensive fissures, 12 and 13, Macacus, fig. 109, and Cebus, fig. 116, which, from their respective correspondence in position with the coronal and lambdoidal sutures, bear the same names. In Cebus the sylvian fissure, fig. 116, 5, is overarched by a subangular one defining the fold, g ; from the angle a fissure, 13, extends to the inter- hemispheral one, and is continued deeply down the inner or mesial surface. Out- wardly the lambdoidal fissure, 13, defines and undermines a posterior part of the hemi- sphere, by raising w^hich the continuation of the postsylvian fold, jf, may be traced beneath it. The chief difference between the cata- rhine and lemurine hemispheres, at the inner surface, is the superaddition and interposition of the entolambdoidal fissure, is', between the post-hippocampal, 4', and marginal or super-callosal, 7',fig. 117; the entolambdoidal being sometimes continued into the post- hippocampal fissure, as in fig. 118, is' 4'. The almost transverse fissure, fig. 116, 12, di- vides the larore anterior from the middle lobes. CJ In the latter, however, may be recognised the short tract, I, w, combining the ( medial ' and ' medilateral ' folds, but more transversely disposed than in Carni- vora ; pushed out, as it were, by the backward growth of the anterior lobe. Secondary fissures there indicate frontal, n, mid- frontal, n" ', and superfrontal, n f , folds. One or two longitudinal occipital fissures mark out corresponding folds, q" ', q" f . The ecto- rhinal fissure, fig. 111,2, sinking into the sylvian one, 5, may have a continuation in the anteropostcrior fissure, ib. 2', which divides the ' natiform protuberance' into a medial or basirhinal, b, and a lateral moiety, f . In most Catarhines the coronal fissure, 12, figs. 114, 116, extends, from within, more obliquely forward and outward; the homologues of the platyrhine fissures and folds are clearly seen, as marked by the figures and letters in Macacus and Cebus, Under surface of cerebral hemi- sphere, Mitcacus. PROSENCEPHALON OF MAMMALS. 127 112 fig. 116. Secondary fissures subdivide the orbital as well as the frontal and falcial surfaces of the anterior lobe : the surface resting on the orbital plate of the frontal bone, in the Orang's brain, fig. 112, shows the following con- volutions : ( postorbital,' o, mid- orbital, o', entorbital, o", ect- orbital, o' f , and antorbital, o*. That which lies external to the rhinal fissure or depression is not subdivided into ectorhinal and entorbital folds as in Man, fig. 120, d, o". Similar secondary chinks furrow the occipital lobe, on the tentorial surface of which the tentorial fold, fig. Ill, r, the entotentorial, r', and ecto- tentorial, r" , are now defined by the fisSUreS, 18, 18', IS''. These Base of the I,., Orang-utan. folds are more or less continuous with the basirhinal, b, and sub- sylvian, f, tracts. The increasing number of secondary fissures ..and the greater depth and more winding course of the pri- mary ones mainly characterise the brain in the Orang (vol. ii. fig. 148) and Chimpanzee, fig. 114. The tract between the interhemispheral and supersylvian fissures is subdivided into medial, /, medilateral, m, and supersylvian, g, folds, fig. 116, Chimpanzee : we have evidently here the corresponding parts of the hemispheres that form these folds, or parts of them, in Carnivora. D. Archencephala. The same principle carried abruptly to an extremely greater degree, as in figs. 115, 116, Homo, associated (as compared with Gorilla, e. g.,) with a greater proportional bulk of the brain to the body, and with a still greater proportional size of the cerebrum to the rest of the brain, characterise the Archencepha- lous subclass, from the lowest varieties (Australian, Boschisman, Hottentot) to the highest. These proportions have thoroughly stood the severest tests, as where the diminutive female in such varieties has been selected to exemplify the brain-characters, with a view of reducing the chasm between the gyr- and arch- encephalous brains to a minimum. Before entering into the details of the complex convolutioual surface of the human cerebrum, I may premise some recapitu- latory remarks. 128 ANATOMY OF VERTEBRATES. c We are guided to the homologous parts of the cerebral hemi- spheres throughout their range of dev elopement in the Mammalian class, in a great measure, by their relations to other parts of the bruin. The portions more immediately surrounding the cerebral crura, 1 those which overarch the corpora striata and thalami and overlie the olfactory crura, or at least their beginnings, can hardly be doubted to be corresponding parts in all Mammals. The inferior prominences behind the " crura rhinencephali," forming the " protuberantias natiformes" of some anthropotomists (Z/ basi- rhinal fold), the inverted hippocampal fold, its labia and fissure, are plainly determinable throughout the class, as is also the pylvian fissure, 5, somewhat less constant, dividing the part of the hemisphere terminated by f, figs. 113 and 115, and sometimes called (i inferior lobe," from the part which is in front of it : the superaddcd cerebral substance to the above more constant parts of the hemispheres is that which, in Man, advances, overlaps, and extends beyond the olfactory lobe, and that which extends backward in like relation to the cerebellum. ( If one can predicate homology of any folds or fissures of the cerebral superficies, throughout the Mammalian class, it must be at the above-defined middle part of the more developed hemispheres, and especially at those fissures, viz. 2, ectorhinal, 4, hippocampal, 5, sylvian, 7, callosal, 7' ', supercallosal, that are the most constant throughout the series. The upper surface of the hemispheres, as we have seen, is subject to different ways of folding : in Echidna the plaits go across, in Fells along it, while in Bos and Slmia they run askew, yet contrariwise ; in one from behind forward and inward, in the other forward and out- ward. It may seem, to some, that each leading division of Gyrcncepliala should have its own system of nomenclature and symbolism of brain-folds that homologous convolutions can only be satisfactorily determined within the limits of such groups as Unfjidata, Unguiculata, Quadrumana. In a degree this is true ; the grounds of homology are such in regard to some folds (& and 7') as to leave room for difference of choice ; but there are others that have a surer basis for homologising. Take, for example, the " sylvian fissure," 5 : the fold e, that immediately overarches and forms it, is determinable : one part of the fold forms the anterior, the other the posterior, lip of the fissure : they are united or continuous by the overarching part in most Unyuiculates and Ungulates. The homology of the sylvian fissure and fold is not 1 Subsequently defined as ' prosencephalic.' PROSENCEPHALON OF MAMMALS. 129 cbscured by the minor intersylvian convolutions, which are ex- posed in the Sheep and Elephant, and are concealed in higher Quadrumana and Man, where they constitute the " gyri breves " of Arnold ; l nor is that of the anterior lip by the interruption of the ectosylvian fissure, s', in the Cat, fig. 91, whereby the sylvian is divided into parallel vertical folds, which, w T ith the intervening sylvian fissure, are overarched by the higher supersylvian fissure, ib. 8. In Quadrumana the posterior part of the supersylvian fissure, fig. 109, 8, sometimes runs into one, 9, behind and parallel with the sylvian, 5. In Stenops the detached " post-sylvian," 9, is short and straight, as in the Cat. 6 In the Marmozets (Midas, Geof. Hapale, Bl. Jacclius vulgar is} the sole superficial fissure on the exposed surface of the hemi- sphere is the sylvian, figs. 109, 116, 5, and this determines the con- tiguous part of the hemisphere, e, to be the homologue of the sylvian fold. When the postsylvian fissure appears, as in CaUitlirix, fig. 109, 9, the postsylvian fold, /, is defined : it is certain that we now have the homologues of the folds so named and numbered in Unsmiculates, ficrs. 90-92 ; and the advantage O J O ' O of their determination would be lost were we to apply new names to these folds and fissures as if they were distinct and superadded parts in the quadrumanous and bimanous brains. The next fissure which appears, in the Quadrumana., answers to that marked n, 8, in Putorius, fig. 87, which is longitudinal and bends more or less outward anteriorly : it divides, in fig. 116, Callitkrix, 8, the cerebral surface above the sylvian and postsylvian fissures lengthwise, into two pretty equal tracts, and tends to mark off an anterior part or lobe of the hemisphere. ' Proceeding with the more typical Quadrumana, we find that the progressive expansion of the cerebrum, which has carried it backward over the cerebellum, and augmented the outward and downward extension of the part behind the sylvian fissure, has also added so much to the anterior lobes as seems to have pushed backward the rest of the hemisphere, and gives the sylvian, e, and postsylvian, f } folds a more oblique direction from above, downward and forward, than in most low r er Unauiculates. In the Otter, indeed, and Lion, the sylvian and presylvian fissures are similarly oblique : but the posterior part of the sylvian fold does not project outward so far beyond the anterior part as in Quadrumana : this development, together with the interruption of the supersylvian fissure, and the extension of secondary fissures at right angles and anterior to the sylvian fissure, tend O O v IX' VOL. III. K 130 ANATOMY OF VERTEBRATES. to mark the homology of the forepart of the sylvian fold in Quadrumana. Its upper part is now defined from the forepart or " anterior lobe " of the brain, by the fissure 12, figs. 109, 116, which, instead of being continued with or from the longitudinal one, as in Lemur, fig. 116, 8, extends from without, obliquely inward and backward, to or near to the interhemispheral fissure. It is that which, from being first well defined by the Italian anatomist } in the human brain, has been called " fissura Rolandi," but which I term " coronal," or " coronal part " of the medilateral fissure, in Ferines, figs. 88-92, 12.' In the side view of the human hemisphere, fig. 115, the fissures are indicated as follows: 2, ectorhinal, external to the cms rhinencephali, it is longer and more conspicuous in the lower Mammals, fig. 107, 2, 5, sylvian, 8, supersylvian, 9, postsylvian, 9', subsylvian, 12, coronal, 1.3, lambdoidal, 14, frontal (or post- frontal), u 7 , superfrontal, u", midfrontal, 14"', subfrontal, 14 X , ectofrontal, 17, occipital (or superoccipital), 17', exoccipital, 17'", ectoccipital. The folds or convolutions are : - - d, ectorhinal, e, sylvian, /, postsylvian, f, subsylvian, g, supersylvian, /, medial, m, medilateral (/ and m, as in Quadrumana, are less distinct from each other, as well as shorter and more oblique, than in Garni- vord), n, frontal (or postfrontal) n f , superfrontal, n" ', midfrontal, ft" 7 , subfrontal, n* , ectofrontal,^, lambdoidal, q, superoccipital, , lambdoidal, q, occipital, q", suroccipital, q"' ', suboccipital. The primary fissures on the internal (mesial) surface of the hemisphere, fig. 118, are 4, hippocampal, with its long bifurcate ir Vertical section, brain of Baboon. posterior extension, 4', 7, callosal, 7 X , supercallosal, 6, marginal, 1 13 7 3 entolambdoidal, here continued into the posthippocampal ; the supercallosal fissure, 7', bifurcates anteriorly, as inPapio, fig. 117, /' and Pithecus (vol. ii. fig. 149). The surface applied to the fore part of the falx is impressed by falcial, 1.3, and subfalcial, \z>' ', 1 This is seldom so distinct or continuous as in the larger ungulates. K 2 132 ANATOMY OF VEBTEBRATES. fissures, more or less parallel with ?'. The principal folds defined by the above fissures are : a', posthippocampal, k, callosal, //, supercallosal, //, marginal, h', postmarginal, t, falcial, t', subfalcial (which is the inner surface of c, entorhinal), ;/, entolambdoidal, .s-, septal. Anthropotomists have primarily divided the hemispheric masses 118 Vertical section, half nat. size, Human Brain. XL". into groups of convolutions or ' lobes:' some into three, viz., the 6 anterior,' e middle,' and ( posterior ' lobes ; others into five. These latter are termed f central ' (lobus centralis), ' frontal ' (lobus frontalis), ' parietal ' (lobus parietalis), ' temporal ' (lobus temporalis}, ' occipital ' (lobus occipitalis}. The central lobe (' Stammlappen,' Huschke) answers to the f Insel' of Reil, and is not visible outwardly; it includes the ( gyri breves,' and is, by some, held to be peculiar to Quadru- mana and Bimana (but see figs. 117, 11 8, /',/*'). The ( frontal lobe,' fig. 119, r, includes so much of the anterior lobe as lies in advance of the ( frontal fold,' n, n, and is subdivided above into the superfrontal, n' 9 midfrontal, n" ' , subfrontal, n f " ', ectofrontal, ?i x , and ' prefrontal,' % x x , folds : it is an artificial division of the part, most naturally defined, both in Quadrumana and Man, by the coronal fissure, 12, from the rest of the hemisphere. PEOSENCEPHALON OF MAMMALS. 133 The f parietal lobe,' P, includes the frontal fold, ?i, n, the anterior and superior parts of the sylvian, e, and supersylvian, y, folds, with the medial, /, and medilateral, m, folds. The ( temporal lobe,' T, in- 119 eludes the posterior part of the sylvian fold, the postsyl- vian, and subsylvian folds, fig. 115, f,f, and also part of the supersylvian fold, g. The l occipital lobe,' o, is a more natural division, includ- ing all the part of the hemi- sphere which lies behind the lambdoidal fissure, is. The anterior lobe has three surfaces, one applied to the calvarial part of the frontal bone, another to the orbital plate, a third to the falx. Each of these are impressed by secondary fissures, which I have called ' frontal,' ( or- bital,' and ( falcial,' accord- ingly. The frontal fissures mainly affect a longitudinal direction, but run behind into a transverse one. This is the * frontal,' or ( postfrontal,' fig. 119, u ; it is more or less extensive and parallel with the coronal fissure, ib. 12. The Constant OI tlie lOngltU- superior surface of the right hemisphere of the adult fisSlireS pretty equally human brain, two-thirds nat. size. bisects the frontal surface; it is the ( midfrontal ' fissure, fig. 116, 14"; the fissure above or internal to it is the ( superfrontal,' u', that beneath or external is the ( subfrontal,' fig. 115, 14 /X/ ; beneath this again and upon the outer and back part of the frontal lobe is a deep and constant longitudinal fissure, usually bifurcate, the ectofrontal, ib. 14 X . The fissures on the orbital surface present much analogy to the frontal ones. The posterior one is transverse and usually curved with the convexity forward ; it is the orbital or postorbital, fig. 120, 16 ; the most constant of the longitudinal fissures which 134 ANATOMY OF VERTEBRATES. 120 extend forward from the orbital one, I call ( midorbital,' ib. 1 6' ; that to the inner side is the entorbital, IG"; that to the outer side, the ectorbital, IG'" ; a transverse fissure anterior to these is the antorbital one, u x . The ccto- and ento-rhinal fis- sures, 2, 3, distinct posteriorly, run into each other where they form the groove lodging the slender ' crus rhinencephali ' of the human brain. The cerebral folds thus marked out arc the entorhinal, c (which is the un- der surface of the subfalcial, fig. 118, t') 9 the ectorhinal, d, which, in Ly- and Liss-ence- phala, Unyulata, and most Car- niuora, is continued backward, uninterruptedly, into the basi- rhinal tract, b ; external to d, fig. 120, are the postorbital, o, midorbital, o', entorbital, o", ectorbital, o f " ', antorbital, o x . The postorbital tract passes backward into ' Reil's Island.' The ectorbital, 0"' menyes into * * o the ectofrontal. rc x , fio*. 119, of ** * O ? which it may be called the un- der surface : attention has been called to the coincidence of loss or defect of speech with lesion in that fold or locality of the brain. 1 The tracts connecting some of the folds of which the homology with those of lower mammals is determinable, are noted, in anthropotomy, as ( annectant gyri ' (' plis de passage,' Lix"). On the falcial surface of the frontal lobe the most constant fissures are two that aifect a longitudinal course ; the upper one, which seems to be a continuation of the ( marginal ' fissure, is the * falcial,' fig. 118, 15 ; the parallel one below is the i subfalcial,' is'. ^The posterior lobe of the hemisphere, marked off by the lamb- doidal fissure, 13, has three principal surfaces : one applied to the superoccipital plate, one applied to the falx, and one resting on the tentofium. 1 LXXH" and LXXUI". Under surface of hemisphere, human cerebrum. PPvOSENCEPHALON OF MAMMALS. 135 121 On the occipital surface are several but irregular fissures, which, from their position, may be termed mid-, super-, ent-, and post-occipital; they define, more plainly in Quadrumana than in Man, the lambdoidal, fig. 119, p, suroccipital, q", midocci- pital, q f , suboccipital, q"' ', and postoccipital, q*, folds. On the tentorial surface they affect a longitudinal wavy course, and are commonly three rn number; of these, the middle one is the e tentorial' fissure, fig. 120, is, the inner one the ( entotentorial,' ib. is', the outer one the ' ectotentorial,' is". On the surface next the falx, or septum dividing the hemispheres, fig. 121, the fissures have a radiating tendency from the anterior angle outward : the most constant and important of these, in Man, has already received the name of ' posthippocampal,' being a con- tinuation of that deep fissure the corre- sponding fold of which partly protrudes into the posterior horn of the ventricle, as the ' hippocampus minor ;' the rest I called ( septal ' fissures, reserving the term f falcial ' to those on the corre- sponding surface of the anterior cerebral lobe. The fissure above the ' posthippocampal ' is the ' septal ' fissure, 19; that beneath the posthippocampal is the ( subseptal,' i^' ; the fissure between the septal and entolambdoidal, is', fis- sures is the superseptal, 19'; their outer ends are frequently lost in a fissure following more or less extensively or interruptedly the posterior contour of the posterior lobe; this is the postseptal fis- sure, i'/"; it is peculiar to Man. The folds so defined on the sep- tal surface are : the entolambdoidal, p' 9 superseptal, s' ', septal, s, posthippocampal, a', subseptal, s" ', and postseptal, s'". The human brain, in its development, passes through stages in some degree like those which are permanent in and characteristic of the Quadrumana, in respect to its cerebral folds and fissures ; but it early manifests its distinctive archencephalous proportions, fig. 109, Foetus. About the twentieth week the fissures begin to ap- pear upon the upper surface of the hemispheres, fig. 116, three months' Foatus. After the ( hippocampal ' and 4 callosal ' have cleft the inner surface, and the ( ectorhinal ' and ( sylvian ' the under sur- face, the entolambdoidal ascends upon the mesial side of the upper surface (fig. 116, 13); the postsylvian, 9, appears; then a faint trace of the longitudinal fissure, fis;. 116, 14', indicative of the ~ ' O ' J midfrontal and ectofrontal tracts. The ( coronal,' fig. 113, 12, is Inner or septal surface of posterior lobe, human cerebrum. J36 ANATOMY OF VERTEBRATES. speedily followed by the f postsylvian ' 9. A more or less inter- rupted fissure divides lengthwise the sylvian or supersylvian fold, ib. g, from the median, /, and medilateral, m, tracts. The lamb- doidal fissure, 13, extends toward the outer part of the hemisphere : the pre-coronal tract of brain is fissured into subdivisions, chiefly longitudinal : the foetal brain, at seven months, figs. 1 13, 1 16, resem- bles, in superficial cerebral marking, that of the latisternal apes,ib., Chimpanzee, but is broader anteriorly, deeper and longer behind. In the foregoing summary we have seen that the fissures which break the surface of the mammalian brain are of different kinds, degrees, and values. Some, in the course of development and elevation of the primary masses, divide one from the other ; as the cerebrum from the optic and olfactory lobes, the cerebrum from the cerebellum, and this from the macromyelon. Some subdivide primary masses into symmetrical halves, as e.g., the inter-hemispheral fissure, the inter-olfactory fissure, and the shal- lower indent between the mammalian optic lobes or ' nates.' One or two fissures of the cerebrum make folds that project into the hemispheral cavity or ventricle, e. g. the hippocampal and, in Man, the posthippocampal : most are confined to its crust or wall, and of these, as I showed in 1833, some, from their relative con- stancy, depth, and symmetry, may be termed * primary,' while others are of ( secondary ' or inferior rank. The following are those which are noted by figures in the illus- trations of the present work :- CEREBRAL FISSURES, in the order mainly of their constancy in the Mammalia. Figures. 1. Interhemispheral. 2. Ectorhinal. 2'. Basirhinal. 3. Entorhinal. 4. Hippocampal. 4'. Posthippocampal. 5. Sylvian. 6. Marginal. 6'. Post marginal. 6". Prcmarginal. 7. Callosal. 7'. Supercallosal. 8. Supersylvian. 8'. Ectosylvian 9. Postsylvian. Figures. 9'. Subsylvian. 10. Medilateral. 1 1 . Lateral. 1 2. Coronal. 13. Lambdoidal. 13'. Entolambdoidal. 14. Frontal or Postfrontal. 14'. Superfrontal. 14". Midfrontal. 14'". Subfrontal. 14 X . Ectofrontal. 1.5. Falcial. 15'. Subfalcial. 16. Orbital or Postorbital. 16'. Midorbital. Figures. 1 6". Entorbital. 16'". Ectorbital. Antorbital. Occipital orMidoccipital. Superoccipifal. Entoccipital. Ectoccipital. Postoccipital. Tentorial. Entotentorial. Ectotentorial. Septal. Supcrseptal. Subseptal. Postseptal. 16* 17. 17'. 17". 17'" 17 X . 18. 18'. 18". 19. 19'. 19". 19'" The following are the cerebral folds which are indicated by letters in the illustrations of the present work, with the synonyms of original labourers in this field of anatomy :- PROSENCEPHALON OF MAMMALS. 137 GRATIOTLE. LIX". Partie anterieure du grand marginal. Orbital interne. Pli parietal ascendant. Pli temporo-sphenoidal. d d o N3 8 f 1 ^3 i-H P. H ' S . "^ c5 c3 r^ i ' jj Lobule quadrilaterale. Pli du corps calleux. Deuxienie pli parietal ascendant, et Stage superieur du grand marginal, ib. Premier pli parietal ascendant. Frontal superieur. Frontal moyen. Frontal inferieur. Orbital posterieur. ib. inoyen. ib. intenie. ib. exterue. Premier pli de passage externe, ou Stage superieur du lobe occipital. Pli interne du lobe occipital. Pli superieur du lobe occipital. Occipital moyen, et second pli de passage ext. Occipital inferieur, ct troisieme pli de pus- sage externe. Pli temporal inferieur. Pli temporal moyen anterieur. Pli temporal inferieur. Lobule occipital, ib. Pli temporal moyen anterieur. *c3 '> M 03 g a a (H bo d 2 LEUKKT. XL". Lobe d'Hfppocampe. in. P. Troisieme circonvolution postei'ieure. Crochet. *t* * Circonvolution d'enceinte de la scissure de Sylvius : its hind part is (in Man) . . i. P. Premiere circonvolution superieure. ii. P. Seconde circonvolution postirieure. in. P. Troisieme circonvolution posterieure. *** A. Partie interne de la troisieme circonvolu- tion anteiieure. I. Circonvolution interne qui se contourne sur le corps calleux. Circonvolution de I'ourlet, Foville. s' (and part of) circonvolution transverse medio-parietale. ib. s Premiere circonvolution supCrieure . in. A. Troisieme circonvolution anterieure. ii. A. Seconde circonvolution anterieure . I. A. Premiere circonvolution anterieure . f-t -t-> c/] a . . . . c "p m o o 1 ... 3 o J-. . .0 . I-H . - 1 , ^ CO r Q\ SH c3 . . > "T 1 b O> >> CJO .^3 DO "i o "^ . "3 2 . * cristato : gyrus fornicatus, Arnol< B.H S ^ ' ' ' S 3| 1 .2 | g 3,93 3 X " M |gh. s 1 .'5 ^ *~^ ^^ 'i-H 1 <3 O O ra tn Ili.i -i ...1 11 III L * fl a ^ 0> ^ .... C o a, i-4 to 'r cs'Co.s S 2 I ;i o Si I c2 Sg -g-3 o ' '45^ c3 >> c3 L ? uJ rb Cu p .0 O 5o ii ^ | -| fi o g Supersylvian . h Marginal Ou ( |"3 |l k f Supercallosal ."os ,2 n Frontal (or post-fi n' Snperfrontal n" Midfrontal . n f " Subfrontal . n* Ectof rental, r I _. Cg r* _ 2 fto ri -C-S SHO-^IS -3 S^S.S Ii It'll aslls Is I'll"! w S P ^ ^> =-

