THE EQUID^:, OE HORSES. 203 



the two side toes, which, although shortened a 

 little, and accordingly somewhat more perpen- 

 dicular, yet fully touch the ground, and take 

 their share in the work as bearers of the weight 

 of the body. Now in the genera which gradually 

 arose in the course of time Pcdaothermm, Anchi- 

 therium, Hipparion, and Horse we can trace how 

 the two side toes, n and iv, were more and more 

 withdrawn from the ground, and became rudi- 

 mentary, whereas the middle toe increased in size, 

 stretched out, and finally became that of the Horse, 

 the incomparable runner and fellow- worker of man. 

 Owen looks upon this as a providential transforma- 

 tion designed for the benefit of mankind ; we look 

 upon it as an adaptation to the formation of the 

 ground, to the incoming of plains, which originated 

 during the Tertiary period. Thus in Anchitkeriitm 

 aurdianense (Fig. 36), which is still met with even in 

 the Eocene, the tips of the outer toes are scarcely 

 withdrawn from the ground, hence might still have 

 been of use to the animal in walking through a less 

 firm soil. 



The Hipparion also, from the Middle Tertiary, 

 possesses the lateral toes (Fig. 35), but these are only 

 rudiments of the original toes. They have become 

 wholly useless, and in accordance with this inaction 



