232 DEFINITION OF DENTAL TISSUES. 



circulates, by anastomosing branches of the tubuli and 

 by the plasmatic cells of the intertubular substance, 

 through the dentine, maintaining a sufficient though 

 languid vitality of the tissue. The delicate nerve- 

 branches on the pulp's surface, some minute production 



Fig. 54. 



SECTION OF HUMAN TOOTH (highly magnified). 



of which may penetrate the tubuli, convey sensations of 

 impressions aflecting the dentine — sensations of which 

 every one has experienced the acuteness when decay has 

 affected the dentine, or when mechanical or chemical 

 stimuli have "set the tooth on edge;" but true "dentine" 

 has no canals large enough to admit capillary vessels 

 with the red particles of blood. 



The first modification of dentine is that in which capil- 

 lary tracts of the primitive vascular pulp remain uncal- 

 cified, and permanently carry red blood into the substance 

 of the tissue. These so-called " vascular canals" present 

 various dispositions in the dentine which they modify, 

 and which modification is called " vaso-dentine." It is 

 often combined with true dentine in the same tooth, e. g.^ 



