150 THE GERM THEORY OF DISEASE. 



than the vitality of the suffering organ, and therefore cannot 

 be the result of inflammation; it must be some force external 

 to the tooth, something which attacks the tooth from without. 

 This point seems to have been very thoroughly established, 

 and we supposed it was well settled in the minds of all 

 modern thinking men. But, curiously enough, the old notion 

 has recently been revived by certain gentlemen in New York. 

 The effort to maintain such an hypothesis, however, must 

 inevitably result in failure ; for in it there is a plain want of 

 consideration of the known facts of the subject. It need not, 

 therefore, detain us longer. 



Caries of the teeth has been defined as a molecular disinte- 

 gration of the tooth's substance, or a breaking down of the 

 chemical constituents of the tooth, molecule by molecule. 

 This destruction always has its beginning on the surface of 

 the tooth, or in some pit, crevice, or other imperfection in the 

 enamel. And it spreads from this point, as the focus, in 

 every direction, the dentine being destroyed more rapidly 

 than the enamel ; hence, it usually happens that the cavity is 

 larger within than on the surface of the tooth. Caries does 

 not seem to be a simple solution of the tooth's substance; 

 sometimes we find nearly all of the material removed from 

 the cavity, in other cases we find the dentine reduced to a 

 pulpy or semi-gelatinous mass, in which the structure of the 

 dentine is more or less perfectly preserved. Some decays are 

 white, some are black, some have a yellow tinge all the 

 shades from white to black may be found. But it was not 

 my intention to give a lengthy description of the results of 

 caries, but rather to confine myself as closely as possible to 

 the discussion of the probable cause of the affection ; I say 

 probable cause, for I do not assume that the cause or causes 

 are certainly known. Indeed, we may say that at the present 

 time there is the greatest disagreement among even the best 



