OSTEOLOGY AND ARTHROLOGY 



47 



the fibrous tissue which surrounds the articulation. We 

 also meet with such structures, but more rarely, at the level 

 of the corresponding articulation of the index and auricular 

 digits ; and, more rarely still, at those of the middle and 

 ring fingers. In quadrupeds, these bones are normally 

 developed, and we shall see afterwards that in some 

 animals, as they reach a considerable size, they are able to 

 influence the external outlines ; we shall see this, for example, 

 in the horse. 



The hand, in birds, is directed obliquely downwards and 

 backwards (Fig. 31). For the better understanding of its 



Fig. 31. — Skeleton of the Superior Limb of a Bird (Vulture): 

 Left Side, External Surface. 



I, Humerus ; 2, radius ; 3, ulna ; 4, radial bone of the carpus ; 5, ulnar 

 bone of the carpus ; 6, first metacarpal ; 7, second metacarpal ; 8, third 

 metacarpal ; 9, first digit, the homologue of the thumb ; 10, first plialanx 

 of the second digit; 11, second phalanx of the second digit; 12, third 

 digit. 



position in relation to the forearm, we should remember 

 that this latter, as we have described (p. 44), directed 

 obliquely upwards and forwards, has the radius placed 

 aboVe the ulna ; the hand being oblique in the opposite 

 direction and placed under the forearm is, by this arrange- 

 ment, inclined towards the ulnar border of the latter. 



For the rest, in order to be able to distinguish readily the 

 corresponding parts in the hand of a bird and that of a man, 

 we merely have to place the human forearm obliquely, in a 

 direction upwards and forwards (Fig. 32), the radius being 

 above ; this position we can obtain by semi-pronation ; 