^ > - 1 ^ "rf '-2 ^ "S '? '2 3 3 '> % 1 -^ '3 IIHlll ||| * ^ ^ ^ -. ^ s q" Suroccipital q'" Suboccipital q* Postoccipital r Tentorial r Entotentoria] r" Ectotentorial s Septal . s' Superseptal s" Subseptal a/11 T5,N, J.-1 138 ANATOMY OF VERTEBRATES. Each hemisphere is a bag of neurine folded or laid upon its expanding stem, the hollow of the bag being the ventricle. This, in the embryo, is capacious and simple, the wall being very thin. It becomes thickened in different degrees at different places, most so at the upper and outer sides. The wall, thus thickened, pro- trudes at certain parts into the cavity, dividing and shaping it into parts or recesses which Anthropotomy calls ( horns,' from their curvature in Man. In lower Mammals the primitive cavity com- monly retains more of the general shape of the hemisphere, and in most Quadrumana, the lower more especially, the part accom- panying the broad supracerebellar expansion of the hemisphere is of corresponding capacity. The Orang, among Apes, still shows the primitive character of this part of the ventricle : in the Chimpanzee and Gorilla the growing walls reduce and begin to shape it as a f horn,' showing also a beginning of a protu- berance within it. In Archencephala the moulding of the ' pos- terior horn ' is completed by the predominance of the internally protruding wall ( : partie enroulee,' Leuret), to which, now, the term ( hippocampus minor,' or ' pes hippocampi minor,' rightly applies. 1 The fibres of the stem, augmented in number at each accumulation of grey reuniting matter, diverge into and form the main part of the wall in greatest proportion in the Lyen- cepliala. The stem or ' crus ' is formed by the prepyramidal tracts, fig. 66, ]), the olivary tracts f, the teretial and postpyramidal tracts, fig. 49, Y, and so much of the cerebellar tracts, fig. 66, t, as may not have been expended in the formation of the ( nates,' b, ( testes,' n, ( geniculate bodies,' y, and their common basis. Thus the crus or stem of the hemisphere includes tracts of the myelon, connected respectively with the sensory and motory roots of the nerves. The part of the ' crus proseiicephali,' below or in front of the ( locus niger,' consists of white fibres in a coarsely ( fasciculate ' arrangement, fig. 123, d: the part above, derived from the tere- tial, postpyramidal, and cerebellar tracts, is softer, with mixed grey matter, and forms the f tegmentum,' ib. c. The fasciculate fibres, after passing through and being reinforced by the grey matter of the striated body, diverge in curves, fig. 66, c, fig. 122, s, 1 The judicious and painstaking anatomist GRATIOLET seems to have foreseen some late misconceptions of the nature of the hind part of the primitive ventricular cavity in the Quadrumanous brain, in the following note : ' Toutefois, il ne peut etre considere comme un signe A' elevation, car il est beaucoup plus grand en egard a la partie enroulee du ventricule dans les singes, ou son developpement est enorme, que dans I'homme, ou la partie enroulee 1'emporte evidemment sur lui. Cette remarque,' he justly adds, ' est d'une haute importance.' XL", vol. ii. p. 75. PROSENCEPHALON OF MAMMALS. 139 of which many bend downward and outward, suggesting the term ( fibrous ' or e radiated ' cone ; in Man they are traceable chiefly in the sylvian, postsylvian, entosylvian, supersylvian, medilateral, medial, and marginal folds, and into the major part of those of the anterior lobe, fig. 122, a. The tegmental or posterior fibres are, in Man, more directly connected with the transversely arched 122 Dissection of cerebrum and cerebellum, from the outer side, xxxiii". fibres of the great commissure : others, diverging to the posterior lobes, e, b, become connected or continuous with the longitudinal commissural system of the fornix. Figure 123 is a dissection of the inner surface of the hemisphere, c is the section of the corpus callosum, the fibres of which diverge upon the roof of the ventricle, intersecting the radiating fibres, fig. 122, s, and passing into all the folds, which are thus brought into communication with those of the opposite hemisphere. The fibres of the f callosal ' fold, fig. 123, o, o, are chiefly longitudinal, are continued behind, into those of the hippocampus, and in front into those extending from the fornix upon the falcial surface of the anterior lobe : externally 140 ANATOMY OF VERTEBRATES. they form the ( superior longitudinal commissure,' fig. 122, o ; and fibres are traceable from both extremities to the ( perforated space,' figs. 82, 120, x. The dissection, fig. 122, shows also the longitu- dinal fibres extending from the anterior to the inferior and poste- rior lobes, and forming the e external longitudinal commissure,' c, above which are seen part of the radiating fibres, s, interlacing with those of the corpus callosum, c ; which is overarched by the outer- most of the superior longitudinal commissural fibres, o. Above Dissection of the left hemisphere of the brain, from the inner side, xxxni". these are shown the fibres which mainly form the convolutions, but which include not only the ( radiating ' fibres, but those of the f transversely commissural' and 'longitudinally commissural 'kinds: they terminate in or blend with the grey matter which forms the outer crust of the hemisphere. In a section of this substance in a recent brain, a white line is seen to separate it into two layers, as in fig. 124. More closely scrutinised, the following strata have been defined from the surface downward : a thin superficial white layer, a thick reddish grey layer, the intermediate white layer, a thicker grey layer, a third thin white layer, and the deepest grey layer receiving the radiating fibres of the white or medullary cere- bral neurine. 1 1 In the contemporary Reports of my Hunterian Course of Lectures, 1842, the chief conclusions of the comparative anatomy of the superficial grey substance in PKOSENCEPHALON OF MAMMALS. 141 124 Section of grey and white neurine of prosencephalic convolutions. Man. The anterior commissure --the most constant of the trans- verse system is relatively largest in Lyencepliala., figs. 69, 73, c. In the human brain a similar transverse section of it shows its insignificant dimensions, fig. 123, a. Traced trans- versely, in them, it passes, as in a special canal, across the lower part of the corpora striata, bends backward, and expands as it radiates into the middle of each hemi- sphere. It indicates the small part of the human cerebrum which is homolo- gous with the main part of that of birds and marsupials. But the increase of the mammalian over the avian brain begets the added structures for asso- o ciation of added parts, already de- scribed. In Man, each anterior pillar of the fornix, after leaving the ' tha- lamus,' descends and is bent upon itself before ascending, the bend projecting at the base of the brain, behind the ( infundibulum,' as the ' corpus albi- cans,' or e mammillare,' fig. 128, m. In the Lissencephala, where a corpus callosmn is first esta- blished, it might seem, in a dissection from below, that the outer fibres of the ' radiating cone ' curved over the lateral ventricle, and were constricted lengthwise as they ran into each other across the interhemispheral fissure, as in the dissection of the Beaver's brain, fig. 78 : but it is deceptive. There is no actual continuity of any of the ascending radiating fibres of the crus cerebri with those which spread out in transverse curves from the corpus callosum. The two systems are everywhere closely inter- laced; but the fibrous character of the commissural series is lost, mammalian brains was summarised by the Eeporter for the ' Medical Times/ as fol- lows : 'A symmetrical arrangement, more or less regular or complex, can always be traced between the foldings of the two hemispheres, and the more regular in propor- tion to the simplicity of the convolutions : the foldings of the cerebral substance iollow likewise, both in the embryonic development of a complex brain, and in the progressive permanent stages presented by the mammalian series, a regular determi- nate law: some convolutions being more constant than others, and these being trace- able through the greatest number of brains, and recognisable even in the human brain, where, at first sight, they are obscured by so many accessory convolutions.' ' The Lecturer then demonstrated, in a considerable number of prepared brains of different animals, and in a large series of diagrams, in which the corresponding con- volutions in the brains of different animals were marked by the same colours, the facts establishing this important generalisation.' The Medical Times, Nov. 12, 1842, vol. vii. p. 101. Report of 13th Lecture, delivered May 16th, 1842. 142 ANATOMY OF VERTEBRATES. under the microscope, before it quits the ventricular wall to descend, -with the radiating fibres, into the crus. From this stage in the mammalian series the great transverse commissure grows with the growth and complexity of the hemisphere. It consists mainly of white or fibrous neurine, but some grey matter ( f nucleus lcnticularis')is superadded to the inferior fibres external to the radiated cone, and between this and the ' island of Keil ' there is also a thin layer of grey neurine (' nucleus tamire- formis '). Always maintaining its closest connection with the part of the fornix called e lyra,' or hippocampal commissure, whence its development began, the increasing body of transverse fibres extends forward and upward, with a bend or ( genu,' fig. 123, C, O, corresponding in extent with elevation and expansion of the front lobes of the cerebrum. In Man its narrow anterior beginnino; is O o connected by the ( lamina cinerea ' with the optic commissure, receives a small part of the grey substance of the thalamus, and sends off two bands, called ' peduncles of the corpus callosum,' which, diverging, pass backward across the ( perforated space ' to the lower part of the sylvian fold. The corpus callosum, expand- ing as it rises, bends backward, and presents on its upper surface a medial longitudinal groove, called ( raphe,' bounded laterally by the white f strire longitudinales : ' it terminates behind in a slightly down-bent, thickened, free border or ' pad.' Some way in advance of this the attachment of the under surface of the corpus callosum to the fornix begins, and, as the hemispheres increase in the pla- cental series, so does the extent of the filmy inner walls of the lateral ventricles (' septum lucidum,' Anthro.,fig. 123, b) between the body of the fornix and the great superadded transverse com- missure, the fibres of which extend over the roof of those ventricles. The most intelligible illustrations of the comparative anatomy of this interesting part of the cerebral structure is obtained by dis- secting and exposing the lateral ventricle from the outer side, as in the views of the brains of the Opossum, Kangaroo, and Ass, showing the relative proportions of the hippocampus, and of the part of the inner wall distinct therefrom, called ' septum lucidum,' in LXX', pi. vii. In fig. 5, the vascular fold of pia mater called ( choroid plexus ' is shown passing beneath the fore part of the f taenia hippocampi ' through the canal of communication between the lateral ventricles, in both marsupial and placental brains. The supraventricular neurine, being folded upon its stem, the cavity is a reflection of the external surface, and is lined by a continuation of the pia mater, although the fissure by which it SIZE OF BRAIN IN MAMMALIA. 143 enters the ' ventricle ' becomes contracted to a very small extent of the base exterior to the cms. From this point begins the fold extending, as ' choroid plexus,' from one ventricle to the other by the fissure called e foramen Monroianum ' in Anthropotomy. On the interior surface of the hemisphere the pia mater is reduced to an epithelium, the cells of which are less flat in the lateral ven- tricles than in that continuation therefrom called ' third ventricle.' The part of the interhemispheral fissure overarched by the great transverse commissure is the ' fifth ventricle. ' For other dif- ferentiated and definite parts in the archencephalous brain the subjects of the ( bizarre ' nomenclature of Anthropotomy reference may be made to the minute and exact monographs which have been published on that part of the human structure. 209. Size of Brain.- -The brain grows more rapidly than the body, and is larger in proportion thereto at birth than at full growth. But there is a difference in this respect in different Mammalian orders. The brain of the new-born Marsupial is less developed relatively than in higher Mammals, and grows more gradually or equally with the subsequent growth of the body. 1 So, in the degree in which a species retains the immature character of dwarfishness, the brain is relatively larger to the body : it is as 1 to 25 in the pygmy Petaurist, but is as 1 to 800 in the Great Kangaroo ; it is as 1 to 20 in the Harvest Mouse, but is as 1 to 300 in the Capybara ; it is as 1 to 60 in the little two-toed Ant-eater, and is as 1 to 500 in the Great Ant-eater. The brain weighs 6 grains in the Harvest Mouse (Mus messorius), and the same in the Common Mouse (Mus musculus)', but the weight of the Harvest Mouse is 112 grains, whilst that of the Common Mouse is 327 grains. The brain of a Porpoise, 4 feet long, may weigh 1 Ib. avoird. ; that of a Whale (Bal&nopterci) 100 feet in length does not exceed 4 Ibs. avoird. 2 In Artiodactyles the brain of a pygmy Chevrotain ( Tragulus pygm&us) is to the body as 1 to 80; in the Giraffe 3 it is as 1 to 800. In Perissodactyles the brain of the Hyrax is as 1 to 95, whilst that of the Indian Rhinoceros is as 1 to 764. 4 The brain of the Elephant may be three times heavier than that of the Rhinoceros, but a full-grown male would probably weigh down four Rhinoceroses. In Car- nivora the brain of the Weasel is to the body as 1 to 90 ; in the Grisly Bear it is as 1 to 500 ; in Quadrumana the brain of the 1 LXXV', p. 347, pi. vii. figs. 9-12. 2 SCORESBY, in a Balcena mysticetus of 65 feet in length, found the weight of the brain to be 3 Ibs. 12 oz. 8 xcvii-. 4 v". 144 ANATOMY OF VERTEBRATES. Midas Marmoset is to the body as 1 to 20 ; in the Gorilla it is as 1 to 200. But such ratios do not show the grade of cerebral organisation in the Mammalian class: that in the Kangaroo is higher than that in the Bird, though the brain of a Sparrow be much larger in proportional size to the body : and the Kangaroo's brain is superior in superficial folding and extent of grey cerebral surface to that of the Petaurist. The brain of the Elephant bears a less proportion to the body than that of Opossums, Mice, and proboscidian Shrews, but it is more complex in structure, more convolute in surface, and with proportions of pros- to mes-encephalon much more nearly those in the human brain. The like remark applies to all the other instances above cited. The weight of the brain, without its membranes, in a full- grown male Gorilla is 15 oz. avoird. I estimate that of the entire body as being nearly 200 Ibs. : in the relatively larger brains of the small species of Quadrumana the convolutions are feAver, or may be absent, as in Midas. In Man alone is a bulk of body, greater than in any Quadru- mana save Gorilla, associated with a large size as well as with the highest stage of complexity of the cerebral organ. This is, perhaps, the most notable and significant fact in Comparative Anatomy. The weight of the brain in the adult male averages about 49 oz. avoird., and ranges from about 35 oz. to 65 oz. In the adult female the weight of the brain averages about 43 oz. and a half, and ranges from 32 to 54 oz. The mean difference is thus about five ounces and a quarter. The brain has advanced to near its term of size at about ten years, but it does not usu- ally obtain its full development till between twenty and thirty years of age, and undergoes a slight decline in weight in advanced life. 1 The brain, without dura mater, of an Australian female, of 5 feet 3 inches high, weighed 32 oz. ; that of a Bushwoman, 5 feet high, is estimated, in Lin", 2 at 30*75 oz. In European females the brain has been found as low in size ; but the requisite observations to determine the range and the average of cerebral development have hitherto been made only on Europeans. 3 The weight of the brain of the male Hottentot. 3 Ibs. 2 oz. avoird., c3 " dissected by WYMAN/ encourages the expectation of analogous 1 If the capacity of a cranium in cubic inches be ascertained, a fair and instructive notion of the weight of the brain may be obtained by estimating that of a cubic inch of it at 259-57 grains. 2 LVJII '. 3 XLIX", L", LXI". 4 LYIII". MEMBRANES OF BRAIN IN MAMMALIA. 145 results. The human brain is exceeded in weight by that of the Elephant and the Whale, but is absolutely heavier than in all other animals. In the proportionate size of the cerebrum to the cerebellum the human brain surpasses that of all Mammalia : it is as 8 to 1. The brain in some individuals distinguished for intellectual power has been found of unusual size, and remarkable for the number and depth of the cerebral convolutions : the brain of Cuvier weighed upwards of 64 oz. The superficies of the cerebrum of the mathematician Gauss was estimated by "Wagner at 341 square inches, while that of an ordinary wage-man was 291 inches. We know not the size of brain in the Melanian inventor of the ' throwing-stick,' or of that of the deductive observer of the pro- perties of the broken branch bent at the angle of the ( boomerang.' Such benefactors of their race were, perhaps, as superior to ordi- nary Australians in cerebral development, as the analogous rare exceptions in intellectual power have been found to be among Europeans. l 210. Membranes of the Brain. The encephalon, like the myelon, is immediately invested by an areolo-vascular tunic called ' pia mater : ' it adheres to and follows all the foldings of the surface, is continued into the ventricles, and there forms processes called f velum interpositum' and ' choroid plexus.' It is the area on which the vessels undergo the requisite degree of diminution for penetrating the cerebral substance ; and, when with- drawn, the proportion of such vessels pulled out of that substance gives the flocculent appearance of the inner surface of the mem- brane which Anthropotomy calls ( tomentum cerebri.' The movements of the brain are served by a delicate serous sac, called the ( arachnoid.' The outermost membrane, called 6 dura mater,' adheres to the inner surface of the cranium, and consists of a dense inelastic fibrous tissue. It sends a process or duplicature inwards between the cerebrum and cerebellum called ( tentorium,' and a second between the cerebral hemi- spheres called ( falx.' In the Ornithorhynchus a bony plate extends from the cranium into the falx (vol. ii. p. 323, fig. 204, B). A ridge of bone extends a short way into the ten- torium in some marsupials : it is thin in Kangaroos and Phal angers, thick in Thylacines, but of less extent here than in the Wolf, (vol. ii. p. 504). In the Cachalot a bony plate projects from the 1 Tables of size and weight of Mammalian brains will be found in xn, XLI xii". VOL. III. L XXXIl" 14G ANATOMY OF VERTEBRATES. superoccipital into the back part of the falx 1 : the tentorium re- ceives a bony plate in many Delphini. 2 In Seals both the tento- rium and hind part of the falx are ossified, and a thick ridge enters the fore and under part of the falx between the rhinencc- phalic fossa). The tentorium is ossified in the Carnivora to the extent, and in the families, noted in vol. ii., where the conditions of such bony plate are discussed at p. 506. 3 A short tentorial ridge projects anterior to the cerebellar fossa of the petrosal in Lemur macaco.* The tentorial margin of the petrosal is slightly produced in Cebus, and to a greater extent in Aides. In other Quadrumana, as in Man, the sole ossification co-extended with any part of the dura mater is that called * crista galli ' in Anthropo- tomy. An unossified process from the middle of the posterior border of the tentorium, extending from the internal occipital crest, projects into the notch between the hemispheres of the human cerebellum, and is termed ' falx minor ' and f falx cerebelli.' 211. Nerves of Mammals. The olfactory nerves are absent in all the Cetacea save those with baleen, in which they are few and small; they are present in all other Mammals, and are sent oft in greater number from their cerebral centre the rhinencephalon than in lower Vertebrate classes. 5 The Ornithorhynchus is the 1 XLIV. p. 442. Ib. No. 2500, p. 453. 