THE TEETH 



333 



fied to take on the characteristics of the distal end of a columnar cell. 

 A cuticular border appears upon the inner (originally basal) extremities, 

 and as the calcareous substance of the enamel begins to be deposited fine 

 processes are seen extending inward from the extremities of the enamel 

 cells, Tomes' processes. It is around these processes that the permanent 



FIG. 314. DEVELOPING TOOTH FROM A HUMAN FETUS 30 CM. LONG. 



D, dentin; K, bone of the jaw; RM, germinal layer of the oral mucosa; S, enamel 

 organ; SK 2 , enamel anlage of the permanent tooth; VB, epithelial bridge still uniting 

 the anlages of the temporary and permanent teeth; ZL, disintegrating dental lamina; 

 SP, enamel pulp. X 30. "(After C. Rose.) 



enamel is deposited first in the form of globules, which become calcified 

 and meanwhile fuse to form the enamel prisms. 



The deposit of lime salts by the cylindrical cells of the inner enamel 

 layer, ameloblasts (adainantobhtsts) , occurs earliest at the apex of the 

 dental germ. Thus, it is the enamel of the face of the tooth crown which 

 is first formed, and this is therefore its thickest portion. The enamel 

 on the sides of the tooth crown appears later and hence it gradually 



