PACHYDERMATA. 



863 



some of the hog tribe, the two bones of the 

 fore-arm are completely consolidated into one 

 mass, the only vestiges of their having been 

 originally distinct being the indication of a 



suture near the distal extremity of the fore-arm 

 and a deep groove running along the middle third 

 of the bone for the lodgement of the inter-osseous 

 artery. In the Rhinoceros and Tapir, (Jigs. 475 



Fig. 475. 



Skeleton of American Tapir. 



and 476,) however, these bones remain perma- 

 nently distinct, the elbow-joint being formed by 

 the radius in front, which articulates with both 

 condyles of the humerus and the ulna pos- 

 teriorly, which completes the articulation. At 

 their distal extremity the radius lies in front and 

 to the inner side of the ulna, with which it is 

 either anchylosed or immoveably connected by 

 ligaments, both assisting to form the radio- 

 carpal articulation. In the Elephant, the 

 arrangement of these bones is very curious and 

 perhaps unique: the upper head of the radius 

 is firmly fixed between two projections in front 

 of the head of the ulna, and assists in forming 

 the elbow-joint articulating with the outer con- 

 dyle of the humerus only. It then passes 

 obliquely downwards across the anterior face of 

 the ulna to its distal extremity, where it expands 

 into a broad articulating surface, and assists 

 almost coequally with the ulna in forming the 

 carpal joint. 



Carpus. The bones of the carpus are chiefly 

 remarkable for their large dimensions; they 

 are, however, always distinct and generally 

 the same in number as in Man, although from 

 their altered shape they little conform to the 

 names bestowed upon them in the human sub- 

 ject. The first row, consisting of the analogues 

 of the scaphoid, the lunar, the cuneiform, and 

 the pisiform bones, is firmly connected by liga- 

 ments with the distal extremities of the ulna 

 and radius to form the wrist-joint, which, how- 

 ever, is here only capable of the movements of 

 flexion and extension. The second row consists 

 of the representatives of the trapezium; the 

 trapezoid, the os magnum, and the unciform 

 bones support the metacarpus and are generally 

 quite distinct, although occasionally two or 

 more of them are consolidated into one mass. 



In the Rhinoceros, which has but three toes, 

 the trapezoid, the os magnum, and the unciform 



bones each support a single metacarpal bone. 

 The trapezium is totally wanting, but there are 

 two supernumerary pieces in connection with 

 the scaphoid and unciforme. 



Metacarpus. The metacarpal bones are ge- 

 nerally short and excessively robust, their num- 

 ber of course corresponding with that of the 

 toes. Thus in the Elephant there are five, and 

 in the Hippopotamus, Hog, and Tapir only 

 four, which are small and extremely massive 

 in proportion to the weight they have to sus- 

 tain. In the genus Sus, where the whole bur- 

 den of progression is thrown upon the two 

 middle toes, and a considerable degree of ac- 

 tivity is permitted, the corresponding metacarpal 

 bones are much elongated, and far surpass in 

 size and strength those which support the ex- 

 ternal and internal fingers, which have rather 

 the appearance oi appendages to the outer and 

 inner sides of _the metacarpus, than bones ar- 

 ticulated with the carpal series. 



The metacarpus in the Rhinoceros consists 

 of only three bones conformable to the number 

 of fingers. 



P/talanges. The Elephant alone of all the 

 Pachydermata has five complete fingers; but, 

 although the bones are thus perfectly developed, 

 they are so concealed in the living animal by 

 the hoof and overhanging skin of the fore-foot, 

 that such a condition of this part of their 

 skeleton would hardly be suspected. 



In the ungulate tribes, which have only four 

 fully formed fingers, there is still a little bone 

 representing the rudiment of a thumb, although 

 in the generality of artificial skeletons this 

 ossicle is wanting. In the Suidte the two 

 lateral fingers are much shorter than the two 

 middle ones, so that in walking the former do 

 not touch the ground at all ; they are, however, 

 quite complete as relates to the number of their 

 phalanges ; and the last phalanges of all the 



