56 THE ARTISTIC ANATOMY OF ANIMALS 



The ulna is furnished at its superior extremity with an 

 olecranon process, which is more prominent than that of 

 the human ulna ; this process is compressed laterally, and 

 its internal surface is hollowed ; there we also find a great 

 sigmoid cavity, and a coronoid process situated at the 

 internal part of the anterior surface, a process which, as we 

 have previously shown, it shares with the radius. 



The shaft of the bone, prismatic and triangular, diminishes 

 in thickness as it approaches the lower extremity, which 

 articulates with the corresponding extremity of the radius. 

 In the dog, the ulna terminates interiorly in a blunt point, 

 without enlargement, analogous tc the head of the human 

 ulna ; in the cat, by a head which is prolonged into a 

 styloid process, by which it articulates with a portion of 

 the carpus. 



The carpus consists of seven bones — three in the superior 

 row and four in the inferior. In the superior row the 

 scaphoid and semilunar bones are fused together. The 

 pisiform is elongated and expanded at its two extremities ; 

 it forms a prominence which, directed backwards, projects 

 beyond the level of the other bones of this region. 



The metacarpal bones are five in number ; they are enume- 

 rated from within outwards ; they articulate with the carpus 

 and with each other. The inferior extremity of each meta- 

 carpal bone presents the form of a condyle in front ; and is 

 divided behind so as to form two lateral condyles, which are 

 separated by a median crest ; on these posterior condyles 

 are applied two small sesamoid bones. The metacarpal 

 bone of the thumb is very short ; the third and fourth are 

 the longest. The metacarpus, as a whole, is directed verti- 

 cally. 



The phalanges are three in number for each finger, except 

 the thumb, which has but two. The first phalanx, directed 

 almost horizontally forwards, is the longest ; the second is 

 directed downwards and forwards ; the third consists of 

 two portions : a posterior part, which forms a sort of sheath 

 into which the base of the nail is received ; and an anterior, 

 conical in form, and curved in crochet shape, which forms a 

 support for the nail (Fig. 37). 



