The Evolution of the Horse 



are so similar to horses that you may follow 

 descriptions given in works upon the anatomy 

 of the horse upon the skeletons of these animals 

 — but which differ in some important particu- 

 lars. For example, the structure of their fore 

 and hind limbs is somewhat different. The 

 bones which, in the horse, are represented by 

 two splints, imperfect below, are as long as the 

 middle metacarpal and metatarsal bones; and 

 attached to the extremity of each is a digit 

 with three joints of the same general character 

 as those of the middle digit, only very much 

 smaller. These small digits are so disposed 

 that they could have had but very little func- 

 tional importance, and they must have been 

 rather of the nature of the dew-claws, such as 

 are to be found in many ruminant animals. 

 The Hipparion, as the extinct European three- 

 toed horse is called, in fact, presents a foot sim- 

 ilar to that of the American Protohippus (Fig. 9), 

 except that in the Hipparion the smaller digits 

 are situated farther back and are of smaller 

 proportional size than in the Protohippus. 



The ulna is slightly more distinct than in the 

 horse; and the whole length of it, as a very 

 slender shaft intimately united with the radius, 

 is completely traceable. The fibula appears to 

 be in the same condition as in the horse. The 

 teeth of the Hipparion are essentially similar 

 to those of the horse, but the pattern of the 

 grinders is in some respects a little more com- 

 plex, and there is a depression on the face of 

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