138 ANIMALS OF THE PAST 



Going back into the past a step farther, though a 

 pretty long step if we reckon by years, we come upon 

 a number of animals very much like horses, save for 

 certain cranial peculiarities and the fact that they had 

 three toes on each foot, while the horse, as every one 

 knows, has but one toe. Now, if we glance at the 

 skeleton of a horse, we will see on either side of the 

 canon-bone, in the same situation as the upper part of 

 the little toes of the Merychippus, or Hippotherium, as 

 these three-toed horses are called, a long slender bone, 

 termed by veterinarians the splint bone; and it re- 

 quires no anatomical training to see that the bones in 

 the two animals are the same. The horse lacks the 

 lower part of his side toes, that is all, just as man will 

 very probably some day lack the last bones of his little 

 toe. We find an approach to this condition in some of 

 the Hippotheres even, known as Protohippus, in which 

 the side toes are quite small, foreshadowing the time 

 when they shall have disappeared entirely. It may also 

 be noted here that the splint bones of the horses of the 

 bronze age are a little longer than those of existing 

 horses, and that they are never united with the large 

 central toe, while nowadays there is something of a 

 tendency for the three bones to fuse into one, although 

 part of this tendency the writer believes to be due to 

 inflammation set up by the strain of the pulling and 

 hauling the animal is now called upon to do. Some of 

 these three-toed Hippotheres are not in the direct line of 

 ancestry of the horse, but are side branches on the 

 family tree, having become so highly specialized in 

 certain directions that no further progress horseward 

 was possible. 



Backward still, and the bones we find in the Miocene 

 strata of the West, belonging to those ancestors of the 

 horse to which the name of Mesohippus has been given 



