ODD-TOED UNGULATES (pERISSODACTYLa) 269 



especially by the excellent arrangement of these 

 skeletons in the British Museum of Natural History^ 

 the striking modifications of the bones of the legs of 

 the horse are realised (Fig. 61). The humerus or 

 bone which forms the upper arm from the shoulder 

 to the elbow is iu the horse very thick and short 

 and curiously bent. In the living horse this joint is 

 not apparent. The forearm of man from the elbow 

 to the wrist corresponds with the free part of the 

 " leg '^ of the horse from the elbow to the " knee." 

 In man this part of the arm consists of two bones^ 

 the radius and ulna^ which are, we have seen, 

 separate bones in the skeleton of the cat (Fig. 8). 

 They are so formed as to slide over one another, and 

 thus give considerable play in twisting the arm and 

 hand. In the horse only a vestige of the ulna 

 remains, and the wrist or " knee " is permanently 

 fixed in the prone position. The remaining portion 

 of the horse's foreleg represents all that is left to 

 him of the five-fingered limb or hand of man. That 

 portion from the '^ knee " to the fetlock joint consists 

 of one central bone and two smaller bones called 

 '^ splint ^' bones on each side of it, which in full-grown 

 animals become united with the larger one. The 

 cannon bone represents the metacarpal, or that part 

 of the second finger (third digit) which is imbedded in 

 the palm of the hand of man. The '^ splint '^ bones 

 represent the metacarpals of the first and third fingers, 

 the importance of which in the geological history of 

 the horse we shall refer to later on. The fetlock and 

 hoof represent our second finger and its nail. 

 Similarly, in comparing the hind leg of the horse 



