38 



THE HOUSE 



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 rudi- 

 mentary metapodials, or c splint bones ' of veterinary 

 anatomy (fig. 6, 2 m and 4 m), though independent 

 bones in the young animal, have a great tendency to 

 become united with the large middle bone as life goes 

 on ; but in horses of the pre-historic or still earlier 

 periods they are always found free, and were also rela- 

 tively longer than they are now. 



These modifications of the limbs thus gradually 

 acquired in the course of time must have been associated 

 with gradually increased speed in running, especially 

 over firm and unyielding ground. Short, stout legs and 

 broad feet, with numerous toes, spreading apart from 

 each other when the weight of the creature is borne on 

 them, are sufficiently well adapted for plodding delibe- 

 rately over marshy and yielding surfaces, and the tapir 

 and the rhinoceros, which in the structure of the limbs 

 have altered but little from the primitive Eocene forms, 

 still haunt the borders of streams and lakes and the 

 shady depths of forests, as was probably the habit of 

 their ancient representatives ; while the horses are all 

 inhabitants of the open plains, for life upon which their 

 whole organisation is in the most eminent degree 

 adapted. The length and mobility of the neck, position 

 of the eye and ear, and great development of the organ 



