LESSON 55.] THE STKUCTURE OF THE TEETH. 



195 



836. A transverse section of the canine tooth of a Horse pre- 

 sents the same tissues under a different aspect. The section has 

 been made so near to the crown of the tooth, that the enamel forms 

 a ring nearly surrounding the dentine (Fig. 315), with the apex of 



FIG. 314. 



FIG. 315. 



Molar Tooth, Cat. . Canine Tooth, Horse, transverse. 



the pulp cavity in the centre. Another section of the same tooth 

 (Fig. 316), made below the former, shows the enamel (a) round only 

 one half of the section, the other half being the crusta petrosa (b). 

 Between these tissues is the dentine (c), and in the centre the pulp 

 cavity (d). A third section (Fig. 317), made still lower than the 

 second section, from the same tooth, shows an entire absence of 



FIG. 317. 



FIG. 316. 



Canine Tooth, transverse, Horse. 



Canine Tooth, transverse, liurse. 



enamel, and the crusta petrosa (a) surrounds the section. The den- 

 tine, in all these sections, is very nearly the same ; the pulp cavity 

 grows gradually larger from its apex to the base, but the most satis- 

 factory part of the demonstration is the number and density of the 

 bone cells, as seen in the last figure, but which is not sufficiently 

 magnified to be apparent in the representation of it. 



