60 



A MANUAL OF DENTAL ANATOMY. 



The effect of an elongated spiral viewed on its side will of 

 course be only slight undulations, such as are the secondary 

 curvatures of the tubes. The spiral course of the dentinal 

 tubes is most strongly marked in the roots of teeth. 



When a transverse section of dentine is viewed, bands or 

 rings, concentric with the pulp cavity are seen, and the same 

 bands may be seen in longitudinal section. Such a striated 

 or laminated appearance in the dentine may be due to two 

 causes ; and some little confusion has arisen in the nomen- 

 clature, owing to its double origin not having always been 

 kept in view. Such strise may be due to the presence of 

 rows of interglobular spaces, or to the coincidence of the 

 primary curvatures of neighbouring dentinal tubes : that 



FIG. 25 



i 



-V-7- 



is to say, each tube bends at the same distance from the 

 surface, and the bend makes a difference in the optical pro- 

 perties of the dentine at that point. 



Schreger described these latter: the lines of Schreger, 



(*) Dentine and cementuni of a Narwal, showing contour lines due to 

 rows of interglobulav spaces. 



