562 CLASS XVII. 



{olecranon), which is received in the posterior cavity of the inferior 

 extremity of the humerus. The radius is shorter, connected more 

 with the carpus or root of the hand, and can roll round the ulna, so 

 that either the back or the palm of the hand can be turned upwards 

 {pronatio et sujnnatio). From this perfection most of the mammals 

 recede, especially such as make use of their limbs for standing and 

 running only, and not for seizing also. In some the two bones 

 of the fore-arm have even coalesced; in others they remain dis- 

 tinct indeed, but still their relative motion is little or none. The 

 cetaceans have the bones of the fore-arm short, flat, and immove- 

 ably connected. In most of the ungulates the two bones of the 

 fore-arm have coalesced downwards. In the horse the ulna is 

 very imperfect and consists only of the olecranon process and a 

 thin bony stile, which unites with the radius and does not extend 

 to the carpus. A rotation of the hand does not occur in ungulate 

 animals, but the dorsal surface is constantly turned upwards {manus 

 prona). In the carnivores and rodents radius and ulna remain 

 indeed distinct, but in many the rotation is nevertheless very im- 

 perfect. A greater relative mobility of the two bones of the 

 fore-arm occurs in the quadrumanous mammals, which in this, as in 

 the rest of their structure, make an approach to man. In the wing- 

 handed mammals (the bats) the ulna is sometimes entirely absent 

 or is merely a thin spine-like bone, that is situated under the 

 radius^. 



The root of tlie hand (carpus) consists of various small bones 

 (from 5 to 11), that of man of eight, arranged in two rows; the 

 bones of the second row in most ruminants are only two. — The 

 pisiform bone forms in the apes, and especially in the carnivores, a 

 species of heel at the back part of the cai*pus. In the mole a sickle- 

 shaped little bone, which lies at the inner margin of the hand and 

 extends from the radius to the thumb, deserves special notice. 



The fore-hand {metacarpus) consists commonly of five small, 

 elongated, cylindrical bones placed side by side. Sometimes there 

 are fewer, and on the whole their number corresponds to that of 

 the fingers. In the ruminants there are originally (in the emhryo) 



1 The name of addltamentum ulnce, which Albinos with so much reason gave to 

 the radius in man, thus has no propriety in Zootomy. Rather is the radius the chief 

 bone of the fore-arm in animals. 



