A STUDY OF THE SKELETON 



191 



on the tips of which the weight of the body is supported. 

 Finally, horses have but a single digit on each foot, the end 

 bone of which is covered with the hoof (Fig. 84). 



The story of the horse, as it is learned from the fossil 

 bones obtained from 

 the rocks, is an in- 

 teresting one. The 

 earliest horse of 

 which we know any- 

 thing was about the 

 size of a fox, and 

 walked on the dis- 

 tal part of four fin- 

 gers of each front 

 foot and of three 

 hind toes, all of 

 about equal size. 

 Gradually, how- 

 ever, the descend- 

 ants of this animal 

 came to walk more 

 and more on the 

 tips of the middle 

 fingers and the mid- 

 dle toes. The little 

 fingers were there- 

 fore too short to 

 touch ground, they 

 became smaller as 

 the ages passed, and 

 have altogether dis- 



FIG. 86. The Development of the Fore and 

 Hind Feet of a Horse. Feet of Modern Horse 

 are figured at the Top. From diagram in 

 American Museum of Natural History. 



appeared in the modern horse. As the middle digit came to 

 be used more, its size notably increased, while there was a 

 corresponding decrease in the size of the digits on either side. 

 In skeletons of horses that lived nearer modern times, we lose 

 all trace of the phalanges of these two side digits, and in the 



