298 



EVOLUTION OF THE HORSE, 



appears as a true three- toed mammal ; having lost its first 

 and fifth digits. In the Hipparion gracile, the second and 

 fourth digits have begun to disappear ; and have done so 

 completely in the horse of the present day, whose ancestors, 

 from the foregoing considerations, are classed among odd- 

 toed animals [Perzssodactyla). We must further observe that, 

 from the Phenacodus to the horse, as we now know him, 

 the third digit has remained the principal one of both fore and 

 hind limbs. It is instructive to note that the phalanges and 



Fig. 394.— Phenacodus PRiMiEvus (rVth real length). 



digits of the hind limb have a greater tendency to decrease in 

 number than those of the fore leg. As the fore foot is nearer 

 to the head than the hind foot, its functions are more various, 

 and its digits are less liable to become affected by disuse. In 

 man, we find that the toes are smaller than the fingers ; and 

 that, in many cases, the little toe has lost its third phalanx ; 

 although the little finger still retains that bone. In the case 

 of the re-appearance of the second (as in Fig. 290) and fourth 

 digits in the horse, the fore legs are far more frequently 

 supplemented in this way, than the hind ones. 