3 A more extensive scries of comparisons of the interior of the skull has tended to rectify the physiological view entertained at the period of the publication of the posthumous edition of the ' Lcgons d' Anatomic Comparee,' of Cuvier, vol. ii. p. 290 ; vol. iii. p. 155. 4 XLIV. p. 722. 5 Anthropotomists still describe the connections and course of the ' crnra rhinen- cephali ' as the origins of the olfactory nerve ; although they recognise that, ' unlike other nerves, a large proportion of grey matter is mixed with the white fibres,' &c. (LXII". vol. ii. p. 583, 186G), and might rectify the notion by many weightier anatomical conditions. Some even maintain the view by such remarks as the following : ' As it is known that in the first development of the ear the peripheral part or vestibular expanse, as well as the rest of the acoustic nerve, is originally formed by the extension of a hollow vesicle from the first or hindmost foetal encephalic compartment, so in the case of the crus cercbri, although the peripheral or distributed part (crus rhinencephali or olfactory nerve) is of separate origin from the hemispheric bulb, this latter part is comparable in its origin with the acoustic vesicle.' I have paraphrased the argument of the editors of LXII" (vol. ii. p. 584), to show that development, as a vesicle in connection with nervous centres, is no ground of homology or homotypy. Whenever a false homology has to be maintained, the earliest and obscurest phenomena of embryonal development are usually resorted to in support of such view. The terminal expansion of the acoustic nerve is in an organ Avhich begins as 'a follicle or hollow vesicle;' the terminal expansion of the optic nerve is also in a vesicle; arid the true olfactory nerves expand terminally on what began as a follicle or vesicle, which form is retained, little altered, in Fishes. The vascular pituitary membrane supporting that expansion is the homotype of the choroid supporting the retina. No doubt the cerebellum is at first a vesicle, as is the optic lobe, and the hemisphere, and the olfactory lobe ; and each may claim to be regarded as the NERVES OF MAMMALIA. 1-17 sole known instance of the olfactory nerve quitting the skull by a single foramen, as in Birds and Lizards (/. e. one from each rhiii- encephalon). In the Echidna the contrast in the vast number of nerves and the concomitant extent of the f cribriform plate ' is extraordinary. Those from the grey tract proceed to ' Jacob- son's organ.' The number of olfactory nerves and extent of the pituitary surface on which they spread is very great in Marsupials. In the Insectivora the Hedgehog is most remarkable in this respect. Both Herbivorous and Carnivorous Gyrencephala have numerous olfactory nerves : some of the Phocidce show this character in excess. The number of the olfactory nerves decreases, with the diminished size of the rhineucephalon, in Quadrumana, up to Man, where they seldom exceed twenty in number, and are least in proportion to the size of the body. They become flattened and expanded where they spread upon the vascular pituitary mem- brane. The optic nerves are smallest in the Moles ( Talpa), largest in the Giraife. They arise from the bigeminal bodies, chiefly from the nates and optic thalami, in Lyencephala and in some Lissence- phala, to which origin are superadded in other Lissencephala and in Gyr- and Archencephala, fibres from the corpora geniculata, along the tract marked d, fig. 68. In the groups in which the eyes are relatively largest, Unyulata and Rodentia, e. y., the larger proportional size of the homologue of the optic lobes, fig. 68, , is significant of its important relationship with the origin of the nerves of vision : the ( thalami ' do not show the like increase ; their larger size in Quadrumana and Bimana relates more to their function as recruiting ganglia of the prosencephalon. The optic nerves, never- theless, seem to be derived more wholly from the ' thalami ' in Man than in most lower Mam- mals, whence the Anthropoto- mical name of those parts. This character is shown in the foetal brain at the fourth month, fig. 125, where c shows the optic tract quitting the thalamus, e the OptlC lobe, J 3 haS not yet origin of optic nerves. Fcetal brain at four months. undergone its subdivision into ( nates and testes.' The liberated nerves bend downward and homotype of the eye-ball, on the ground taken, in LXII" for viewing the olfactory bulbs as nerves, and not as encephalic lobes. The grand old anatomists had truer views of these ' processes of the brain,' as on some other points, than their successor? L 2 14S ANATOMY OF VERTEBRATES. 126 a - Optic cliiasma ; Man. ecu. 127 forward,, converging and meeting beneath the brain at their con- fluence, called ' cliiasma opticum,' a, b. The fasciculi of primitive fibres arc here arranged as shown in fig. 126. The outer ones, b, pass onward to form the outer side of the nerve a, the middle fasciculi cross the cliiasma obliquely, and, after decussating the corresponding fasciculi of the other tract, contribute to the formation of the opposite nerve : the inner fasciculi curve across the back part of the cliiasma, and are continuous with the corresponding fasciculi of the opposite tract, being strictly ( commissural : ' a similar arrangement prevails with a few fasciculi at the fore part of the cliiasma. The hinder commissure is more common, and appears as a little trenial border of the cliiasma, in some Mammals, down to the rodents. Pathology gives evidence of a partial decussation, in some instances, as in the preparation, fig. 127 ; in which the right optic nerve, a, was atrophied ; the left one, by healthy ; with a partially wasted left optic tract, c, while the right, d, retained more of its normal size. 1 The Mammalian chiasma ceases to show the laminated arrangement (vol. ii. p. 122, fig. 47) common in Birds and Reptiles. The nerve, beyond the chiasma, has a strong iieu- rilemma, which sends processes from its inner surface : in some, e. g. Cetacea, converging as lon- gitudinal septa from the circumference to the centre of the nerve ; in most forming longitudinal canals for the neurine, and giving it the character of a cylindrical aggregate of tubes. This is enclosed in a sheath of dura mater, extending to the sclerotic, into which it is partly continued, where the nerve pierces that coat of the eye-ball. Another peculiarity is seen in the small artery running along the centre of the nerve, and ramifying upon its terminal expansion as the f arteria centralis retinas.' Atrophied right optic nerve and tract ; Human, ecu. 1 There have been cases, however, where the tract of the same side as the atrophied nerve showed more wasting than that of the opposite side. NERVES OF MAMMALIA. 14D In some Marsupials the optic nerve grooves the orbito-sphenoid, escaping by a cleft continuous with the fissura lacera anterior 1 : in higher Mammals the nerve escapes by a special ' foramen opticum.' The extra-cranial parts of the nerves are remarkably long in Whales, 2 and in all Cetacea they diverge from the chiasma 1-28 Base of human brain, with origins of nerves ; half natural size. at a wide angle, fig. 60, 2, 2. This becomes less open as the Mammals rise to Man, fio\ 128, b. ? ^5 3 The oculo-motor or 'third' nerve, fig. 60, 3; fig. 128, c, and 1 XLIV. pp. 323, 329. 2 xoiv. p. 387. ]50 ANATOMY OF VERTEBRATES. the * fourth,' fig. 128, c/, have the same origin, distribution, and connections with the sympathetic, as in Man. The branch of the ' third ' nerve, which runs along the lower part of the eye-ball, between the 'inferior' and ' external' rectus muscles, and supplies the ' obliquus inferior,' is connected, usually by a short thick cord, with a ' lenticular ganglion ; ' but this is not so well defined in some Mammals, and the ciliary nerves are usually feAver than in Man. The ( fourth ' nerve supplies the ' obliquus superior ' muscle. In the Sheep this nerve receives some branches from the ophthalmic division of the ( fifth ' nerve. Besides the ( rectus ex- ternus,' the sixth nerve, fig. 128, f, in most Mammals, supplies an additional muscle, the ( retractor oculi.' The ( fifth ' or ( tri- geminal' nerve, fig. 128, e, e', is commonly the largest of the cerebral nerves, and resembles the myelonal nerves, fig. 136, in having a gaiiglionic, fig. 230, 9, 10, and a non-ganglionic, ib. n, portion, the latter being ( motorj,' supplying muscles, the former distributed to sensitive and secerning surfaces. This distinc- tion is better marked in Mammals than in Birds and Reptiles : like which, however, the ganglion is single, not divided, as in most Fishes (vol. i. figs. 201, 202). The size of the 'fifth' nerve relates to the perfection or sensitiveness and application of those surfaces, not to the proportion of the facial to the cranial part of the head. Thus we find the fifth or trigeminal nerve of largest relative size in the Ornithorhynchus paradoxus, which uses, like the duck, its beak as a tactile instrument in the detec- tion of its food. Emerging from the ganglion, fig. 51, o ', anterior to the pons, ib. c, it soon divides into three branches, the first and second appearing as one. The first and smallest division divides into two equal branches : the superior or ethmoidal branch enters the nose, combines, in part, with the olfactory, for the service of the pituitary membrane ; but mainly emerges from the nasal cavity, supplies the skin at the upper part of the face, and, by a branch continued from between the nasal and premaxillary bones, is distributed to the nostrils and contiguous integument. The second division of the fifth is two lines broad and one line and a half thick : after emerging by the foramen rotundum, the chief part of it passes through the ant-orbital canal, and divides into two branches, distributed, the one to the nasal or upper parietes of the face, the other to the lateral or labial integuments. The palatine branch divides into a posterior smaller nerve, which passes through the posterior palatine foramen : the anterior and larger branch emerges from the anterior palatine canal, and supplies Jacobson's organ at the floor of the nose and the palatine membrane. NERVES OF MAMMALIA. 151 The third division of the fifth is broader but thinner than the second ; it leaves the cranium by the foramen ovale, and is distri- buted as usual, mainly to the sensitive labial integument of the lower jaw, fig. 3, , a : its non-ganglionic part goes to the mandu- catory muscles. In the Echidna the triffeminal is of smaller size, and its first O ' and second divisions are much less in proportion to the third, which supplies, from its ganglionic part, the sensitive and secreting surface of the long tongue. This size of the lingual branch of the trigemmal is still more marked in the Pangolins and Ant- o o eaters, especially in Myrmecopliagajubata. A distinct gustatory nerve, communicating with a motory ( facial ' nerve by a ' chorda tympani,' is a mammalian characteristic of the trigeminal. In the Hedgehog the nasal branch is the largest of the first division : after dismissing a few ciliary nerves it quits the orbit and enters its special canal at the fore part of the large cribriform plate, and divides on entering the nasal cavity into the external and septal branches, the latter being the largest, and richly spread upon the pituitary membrane of the septum and inferior turbinal. The 129 Lower jaw of the Porcupine (Ilystrix uristata). bulbs of the vibrissre in the Hedgehog and other Insectivora use a large proportion of the facial branches of the maxillary and man- dibular divisions of the fifth. In Rodents the dental branches of these divisions are large, and especially the nerves sent therefrom to the active and persistent pulps of the scalpriform incisors ; and they show, especially in the mandible, a recurrent course, as I found in the dissection of the Porcupine, fig. 129, *L l The nasal and labial nerves are large in Moles and Shrews, especially the long-snouted kind {Rhynchocyori). But the chief peculiarity of 1 xx. vol. i. p. 103, prep. no. 357B. 152 ANATOMY OF VERTEBRATES. the triovniinal in Talphlcc. is the share which the ophthalmic divi- sion of the 4 fifth ' takes in the function of the reduced eye-ball, as ]1>0 a warner of light. In fig. 130, a is the trige- ininal, b the ganglionic part, c the third or mandibular division, f the second or maxillary division, d the first or ophthalmic division, of which the branch going to the eye, e, is large, while that going to the nose, g, is small, reversing the proportions in the Hedgehog. In many Lisse?icephala the part to which the root of the trigeminal can be traced makes a small prominence on each side the fore end of the ' calamus scriptorius.' In the Elephant the superorbital and superficial nasal branches of the ( first ' division, but more especially the ' facial ' branch of the ( second ' division, which emerges from the antorbital foramen, present a large size in relation to the proboscis. The size of that foramen is not, however, always indicative of that of the nerve. In many Rodentia a part of the masseter traverses, with the antorbital nerve, the foramen in question, which is, then, enormous, as in figs. 234, 238, 241, v (vol. ii. p. 377). The dentary branch of the maxillary exceeds that of the mandibular division of the fifth in the Elephant, to meet the demands of the persistent matrix of the tusk. But this difference in the size of the nerves supplying the upper and lower jaws is maximised in the Balcenidce, in relation to the active and extensive growth of baleen in the upper jaw, and the absence of teeth or their substitutes in the lower jaw. The palatine nerves supplying the baleen-pulps are as thick as the finger in Balana mysticctus. In the Porpoise (Phoccsna) an orbital branch joins a plexus near the fore part of the orifice of the eye-lids, sent off from the ( seventh ' or facial nerve, from which union branches pass to the muscles and membrane of the blow-hole. The maxillary brunch sends off a ( subcutaneus mala?,' which combines with the facial nerves to supply the inferior palpebral muscle, and spread upon the hind part of the palpebral opening. There are five or six antorbital branches which run forward between the maxillary periosteum and the superincumbent muscular and tegumentary layer, emerging to spread upon the latter where it forms the upper lip or margin of the mouth, and also sending a recurrent branch to the blow-hole. A large branch of the maxillary passes Trigcmin.nl nr-rve of Jlole. LX1U". NERVES OF MAMMALIA. 153 through the foramen near the upper opening of the nasal passao-e, and ramifies upon the plicated membranes of the blow-hole. The dental nerves are large from both maxillary and mandibular divisions of the fifth : the gustatory branch is, relatively, small ; and sends off a filamentary ' chorda tympani,' which may be traced to the trunk of the facial, and is connected, in its course, with the carotid plexus of the sympathetic. In Ruminantia the first division of the ( fifth ' subdivides into frontal and nasal : the latter supplies the upper part of the septum and the superior turbinal, and sends a few branches to the fore part of the nose, which meet these filaments reflected from the second division of the fifth. The branches to the lacrymal and harderian glands, to the eyelids, and the larger one which passes out of the orbit to the integuments of the temple, and which chiefly supplies the horn-core, or the growing antler, may be traced back distinctly to the Gasserian ganglion. The second division of the fifth, escaping by the foramen ro- tundum, sends antorbital branches to supply the upper lip, the nostril, and the pituitary membrane at the lower part of the nose. It also sends off the lateral nasal, receiving the ( vidian ' nerve, and supplying the inferior turbinal : lastly, the ( palatine ' and upper dental nerves. The ganglionic part of the third division gives off the ' buccal nerve,' connected with an ' otic ganglion,' supplying the superficial muscles and skin behind the angle of the mouth, and communicating with branches of the 6 seventh ' or facial nerve ; the large branch dividing into the inferior dental and gustatory nerves, the latter receiving the e chorda tympani : ' lastly, the external auricular, passing behind the mandibular ramus, joining the middle branch of the ( seventh,' and supplying the muscles of the ear, but mainly distributed to its sensitive surface. 1 The non-ganglionic part of the fifth supplies the temporal, masseter, and pterygoid muscles, also the mylohyoid and anterior part of the occipito-hyoid or digastric : the part going to the otic ganglion is continued therefrom to the internal pterygoid and to the muscles of the soft palate. A ganglion called ( submaxillary ' and situated near the deeper part of the gland so named, is connected by filaments with the gusta- tory nerve. In Swan's dissection of the cerebral nerves of the jaguar he found the superior nasal sending a branch to join the one from the lenticular ganglion to form ciliary nerves, and then pass forward to send one branch into the nose and another to the skin 1 See dissection of the trigeminal of Bos. in LIV, \>l. xxxii. fig. 3. 1.74 ANATOMY OF VERTEBRATES, 131 :ii the inner angle of the eye. The naso-palatine received the vidiaii nerve, and the { spheno-palatine ' ganglionic enlargement was conspicuous at the junction. 1 The largest portion of the maxillo- dental nerve supplied the great canine tooth. The gustatory nerve gave a branch to the lining membrane of the mouth and passed forward dividing into branches which communicated with the 6 ninth ' in their course to the surface of the tongue. Such Quadrumana as have been dissected with this view show all the main characters, connections, and accessory ganglions, of the fifth, which are so fully described in late works on the anatomy of Man. The apparent origin or place of emergence of the fifth nerve is at the middle ' crus ' of the cerebellum, fig. 128, . SWAN also ?hows it in the calf, pi. xxxvi. fig. 3, 11. ALCOCK found the spheno-palatine ganglion in a rabbit, dog and horse, as well as in ihe eat and cow. CCYIII. p. 28G. Macromyelon and origin of thttmi nerve, Man; natural size, ocvui. NERVES OF MAMMALIA. 155 olfactory : ( the other nerves of this part, derived from other origins, only conveying common sensation.' ' It is upon this principle the fifth pair of nerves may be supposed to supply the eye and nose in common with other parts, and upon the same principle it is more than probable, that every nerve so affected as to communicate sensation, in whatever part of the nerve the im- pression is made, always gives the same sensation as if affected at the common seat of sensation of that particular nerve,' ib. p. 190. 1 The nerve which is homologous with the e ramus opercularis sen facialis,' and some other branches of the non-ganglionic part of the ' fifth,' in Fishes (vol. i. p. 303), is more distinct in its origin, at least its apparent one, in Mammals, and is reckoned in Anthropotomy as a separate cerebral nerve, under the name of 6 facial,' or as a part, e portio dura,' of the ( seventh pair,' with which it has less real relation or connection than with the fifth. It is essentially the complementary proportion of the motory or non-ganglionic part of that great myelonal nerve of the head. In fig. 131 is shown the point, behind the olivary tract, where the facial, 16, diverges from the smaller portion of the motor division accompanying the sensory division of the trigeminal : its angle of divergence is wide, and its place of emergence is behind the c pons,' close to that of the acoustic nerve, fig. 128, y. It enters, therewith, the internal auditory foramen, leaves the acoustic to enter its own canal in the petrosal, called ( aqueduct of Fallopius ' in Anthropotomy, passes downward behind the tympanic bone (as in Birds), and emerges by a foramen called ( stylo-mastoid.' The facial nerve supplies the muscles of the mouth, nose, eyelids, ear-conchs, and the cutaneous muscles of the head and beginning of the neck. In the Porpoise, the facial nerve, on quitting the petrosal, gives small branches to the cutaneous muscular layer of the ear-opening and parts behind, communicating; with filaments of the cervical nerves : a branch o ramifies on the mylohyoid muscle. From the trunk of the facial a slender nerve passes to above the mandibular joint, then bends forward, enters into, and receives a filament from, a sympathetic plexus, and quits it to join the third division of the fifth : this answers to the f chorda tympani.' The trunk of the facial is, 1 One of the observations and experiments on which Hunter founded this conclu- sion, is given, in Latin, by Sir C. Bell, in his original Essay, LXIV", p. 11 (1811). So, also, Sir Charles writes: ' The key to the natural system of the nerves will be found in the simple proposit'on, that each filament or tract of nervous matter has its pecu- l ; ar endowments independently of the others which are bound up along with it, and that it continues to have the same endowment throughout its whole length.' LXV", p. 70. 156 ANATOMY OF VERTEBRATES. then, continued forward, superficially, along the slender jugal bone, toward the eye-opening, supplies the ' angularis oculi pos- ticus,' and the muscles of the under eyelid : in advance of this it supplies the ( angularis oculi externus,' and forms a large plexus, in connection with branches of the trigeminal. From the plexus pass filaments to the muscles of the blow-hole and its plicated sacs. In Mammals with a well developed parotid the facial traverses that gland; it divides there into three principal branches in the Calf 1 and Dog; 2 whilst in the Hog, the trunk is continued forward to near the fore part of the masseter, before dividing into maxillary and mandibular portions, and the auriculo-palpebral branches come off more separately from the long trunk. In Quadrumana, as in Man, the chief branching of the trunk takes place at the hind margin of the masseter after the post-auricular nerve is sent off: from the upper of the main divisions pass the nerves to the temple and eyelids as well as to the nose and upper lip. A slight enlargement of the facial near its entry into the e fallopian aqueduct '- -its petrosal canal is called f geniculate a-ano-lion ' which receives a petrosal branch of the vidian nerve, and one from the superficial petrosal which unites the otic gan- glion with the tympanic nerve. Prior to the ganglion the facial is connected by one or two filaments with the acoustic nerve : be- yond the ganglion it receives a petrosal filament of the sympathetic. The ' chorda tympani,' fig. 259, c, leaves the trunk of the facial before it quits its canal, enters the tympanum, crossing the tym- panic bone and the ear-drum, behind the handle of the malleus, b, to emerge by an aperture at the inner end of the ' glaserian fissure:' then passing downward and forward it joins the gusta- tory. In the Horse and Calf I traced, in 1836, 3 the superficial petrosal branch, or backward continuation of the vidian nerve, fig. 132, li, into the seventh, penetrating its sheath, but remaining distinct, and separating into many filaments, ib. b, with which filaments of the seventh nerve, ib. b, k,f, are blended, and a ganglion formed, ib. ^7, by the superaddition of grey matter ; the chorda tympani, ib. m, is here continued partly from this ganglion, partly from the seventh or portio dura, ib. 6. I did not at that time distinguish the fasciculus, b, called ( portio intermedia ' of the facial from the main trunk, a. The chief point, however, as to the ( chorda tympani' not being a branch of that main trunk 1 LIV. pi. xxx. fig. 3. 