40 THE HOESE. 



met with when the Pleistocene, or latest geological 

 period, set in j but then, for the first time, appeared 

 the true horse, in its development exactly or very 

 nearly as we know it now. The outer toes (second 

 and fourth) were reduced to rudiments of the meta- 

 carpals or metatarsals entirely concealed beneath 

 the skin, while the middle or third toe was greatly 

 elongated and had its last bone or ungual phalanx 

 much expanded in breadth (Fig. 6). At the same 

 time, the stability of the forearm and leg was in- 

 creased by the two bones contained in each limb in 

 the primitive forms becoming completely fused into 

 one. Even since the Pleistocene period a change 

 has taken place, as in horses of the present time the 

 lateral rudimentary metapodials, or " splint bones " 

 of veterinary anatomy (Fig. 6, 2m and 4m), though 

 independent bones in the young animal have a 

 great tendency to become united with the large mid- 

 dle bone as life goes on ; but in horses of the pre- 

 historic or still earlier periods they are always found 

 free, and were also relatively longer than they are 

 now. 



These modifications of the limbs thus gradually 

 acquired in the course of time must have been asso- 

 ciated with gradually increased speed in running, 

 especially over firm and unyielding ground. Short, 

 stout legs and broad feet, with numerous toes, spread- 



