246 MICROSCOPIC ANATOMY OF THE TEETH 



offsets from the dentinal tubes, the evidence that they 

 exist and arise from the tubes is, we think, not capable 

 of contradiction. In fig. 124 the fine terminations 

 are seen at the cement margin of the dentine, and in 

 the photograph of the ground section (fig. 151) they are seen 

 just beneath the enamel. The decalcified sections afford 

 very beautiful microscopic objects, especially under a low 

 power, the ground substance being everywhere traversed 

 by these delicate ramifying processes passing in every 



FIG. 150. Branching of dentinal tubes. Transverse section 

 (silver pyridin). ( X 250.) 



direction and seen in transverse as well as longitudinal 



section. In fig. 149 there is an appearance of very minute 



thorny projections bordering these fine branches. Both 



the ground and decalcified sections were made from teeth 



in which the soft parts had been retained and fixed in formol. 



Primary The tubes do not pass in a straight course from the pulp 



secondar ^ ^ e margin, but in an undulatory manner, and the curves 



curva- or undulations are seen to be both short and abrupt and 



longer and more open. The long undulations are called the 



' primary curvatures ' and the shorter ones the ' secondary 



curvatures '. This appearance of curvature is due to the 



