THORACIC LIMBS 653 



The Digits (Fig. 514) have the same number of phalanges as in 

 the cat, namely, three for every finger except the thumb, which has 

 but two. The middle digit is the longest, the ring finger the next in 

 size, the second the next, the little finger the next, and the thumb the 

 shortest. 



The proximal phalanges resemble those of the cat, but the articular 

 surfaces on the ends are less deeply concave transversely. 



The middle phalanges are like the proximal, but are shorter and 

 flatter, and the proximal articular surface is transversely biconcave. 



The terminal or ungual phalanges are small, flat, tongue-shaped 

 bones, with transversely biconcave proximal surfaces and roughened 

 arcuate distal borders. 



The human hand is relatively shorter and broader than the hand 

 of the cat. If the arm be allowed to hang vertically and the humerus 

 be held immovable, the hand can still be turned to the supine position 

 with the palm forward, or to the prone position with the palm back- 

 ward ; this is due to the extensive rotation of the lower end of the 

 radius about the lower end of the ulna. The cat walks on the digits, 

 with the palm of the hand facing backward and the humerus directed 

 from above downward and outward. If the humerus be fixed in this 

 position, the palm of the hand can be brought only to a partial supi- 

 nation, so as to face inward. 