2 Ib. fig. 2. 3 In reference to the expression of Hunter, relative to the chorda tympani, ' I am almost certain it is not a branch of the seventh pair of nerves, but the last described branch from the fifth pair.' xciv. (1837) p. 194, and ' Note a.' NERVES OF MAMMALIA. 157 liiagraui of the ' portio intermedia,' with the ganglionic origin of the ' chorda tympaui.' LXXII". of the facial, receives corroboration from the special researches of Morganti l into this intricate and difficult part of neurotomy. In the subjoined diagram of the 132 result of his dissections, fig. 132, the portio intermedia, b, is separated from the vestibular division of the acoustic c, and from the main trunk of the facial , with both of which it lies in close contact. The filament d connects b with c, and receives one from the latter. Two filaments e connect the ( intermediate ' with the main portion of the facial, a. The intermediate portion is resolved into filaments, b, before joining the ganglion, y, the nature of the f grey or ash-coloured tissue ' of which has been established by the microscopic demonstration of the ( ganglion-corpuscles ' (LXVI", p. 549). With this ganglion are connected the superficial petrosal branch of the vidian, h, from the spheno-palatine ganglion, and the smaller 133 nerve, i, from the f otic ganglion : ' filaments k, /, from the facial, , and the chorda tympani, m. Morganti, however, traces a filament n to that nerve directly from the facial. In the Sheep, fig. 133, the ' portio inter- media ' b, is more closely connected, by d, with the acoustic nerve, c ; and sends a shorter and thicker division to the ( geniculate ' ganglion c/, by which it is more directly continued into the ' vidian ' branch e ; the ' chorda tympani,' f, being continued mainly from the ganglion, but also, in a smaller degree from the facial, a. The branch from the ' portio intermedia,' b, I described as the ' vidian ' crossing the ' portio dura,' a. The acoustic nerve, fig. 131, is, rises from the floor of the fourth ventricle, chiefly in connection with grey matter consti- tutino' the ' acoustic nucleus.' The nerve consists of an anterior o and posterior portion the course of which is more oblique in Man than in most Mammals owing to the great thickness of the cere- bellar crus, ib. 7. In the Cat the posterior root is very large, is a thickened band of fibre from the fusiform cells of the posterior portion of the nucleus; the band passes along the floor of the Relations of the chorda tympani and vidian nerve to tho 'seventh' nerve Sheep, magnified two dia meters. LXVI". LXX". 168 ANATOMY OF VERTEBRATES. fourth ventricle, joining fasciculi from the cerebellar cms and those of the anterior root. This ' consists of two portions, of which the chief penetrates the medulla beneath the restiform body and enters both parts of the acoustic nucleus : the other portion runs backward along the upper border of the restiform body, which it accompanies over the superior peduncle to the inferior vermiform process of the cerebellum.' 1 The ( flocculus,' fig. 64, ?z, with which the acoustic nucleus is connected, is large in the Cat, the Aye-aye, the timid Rodents, and all the small Mammals with acute hearing ; it is relatively small in the Sheep and most Ungulates. The acoustic nerve quits its origin in contact with the facial, fig. 128,^7, a small artery to the labyrinth runs between them: it takes a short course to the ( meatus internus,' longer in Cetacea than in other Mammals, receives a filament or two from the intermediate part of the facial, figs. 132, 133, d, on entering the meatus, and then divides. The part penetrating the fore half of the cribriform plate supplies the cochlea ; its large size is a mam- malian characteristic, and is most remarkable in the Cetacea : the posterior division, answering to the main part of the acoustic in lower Vertebrates, is spent upon the vestibule and semicircular canals. The eighth cerebral nerve, in anthropotomical enumeration, includes the three nerves called f glosso-pharyngeal,' ' vagal,' fig. 128, h, and ' spinal accessory/ ib. /. The roots of the glosso- pharyngeal are traceable to a nucleus of grey matter at n, fig, 57. The vagal nuclei, ib. h, are forward (in Man upward) extensions of the grey or vesicular myelonal columns from which the spinal accessory rises : they lie on each side of the hypoglossal nuclei, ib. g, on the floor of the fourth ventricle, but are united by the commissure forming the roof of the central canal before this opens into the ventricle : higher up the vagal roots penetrate the ' caput cornu,' like the posterior or dorsal myelonal roots. There is a partial decussation at the raphe. Both glosso-pharyngeal and vagal nerves emerge at the angle between the olivary and restiform tracts of the macromyelon, k, k, fig. 57, and are soon joined by the aggregate of the roots of the ( spinal accessory : ' these, commencing at about the fifth cer- vical, advance, between the dorsal roots of the cervical nerves and the ligamentum denticulatum, gathering successive slender accessions, all of which, originating as above defined, emerge at the dorsal border of the restiform tract. The glosso-pharyngeal is relatively smaller in Mammals than 1 xx". NERVES OF MAMMALIA. 159 134 in Birds (vol. ii. p. 124), is mainly distributed to the back part of the tongue and to the pharynx in all Mammals ; passing thence to the ' flocculus ' in its way to the jugular foramen, it retains its proper fibrous sheath, and usually presents the two enlargements called 'jugular' and ' petrous ' ganglions, before emerging from the skull. From the petrous ganglion a filament enters the tympanum, where it joins a plexus from the sympathetic, and supplies the membrane continued into the eustachian tube. The pharyngeal branches are joined by filaments from the vagus and sympathetic to form the pharyngeal plexus. Filaments are sent to the tonsils and fore part of the epiglottis ; those to the tongue supply the muscles at its base and the mucous membrane covering the base and sides of the tongue, some filaments terminating in the fossulate papilla?. In the Porpoise the glosso-pharyngeal divides at its exit from the skull into a smaller and larger branch. The former is dis- tributed to the sphincter of the lower or palatal part of the nasal canal, and unites there in a plexiform way with a branch of the vagus. The larger division supplies the palate and base of the tongue, and the muscles between the pyramidal larynx and the hyoid. Some filaments pass to the anterior ganglion of the sympathetic. The glosso-pharyngeal is fi- gured, in LIV. pi. xxxi. fig. 2, 9, and pi. xxxii. fig. 3, 22 (Uos), showing its communications with the e vagus ' and sympa- thetic ; also ib. ib. fig. 3, 1.3 (Felis) showing connections with the gustatory branch of /?, the trigeminal. In fig. 134, from the human subject, the emergence of the glosso-pha- ryngeal, 4, from the post-pyra- midal, c, and post-myelonal, y, tracts is shown at 2 : the petro- sal o*ano'lion and connecting o o o filaments with that of the upper vagal ganglion at 8 and 10 : 7 is the auricular branch of the vagus, 9 the 'ramus anastomo- ticus ' of Jacobson, 13 the trunk of the glosso-pharyngeal. The vagus, fig. 134, 3, or ' pueumogastric ' from the important Origins and connections of the constituents of the ' eighth' or pneumogastric nerve, Man. LXVII". ICO ANATOMY OF VERTEBRATES. organs the lungs and stomach which it supplies, sends branches ^^ ^5 * J- also to the larynx, trachea, and heart. As in other Vertebrates, it has the longest course, widest distribution, and most numerous connections, of any of the cerebral nerves; but is noted, in Mam- mals, by receiving the accessory nerve, ib. 5, 11,12, from a greater extent of the myelon : the recurrent branches of the vagus are more exclusively distributed to the trachea and larynx, and send a smaller supply of nerves to the rcsophagus than in Birds or Reptiles. From the remarkable length of the neck of the Giraffe, the condition of the recurrent nerves attracted my attention in dis- secting that animal : they were readily distinguishable at the upper third of the trachea, but when sought for at their usual origin, this was less obvious. Each nerve was not due. as in the & ~ ' short-necked Mammals, to a single branch given off from the vagus, continued of uniform diameter round the contiguous great vessel and throughout their recurrent course, but it received several small filaments derived from the trunk of the vagus at o different parts of its course along the neck. 1 Branches of the superior laryngeal nerve directly perforated, as in some other quadrupeds and in the Porpoise, the thyroid cartilage, and were joined, in a greater proportion than in Man, by branches of the recurrent, before distribution to the laryngeal muscles, of which, however, the crico-thyroid owes its supply chiefly to the upper laryngeal and the rest to the recurrents. In Quadrumana, as in Man, the internal laryngeal perforates the thyrohyoid membrane at the interval between the hyoid bone and thyroid cartilage. The upper laryngeal is proportionally larger in the Orang, Chimpanzee, and Gorilla, and mainly supplies the capacious laryngeal sac in those apes. In the Porpoise the left recurrent winds round the end of the arch of the aorta, near the remains of the ductus arteriosus ; the right recurrent winds round the subclavian immediately before the origin of the posterior thoracic : both recurrents send filaments to the oesophageal plexus from the sympathetic on their forward course to the larynx. After the origin of the recurrents, the vagal trunk sends off the cardiac branch, which, unitino- with c5 sympathetic filaments, forms the plexus supplying the heart. Next are sent off the nerves to the bronchial plexuses ; finally the vagal trunks pass with the rcsophagus through the diaphragm, the left on the ventral, the right on the dorsal side, and combine 1 xcvn'. NERVES OF MAMMALIA. 161 with branches from the sympathetic to supply the complex stomach and the numerous spleens. Most Mammals exhibit the grey enlargement of the vagus after its exit from the jugular foramen, but less distinctly divided into an upper, fig. 134, 6, and lower, ib. is, ganglion, than in Man. The principal branches e.g. 7, auricular; 10, interganglionic; 15, pharyngeal, deriving one filament, 16, from the vagus, the other, 17, from the ( spinal accessory ; ' 19, 20, superior laryngeal, the re- current, cardiac, pulmonary, oesophageal, and gastric are the same as in Man, likewise their connections with contiguous o nerves, and especially, as by the l filaments,' 21, 22, with the upper sympathetic ganglion. The spinal accessory, besides its portion, ib. 11, blending with the trunk of the vagus, distributes branches to the trapezius, masto-humeralis, and sterno-maxillaris, in Ungulates ; to the cleido-cucullaris and cleido-mastoideus, in Carnivores ; and to the trapezius and sternomastoid in Quadrumanes and Man. The condition of existence of a spinal accessory is not the extension of muscles from the skull to the thorax for the acts of respiration, but the general homology of the scapular arch as the haemal one of the occiput : accordingly the nerve is found in all Vertebrates ! ; and only when the development of the appendage of that arch calls for its displacement, and attracts for the manifold motive and sensitive requirements of the limb, successive nerve-bundles from the part of the myeloii co-elongating with the neck, are the root-filaments of the ' accessory ' drawn down beyond their normal, intercranial, place of origin, as at 5, 5, fig. 134. The macromyelonal, by some called ( respiratory,' centres, to which the origins of the several divisions of the ' eighth pair ' have been traced, are connected by means of longitudinal fasciculi and cell-columns, continuous with those in the cervico-dorsal regions of the myelon, with the trigeminal nerves, and with both anterior (lower and middle roots of the ' accessory') and posterior cornua of the myelonal grey matter, fig. 40, g, h : thus minis- tering to a series of motions, both direct and reflex, of high importance. The roots of the ninth or hypoglossal nerve may be traced to groups of nerve-cells in front of the central canal, ib. b, just above the upper cervical nerves, apparently a continuation of the cell-columns from which the ventral or motor roots of the spinal nerves arise : some of the roots decussate at the raphe, but most 1 For the homologue of this nerve, see, in Fishes, vol. i. p. 307 ; in lieptilcs, ib. p. 313 ; in Birds, vol. ii. p. 125. VOL. III. M 1G2 ANATOMY OF VERTEBBATES. of them sink deep into the nucleus. They are connected with each other, with the roots of the vagus, and with those of the spinal accessory by means of large multipolar cells. In the Giraffe the lower roots emerge, like a small ( accessory,' from the cervical part of the myelon. The main roots of each hypoglossal quit the macromyelon, be- tween the prcpyramid and olive, figs. 81, 82, 9, usually in two bundles, which escape, in many Marsupials, by two precondyloid foramina : but in most Mammals the bundles, perforating sepa- rately the dura-mater, pass out by a single precondyloid foramen, and then unite. The nerve is closely connected with the vagus, and contiguous cervical ganglion of the sympathetic, passes between the carotid and jugular, then forward between the basi- hyal and hyoglossus, and is continued into the substance of the geniohyoglossus beneath the tongue to its tip. In the Porpoise a small branch of the ( ninth ' is distributed to the sphincter muscle of the posterior nostril, before the supply to the muscles of the hyoid and tongue is sent off from the main part of the nerve-trunk, which is relatively small in Delphinidcs. In the Giraffe the motor nerve of the tongue is larger in proportion to the body than in the Ox : it is largest in the Pangolins and Anteaters, in relation to the great length of the tongue, and frequency and extent of its muscular motions. As the size of the ( ninth ' governs that of its special outlet from the skull, the precondyloid foramen indicates that the great ex- tinct tree-uprooting Sloths (Mylodon, Megatherium} applied a long flexible prehensile tongue to the plucking off the branches of their prostrated aliment, in a greater degree, even, than is now witnessed in the Giraffe. 1 Among the connections of the ninth are some with branches of the superior laryngeal to the sterno-hyoid and sterno-thyroid, associating the movements of the tongue with those of the larynx. 2 In Quadrumana the cervical branch assumes more the characters of the ( descendens noiii ' of Anthropotomy, and supplies the additional differentiated muscles of the hyoid. The ninth, like the ' accessory,' is essentially a motor nerve, and I have not seen a distinct ganglionic or dorsal root in any Mammal. The last, lowest, or hindmost, of the motory nerves of the head is that which supplies the muscles of the occipital or fourth haemal, or scapular, arch; and the origins of which, fig. 134, 5, 5, in the course of growth of the neck and cervical part of the 1 For the light which may be derived from both nervous and arterial foramina in the interpretation of fossil bones, see xcv', pp. 37, 57, pis. vi. vii. xvi. fig. 2, c. 2 A good view of the distribution of the ' ninth' in the Jaguar is given in LIV, pi. xxxi. fig. 3, 19, NERVES OF MAMMALIA. 163 myelon are drawn down beyond the cranium. In the Vertebrates, retaining the typical connections of the arch, the homologue of the s spinal accessory ' retains its cranial place of origin, as well as the connections with the ganglionic or sensory part of the nerve. The next cranio-motory nerve, in advance, is that which supplies the muscles of the parietal or third haemal, or hyoidean, arch. Both ninth and spinal accessory have their ganglionic or sensory complement in the f vagus : ' and, with reference to the place of origin of that nerve, it may be remembered that both heart and breathing organs belong to the head in Fishes, The second, or frontal, or mandibular, haemal arch has its gan- glionic nerves from the third division of the fifth, its non-o-anglionic 7 C3 C5 by that part of the trigeminal supplemented by certain branches of the e facial.' The rest of the facial represents the motory por- tion, as the first and second divisions of the ganglionic part of the fifth are the sensory portions of the nerve of the nasal or maxillary haiinal arch and its clothing. The ( sixth,' ( fourth,' and ( third ' are parts of the cranial motory nerve-system applied to a special organ of sense. The myelonal nerves indicate the segments of the axis enclosed in their protecting vertebral rings : both segments and nerve- pairs being called into being according to the requirements of the trunk and limbs of the species. The head-segments and trunk-segments directly succeed each other in Protopteri and Teleostomi (vol. i. pp. 7, 14) ; but in Mammals, as in other air- breathing Vertebrates, neck-segments and nerves are interposed ; and, as the scapular appendage becomes developed into a jointed limb, requiring a more backward position, through its size, or one of more freedom for the exercise of various movements, it attracts, as it were, the requisite nerve-force from the successive points or segments of the myelon, and chiefly from a post-cranial or cer- vical portion. The development of nerves, as of vessels, is not primary and independent, but secondary and subordinate to the parts needing them. If the appendage of a haemal arch retain its archetypal simplicity, as in Protopterus (vol. i. p. 163, fig. 101), one pair of nerves serves it : if it grows to a maximum of size and number of digital divisions, it may attract its nerve-supply from fifty successive segments of the myelon (LIY. pi. xi. Raia batis). In Mammals eight or nine segments succeeding the encephalon minister nervous power to the scapular arch and its appendage, the latter chiefly drawing upon the last three, four, or five pairs, which are proportionally large. M 2 164 ANATOMY OF VERTEBRATES. Because the neural arch and corresponding muscular segment have conditioned the beginning of the corresponding pair of spinal nerves, it does not follow that the specially enlarged and endowed appendage of such segment is arche typically an aggre- gate of as many appendages as the nerve-pairs from which it has attracted branches in the course of its growth and development. But, on this assumption have rested the conclusions that the scapula was an aggregate of all the cervical pleurapophyses, and that the humcrus was the coalescence of the five diverging appendages retaining their primitive and typical freedom in the five digits : and,, by parity of reasoning, the scapula of the Skate should be an aggregate of more than fifty pleurapophyses, &c. I assume that anatomists are agreed that the bone, vol. i. fig. 101, B, 51, is the homologue of 51, in fig. 101, A: that the scapula of the Amphiuma answers to the bone so called in other Reptiles and in Birds : and that the occipitally attached scapula of the Lepidosiren is the homologue of the similarly named and con- nected bone in other Fishes. But the long cylindrical rib-like ' scapula ' of the Lepidosiren is one element, and the diverging segmented appendage of the scapular arch manifests the like essential unity. Now, the bifurcation of the distal segment of the homologous diverging appendage in Amphiuma does not make the unsplit part (fig. 101, B. 53) an aggregate of two appendages, nor its scapula, ib. si, an aggregate of two ribs. And the same may be predicated of five or any greater number of radiated divisions of the terminal part of the scapular appendage. But the pectoral fin of the Skate is the pectoral filament of the Mud- fish, the fore-leg of the Quadruped, the wing of the Bird, the arm and hand of Man : i. e. they are homologous parts though with a supply of muscles, nerves, and vessels, according to their respec- tive sizes, shapes, and uses. Say that the appendage in Lepidosiren, fig. 101, A, 53-57, is a dermal development, and that the humcrus, radius, &c. in its higher homologues, are skin-bones, and not parts of the endo-skeleton : it does not follow that the scapular arch, ib. 51, 52, is, also, part of the dermo-skeleton. What, then, is it? This question I propounded, in 1846, l in reference to all the parts of the vertebrate skeleton of which anatomists were at one in respect to their special homology : it applies to the basi- occipital (vol. i. fig. 77, i) and other elements of the occiput of the Fish, as well as to the scapular arch therewith connected. What is the basioccipital ? Anatomists are agreed that the ' basilar process of the occipital bone' (Anthropotomy) is its homologue: in 1 LXXIV, p. 276. NERVES OF MAMMALIA. 