OSTEOLOGY AND ARTHROLOGY 125 



The pig has forty-four teeth disposed in the following 

 manner : 



44. 



Of the incisors, the nippers and the intermediate ones of the 

 upper jaw have their analogues in those of the horse ; in the 

 lower jaw, the corresponding teeth, straight, and directed for- 

 ward, rather resemble the same incisors in rodents. The 

 corner incisor teeth are much smaller, and are separated from 

 the neighbouring teeth. The canine teeth, also called tusks 

 or tushes, are greatly developed, especially in the male. The 

 molars increase in size from the first to the last ; they are not 

 cutting, as in the carnivora, but they are not flattened and 

 provided with tubercles on their surfaces of contact as in the 

 herbivora. 



In the ox and the sheep the teeth are thirty-two in 

 number : 



6m. oc. o*. 

 6m. oc. 4*'. 



oi. oc. 6m. 

 4*. oc. 6m. 



As we see from this dental formula, the incisors are found 

 only in the lower jaw ; they are replaced in the upper jaw 

 by a thick cartilaginous pad on which the inferior incisors 

 find a surface of resistance. 



These have their crowns flattened from above downwards, 

 and gradually become thinner from the root to the anterior 

 border, which is edged and slightly convex. These teeth 

 gradually wear away. In proportion to the progress of this 

 wear, on account of the fact that it involves the anterior 

 borders and upper surfaces of the incisor teeth, and that 

 these teeth are narrower towards the root than at the oppo- 

 site extremity, the intervals which separate them tend to 

 become wider and wider ; and when the roots become ex- 

 posed by the retraction of the gums, they are then separated 

 from one another by a considerable interval. The molars 

 have their grinding surface comparable to that of the horse ; 

 they increase in size from the first to the sixth. 



