EVIDENCE FROM COMPARATIVE ANATOMY 45 



"splint-bones." The wrist has seven bones, one of 

 the lower row being suppressed as needless, in corre- 

 lation with the reduction in the number of digits. 

 One of the forearm bones, the ulna, is very greatly 

 reduced, so that only the two ends remain and these 

 are firmly co-ossified with the radius, which is cor- 

 respondingly enlarged and bears the whole body- 

 weight. 



The fore leg of the ox, like that of the horse, is 

 exclusively locomotive in function and can move 

 only backward and forward, there being no power of 

 rotation of the hand on the forearm or of the whole 

 leg on the shoulder. In the forearm the enlarged 

 radius carries all the weight and the two ends of the 

 reduced ulna are co-ossified with it. The most 

 striking difference from the horse is to be found in the 

 fact that the foot has two functional digits, the third 

 and fourth, between which the weight is equally 

 divided, and the two hoofs are so shaped as to have a 

 split appearance, which is expressed in the term 

 "cloven-hoofed." While accurately descriptive of 

 the appearance, this term is erroneous if taken to 

 mean that an originally single hoof has been divided. 

 The long bones of the hand, or metacarpals, are 

 completely fused together into a compound "cannon 

 bone" and, in addition to the two functional digits, 

 there are two rudimentary, externally visible ones, 

 the "dew-claws," which are small, nodular hoofs be- 

 hind the principal ones. In the horse and ox, then, 

 we see two slightly divergent modes of converting 



