250 • STEUCTURE AND ADxVPTATlON OF TEETH 



tion of food than the ruminants, whose cloven 

 hoofs, by their expansion in soft ground, enable 

 them to feed on the rank herbage in marshy 

 places, where the horse would be inevitably pre- 

 vented from grazing. The horse selects the more 

 tender grasses, eating them down to the very 

 roots and leaving the coarser herbage untouched. 

 As the food is swallowed but once, it is masticated 

 thoroughly ; and I have been informed by an intel- 

 ligent farmer, that he never knew of an instance 

 of a horse being similarly affected with the ox or 

 sheep, after indulging in a feast of green corn. 



In the hog tribe, we have an example of the true 

 tusk of the ungulated animals ; a tooth of conical 

 shape, with a persistent formative pulp, a charac- 

 teristic which receives its fullest development in 

 the canines of the hippopotamus and the incisors 

 of the elephant. The teeth of the common hog 

 are the same in number as in the horse, w4th the 

 addition of one premolar in each row ; and among 

 other distinguishing features may be noticed the 

 progressive increase in size from the first molar to 

 the last. The wild boar, the stock from which 

 our domestic breed is derived, usually harbours in 

 the most secluded recesses of the forest ; and if 

 aroused to combat, employs the tusks with terrific 

 force, as it rushes past its assailant, inflicting 

 fearful wounds, and sometimes ripping open the 

 abdomen. 



The incisors are levelled forwards and are 



