INCISORS. 



159 



The incisors, instead of being fixed solidly in their alveolar 

 cavities like those of the horse, are imbedded in them on a layer 

 of cartilage, which allows of a considerable amount of motion, 

 and thereby probably protects the 

 cushion of the upper jaw from in- 

 jury in seizing food, which is crushed 

 rather than cut off. 



The two middle incisors are 

 known as pinchers, the next ones on 

 either side 3,sji7^st intermediate teeth, 

 the next as second intermediate, and 

 the outside ones as corner teeth. 



The two pinchers are slightly 

 separated on account of the cartilagi- 

 nous symphysis of the maxillary 

 bones in the ox ; this is much more 

 marked in the first dentition. The 

 other teeth touch each other by their 

 extremities and form a complete arch, 

 but, from their shovel shape, are not 

 in contact along their borders as the 

 wedge-shaped incisors of the horse 

 are. 



The incisors are composed of a 

 crown and a root, separated by a dis- 

 tinct neck, giving them a somewhat 

 shovel shape. The crown or free 

 portion is flattened from above to 

 below, and becomes (Fig. 160) thin- 

 ner and broader at its anterior ex- 

 tremity. 



The external or under face is convex in both directions ; it 

 is of a milky-white color and is striped with little longitudinal 

 ridges and gutters, which become polished smooth with age. 

 The internal or upper face is almost flat, but has a conical ele- 

 vation, the base of which is directed toward the free border 



Fig. 160. 

 Left pinclier teeth of the ox. r. 

 External faces. II. Internal faces. 

 a a. Permanent incisors, b b. Tem- 

 porary incisors. (Natural size.) 



