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 2iB pinchers, the next ones on 

 either side as first 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 firee border 



Fig. 160. 

 Left pincber teeth of the ox. I. 

 External faces. II. Internal faces, 

 a a. Permanent incisors, b b. Tem- 

 porary incisors. (Natural size.) 



