OSTEOLOGY AND ARTHROLOGY 



57 



The third and fourth digits are the longest ; the second 

 and iifth are of equal length ; the thumb is the shortest ; 

 it does not touch the ground, and does not even reach the 

 articulation of the metacarpal bone and first phalanx of the 

 second finger. 



In the cat, the metacarpal bone of the thumb, although 

 shorter than any of the others, is quite as thick. The 

 third digit is a little longer than either the second or 

 fourth. In animals of this genus, the claws, in the condi- 

 tion of repose, are retracted, and removed from the 

 ground ; this prevents their being worn, and thus pre- 



tax. 



Fig. ■^j. — Skeleton of the Finger of a Felide (Lion) : Left Side, 



Internal Surface. 



I, Metacarpus ; 2, sesamoid bones ; 3, first phalanx ; 4, second phalanx ; 

 5, third phalanx ; 6, gutter for the reception of the base of the nail; ■j , 

 prominent osseous crest formed to lodge in the concavity of the nail. 



serves their sharpness. At such times the third phalanx 

 is received into a groove which is found on the external 

 surface of the second phalanx. In the dog, the claws are 

 not tractile. 



Unguligrades: Pig (Fig. 38). — The scapula is markedly 

 narrowed in the region above the glenoid cavity. The 

 spine is atrophied at both its extremities, so that at its 

 inferior part we do not find the acromion process. In 

 its middle portion the spine is prominent, and presents a 

 triangular process which turns backwards, overlapping a 

 part of the infraspinous fossa ; this latter is much larger 



