52 



A MANUAL OF DENTAL ANATOMY. 



as the " brown striae of lletzius," and as they coincide with 

 what was at one time the outer surface of the enamel cusp, 



FIG. 22 ('). 



are in some sense marks of its stratification, in its original 

 deposition. 



Pigme.nt is seen in the enamel of many rodents ; it is in 



Cavities in human enamel, which communicate with the dentinal 



tubes. 



