STRUCTURE OF TEETH. 



Fig. 44.* 



The canine teeth (cuspidati) follow the incisors in order from before 

 backwards f^two are situated in the upper jaw, one on each side, and two 

 in the lower. The crown is larger than that of the incisors, convex be- 

 fore and concave behind, and tapering to a blunted point. The root is 

 longer than that of all the other teeth, compressed at each side, and 

 marked by a slight groove. 



The bicuspid teeth (bicuspidati, small molars), two on each side in each 

 jaw, follow the canine, and are intermediate in size between them and 

 the molars. The crown is compressed from before backwards, and sur- 

 mounted by two tubercles, one internal, the other external ; the neck is 

 oval : the root compressed, marked on each side by a deep groove, and 

 bifid near its apex. The teeth of the upper jaw have a greater tendency 

 to the division of their roots than those of the lower, and the posterior 

 than the anterior pair. 



The molar teeth (multicuspidati, grinders), three on each side in each 

 jaw, are the largest of the permanent set. The crown is quadrilateral, 

 and surmounted by four tubercles, the neck large and round, and the root 

 divided into several fangs. In the upper jaw the first and second molar- 

 teeth have three roots, sometimes four, which are more or less widely 

 separated from each other, two of the roots being external, the other in- 

 ternal. In the lower there are but two roots, which are anterior and pos- 

 terior ; they are flattened from behind forwards, and grooved so as to 

 mark a tendency to division. The third molars, or dentes sapientias, are 

 smaller than the other two ; they present three tubercles on the surface of 

 the crown ; and the root is single and grooved, appearing to be made up 

 of four or five fangs compressed together, or partially divided. In the 

 lower jaw the fangs are frequently separated to some distance from each 

 other, and much curved, so as to offer considerable resistance in the ope- 

 ration of extraction.! 



Structure. The base of the crown of each tooth is hollowed in its in- 

 terior into a small cavity which is continuous with a canal passing through 

 the middle of each fang. The cavity and canal, or canals, constitute the 

 cavitas pulpaB, and contain a soft cellulo-vascular organ, the pulp, which 

 receives its supply of vessels and nerves through the small opening at the 

 apex of each root. Mr. Nasmyth, to whose investigations science is so 



* Temporary teeth, a. Central incisor, b. Lateral incisor, c. Canine, d. First mo 

 lar. e. Second molar. 



f-See an excellent practical work, " On the Structure, Economy, and Pathology of the 

 Teeth," by Mr. Lintott 



