666 



THE TEETH. 



depressions. No reaction whatever follows this process. The glue-yielding- 

 basis-substance being deprived of its lime-salts, shows a yellow discolora- 

 tion, and only traces of the dentinal canaliculi. The basis-substance then 

 breaks down into an indistinct granular mass, which is immediately filled 

 with a new growth of low vegetable organisms, viz. : micrococci and 

 leptothrix. 



My specimens plainly show that these organisms are not the advance- 

 guard in the process of decay. The first change that takes places is expos- 

 ure of the basis-substance by the chemical action of some acid, independent 

 of the named organisms, which come to view only after complete disinte- 

 gration of the basis-substance. I never have seen the penetration of these 

 organisms into the dentinal canaliculi before a thorough decalcification of 

 the basis-substance had taken place. 



In the great majority of my specimens I have met with formations on the 

 diseased boundary of the dentine which demonstrate a considerable degree 



\ Wlmln 



FIG. 292. ACUTE CARIES OF DENTINE. 



E, E, fissures in which the decay penetrates into the dentine ; I, small islands of un- 

 changed dentine. Magnified 200 diameters. 



of reaction, produced by the irritating power of the same agent to which 

 the lime-salts of the dentine yield. In fact, this was the case in all teeth 

 which were alive when attacked by the carious process, or rather when 

 removed from the jaws. On the boundary of this process we see irregularly 

 shaped elongations running a certain depth into the tissue of the dentine. 

 The more superficial the elongations are, the surer the morbid process 

 may be termed a slow one ; and, on the contrary, the deeper the elongations, 

 the more certain we may be that the morbid process has advanced rapidly. 

 The elongations mainly have the shape of fissures filled with a dark, granular 

 material, if viewed with a low power. These fissures run independently of the 

 direction of the dentinal canaliculi ; nay, very often cross them. (See Fig. 292.) 

 On the surface of the carious portion of dentine we see irregular cavities 