165 other words, that the same bone or osseous element may be pointed out from the Cod-fish up to Man. But at this point the above question may be met by the averment, that it need not be asked : that there is no ground for homological generalisation higher than the special one. Such anatomists rest on the step beyond which Cuvier refused to pass. With him parts were homologous because they served similar purposes, or were under like teleo- logical conditions of existence. Neither the final nor the me- chanical causes of separate basi-, ex-, and super-occipitals, of basi- and ali-sphenoids, parietals, &c. in the skull of the foetal Bird or Kangaroo, have been explained l ; and as I am unable to conceive of them, and am in 110 wise helped by the averment of inhe- ritance, I retain my conviction that the basilar process of the human occipital bone is the centrum of the hindmost cranial ver- tebra ; having, moreover, traced the scapular arch and appendage to its extreme of simplicity in Protopterus and Lepidosiren, I accept the light which such condition throws upon its general ho- mology, as the hasmal arch of the same (occipital) cranial vertebra. If there be cartilaginous fishes that combine a foetal gristly con- dition of skull with a maximised development of scapular append- age, I conclude that the backward displacement of the sustaining arch, from its type-position, is a consequence of such development, and prefer to allow my reasoning as to the nature of a limb to be guided by the state and conditions of such appendage in the verte- brate series, rather than by the state of the cranium in one part thereof. It is not probable that the pectoral fin of Shark or Skate shows the condition under which the appendage of the scapular arch first appeared in fishes. 2 On laying open the neural canal, and exposing the myelon by slitting up and reflecting the ' dura-mater,' as in fig. 135, the roots of the nerves are seen, which go off in lateral pairs, and escape at the intervals of the vertebras: they are called the ( spinal' or ' myeloual' nerves. One bundle of the radical filaments proceed from the antero-lateral, the other bundle from the postero-lateral 1 Messrs. Seeley and Spencer dispute the priority of such explanation and don't give it. xci" and xcn." 2 Respect for the conductors and editor of LXXV has led me into the above digres- sion; and as they meet what they consider the 'main defect ' (ib. p. 123) of the present work by an ' argumentum ad verecundiam,' I would observe that the individual who first perceives, or discovers, the general homology of the basioccipitil, the scapula, or other part of the hindmost segment of the skull of a cod-fish, puts himself in advance of, and more or less in antagonism with, others. If his perception be true, but not accepted, it is not his fault that ' he be right and everybody else wrong.' -Such a state of things has happened more than once in the history of science, but it is happily transitory; the many moving one-ward, the one onward. 1G6 ANATOMY OF VERTEBRATES. 135 fissure, and between the bundles passes a delicate fold of the arach- noid, which is attached by an angular process, d, to the dura-mater at the interval, usually, of each nerve (p. 7 8), The anterior or ventral and the posterior or dorsal bundles converge, separately per- forate the dura-mater, and unite, at the in- ter vertebral foramen, into a single ( nerve.' In the Elephant the posterior roots come off abruptly in a few, large, and distinct bundles : the anterior roots emerge from a longer extent of their furrow, are nume- rous and small, and form several bundles before passing through the dura-mater. The same characters of the anterior and posterior origins are seen in Cetacea, in which the two roots preserve their distinct course before uniting, after perforating the dura-mater, longer than in other Mam- mals. In the human subject, especially at the cervical part of the myelon, the anterior root, fig. 136, A, is the small- est ; its finer fila- ments form more delicate fasciculi, aggregating into two, before uniting, as a flat band, with the posterior root. Of this the fila- ments, P, are larger, and blend with the cell-substance of a ganglion, G, before uniting with the anterior root to form the nerve-trunk, c. The capital experiment which has immortalised the name of CHARLES BELL was suggested by the above anatomical fact, and I quote his original account of it from the extremely rare little tract, which he printed for private distribution in 18 II. 1 1 LXIV. Portion of myelon, with roots of nerves of one side. Human, natural size. Roots of myelouaJ uerve, magn. NERVES OF MAMMALIA. 167 Believing that he could f trace down the crura of the cerebrum O into the anterior fasciculus of the spinal marrow, and the crura of the cerebellum into the posterior fasciculus, I thought/ he writes, p. 21, ( that here I might have an opportunity of touch- ing the cerebellum, as it were, through the posterior portion of the spinal marrow, and the cerebrum by the anterior portion. To this end I made experiments which, though they were not conclusive, encouraged me in the view I had taken.' ' I found that injury done to the anterior portion of the spinal marrow convulsed the animal more certainly than injury done to the posterior portion, but found it difficult to make the experi- ment without injuring both portions.' ( Kext considering that the spinal nerves have a double root, and being of opinion that the properties of the nerves are derived from their connections with the parts of the brain, I thought that I had an opportunity of putting my opinion to the test of experi- ment, and of proving at the same time that nerves of different endowments were in the same cord, and held together by the same sheath. ' On laying bare the roots of the spinal nerves, I found that I could cut across the posterior fasciculus of nerves, which took its origin from the posterior portion of the spinal marrow, without convulsing the muscles of the back ; but that on touching the anterior fasciculus with the point of the knife, the muscles of the back were immediately convulsed' (ib. p. 22). The ventral as well as the dorsal roots of the spinal nerves are traceable to the contiguous parts of the grey tract, the latter more immediately, as at k, fig. 40. They are severally connected with, but do not constitute, the white columns from which they emerge. Comparative anatomy testifies plainly against the anterior and posterior columns being aggregates and brainward continuations of the motory and sensory roots. Thus, in the instance of such unusual elongating growth of the myelon as takes place in the neck of the foetus of the Giraffe, as many of the roots of a nerve, the origin of which may be so extended by interstitial myelonal increase, incline tailward as head ward (p. 75). And accurate experiment gives the same response, sensation continuing or being heightened in parts supplied by nerves beyond the place of the myelon of which the dorsal or posterior columns have been divided. The most constant anatomical concurrence with sensory func- tion is the ganglion, fig. 136, G, fig. 131, 9. In all Mammals the trunk, fig. 136, C, formed by the union of the two roots soon divides into an anterior and a posterior pri- 168 ANATOMY OF VERTEBRATES. inary set of nerves. The posterior or dorsal are usually the smaller division, and, bending backward, soon subdivide into external and internal branches. The pairs of nerves are classified, according to the regions of the vertebral column where they emerge, into ' cervical,' ' dorsal,' * lumbar,' ' sacral,' 6 caudal,' and offer numerical differences corresponding with those of the verte- bras, in the Mammalian series. Each is anterior to the correspond- ing bony segment, and, for the most part, escapes between that and the segment in advance ; but the notch of the ( conjugational foramen ' is always deepest at the fore part of the neurapophysis answering to the nerve, and is directly perforated thereby in many instances ; as, e. g. that of the atlas by the first cervical in the Tapir, 1 and also that of the axis by the second cervical in the Hyrax. 2 Most of the cervical and the dorsal vertebrae are perforated by their corresponding nerves in the Hog and Pec- cari ; 3 and some dorsals and lumbars are so perforated in most Ruminants. 4 Therefore, I count the ( suboccipital ' nerve as the first cervical one, and reckon the f eighth cervical ' of Anthropo- tomy as the f first dorsal.' Some details of the distribution of the myelonal nerves in Monotremata are given in LXXXI*. In the Cetacea they have been described by Stannius 5 and Swan 6 in Phoc&na communis. In the Porpoise, the first cervical has a distinct posterior root, smaller than the anterior one, but with a small ganglion ; be- yond which the two unite, as usual. The posterior or dorsal branches supply the occipital and contiguous integument, and the tegumentary and other muscles passing to the occiput ; supplying, also, small branches to the f masto-humeralis.' The anterior or ventral branch passes along the scalenus, joins cor- responding branches from the second and third cervicals, and, in combination with the f descendens noni,' supplies the sterno- hyoid and sterno-thyroid muscles. The second and succeeding cervical nerves are larger. A posterior branch of the second perforates the masto-humeralis, and supplies the integument of the neck. Other posterior branches of this and following cer- vicals supply the interspinales, spinalis cervicis, splenius capitis, and the more superficial muscles and integument at the fore and dorsal parts of the trunk : ventral branches go to the scalenus anticus, levator anguli scapula?, and contiguous muscles. The fourth cervical contributes the largest part of the ( phrenic nerve,' but it receives a filament from the third cervical, sometimes from the second ; always from the fifth. The left phrenic passes a 1 XLIV, p. 501. 2 Ib. p. 522. 3 Ib. pp. 543, 563. 4 Ib. p. 579. 5 Lxxvr-. LIT, 2d ed. p. 156. NERVES OF MAMMALIA. 169 short way along the scalenus anticus ; as it sinks deeper, it gives a filament to the pectoralis major, passes over the aortic arch and trunk of the vagus in entering the thorax, passes along the anterior mediastinum, and then along the pericardium to the left side of the diaphragm. The right phrenic crosses the subclavian, or trunk of the brachial artery, in entering the thorax, and supplies the right half of the diaphragm. A small branch of the anterior division of the fifth cervical, a large branch of that of the sixth, a still larger one of the seventh, and a smaller contribution from the first and second dorsal nerves combine to form the axillary plexus, prior to which are sent off nerves to the scalenus anticus, subscapularis, teres major, and latissimus dorsi. From the plexus is continued a branch beneath the triceps, which quickly radiates small filaments, one of the largest of which is continued along between the radius and ulna ; a second branch passes along the inner side of the triceps to the olecranon ; a third branch goes between the hind border of the scapula and the triceps outward and forward, it supplies the infraspinatus and deltoid, and ends in the periosteum and skin at the fore part of the humerus. Many small twigs are sent to the subscapularis muscle. The hindmost and strongest branch goes obliquely outward and backward, giving filaments to the latis- simus dorsi, and bends over the chest to the sternum, along the side of which it distributes itself to the serratus magnus and con- tiguous muscles attached to the ribs ; it answers to the ( external o thoracic nerve.' There are thirteen pairs of dorsal nerves, each dividing into a dorsal and intercostal part. The dorsal division bends over the rib-neck in the anterior vertebras, and over the lengthening diapophysis in the posterior ones, and subdivides into a superficial and deep part ; the latter supplies the spinales, interspinales, and the fascia of the muscles of the back ; the superficial nerves contribute to the longissimus dorsi, and levatores costarum, in their way to the skin of the back and its muscles. The ventral divisions of these nerves are less distinctly subdivided into external and internal fasciculi than in quadru- peds. The first intercostal sends a communicating branch to the axillary plexus, before its normal distribution, as in the other intercostals, to the muscles so called, which are perforated toward the sternum by the branches going to the ventral integument. The nerves answering to lumbar and sacral of Quadrupeds divide into dorsal and ventral fasciculi. The former go to the inter- transversales, spinales, interspinales, sacrolumbalis, and longis- simus dorsi; and to the superincumbent fascia and tegument. There are intercommunicating filaments between the dorsal divi- 170 ANATOMY OF VERTEBRATES. sions of the second, third, and fourth lumbar nerves. Some of the ventral branches pierce the intertransversalis before penetrating the fascia of the psoas, on their way to the oblique and straight abdominal muscles ; but the main proportion is taken by the psoas. Anterior branches from the seventh, eighth, and ninth lumbar nerves diverge from the ordinary course or distribution, and partially unite with a plexus extending to and supplying the muscles which connect the ischial or pelvic bones with the abdo- minal and caudal muscles and those of the attached parts of the sexual organs. The above nerves evidently represent the lumbar plexus developed in Quadrupeds for the hind-limbs, but their chief distribution is as ( pudenda! ' nerves. The anterior or ventral divisions of the caudal nerves mainly combine to form a nerve-trunk on that aspect of the tail, which is resolved into many small parallel transverse branches, from which are supplied the muscles and teguments of that part of the tail. The dorsal divisions are similarly distributed, but only a very small propor- tion goes to the skin. 1 In the Ungulate series the distribution of the spinal nerves has been followed by the hippotomists in the Horse and Cow; by Swan in the Ass ; 2 and I have made observations on that part of the anatomy of the Rhinoceros and Giraffe. Several branches from the superior cervical ganglion of the sympathetic join, in a plexiform manner, the anterior division of the first cervical ; this also receives a filament from the descendens noni, which previously communicates either with the trunk or a filament from the par vagum ; afterwards it joins the pharyngeal plexus, and is distributed to the steruo-hyoid and sterno-thyroid muscles. The nerve given to the serratus magnus proceeds from the sixth cervical with the phrenic ; but the phrenic after- Avards communicates with a branch of the seventh, given to the pectoralis major. The axillary plexus in the Ass, also in the Pig, is formed from the seventh cervical and the first and second dorsal nerves. The superior scapular nerve proceeds chiefly from the seventh cervical ; but in some degree from the first dorsal, and is sent to the supra- and infra-spinati muscles of the scapula. Branches proceeding from all the nerves forming the plexus are given to 1 SWAN well notes the difference between the mode of supply to the natatory tail, i.e. by a few trunks in Cetacea derived from a remotely situated myelon, and that in Fishes, by many nerve-pairs from a contiguous myelon: also the great proportion of motory as compared with sensory filaments ; the tail being not only the main motive instrument in Whales, but capable of ' giving hard blows without feeling much pain.' LIV. p. 165. 2 LIV, 2d ed. pp. 153, et. seq. NERVES OF MAMMALIA. 171 the great pectoral muscle ; a nerve proceeding principally from the last cervical and first dorsal supplies the subscapularis. teres major, and latissimus dorsi, then takes a circumflex course to the deltoid, and external head of the triceps, and finally passes down the limb to the skin. The external branches of the third and fourth dorsal nerves, also, supply the skin ; the internal cutaneous nerve is sent off from the ulnar. The musculo-cutaneous is formed chiefly by the last cervical, and partly by the first dorsal ; it contributes to the formation of the median nerve, then pierces the coraco-brachialis to terminate on the biceps. The median is mainly formed by the first two dorsal nerves ; it sends a branch to the biceps, brachialis internus, and supplies the skin on the posterior and inner part of the fore-leg. After supplying the flexors on the fore-leg, it sends a nerve close to the bone which gives filaments to the periosteum, and passes to a muscle answering to the flexor longus pollicis : it then passes underneath the annular ligament, and sends a large branch obliquely over the flexor tendons to communicate with the ulnar nerve, and descends, giving off branches to the skin at the inner side of the foot, which communicate with the inner portion of the deep palmar branch of the ulnar : it then passes to vascular lamella? attached to the hoof, fig. 17, 17, to terminate on these, on the villous part of the sole and the ligaments of the joints. The ulnar nerve arises from the first and second dorsals ; at the middle of the arm it sends off the internal cutaneous nerve, and at the elbow gives some branches to the short extensor and the elbow joint; it passes down, covered by some fibres of the flexor muscles, and at the wrist sends off the dorsal branch to the skin at the posterior and outer part of the fore-leg ; it passes under- neath and to the inner side of the flexor carpi ulnaris, and then underneath the annular ligament, and gives off the deep palmar nerve : it receives the branch from the median, and descends, o-ivino; branches to the skin and ligaments at the outer side of the O O o foot, after these have communicated with the outer branch of the deep palmar ; it passes into the foot, covered by the vascular lamellae connected with the hoof, and terminates on these, the villous part of the sole and the ligaments of the joint. The deep palmar gives some filaments to the ligaments, and divides into two principal branches, one to pass on the inner side to give filaments to the joints, the periosteum, and ligaments, and com- municate with the branches of the median sent to the skin and ligaments at the inner side of the foot, the other to s;ive filaments O 3 O to the periosteum and ligaments, and communicate with branches 172 ANATOMY OF VERTEBRATES. of the ulnar, having a similar destination on the outer side of the foot. The musculo-spiral nerve arises from the seventh cervical and first and second dorsal nerves : after supplying the heads of the triceps, it passes round the humerus, and gives branches to the two large extensors at the back of the fore-leg, and sends a branch, somewhat expanded, down to the carpal joints, but not swelling into a ganglion, as in Man ; it then pierces the rudiment of the short supinator, to supply a muscle answering to the long supinator on the outer side of the back of the fore-arm. In the Pig, the median in the fore-arm is much larger than the uluar; it receives a small communicating branch from the ulnar near the wrist, and then supplies the inner small toe (zV), both sides of the inner large toe (iii), and the inner side of the next (iv). The ulnar gives off the dorsal branch, and then sends the deep palmar to the interosseous muscles ; it contributes a small branch to the median, and then supplies the outer side of the large toe (iv), and the adjoining small toe (v). The greatest portion of the dor sum of the foot is furnished by the radial branch of the spiral nerve, and the rest by the dorsal branch of the ulnar. In the Ass there are eighteen pairs of dorsal nerves, the anterior or ventral divisions of which pass between the ribs, are distributed to the intercostal and abdominal muscles, the hind- most perforating the psoas muscle. There are five lumbar and six sacral nerves, besides four or five caudal. The third lumbar sends off a branch, which gives a branch to the great psoas muscle, and one to join the fourth for the anterior crural nerve ; it then becomes the external cutaneous nerve to pass on the outer side of the thiffh ; it sends off another laro;e branch O '' O corresponding with the external spermatic, which communicates with a large branch of the third lumbar ganglion of the sympa- thetic, gives a branch to the small psoas muscle, and then passes underneath the lower border of the abdominal muscles, to which it sends a branch, and becomes distributed on the mamma. The anterior crural nerve arises from the third, fourth, and fifth lumbar nerves : the obturator arises from the fourth and fifth lumbar, and first sacral nerves : the sciatic arises from the three first sacrals : the principal part of the third and fourth sacrals, joined by a small branch from the portion of the sciatic arising from the second, give off the internal pudenda! to pass at the side of the arch of the pubes, distribute filaments to the neck of the bladder, and terminate on the clitoris, vagina, and external parts, and the connecting muscle and membrane between these and the mamma. A branch of the external sper- NERVES OF MAMMALIA. 173 matic may be traced downward, and a branch of the internal pudendal upward, towards each other. Another part of the junction of the fourth and fifth, with sometimes a branch from the sixth sacral, joins the hypogastric plexus, and sends branches along the inferior uterine artery to the neck of the uterus and vagina, and is then distributed to the bladder, urethra, vagina, and rectum. The remaining part of the fifth and sixth sacrals forms the beginning of the anterior caudal nerve, to which the anterior trunks of the remaining spinal nerves below it become united ; the posterior trunks of these nerves form the posterior caudal nerve ; both of these are continued to the extremity of the tail, communicating by branches, and supplying one-half of each anterior or posterior surface. 1 The gluteal nerves are sent from the two first sacrals at their junction with the sciatic, and terminate on the glutei and tensor fascia?. A nerve given off from the sciatic supplies the gracilis and gemelli, and is continued down to the quadratus femoris. The anterior crural nerve sup- plies the sartorius, rectus femoris, vasti, and cruraeus. The sa- phenus nerve descends with the vein, giving numerous filaments to the ligaments and skin, and communicating at the side of the foot with the inner branch of the deep plantar nerve, and through this with a branch of the inner plantar, to be distributed on the skin at the side of the foot. The obturator nerve supplies the adductors and the large muscle corresponding with the gracilis. The sciatic nerve gives branches to the semimembrancsus, semitendinosus, and biceps ; it then divides into the posterior tibial and the peroneal, both of which give branches to the biceps. The posterior tibial sends a branch down at the back of the gastrocnemius, and on the outer side of the tendo Achillis to the fascia, on that side of the hock : it then passes between the heads of the gastrocnemius muscle, to which and the large muscle representing the posterior tibial and the flexors of the toes it gives branches ; it descends on the inner side of the tendo Achillis, giving branches to the fascia, &c. on the inner side of the hock, near which it divides into the inner and outer plantar nerves ; the inner sends off a large branch obliquely over the flexor tendon to join the external plantar nerve ; it passes down on the inner side of the tendon, giving branches to the sheath, fascia, and integuments ; near the foot it gives off a large branch, which communicates with the inner branch of the deep plantar nerve, to be distributed on the skin at the inner side of the foot ; it gives branches to the skin of the heel, and then passes down to the hoof, covered by the vascular lamella?, and distributing 1 LIV, p. 160. 