152 NORMAL HISTOLOGY AND ORGANOGRAPHY, 



lateral walls should be beveled, as shown in the above 

 figure. The historic requirements for strength in 

 enamel walls are : 



1. The enamel must be supported upon sound 

 dentin. 



2. The rods which form the cavo-surface angle 

 must run uninterruptedly to the dentin. 



3. They must be supported by short rods, with 



Enamel rods horizontal 



:-. Dento-enamel margin. 

 Enamel. 



Fig. no. Drawing, showing the direction of the rods over the mesial 

 marginal ridge of a bicuspid (Noyes). 



their inner ends resting on the dentin and their 

 outer ends abutting upon the cavity wall, where they 

 will be covered by the filling material. 



4. That the cavo-surface angle be cut in such a 

 way as not to expose the ends of the rods to fracture 

 in condensing the filling material against them. 



"The first step in the preparation of an enamel 

 wall is to determine the direction of the enamel rods 

 by cleavage with a chisel or hatchet. Then the wall 



