ENAMEL 77 



surface of healthy enamel indicating that the portion 

 behind a was incompletely formed. 



Other markings in the enamel are known as Schreger's Schreger' 

 lines. These lines, which appear white by reflected light, lmes 

 are said by Von Ebner to be quite invisible by transmitted 

 light ; in thin sections this would appear to be the case, 

 but in thick sections they are seen as dark cloudy bands. 

 Von Ebner considers that they depend upon the different 

 directions of contiguous groups of prisms, and Pickerill 

 speaks of them as due to the different optical densities of 



FIG. 34. Hypoplastic enamel showing incremental lines, 

 a, 6. Incremental lines. ( x 45. ) 



contiguous groups of prisms. They are evidently due to 

 optical phenomena and have little histological significance. 



The line of junction of the enamel and dentine (fig. 34), Amelo- 

 or the amelo-dentinal junction as it is usually called, shows junction, 

 a festooned margin, the enamel terminating in rounded 

 contours, the convexities of which are directed towards 

 the dentine. 



These contours are formed by the calcified substance 

 of the enamel and have a very strong resemblance to those 

 at the margin of the dentine, where the coalesced calco- 

 spherites which form the calcified dentinal matrix are 