174 ANATOMY OF VERTEBRATES. branches to these and the villous stratum of the sole. The external plantar passes between the flexor tendons, and then on the outer side of these, and gives off the deep plantar nerve ; it is continued down on the outer side of the tendon, gives filaments to the sheath and fascia, receives the branch from the inner plantar, and gives off a branch which communicates with the outer branch of the anterior tibial nerve, and is distributed on the side of the foot ; its ultimate distribution resembles that of the posterior tibial. The deep plantar gives filaments to the ligaments, then divides into two branches ; the inner passes down beneath the tendon, then near the edge of the bone to the foot to communicate with a branch of the saphenus nerve, and of the inner plantar, to be dis- tributed on the skin at the inner side of the foot; the outer branch passes near the edge of the bone, gives a branch to the ligaments, and then joins the outer branch of the anterior tibial nerve. The peroneal nerve passes to the outer side of the leg, and gives small branches to the fascia and skin ; it sends the long branch dow r nward which gives filaments to the fascia, and termi- nates in the skin covering the dorsum of the cannon-bone. It gives filaments to the ligaments and fascia on the outer side of the knee-joint, and branches to the peroneal muscle, the extensors of the toes, and the anterior tibial muscle. It gives off the anterior tibial nerve, which passes down the leg between the peroneal and anterior tibial muscles, then between this and the bone along with the anterior tibial artery underneath the annular ligament, where it divides into two branches ; the outer one gives filaments to the joint, and is contained with the anterior tibial artery on the outer side of the cannon-bone, giving filaments to the periosteum, and on the outer side of the foot receiving the outer branch of the deep plantar nerve ; it then becomes connected with a branch of the outer plantar nerve, and is distributed 011 the ligaments and skin on the outer side of the foot ; the inner branch of the anterior tibial passes down on the cannon-bone, gives filaments to the periosteum and fascia, and terminates on the skin at the inner side of the foot. In the Pig, the posterior tibial nerve, having given branches to the muscles of the leg, and sent the branch down at the back of the gastrocnemius muscle to the outer side of the leg, gives filaments to the inner side of the heel, and near the part divides into the inner and outer plantar nerves ; the inner is continued onwards, and supplies the small inner toe (zV), the first large toe (Hi), and the inner side of the next (iv). . The outer plantar nerve passes underneath the flexor tendon, and is continued on- NERVES OF MAMMALIA. 175 ward to divide for the outer side of the second large toe, and the outer small toe ; it sends the deep plantar into the sole to supply the short muscles situated there. The anterior tibial nerve gives branches to the ligaments at the back of the foot, and sends a branch to supply the toe, ii, and the inner side of in ; the rest of it Drives branches to the small muscles on the back of the foot. o and then passes forward to join the branch of the peroneal given to the outer side of Hi, and the inner side of iu l ; the continua- tion of the peroneal after emerging just above the instep supplie the outer side of Hi toe, both sides of iv and v, the branch sent to the outer side of Hi and the inner side of iv receiving a branch of the anterior tibial. In the order Car?iivora, the distribution of the nerves has been described and figured by Swan, in the Fox (LIV, p. 150, pi. 33), and in the Jaguar (ib. p. 161), from which the following account is chiefly abridged. In the Fox the anterior trunk of the first cervi- cal passes forward, and sends up two filaments to the junction of the trunk of the par vagum with the glosso-pharyngeal, the ninth, the* accessory, and the superior cervical ganglion of the sympathe- tic ; it gives branches to the recti antici, and then joins the descen- dens noni, to be distributed to the sterno-hyoid and sterno-thyroid muscles. The posterior trunk supplies the recti capitis postici and obliqui sup. et inf. The anterior trunks of the second and third cervical nerves give branches to the recti capitis antici, then unite to communicate with the accessory, and divide into branches, which are distributed on the cutaneous muscle and skin at the side of the face and neck and external ear. The fourth cervical gives a branch to join the accessory and others to the trapezius, and is then distributed to the cutaneous muscle and skin at the side of the neck. The fifth cervical nerve gives a branch to the acces- sory, and to the trapezius, and then pierces this to terminate on the skin at the lowest part of the neck. The posterior or dorsal division of the second cervical nerve gives branches to the splenius, complexus, and other muscles, close to the posterior part of the spine, and then sends a branch through the complexus towards the occiput, which gives filaments to the muscles inserted into the back of the ear, but is chiefly distributed on the skin of this part, The posterior division of the third cervical is similarly distributed. That of the fourth cervical gives branches to the complexus and other muscles close to the spine, and then terminates on the skin. The posterior divisions of the sixth and seventh also give branches 1 See vol. ii. p. 308, fig. 193, Hippopotamus, which resembles the foot of the Hog. 176 ANATOMY OF VERTEBRATES. to the muscles and skin ; the first dorsal supplies the muscles only. The phrenic nerve is formed by a branch from the fifth and sixth cervicals : it passes over the pericardium to the dia- phragm, and on the right side is placed close to the post-caval vein. In the Jaguar, the phrenic also arises from the fifth and sixth cervicals, and receives a branch from the first thoracic ganglion. The axillary plexus is formed by the last two cervical and first two dorsal nerves. In the Fox the axillary plexus is formed by the sixth and seventh cervical and first and second dorsal nerves, but the greatest part of the sixth, after receiving a branch from the seventh, gives a large branch to the integuments on the anterior part of the shoulder-joint, and then passes to form the superior scapular nerve, and terminates on the supra- and infra-spinate muscles. Branches from the sixth and seventh cervical and first and second dorsals are given to the pectoral muscles ; a branch from the seventh cervical is given to the serratus magnus, and branches from the sixth and seventh go to the subscapularis. The circumflex nerve arises from the union of the sixth and seventh cervical nerves ; it gives branches to the subscapularis and teres major muscles, and then divides and sends a branch to the infra-spinatus muscle and the deltoid, and branches to the integuments on the. outer side of the arm. The internal cutaneous nerve is sent off by the ulnar ; it passes down the arm, and, near the inner condyle of the humerus, divides into branches to be distributed to the skin at the ulnar side of the fore-arm. The smaller internal cutaneous nerve is the external branch of the third dorsal after its egress from between the ribs ; it pierces the broadest muscle of the back, and divides into branches, to be distributed on the skin at the inner and posterior part of the arm. The musculo-cutaneous nerve arises from the seventh cervical with the outer portion of the median, gives a branch to the pectoralis and coraco-brachialis, and then passes off to terminate on the biceps. The seventh cervical, having given off the homologue of the musculo-cutaneous, the remaining part gives off a branch which sends one back to the brachialis internus, behind the tendon of the biceps, and then gives branches to the skin of the fore-arm, in the place of the cutaneous portion of the musculo-cutaneous nerve in Man ; it then joins the branch from the first and second dorsal nerves, about an inch above. the elbow, to form the median nerve, which is small as compared with that in Man. The nerve thus formed passes under the origin of the pronator teres, and gives branches to this, the flexor carpi radialis, and the superficial and deep flexors of the digits ; it then passes, SERVES OF MAMMALIA. 177 by the side of the radial flexor and between the digital flexors. / ^j through the annular ligament ; it is continued in the fore-paw between the tendons of these muscles, at the division of which it sends off branches ; it gives filaments to the skin of the palm, and a branch to the rudimental pollex, 1 another to the inner side of the index (n), and a branch to be joined by one from the deep palmar for the outer side of the index and the inner side of the medius (in) ; another branch also to be joined by a branch from the deep palmar for the outer side of the medius and the inner side of the annularis (iv). The ulnar nerve is formed by the first and second dorsals ; it descends behind the inner condyle of the humerus, covered by thick fascia and by part of the flexor sublimis ; it then passes down the fore-arm between the flexors of the fingers and the ulnar flexor of the wrist. In the fore-arm it is larger than the continuation of the median nerve : it sends a branch to the ulnar side of the superficial and deep flexors of the digits and the ulnar flexor of the wrist : near the hand it sends a branch to the back of this part to communicate with the radial branch of the musculo-spiral nerve, and then proceeds to the outer side of the fifth digit (v) ; it passes deeply, confined by a ligament at its entrance, into the palm, and sends a branch for the inner side of the fifth digit and the outer side of the fourth ; the rest of the nerve, forming the deep palmar, divides into branches, which terminate on the interosseous and other small muscles situated in the palm, and give branches to join those of the median sent to the outer side of the index and the inner side of the medius digit ; also to the oiiter side of this and the inner C5 side of the annularis. The distribution of the median nerve is nearly the same in the Felines, but the trunk traverses the ento- condyloid canal. The musculo-spiral nerve has a slight com- munication with the sixth cervical, but is principally formed from the seventh and first and second dorsals ; it gives branches to the different heads of the triceps muscle, and winds round between the inner and large heads of the triceps to the outside of the arm, and divides into two large branches ; one gives off a cutaneous branch to the outer side of the fore-arm, and then descends in the place of the radial, giving branches to the skin, and dividing to terminate on the skin at the back of the paw and the side of each digit, except the outer side of the fifth, and communicate with the dorsal branch of the ulnar ; the other, in passing to the back of the fore-arm, gives a branch to the long and the short supinator muscles ; it then divides to terminate in the extensor carpi radialis 1 Vol. ii. p. 306, fig. 191, Hycena, i, which also serves to exemplify the homology of the digits of the fore-paw in the Dog and Cat. VOL. III. N 178 ANATOMY OF VERTEBRATES, and the extensor digitorum, whilst a long branch passes on and gives filaments to the extensors of the pollex and to the wrist- joint, but does not terminate on this part in a ganglion, as in Man and Quadrumana. There are thirteen pairs of dorsal nerves, and their principal deviation from those in Man consists in a smaller size, a more direct course, and a less distribution on the abdominal muscles, and by those at the lower part of the thorax being covered by an extension of the origin of the psoas muscle, also in the anterior cutaneous branches supplying the different portions of the elongated mammary glands in the female, as well as the skin. The posterior or dorsal divisions, after supplying the muscles connected with the spine, the sacro-lumbalis and longissi- mus dorsi, send a branch between these and the latissimus clorsi to the skin. The anterior or ventral divisions of the lumbar and sacral nerves supply principally the parts connected with the lower extremity, the bladder and rectum ; the dorsal divisions of the second and third lumbar nerves supply the skin as well as the sacro-lumbalis and other muscles connected with the dorsal parts of the vertebras ; the dorsal divisions of the succeeding lumbar nerves are distributed to the muscles only ; the dorsal divisions of the sacral nerves supply the muscles on that surface of the tail. The nerves are not very different from those in Man, except in their number, and consequently in their conjunction a little higher or lower for forming the nerves of the lower extremity. The anterior divisions of the three first lumbar nerves give fila- ments to the psoas muscle, and then pass forward to terminate in the abdominal muscles and skin. The fourth gives filaments to the psoas and internal iliac muscles, and sends a branch to join one from the third to form the external spermatic on the external iliac artery, which passes through the external abdominal ring to the spermatic chord ; in the female this was distributed on the posterior division of the mammary gland ; it sends off another branch which gives a filament to the external iliac artery, and then joins the sixth ; the rest of the fifth passes down on the exterior of the thigh to the skin, and forms the external cutaneous o nerve. The sixth receives a branch from the fifth, gives fila- ments to the internal iliac muscle ; part of it is then joined by a large branch from the seventh to form the anterior crural nerve ; the other part, after receiving a large and small branch from the seventh, becomes the obturator nerve. The seventh, having given off the preceding branches, joins the first and second sacrals and a branch of the third for forming the sciatic nerve. The NERVES OF MAMMALIA. 179 junction of the first and second sacral gives a branch to the pyri- forin muscle, and a larger one to pass out at the ischiatic notch to supply the gluteal muscles and the tensor fascia?. Some branches derived from the second and third sacral nerves combine with the hypogastric plexus for supplying the bladder and rectum, and others from the pudenda! nerves for the muscles connected with the anus and tail. A branch of the second sacral nerve joins the third for forming the anterior caudal nerve, which receives the anterior trunk of each remaining spinal nerve, and passes deep in the anterior part of each side of the tail, giving off branches into its course ; the posterior or dorsal trunks of the same nerves form a nerve, which also sends off branches to the dorsal muscles and skin of the tail. The anterior crural nerve passes between fibres of the iliac muscle, then under Poupart's ligament at the inner side of the sartorius ; it gives branches to this, to the rectus femoris, the external and internal vasti, and the cruralis, and sends off the saphenus nerve, which descends across the thigh to the inner part of the leg, communicates with a filament from the obturator, and O 7 is continued to the foot, giving filaments in its course to the fascia and skin. The obturator nerve, on emerging from the y O O pelvis, gives branches to the pectineal muscle, the triceps, and gracilis, and sends a branch to communicate with the saphenus nerve ; several fine branches pass down on the inner side of the thigh for the fascia and integuments. The sciatic nerve, O O * on emerging from the pelvis, communicates with the internal pudendal ; it sends a branch to the internal obturator muscle, and one which gives a filament to the upper portion of the gemelli, and then passes behind the tendon of the internal obturator to the lower portion of the gemelli and quadratus muscles. The sciatic passes close to the insertion of the in- ternal obturator muscle, and upon or behind the gemelli and quadrati muscles, then behind the trochauter covered by the origin of the biceps to which it gives a branch : it sends off a large branch w r hich divides into others for the semimembranosus and semitendinosus muscles. About the middle of the thigh it sepa- rates into the posterior tibial and peroneal nerves. The posterior tibial nerve sends off a long slender branch which descends on the posterior part of the gastrocnemius muscle to the outer side of the leg, sends a branch behind the tendo A chillis to the posterior tibial nerve, and is distributed on the skin at the outer side of the leg and heel. It then gives N 2 ISO ANATOMY OF VERTEBRATES. branches to the gastrocnemius, and passes between the heads of this and gives branches to the flexor of the toes, the tibialis posticus and the flexor longus hallucis ; it then passes down the leo; on the inner side of the tendo Achillis, and receives the O ' branch from tlie long slender branch, sent underneath this tendon. It passes behind the inner condyle of the tibia, and divides into the inner and outer plantar nerves : the inner plantar gives a branch to the inner side of the second toe, and then communicates with a branch of the deep plantar, and divides for the outer side of the second and the inner side of the third ; it also communicates with a branch of the deep plantar given to the outer side of the third toe and the inner of the fourth ; the outer plantar nerve passes between the flexor tendons, and sends a nerve to the outer side of the foot and the last toe ; it gives off the deep plantar, which passes underneath the short flexor of the toes, and divides into branches, and gives filaments to each of the small muscles situated in the sole of the foot, and a branch to communicate with one from the inner plantar nerve : it then divides for the outer side of the second toe (the innermost in the Fox and most digitigrades) and the inner side of the third, and one for the outer side of the third and the inner of the fourth, and another for the outer side of the fourth and the inner of the fifth toe. The peroneal nerve gives a small branch to the biceps and filaments to the fascia near the knee ; it then divides the anterior tibial nerve, sends off branches to the anterior tibial muscle, the long extensor of the toes, and the long peroneal, and descends with the anterior tibial artery, beneath the annular ligament, and gives branches to the ligaments of the foot ; it passes on- wards, and is joined by a branch from the continuation or dorsal branch of the peroneal, and divides for the outer side of the second and the inner side of the third toe. The continuation or dorsal branch of the peroneal, gives branches to the short and third peroneal muscles, and passes behind the long peroneal, and emerges between this and the long extensor of the toes ; it passes over the annular ligament, and sends a branch to the outer side of the foot and the fifth toe ; on the back of the foot it sends the branch to join the anterior tibial nerve ; it separates into two branches, the first divides for the outer side of the third and the inner side of the- fourth toes, the other for the outer side of the fourth and the inner side of the fifth or outermost toe. The chief characters of the minutely detailed distribution of the myelonal nerves of Man, in works on his anatomy, are found in most Quadrumana. Mr. Swan has remarked that the saphenus NERVES OF MAMMALIA. 181 nerve is proportionally larger in a Baboon : and he also notices the large size of this nerve in the Jaguar. The nerves of the palm are proportionally smaller in Apes than in Man, and do not terminate in such thick brushes of filaments at the tips of the fingers ; but the branches from the musculo-spiral and ulnar nerves to the back of the hand are larger in proportion than in Man. 1 Many Quadrumaiia have the ganglion on the termination of the spiral nerve at the back of the wrist ; but in the Felidce there is only a slight enlargement at that part of the nerve. 212. Sympathetic system. This, as an addition to the general nervous system, is a speciality of the Vertebrate subkingdom : as such it dawns in Myxinoids, at the confluence and intestinal production of the two vagal trunks, and is differentiated by pro- gressive steps, till it attains the general condition defined in vol. i. p. 318, 57. 2 TVhere it begins in the series there the chief centres are after- wards established, as the semilunar ganglions and solar plexus, so called from the multitudinous rays that diverge therefrom ; they are early and distinctly visible in the mammalian embryo. The ganglions of the sympathetic vary in the proportion of the grey or cellular and filamentary or tubular constituents. The cellular part forms a greater proportion of the semilunar ganglions in Man than in most lower Mammals : and it is greater in Car- nivora than in hoofed quadrupeds. The filaments radiating from the semilunar o-ano-Kons collect themselves into interlaced o o groups named after the viscera they mainly supply, as, the 4 gastric,' ( hepatic,' ' splenic,' ( mesenteric,' ' renal,' t spermatic,' &c. : the chief branches of all these plexuses attach themselves to the arteries of the several organs : in the large gastric plexus of the Ruminants they accompany these to the several divisions of the complex stomach. In the Carnivora branches of the superior mesenteric pass in a more definite form to the aggregate of mesenteric glands at the root of the mesentery. In Perisso- dactyles, in which the cascum and colon are remarkable for size and complexity, the superior mesenteric plexus, supplying these parts of the large as well as the small intestines, is proportionally larger than in other Mammals, especially as compared with the inferior mesenteric plexus in Carnivora and Quadrumana. In 1 LIV. p. 193. Much of the foregoing description is abridged from this rich store- house of Comparative Neurology. 