DENTITION OF MAN. ' 205 



The incisors are double wedge-shape, — widest at the cut- 

 ting edge, thickest at the neck, slightly concave on the inner 

 and slightly convex on the outer surface. The superior or 

 upper are larger than the inferior or lower incisors, and the 

 central incisors are wider than the lateral. In the case of the 

 inferior incisors, the laterals are wider than the centrals. The 

 incisors, both superior and inferior, have eacli but one root. 

 The use of these teeth in eating is to " bite " or cut off a ])ortion 

 of food, operating on the same principle as a pair of scissors. 

 The cuspids are less concave on the inner surface and more 

 convex on the outer surface than the incisors, and terminate in 

 a point. They have but one root, but this is longer and stronger-* 

 than that of any other tooth in the mouth. The superior cus- 

 pids are larger and have longer roots than the inferior. The 

 use of the cuspids is to seize and tear or lacerate obstinate sub- 

 stances preparatory to mastication. It is an interesting fact 

 that these teeth are more prominent in proportion as the animal 

 approaches the purely carnivorous or flesh-eating class, and are 

 never found in an animal having horns. The bicuspids are 

 smaller than the cuspids, convex on both outer and inner sur- 

 faces, and flattened on the sides. Their long diameter is across 

 the jaw. The roots are conical. The inferior have but one 

 root ; the superior sometimes a single root, often deeply 

 grooved, and sometimes entirely divided, — bifid. The molars 

 have large grinding surfaces, divided by grooves into cusps or 

 points. The crowns of the inferior are larger than those of the 

 superior. In each jaw they decrease in size from before back- 

 ward. The superior first and second molars have, as a rule, 

 three roots each. The inferior first and second molars have 

 each two roots, which are often deeply grooved, and sometimes 

 bifid. The third molars or wisdom-teeth of both jaws have 

 but a single root each, though this is sometimes divided into 

 three in the upper jaw and two in the lower. The inferior 

 third molar is larger than the superior. 



The deciduous or tempomry teeth are much smaller than 

 the permanent, although the roots are generally larger and 



