DIGESTIVE SYSTEM. 



153 



Rods inclined away 

 from cavity. 



Enamel. 



Rods inclined toward camty. 

 Fig. in. Illustrating the two classes of cavities (Noyes). 



Dentin. 



Enamel- 



Fig. ii2. Labio-lingual section of superior lateral incisor, showing 

 a pit cavity (Noyes). 