2 This true idea of the series of ganglions and nerves, called 'sympathetic' in Man, once clearly attained, will leave little room for speculations as to whether the ner- vous system of insects answers to the myeleneephalic or sympathetic part, exclusively, of that of Vertebrates, 1S2 ANATOMY OF VERTEBRATES. 137 Re the Baboon the caecum and about one foot of the colon is supplied by the superior mesenteric plexus, and the remaining five feet of the large intestine by the inferior one. In Carnivora this sup- plies about the terminal half of the large intestine. In the baboon Swan noticed a communication between the right phrenic nerve and the semilunar ganglion. 1 The trunk, advancing or ascending from each semilunar gan- glion, is an aggregate of cords (' splanchnic nerve,' Anthropotomy), which, perforating the diaphragm, separate to form communica- tions with a variable number of the thoracic ganglions of the sympathetic. In the baboon Swan traced the origins or con- nections of the right splanchnic nerve with two thoracic ganglia in advance of the left, this extending over the heads of five posterior ribs, and the other over seven, each ex- panding into a small ganglion at the bottom of the chest. In the hedge- hog the splanchnic nerve extends over the heads of the four last ribs, and, receiving filaments from the sympa- thetic, forms a plexus on the sides of the vertebra?, as in the baboon ; but separates from the trunk of the sym- pathetic higher in the chest. In the jaguar this separation occurs a little above the diaphragm : in the hog at the passage through the diaphragm. But ' these variations do not seem to make any difference either in the for- mation of the semilunar ganglion, or the branches preceding from them.' 2 Kolliker has given the subjoined view, fig. 137, of the communication of the splanchnic, Spl, with the myelon by the ' rami communicantes ' Re, ftc, and with the ganglion of the sympathetic, G, from which it derives its grey fibres. From the trunk of the sympathetic TV and the ganglion the nerve s to the intercostal artery is sent off. In Mammals the parts regarded as ( trunks,' or i main chords' 3 of the sympathetic, form a symmetrical pair extending along the sides of the centrums, forward to the basioccipital, and backward 1 LIV. p. 115. 2 Ib. 3 ' Prolongations,' SWAN. LIV. passim. T Sixth thoracic ganglion of sympathetic, RaVibit. Lxxvui". NERVES OF MAMMALIA. 183 Section of sixth intercostal with communicating branch to sympathetic. Rabbit (mag. 60 diam.). LXXVII-. A 139 to the coccyx : anteriorly, or above, they pass to ganglions and plexuses, within, or about, the cranial -,& 7 cavity ; below or behind, they con- verge and unite, generally, in a ter- minal f coccygeal ganglion. In their course the cords cross, ventrally, the issuing trunks of the spinal nerves, with which they are connected by short threads, including grey and white fila- ments, and there usually swelling into ganglions. The grey or gelatinous thread is most probably a contribution from the ganglion to the myelonal nerve, the white thread is sent from the nerve to the sympa- thetic ganglion : it consists of tubular nerve-fibres, and these predominate in the ' rami communicantes ' of the rabbit and cat. 2 Under a power of sixty diam. after addition of dilute solution of soda Drum- mond found such fibres con- tinued mainly from the mye- lonal end or origin, fig. 138, C, of an intercostal nerve, and converging to form the com- municating branch, RC, with the sympathetic ganglion. A few filaments, , , disappear among those of the intercostal nerve rather in the direction of its outward course. Traced tO the Sympathetic gailgllOn, Fourth thoracic ganglion, with course of fibres received ,1 I by the communicating branch, c, from the myelou. iiiey diverge, (Mag 70 diain.) 1 Lxxvii". p. 446. B in fio- ng. 184 ANATOMY OF VERTEBRATES. spreading over its cellular part , and in greater propor- tion at the surfaces a a, cc. Thus, at certain portions of the tongue, three sets Section of cortical layer, upper part of tongue. O f fibl'CS traVCl'SC til 6 SaillC (30 diain.) CCXL. area, in as many distinct directions and at right angles one with the other ; the arrange- ment being so that the crossing of the fibres of any two sets forms 1 a faces emerge ORGAN OF TASTE IN MAMMALIA, 201 a net, the meshes of which in successive layers become canals through which the fibres of the third set pass ; hence in whatever plane they be viewed, two sets are seen, in profile, crossing, and one, in section, perforating ; by which arrangement they mutually support and conduct each other, independently of connective tissue, the dispensing with which allows for the aggregation of so much more muscular tissue in the tongue's substance. In fig. 147, a magnified view is given of a section from the upper surface, a, in fio-. 145 : a are the vertical fibres extending to that surface, be- O O J yond the uppermost transverse fibres, b, and decussating with the longitudinal fibres shown in section at c. This complex arrange- ment becomes simplified toward the apex : the longitudinal fibres first ceasing, next the vertical ones, and the transverse alone being continued to the tip. 1 The skin of the tongue is divided into the papillose, glandular, and smooth, mucous, or faucial areas : the latter, fig. 141, d, has about half an inch of longitudinal extent when not stretched, and answers to the much more considerable tract in the Lion. The glandular area is defined anteriorly by the fossulate papilla, ib. /, here arranged ( en chevron,' four on each side converging toward the backwardly turned point : behind this is sometimes seen a fossa devoid of papilla, the ( foramen caecum ' of Anthropo- tomy. The papillose area extends over the major part of the tongue to its tip and down the sides along part of the under surface ; it is roughened by papillae which extend from the medial groove in oblique series forward and outward, repeating in the main the arrangement of the fossulate or glandular o o papillae. The tongue-skin presents a basal areolar tissue, so dense in the glandular and papillose area? as to resemble the corium : at the faucial area and under surface of the tongue it softens into the character of that of the mucous membrane of the cavity with which it is continuous : where it overlies the muscular part of the tongue, as in fig. 145, a, it is closely adherent thereto, and is thickest at the middle line : peripherally it projects as ' papillae,' sinks into ' fossulaa,' and is inverted to form the ducts or orifices of mucous follicles. The epithelium is scaly, thick and distinguishable into a deep layer adherent to the corium and a superficial layer which readily desquamates. The so-called 1 papillae ' are processes of the corium, rather analogous to the 1 For further and more minute details of this exquisite arrangement of the mus- cular tissue for the functions of the tongue, reference should be made to the admirable article CCXL, in which the accomplished author, HYDE SALTER, first described it. 202 ANATOMY OF VERTEBRATES. 148 villiform ones in the intestinal mucous membrane of some animals (vol. ii. p. 170), and subdividing, as in those, into the ' villi ' or papillae truly answerable to those of the skin ; the tonguc- papilla) or processes differ, therefore, from the true dermal papilla? in standing freely out from the surface of the epithelium, which is moulded upon them, and does not plaster them over to its own level. The so-called lingual papilla are of three kinds, f fossulate' or circumvallate, ' fungiform,' and f conical,' many of the latter bcins; also called ( filiform.' o The fossulate papilla, fig. 148, a, is large, obtuse, subpedun- culate, and arises from a fossa, b, by the thickened and often crenate borders of which, c, it is surrounded. The nerves and vessels enter the papilla at its pedicle ; and the expanded sum- mit subdivides into the secon- dary true papilla), plastered over by the epithelium. The average number of fossulate papillae in Man is eight, arranged as in fig. 14 1,/: there be sometimes ten, rarely more ; often fewer than eight, but not less than four. Their arrangement may vary to that of an almost transverse line. They are supplied by branches of the glossopharyngeal ; are very vascular ; and, from the thinness of the epithelium, appear red when injected. The 'fungiform papillae/ fig. 149, B, are subpedunculate, but 149 Section of fossulate papilla (10 diam). CCXL. Fungiform papillae, cxi". smaller than the fossulate and rounder : they are scattered over the sides and tip of the tongue, and on the dorsum anterior to the fossulate series. They are rather larger than the filiform, and conspicuous by their red colour. They are covered by ORGAN OF TASTE IN MAMMALIA. 20.-J 150 151 secondary papilla?, ib. A, in which the capillaries diverge and divide to form their brush of loops, as in fig. 149, B, receiving each its capillary loop, into the fasciculus of which the branch of the artery a and vein v sub- divides on entering: the O mushroom-like papilla or process. The conical papillje clothe as in a close-set pile the anterior two-thirds of the dorsum : they are longest at the mid-line near the centre of the tongue, small- est near the sides and at the tip. The cone-form, with secondary papillae down its sides,fig. 150, merges into the cylindrical form, fig. 151, with a terminal brush of filaments. The excess of the scaly covering of these, ib. a, b, c, forms the so-called ' fur ' of the tongue, which becomes separated from the deeper layer of epithe- lium, d. In the conical variety, fig. 150, a is the basal mem- brane, b, c, the ' processes,' sub- dividing into secondary or true papillae, e, the deep layer of epithelium, f, the superficial layer, //, the points from which the filamentary prolongations would have projected : these sometimes resemble fine hairs. The function of such filiform papilla? appears to be ' portative ' and ( protective,' that of the coni- cal papillae mainly ( tactile,' that of the fungiform and fossulate ones ( gustative : ' behind the latter are the principal mucous follicles. The so-called gustatory branch of the fifth supplies the fungi- form, conical, and filiform papillae ; the glossopharyngeal serves Filiform papilla. CCXL. 204 ANATOMY OF VEBTEBEATES. tlic fossulate papilla? and the mucous tract behind : the ninth or hypoglossal is expended upon the muscular tissue. 215. Organ of Smell. Most Mammals are remarkable for the degree in which the sense of smell is serviceable. The class is characterised by the extent of the pituitary surface and the size and number of the olfactory nerves; nevertheless, both ex- tremes are therein exemplified, although the family (JDelpMnidoz) in which the organ is wanting is exceptional and maximised development the rule. The progress is not, as with the organ of taste, pari passu with the rise in the class : both Man and monkeys are below most quadrupeds in olfactory endowments. In hoofed ones smell is important in the the discrimination of wholesome from noxious food : taste would be a tedious test, the sapid matter needing to be moved about or masticated, mixed with fluid, and more or less dissolved, before the tongue can exert its gustative power ; but ( smell is done at once.' 1 Most flesh-feeders scent afar their food. In Mammals, as in all air-breathers, the odorous atoms strike upon the olfactory membrane at the entry of the breathing passages, where the atmosphere is filtered, as it were, through the organ of smell before reaching the windpipe ; and most effectively and instructively in the pinnigrade Carnivora. The olfactory organ in Mammals receives its special endowment from nerves which rise in numbers from their proper encephalic centre, fig. 46, 47, R. They pass out by as many holes in the plate of the prefrontal, which is thence called the ( cribriform,' or, from the Greek-root, ' ethmoid:' but the sieve-like structure is a strictly mammalian peculiarity consequent on the multiplicity of olfactory nerves, and is only affected by a single exception in this class, the Ornithorhynchus adhering to the wider Vertebrate rule. The nerves carry out with them, each an investment of the brain-membranes ; the dura mater losing itself in the periosteum, the pia mater in neurilemma, the arachnoid being reflected back. The nerves are grouped in all Mammals into a set for the septum, and a second for the upper or ethmo-turbmals, a third or middle short set being, in some, distinguishable for the labyrinth or roof of the nasal chamber. The branches of the second set, after expanding on the ethmo-turbinal, usually converge to become connected with the lateral nasal branch of the ( fifth.' Their mode of distribution is best seen on the ethmo-turbinal : 1 xx. vol. iii. p. 86. ORGAN OF SMELL IN MAMMALIA. 205 here they divide, subside, expand, and anastomose with each other, forming a reticulate nervous expanse, with long and narrow meshes, and becoming impacted in the central or inner layer of the olfactive membrane. This membrane is continued into the pi- tuitary one, covering the inferior spongy bone or 'maxillo-turbinal' supplied mainly by the fifth. Both tracts, and especially the latter, are richly supplied with arteries opening into numerous large plexiform veins on the peripheral side of the membrane, occasioning or resembling, there, a cavernous structure, and O o- 7 admitting of such change in the quantity of blood therein as must be attended with concomitant degrees of laxity or tension of the scentino- membrane itself. 1 This at the attachment of the tur- o binals is continuous with the lining of the nasal chamber ; which itself becomes modified into the more delicate and still less vas- cular membrane of the contiguous or accessory air-sinuses. The nasal membranes are finally continued at the posterior aperture into the mucous membrane of the fauces and pharynx, and at the anterior one into the integuments of the face. The pigmental layer of the skin is soon lost within the nose, the colour of the pituitary and olfactory membranes being due -to the abundant blood sent to them. Numerous mucous crypts are imbedded in the pituitary part of the nasal membrane. The cavity containing the organ of smell is formed by the prefrontal, vomerine, nasal, sphenoid, pterygoid, palatine, max- illary, and premaxillary bones, and may be continued by exten- sion of air-sinuses into all the bones of the cranium, figs. 1 54 and 157. The cavity is divided by a medial partition of bone and gristle in varying proportions, the bone being contributed by the prefrontals, the vomer, and by ridges of the nasals, palatines, maxillaries, and premaxillaries, with which the vomer may articulate. Each half of the cavity is a passage for the respiratory currents of air, opening anteriorly upon a more or less produced and mobile part called ' nose,' ' snout,' or f proboscis,' and pos- teriorly into a cavity containing the larynx or beginning of the windpipe; sometimes, as in Cetacea and in Marsupials at their mammary stage, containing the larynx exclusively, but commonly communicating also with more or less of the pharynx. In the section of the human skull, fig. 152, the outer wall of the right nasal passage is shown, with the communicating frontal, 3, and sphenoidal, 4, sinuses ; i is the nasal bone, and a the nasal spine 1 Lxxxii--. p 278, and LIV. p. 123. (The second edition of this valuable aud original work, 4to, 1864, is the one cited in the present volume.) 206 ANATOMY OF VERTEBRATES. 152 of the frontal, forming the fore part of the roof, c, the basi- sphenoid, forming its back part ; the ' cribriform plate and spine ' of the prefrontal completing the roof: I is the nasal plate of the maxillary bounding laterally the anterior aperture; d, pterygoid, similarly bounding the posterior aperture : the floor of the passag< is formed by the premaxillary, 7, the maxillary, k, and the pala- tine, G. At the upper part of the outer wall is a thin quadrilateral part of the prefrontal sculp- tured by grooves and aper- tures for the olfactory nerves; the posterior part, f, is a little curved, and leaves a space into which the sphenoi- dal sinus opens. The con- volute, thin, reticulate, bony, and gristly lamina, called 6 superior turbmal,' is here attached, below which is the division of the general pas- sage, called e superior mea- tus.' This is bounded below by a similar longer and larger ( turbmal, ' called ' middle spongy bone' in Anthropo- tomy, but usually less dis- tinct from the upper part of the * ethmo-turbinal ' in lower Mammals. The part of the passage between the middle and lower turbinal is the ( middle meatus,' into which the ' antrum ' or maxillary sinus opens. The lower turbinal is the largest of the three, and longest retains its indi- viduality : below it is the s inferior meatus,' /, into which the lacrymal canal opens. In most lower Mammals there is a turbinal process from the frontal and nasal bones ; which, from its relative position in their horizontally elongated nasal chamber, is called the ( superior spongy bone ' (oberste muschel, Gurlt), by Hippotomists ; it is not the homologue of that so called in Anthropotomy. At the floor of the lower meatus, close to the premaxillo- m axillary ridge supporting the fore part of the septum, is a depression or groove lined by a glandular tract of the pituitary membrane which, in Ungulates, is extended upon a long and narrow gristly sheath at that part, and communicates with the palate by the foramen incisivum. From one to three of the ei)tal branches of the olfactory, traceable from a yellowish grey A icw of the outer wall of the nasal cavity ou the right side. ORGAN OF SMELL IN MAMMALIA. 207 part of the rhiiiencephalon, are continued clown to this tract ; but it is principally supplied, like the lower turbinal, by the naso- palatine nerve. 1 Characteristic of the mammalian organ of smell is the great O a provision made by bony and gristly laminae for the support of the olfactory membranes. The original extent of these primi- tive capsules is augmented, as in a branchial organ, by manifold plicae and processes, usually so curved and contorted as to suggest the resemblance to turbinate univalves. The neurapophyses transmitting the nerves of the nasal segment of the skull are reduced, as has been shown, in Mammals, almost to their essential function ; as such they appear in Celacea (vol. ii. p. 421, fig. 287, H ). So reduced and withdrawn from outward view, they are further masked in the rest of the class by the agglutination thereto, or outgrowth therefrom, of the turbinal olfactory capsules : the whole, as agglomerated in them, receiving the name of ( sieve-bone ' (ethmoid), from the exceptional pecu- liarity of the number of olfactory nerves in the Mammalian class. In fig. 153 is given an oblique view of this complex bone with the anchylosed sphenoid in the Hog. The confluent mesial 153 Osseous parts of olfactory capsules. Hog. laminae of the prefrontals project as ' crista galli ' dividing the rhinencephalic fossae : to the under or outer part of the cribriform or perforated laminre of the neurapophyses the parts of the olfactory capsules called < labyrinths,' q, and ethmoturbinals, .9, are anchylosed : the maxilloturbinals, p, remain longer distinct, and ultimately coalesce with the superior maxillaries. The con- volute plates attached to the roof of the nasal chamber, fig. 157, /;, here called ' naso-turbinals,' are in most quadrupeds added to those shown in figs. 152 and 153. 1 XC", CXJl"', 208 ANATOMY OF VERTEBRATES. In the Ornithorhynchus one olfactory nerve quits each rhincn- cephalon and escapes from the skull by a single foramen at the fore part of the prefrontal plate : it divides on entering the nasal cavity into septal and turbinal branches. The membrane re- ceiving the former is supported wholly on a bony plate : the turbinals are partly bony, and partly gristly : a prenasal ossicle is formed in the forepart of the nasal septum. The olfactory nerves in the Echidna are extremely numerous, and the cribriform plate is large and encroaches upon the fore part of the cranial cavity as a convex protuberance. The ethmo- turbinals are of corresponding size, composed of a series of vertical processes which expand and subdivide as they pass toward the floor of the very long nasal passage. I have shown the lateral expanse of these turbinals by a horizontal section in No. 1707, XLIV. p. 318. The olfactory nerves and the osseous cavities and laminre destined for the protection and support of the pituitary membrane offer a remarkable proportional development in all the Marsupials, and more especially in the Insectivorous and Carnivorous tribes. Certain species of Kangaroo, of the subgenus Osphranter, Gould, remarkable for their acuteness of smell, have the turbinated bones so large that the lateral expansion of the nasal cavity forms a marked feature in the skull. The characters of the osseous parts of the nasal cavity, in this order, are given in vol. ii. p. 348. Through the defective ossification of the palate the convolutions of the inferior turbinals are visible in the dry skull at that part ; e.g. in Perameles layotis (vol. ii. fig. 222) and in Thylacinus. In the latter marsupial the fine lacework perforation of the inferior turbinals is well shown. In the Hare the inferior turbinal is large, longitudinally la- mellate, and shows in well-injected specimens the highest degree of vascularity : the complexity of its medial or septal surface contrasts with the simplicity of that in Felines. The ethmotur- binals are divided into three principal lamellrc : the nasal cavity is long but narrow : the maxillary sinus is small. In the Agoutis the nasal chamber is more expanded : the ethmoturbinals which consist each of four rather short longitudinal lamella, are divided from the maxillo-turbinals by a protuberance from the mesial wall of the large maxillary sinus : there is a small ' Jacobsoii's' process from the premaxillary at the lower and fore part of the nasal cavity. In the Paca ( Ccdogenys) the olfactory cavity ex- tends backwards beneath the rhinencephalic one. In the Porcu- pines through the enormous development of sinuses from the olfactory cavity it extends backward beyond the rhinencephalic ORGAN OF SMELL IN MAMMALIA. 