496 SPECIAL HISTOLOGY. 



appearance of the fang is not uncommon. Necrosis of the teeth takes 

 place when the periosteum has been stripped off, or the pulp has died. 

 The teeth become rough and dark, even black, and finally fall out. The 

 nature and causes of dental caries are doubtful. It attacks living: and 

 false teeth (Tomes), and always begins on the exterior, from Nasmyth's 

 membrane (Ficinus), whence the fluids of the mouth have been supposed 

 to have considerable influence upon it; it does not follow, however, that 

 one living tooth may not be more disposed to it than another, being ren- 

 dered less capable of resistance either by its chemical composition, or by 

 the mode of its nutrition. Caries, however, is assuredly not a simple 

 solution of the salts by the oral fluids, but a solution accompanied by a 

 putrefactive decomposition of the organic elements of the tooth, which 

 becomes covered with infusoria and fungi ; in fact, according to Ficinus's 

 observations, the latter growths would appear to play the more impor- 

 tant part, inasmuch as the decay of the teeth usually commences in those 

 localities in which undisturbed opportunity is given to these organisms 

 to develop, as in the cracks and pits of the enamel, in the depressions 

 of the molar teeth, in the clefts between the teeth, but not where the 

 dentine is otherwise exposed, as on the masticating surface, in filed 

 places, &c. The usual coui-se of caries is, that the discolored spots of the 

 cuticle of the enamel, covered with living and growing organisms (infu- 

 sorial animalcules, similar to a Vibrio, which Ficiyius calls Denticola, 

 mucedinous fungi (Erdl, Klenke, Tomes), similar to those which are 

 found upon the tongue, and which Ficinus wrongly refers to the Denti- 

 colce) first lose their calcareous salts, and then break up into angular, 

 cellular pieces, as if they had been treated with hydrochloric acid. The 

 decay then penetrates through the enamel to the dentine, always first 

 softening it, so that it yields not more than 10 per cent, of ash (Ficinus), 

 and then decomposing it. The dentine is more aff"ected by this process 

 than the enamel, its canal first becoming filled with the fluids proceeding 

 from its decomposition, which may reach the pulp and give rise to pain, 

 unless, as Tomes found, the dentinal canals in the neighboring healthy 



The deposits of dentine in the walls of the pulp-cavity, the " osteo-dentine" of Owen, he 

 regards as mainly originating from the dentinal globules, which to him are protein-bodies. 

 This osteo-dentine partakes in some instances more of the nature of bone, than of dentine, 

 but consists generally of a central substance and of tubnles radiating from it; it frequently 

 appears to be formed of concentric layers. The central substance Wedl describes as con- 

 sisting either of hyaline dentinal globules, of a grayish, amorphous mass, or of distinct 

 bone-corpuscles of varying shapes, separated by spaces resembling Haversian canals. The 

 newly-formed tubules run from this central mass towards the dentine of the tooth, with the 

 canals of which they communicate. Sometimes they are intersected in their course by 

 the presence of many dentinal globules, or by irregular lacuna;. In all instances of these 

 formations, that he has examined, the dentinal globules existed in great abundance. The 

 dark color of the globules, wherever met with, Wedl is disposed to attribute to their retro- 

 gressive metamorphosis, whilst he regards the dark color of the interglobular spaces as 

 dependent on a deposit of brown pigment in their interior. — DaC] 



