28 THE POPULAR SCIENCE MONTHLY. 



horse than the latter. Our own Anchitherium (D D 1 ) corresponds to 

 the next specimen of the New World Miohippus by name ; and 

 Miohippus evinces a still more important modification in that it pos- 

 sesses a rudiment of the fifth or little finger in addition to the second, 

 third, and fourth digits with which the fore-feet are provided. 



The American horses now continue the history of the race in time 

 past without aid or representative from the eastern hemisphere, in so 

 far, at least, as the latest research has shown. To Miohippus succeeds 

 the Mesohippus (E E 1 ) from the American Miocene, which has three 

 well-developed toes, and in addition shows the rudiment of the little 

 finger (E e) of the fore-feet (seen also in Miohippus, D e) in an enlarged 

 condition. Passing to the Eocene formations, the oldest series of the 

 Tertiary rocks, we meet with the next step in the form of the Orohippus 

 (F F 1 ), in which the little finger (e) appears as a veritable member of 

 the hand, the hind-feet still possessing three well-developed toes only : 

 while, consistently with the development of the toes, the ulna of the 

 forearm and fibula of the leg appear as bones of legitimate size, and 

 present a striking contrast to their rudiments in the horse of to-day. 

 The last discovered horse is from the oldest of the Eocene beds ; it has 

 been appropriately named Eohippus, and presents us with four com- 

 plete toes (second, third, fourth, and fifth) on the fore-feet, and a rudi- 

 ment of the first toe as well ; with a trace of the fifth toe of the hind- 

 feet this last member being, as we have seen, unrepresented in any of 

 the other forms. When the Chalk. Rocks shall have yielded up their 

 fossil horses, it is consistent with logic and reason to expect that the 

 primitive stock of the horses will be discovered with its complete pro- 

 vision of five toes, and its corresponding modifications of form. 



To what conclusions, of reasonable kind, do these stable facts re- 

 garding the pedigree of the horse naturally lead ? The answer is to- 

 ward a belief in the slow and progressive modification and evolution of 

 the one-toed modern horse from a five-toed ancestor. This process of 

 modification must, of course, have affected its entire frame, but it is 

 sufficient for our present purpose to point out that in the structure of 

 the foot alone we discern the evidence for evolution, as clearly as in the 

 entire organization of the animal. An increase of speed, and obvious 

 advantage over its enemies, would be gained by the horse, as its toes 

 grew " small by degrees and beautifully less " ; and the single-toed race 

 has thus practically come to the front in the world of to-day, as the 

 plain and favorable result of the work of degradation among its digits. 



Two bony shreds or rudiments thus lay the foundation of a grave 

 conclusion regarding the horse and its manner of development, and 

 exemplify the adage that great and unlooked-for results sometimes 

 spring from beginnings of apparently the most trifling kind. The 

 " splint-bones " form, in fact, a clew which, when rightly pursued, leads 

 not merely to a knowledge of the evolution of the horse, but to an 

 understanding of the entire scheme of nature. The idea, then, of 