209 one, which it appears to encompass. The latter cavity is defined by a well-marked ridge from the prosencephalic part of the cranium. The vomer is deeply cleft posteriorly, and coalesces with the ethmoturbinals. The fore part of the vomer articulates with the median ascending process of the premaxillary arching over the wide vacuities which lead from the nasal passages to the prepalatine apertures. Besides the maxillary sinuses others are developed in the frontals, squamosals, alisphenoids and orbito- sphenoids, with bony septa converging to the rhinencephalic fossa?. No nasal sinuses or aircells are developed in the skull of the aquatic beavers. In the voles (Arvicola) a canal leads from the crescentic orifice at the fore part of the antorbital aperture into the lower part of the nasal meatus, above the pre- palatine fissures. In the rat (Mus decumanus) it terminates below the attachment of the anterior turbinal to the premaxillary. In all Muridce the olfactory cavity is very narrow ; the ethmo- turbinal small and but little divided ; the lower turbinal is ele- vated in position. The external nose is short and, as in most Rodents, is clothed with hair save at the middle of the septum. In Insectivora the olfactory organ is better developed than in Rodentia. The ethmoturbinal of the mole has not fewer than eight primary lamella? ; but the maxilloturbinal is comparatively simple : the external nose is developed into a snout, with well- marked muscles for various and powerful movements. The de- velopment of this part is such in some African Insectivora, fig. 297, as to have earned for them the name of ( Elephant-Shrews.' The naked outer border of the nose in the common hedgehog is den- tated : and the edge of the snout is fringed in Condylura with a circle of soft processes. But these, like the still more extra- ordinary dermal appendages in certain bats (Rhinolophus) relate to touch. The armadillos and anteaters enjoy an acute sense of smell. In Dasypus sexcinetus the rhinencephalic almost equals the epencephalic division of the cranial cavity : but the olfactory chamber extends backward to beneath the prosencephalic division, and the ethmoturbinals are remarkably extensive and complex : the maxilloturbinal is comparatively simple. The turbinal plate of the nasal almost equals the facial plate in extent. The chief expansion of the cranium is caused by the large olfactory cavity, and the part extending therefrom into the frontals raises them in Chlamyphorus into a pair of domes (vol. ii. fig. 272, a). In most Armadillos the external nose or snout is strengthened by a pair of prenasal ossicles. The rhinencephalic chambers are large in VOL. in. p 210 ANATOMY OF VERTEBRATES. 154 Orycteropus (ib. p. 404) ; but the olfactory ones are far more remarkable for both size and complexity. In the true Anteaters (Myrmecophaga) the cthmoturbinals, though large, are less de- veloped than in armadillos. The inferior turbinal is a long slightly rolled up lamina. In sloths, as described in vol. ii. p. 406, the olfactory chamber extends backward above the rhinencephalic one into the frontal bone, and below it into the sphenoid. The extension of air-sinuses therefrom is still greater in the extinct megatherioids (ib. 407). The baleen-bearing whales are those of the Cctacea which alone have olfactory nerves, although all possess the ( crura rhinencephali.' The pituitary membrane supported by the tur- binal bone is remarkable for the plexus of large vessels behind it. The cetacean modifications of the nasal passages will be described with the respiratory organs, to which they mainly relate. In Sirenia the nostrils are subterminal, at the top of the obtuse muzzle, and provided with movable gristles : the nasal passages contain both ethmo- and maxillo-turbinals, the latter, like the former, gristly ; the small almond-shaped bones wedged into the fore part of the frontals are, as Cuvier held, nasals, not turbinals. 1 The nasal passages are short, narrow, sub vertical : the ethmoturbinal is short and longitudinally lamellate. The olfactory nerves are fewer and the cribriform plates smaller in the Dugong than in the Manatee. In the Elephant that part of the nasal cavity, fig. 154, which is appropriated to the essential parts of the olfac- tory organ is contracted and narrow, and the passages, a, b, are relatively short : they are, however, much prolonged by the accessory appendage, called ' trunk,' at the extre- Scction of Elephant's skull, showing nasal passage. .. r i i -i mity of which open the nos- trils (vol. ii. p. 282, fig. 162, n), and are as much expanded 1 ' Cornets infeiieurs,' De Bl. ; civ'. Gravigvadc=, p. 39. ORGAN OF SMELL IN MAMMALIA. m 1 ;"> 5 by the surrounding air sinuses, Avhich pervade every bone of the cranium. The bony nasal passage is continued in almost a straight line from the anterior aperture, a, to the posterior one, 1. The vomerine part of the septum, 1.3, extends from the pre- sphenoid about half-way to the anterior aperture. At the upper part of the cavity, so divided, the ethmoturbinals are situated, which are moderately plicated : the maxillary turbinal is, also, comparatively simple in character. In the Tapir the shorter proboscis terminates by a small pointed extremity between the nostrils. The snout is covered with hair to the base of the terminal appendage ; the hair on the upper part tending upward or backward, that on the sides toward the tip. The cribriform plate is not simply perforate, but is re- ticulate, with long radiating meshes, the latter closed by dura mater : it sends down curved lamellrc, sheathing the olfactory nerves. The ethmoturbinal consists of as many convolute divi- sions attached to, or continued from, those processes, in a pedun- culate way ; and each is perfo- rated bv many foramina through / / O which branches of the olfactory pass to the pituitary membrane. The maxillary turbinal is elon- gate and simply convolute. The nasal cartilages show the chief modification, the alar portions, fig. 155, n, being continued backward, expand- ing, and filling the peculiar grooves of the skull (vol. ii. p. 449) between the nasal bones and orbits, o : here the cartilages are semiconvolute, convex, and entire outwardly, excavated on the inner side, the cavity being continued by a groove into the nasal one at the sides of the outer aperture : from the character of the lining membrane, it may be regarded as an extension of ' Jacobson's fossa.' The ' levator rostri,' or raiser of the short proboscis, fig. 155, a, arises from the process of the lacrymal, runs in a fibrous sheath, couvero-ino- to its fellow, and is inserted into the upper or fore-side of the part which, together, they raise, or, acting separately, draw to their own side. A broader muscle, ( retractor labii,' Z>, from the same origin expands to its insertion at the side of the labial part of the base of the proboscis. Beneath this is the muscle, c-, which rising from the lower border of the lacrymal, spreads upon the p 2 Alinasal cartilage - and muscle.? of trunk, Tapir. xcni". 212 ANATOMY OF VERTEBRATES. 156 side of the proboscis, and is intimately connected with the ' orbi- cularis oris,' d d; c is the zygomatic, f the depressor anguli oris, y the buccinator. 1 The external nose of the Rhinoceros is com- bined with the upper lip and prolonged in a minor degree, but with a like arrangement of muscles, for prehensile purposes. The nose of the Horse is chiefly peculiar for the power of the dilating and contracting each nostril, such movements being sub- served by a lateral semilunar cartilage, fig. 156, /, ; by a de- pression or fold of contiguous skin, called ' false nostril ' in Hippotomy, and by the homo- logues of the muscles of the combined nose and lip of the Tapir. In fig. 156, a is the ( levator rostri ; ' b is the f re- tractor labii alasque nasi;' c is the muscle called ' transversus nasi,' in Hippotomy ; e is the zygomaticus ; f marks the in- sertion of a muscle, ' pyrami- dalis ' of Hippotomy, which arises by a slender tendon from the maxillary, and gliding be- neath the labial part of b, ex- pands to be inserted, fleshy, into the outer border of the nostril and contiguous skin- folds. The Horse is remarkable for the size of the rhinencephalon and the extent of the cribriform plate transmitting its nerves to Muscles of nostrils and upper lip, Horse. t ] ie noS e : they paSS Upon a series of about ten short longitudinal folds directed forward and a little downward^ forming the ( ethmoidal labyrinth' of Hippotomy, the upper larger division being the ' ethmoturbinal ; ' a longer, larger, more simply disposed plate, attached to both prefrontals and nasals, and chiefly descending from the latter bones, forms the ' nasoturbinal : ' beneath this is the ( maxilloturbinal,' of about the same vertical extent, and almost the same length. The bony septum contributed by the coalesced prefrontals, forms, superiorly, about one-fourth of the general partition : the vomer 1 xcin. pp. 20-26. ORGAN OF SMELL IN MAMMALIA. 213 extends, beneath it, along about three-fourths of the lower third of the septum, but subsides to a point ; the major part of the septum is gristly. In the Hippopotamus the nostrils are relatively small, promi- nent, wide apart, and are served by muscles which open and close them like the eyelids, besides protruding and retracting them. The accessory sinuses of the nasal chamber are very little developed. Their extent and size offer a great contrast in the Hog-tribe, in which the essential parts of the olfactory organ are also relatively larger and more complex. The rhinencepha- lon is large, with many nerves, and the cribriform plate of great extent : the ' labyrinthic ' part of the capsule attached to its under or outer surface forms nine or ten longitudinal, slightly diverging folds, fig. 153, q, the three or four uppermost of which coalesce to form the ethmoturbinal, which is long, slender, subconvolute, and attenuated to a fine point forward, ib. s. This figure gives an oblique view of the e labyrinth,' q, and ethmoturbinal, s, of the right and left sides. The nasoturbinal is of moderate length. The somewhat deeper and more con- volute f maxilloturbinal ' is shown at p : the accessory ( nasopa- latine ' fossa, at k. The pterygoid, f, bounding the posterior nasal opening is excavated and expanded above by a sinus continuous with those of the sphenoid, ?i. The accessory sinuses of the nasal chamber are very considerable in the Hog-tribe : the frontal ones (vol. ii. p. 468, fig. 315, 11, young Pig) extend back- ward over the calvarium to the occiput in the Boar: a structure well shown in the Babyroussa, No. 3346, * in which preparation the extension of the sphenoidal sinus (ib. fig. 315, f) into the base of the pterygoid is demonstrated, where it is divided into an external and internal compartment. In Phacochcerus the pterygo-nasal fossa is simple, and the frontal are almost separated from the parietal sinuses by the near approximation of the inner to the outer table of the skull. The pterygo-nasal fossa? are absent in Dicotyles. In all Suidce. the external nose is somewhat prolonged and truncate, the nostrils opening upon a naked disc : the cartilages of the nose form a complete tube, which is a con- tinuation of the bony nostrils, and near the end of the snout the cartilaginous septum becomes ossified, and forms the prenasal ossicle (ib. fig. 315, o). In the Ox the cribriform plate is relatively smaller and the olfactory nerves fewer than in the Horse : the labyrinthic part of the ethmoid consists of about six short narrow longitudinal 1 XLIV. p. 557. 214 ANATOMY OF VERTEBRATES. folds, most of which coalesce to form a larger and more simple ethmoturbinal than in the Horse; the nasoturbinal is very long and slender : the maxilloturbiual of much greater extent, espe- cially in vertical diameter : it terminates forward obtusely. In the Sheep the nasoturbinal is relatively deeper and less pointed than in the Ox. The nasal passages, from the lower border of their anterior outlet, traverse nearly three-fourths of the lonin- & tudinal extent of the long and slender skull of the Giraffe, fig. 157. The upper folds of the 'labyrinth' coalesce, and are pro- duced into the moderately long and deep ' ethmoturbinal ' a : the ' nasoturbinal,' I, deepest behind, is longer and more pointed 157 Left half of na*al cavily and lurbinals, exposed ia section of cranium ; Giraffe, xcvn' anteriorly than in other Ruminants ; the ( maxilloturbinal,' c, is large and deep, finely reticulate or perforate ; it is crossed by part of the vomer in fig. 157. The extent to which the air- sinuses communicating with the nasal chamber are extended is shown in this section, and noted in vol. ii. pp. 477, 478. The nasopalatine nerve entering the chamber below the fore-end of the ethmoturbinal receives some part of the olfactory filaments converging toward that end, then sends upward and forward a small branch to the nasoturbinal ; a larger branch downward and outward to the chamber-wall and its lining ; the main part being expanded on the long nasoturbinal. In the Ruminants a gradation may be traced in the extent of the glandular and, in health, moist part of the skin of the ex- ternal nose, from the Sheep, where it is a mere linear tract from the mid-furrow of the upper lip bifurcating to each oblique nostril, ORGAN OF SMELL IN MAMMALIA. 215 through the Roebuck, Fallow-deer, Red-deer, to the Ox, where it constitutes the broad naked muzzle. 1 The organ of smell in Carnivora mainly differs from that of hoofed Herbivora in the greater relative size and strength of the ethmoturbinal, the shorter, deeper, more massive and much more subdivided ' maxilloturbinal.' In the Lion the ethmoturbinal is of a pyramidal form, its broad base continued from the short labyrinthic part attached to the cribriform plate, its apex termi- nating forward, between the naso- and maxillo-turbinal. The o mesial surface of the ethmoturbinal shows numerous furrows, two of which are longitudinal and parallel with the upper margin of the bone, the others radiating from the lower part of the attached base : the lateral or outer surface is less complex and extensive ; but, on removing the outer layer, a series of con- centric curved folds are exposed. The ' nasoturbinal,' holding as in Ungulates the highest position, is an elongate cone, co- extensive with the roof of the nasal cavity and with its base opposite to the frontal sinus : the mesial surface shows a series of deep arched folds ; the lateral one seems more even, but when the peripheral lamella is removed a series of longitudinal folds of the bone is brought into view, beneath which are concentric folds -. o arched or curved in the opposite direction to those in the ethmo- turbinal. The maxilloturbinal is fusiform ; the hind end is at- tached to the outer wall of the nasal chamber below the middle of the nasoturbinal ; whence the bone rises and expands, crossing the anterior end of the ethmoturbinal, and again diminishing to its anterior and upper attachment behind the external bony nostril. From its position, therefore, the odorous atoms, in inspiration, must first impinge upon this bone, and the pituitary membrane is thicker and more vascular than on the other turbinals. Its mesial or septal surface presents one curved groove, parallel with and near to the lower margin of the bone : the outer surface has a like character. The more glandular part of the pituitary mem- brane is at the fore part of the floor of the nasal chamber, not occupying so deep a fossa as in Ungulates. The sources and distribution of the nervous supply corresponds with that noted in the Giraffe : the septal branches of the olfac- tory curve down toward the thickened base of the partition. In the Dog, the longitudinal folds of the ( labyrinth ' are about four, fewer in number but larger than in the Sheep : the aethmoturbinal is continued from the undermost and curves upward slightly to 1 This was pointed out to me by the estimable and justly famed \vater-colour artist and animal painter, ROBERT HILLS, F.L.S. 210 ANATOMY OF VERTEBRATES. the nasoturbinal as it advances : the maxilloturbinal is shorter, relatively broader and deeper, and much more extensively folded than in the Lion. This is the part of the olfactory organ that reaches the extreme of turbinal development in the Seal-tribe. In the large species dissected for the preparation, No. 1557, the maxilloturbinal is attached by its contracted extremities, the intervening enormously swollen mass is divided by a deep longi- tudinal furrow into two parts ; the free surface of which is singu- larly complicated by folds, radiating from both extremities of the bone and subdividing dichotomously. 1 These turbinals seem to block up the entry of the nasal respiratory passages, and must warm the air in arctic latitudes as well as arrest every indication from the effluvia of alimentary substances or prey. The nasotur- binals, in some Otariae, extend backward, with the nasal chamber, above the long rhinencephalic compartment of the cranium. In the Quadrumana the nasal chamber loses length and gains, but in less proportion, depth and breadth, from the Lemurs up to the Apes : the maxilloturbinal ceases to be suspended by its ex- tremities, and acquires a linear longitudinal attachment externally to a ridge on the maxillary wall of the nasal chamber. This tur- binal is divided into two chief parts lengthwise, in Lemuridce, where it is longest : the nostrils are here terminal, the anterior expan- sion of the septal cartilage curves outward and downward on each side, and, with a corresponding degree of curvation of the principal alar cartilage, gives a subconvolute form of nostril to most Strepsirhines. In the Aye-aye they describe a semi- circle ; and the nasal chamber by its shortness, depth, and pre- dominance of the ethmo- over the maxillo-turbinals exemplifies the quadrumanous affinities of the species. 2 In Platyrhine monkeys, the septal cartilage is remarkable for the transverse extent of its anterior terminal expansion between the nostrils, pushing them and their alar cartilages outward. In Catarrhines this expansion is much reduced ; and the nostrils are obliquely approximated. In both groups the nostrils cease to be ter- minal ; in a Bornean Douc ( Semnopithecus nasicus\ the nos- trils are produced upon an ill-shapen prominent subcylindrical nose. In the Gorilla each nostril is surmounted by a broad prominence, arching outward from a lower part impressed by a median furrow ; a deeper indent divides the nasal ala from the cheek : the aspect of the nostrils is forward and a little out- ward. The septal cartilage extends to the tip of the interalar prominence. 1 xx. vol. iii. p. 100. : cn'. p. 18, pi. viii. fig. 6. ORGAN OF SMELL IN MAMMALIA. 217 In Man the number of olfactory nerves varies from fifteen to twenty: after traversing the cribriform plate, they divide into two chief sets, ( septal ' and ( turbinal,' and ramify between the periosteum and the pituitary membrane before terminating on the latter. The septal nerves, fig. 158, , are about twelve in number, are quickly resolved into brushes of filaments, which unite together to form 159 plexuses, and send off branches forming 158 Branches of the olfactory and nasopalatine nerves on the septum of the nose. xciv. Alar cartilages, human tiose, xciv". finer plexuses, traceable to near the base of the septum. The posterior fourth of the septal membrane is chiefly supplied by the nasopalatine nerve, b. The ' turbinal ' or labyrinthic olfactory nerves are more numerous, rather smaller, and more plainly anastomotic in their course over the upper and middle ttirbinals, lying in grooves of the former, and extended chiefly upon the inner and lower front of the midturbinal ; a few combine with that part of the nasopalatine which supplies the lower part of the middle turbinal. The lower turbinal is almost exclusively sup- plied by a branch of the ( nasopalatine.' The main charac- teristic of the human organ of smell is the prominence of the fore-part of the chamber, having the nostrils on its lower surface, and constituting the feature emphatically called the f nose,' figs. 159, 161. The formative fold of integument is supported by eleven cartilages, of which one is medial, the others lateral, in live pairs. The medial or ( septal ' cartilage, fig. 160, is usually triangular, with three unequally curved margins : the upper one, 2)8 ANATOMY OF VERTEBRATES. IfiO Septal cartilage, xciv' 161 n, is fixed iii the groove of the ' perpendicular plate of the ethmoid,' the lower border, b, fits into the front groove of the vomer; the anterior border, c, extends from the nasal bones, where it is thickest, as at 2, d, and grows thinner down toward the apex of the nose. The varying proportions and form of the septal cartilage mainly govern the shape and prominence of the nose : it is least developed but thick- est in the Negro and Papuan races. The lateral cartilages vary in size and shape, the upper one, fig. 159, a, is triangular, continuous in front with its fellow, where they are closely connected with the tipper half of the anterior border, fig. 160, c, of the septal cartilage. The largest of the ( alar ' or e pinnate ' cartilages, fig. 159, b, is bent upon itself, almost surrounding and go- verning the shape of the nostril : it is movably connected with the lower and outer part of a. To the outer and hinder apex of the carti- lage by is joined the first of the three small cartilages, c, d, e, which sup- port the posterior convex part of the 4 ala ' or wing of the nose. The flex- ible fibrous tissue connecting these o elastic cartilages allow of the move- ments of the parts to be readily pro- duced, and the muscles are accord- ingly feeble. The ( pyramidalis nasi,' fig. 161, c, is continued from the medial portion of the ' frontalis,' fig. 28, f f which descends over the upper part of the nose to the cellular tis- sue covering the cartilage, a, and thence onward to combine o o y with fibres of the 'triangularis nasi,' fig. 161, e, and fig. 29, n. The ' leA^ator labii superioris alajque nasi ' is shown at dd, fig. 161 ; in the degree in which the alar is distinct from the labial portion, or has been distinctly exercised, the wings of the nose can be ex- Muscles of human nose, xciv ORGAN OE HEARING IN MAMMALIA. 219 paneled independently of any other movement of the face. The 6 depressor alae nasi,' ib. f, arises from the outer border of the sockets of the canine and contiguous incisor : the fibres ascend to the alrc, many of them arching over the outer and back pro- minence of the nostril. The 4 depressor septi,' ib. k, is detached from the upper part of the e orbicularis oris,' fig. 29, oo, the fibr