38 THE HORSE AND ITS RELATIVES 



double-lobed ox-molars. In consequence of this 

 greater complexity of its premolars (which is 

 common to both upper and lower jaw), the dental 

 mill of the horse, as Professor Osborn calls it, 

 forms a more powerful and more efficient grinding 

 instrument than that of the ox. 



And the reason for this greater masticating 

 power in the dentition of the horse is, I think, 

 not very difficult to discover. As is stated in 

 my volume on that animal, the ox, in common 

 with other ruminants, gathers its food quickly, 

 swallows it, and subsequently, owing to the complex 

 structure of its stomach, regurgitates and remasti- 

 cates it at leisure when in repose in a position of 

 more or less security. The horse, on the other 

 hand, who has a stomach of ordinary structure, has 

 to completely masticate his food and swallow it 

 once for all as soon as it is gathered, and this, too, 

 in places where he may be exposed to attack from 

 enemies. Consequently, it is of vital importance 

 that the process of mastication should be accom- 

 plished not only in the most efficient manner, but 

 likewise with the greatest possible rapidity. Hence 

 the complexity and powerful grinding action of 

 his cheek-teeth. 



There is, however, another point in connection 

 with these same cheek-teeth to which attention 

 may now be directed. As already mentioned, these 

 teeth are characterised by the great vertical height 



