THE TEETH. 



489 



sist of two so-called incisor teeth, one canine, and two molar teeth. The 

 formula of these teeth is thus written, 



M2 Cl 14 01 M2 

 M2 Cl 14 Cl M2* 



When these teeth are shed, they are succeeded, at intervals, by 

 the permanent teeth, which are thirty-two in number, sixteen in each 

 jaw, eight in either half of each jaw; viz., commencing at the middle 



Pig. 84. 



Fig. 84. Human teeth, i, lower lateral incisor, seen from behind, c, lower canine, seen from within, b, 

 second upper bicuspid, seen sideways, m, second lower molar, seen from without, i', section of an in- 

 cisor tooth, showing the pulp cavity, extending from the point of the fang, the dentine, or tooth sub- 

 stance, the enamel on the crown, and the layer of cement on the fang, m', section of a molar tooth, 

 showing the same parts, and the pulp cavity extending into each fang. (Blake.) 



line, two incisors, one canine, two bicuspids, and three molars. 

 formula of these teeth is therefore, 



The 



M3 B2 Cl 14 Cl B2 M3 

 M3 B2 Cl 14 Cl B2 M3* 



Each tooth, Fig. 84, i to m, consists of an exposed part, called the 

 crown or body, and of a part buried in the gum and jaw, named the 

 root or fang; at the junction of the crown and fang, is the slightly 

 constricted cervix or neck. The several kinds of teeth differ in the 

 form of their crowns, and in the number of their fangs; hence their 

 different designations. The incisor teeth, i, have wide, thin, crowns, 

 slightly convex in front, and smooth or marked with longitudinal fur- 

 rows, but somewhat concave, or bevelled off, on their hinder surface ; 

 their edges, which, at first, present three small prominent points, are, 

 when worn, long, narrow, and chisel-shaped, being well adapted for 

 cutting purposes; hence their name. The fang is long, single, and 

 somewhat compressed from side to side. In the temporary teeth, but 

 much more markedly in the permanent set, the upper incisors are 

 larger, and occupy more space transversely, than the lower ones ; in 

 the upper jaw, the middle incisors are larger than the lateral ones ; in 

 the lower jaw, the reverse is the case. The canine teeth, c, larger and 

 thicker than the incisors, are distinguished by the pointed character 

 of their crowns, which are very convex in front, and a little hollowed 

 behind, and also by the great size arid length of their single fang, 

 which presents, on its sides, a slight longitudinal furrow. The upper 

 canines, popularly called the eye-teeth, are larger and longer than the 

 lower ones, and on their posterior surface, close to the gum, is found 



