64 



THE IIURSE IN HEALTH AND DISEASE 



2 and 3 per cont. had visible canines in each jaw; 6 to 7 per cent. 



had tlicm in the upper jaw; while 20 

 to 30 per cent, had them in the 

 lower jaw. 



Anatomically, an incisor tooth is 

 divided into the crown, neck, root, 

 infundibulum, and cup. The crown 

 refers to the projectinf!; portion or 

 that part that is visible. The neck is 

 the ]5art covered with the gum. The 

 root is the portion that is embedded 

 in the ja\\' Ijone. The infundibulum 

 is the cavity on the table surface 

 l^roduced by the infolding of the 

 enamel. The cup refers to the un- 

 filled portion of the infuncUbulum of 

 an incisor tooth. 



Teeth are composed of dentin, 

 which is capped with enamel and 

 encrusted over the remaining por- 

 tion with cement (Figs. 13, 14). 

 The (lentin is dense in consistency, 

 yellowish-white in color, and forms 

 the bulk of most teeth. The enamel 

 forms a thin cap over the dentin of 

 the crown. In herbivora it is folded 

 into the table surface. In the vir- 

 gin tooth it covers the entire table 

 surface, but soon wears off on the grinding portion, leaving only 

 projecting edges. Enamel is a secretion of epithelial cells and 



P'i,H. 13. — Longitudinal .sec- 

 tion of lower incisor teeth: C, 

 Pulp cavity. Cement i.« shown 

 in the infuDilibulum, but is not 

 marked. (Sisson, .\natomyof 

 Domestic Animals.) 



Periphiral diamd Cement 

 Dn.ti,, ^ ^^^Jsi^ 



Central ,Nai„< I 

 Cement 



Fig. 14. — Cross-section of lower incisor tooth: /, Infundibulum. (Sisson, 

 Anatomy of Domestic Animals.) 



caimot be reproduced when it is once destrojTd. The cement is 

 the external covering of the root. In complex teeth, like those of 



