162 THE GERM THEORY OF DISEASE. 



have been definitely and completely studied until this soluble 

 ferment, or diastase, be found, isolated, and its capabilities 

 separately determined.* 



It is by no means probable that this is the only organism 

 that may stand in a causative relation to caries. The organ- 

 ism of butyric fermentation, possibly that of acetic fermenta- 

 tion, and a large number of others of the acid fermentations 

 may cause decay; nor is it by any means a settled fact that 

 decay of the teeth may not be brought about in part by other 

 vital processes than the acid fermentations. Of this, how- 

 ever, we will speak later. 



Another question may arise in this matter, and need ex- 

 planation. I have repeatedly said that the waste products 

 of an organism prevented the activity of that organism, when 

 collected in a certain amount. How, then, can this organism 

 continue to thrive in its own waste product, and thus con- 

 tinuously promote caries by furnishing more, and still more, 

 of this waste product? Simple enough. Every chemist who 

 has studied lactic fermentation has been in the habit of intro- 

 ducing some form of lime into the fermenting fluid to "fix" 

 the lactic acid in the form of a lactate of lime, in which case 

 it does not hinder the progress of the fermentation. In this 

 way a much larger amount of the lactic acid may be obtained, 

 as it is readily regained from its salts. This was learned long 

 before the organism was found. Now in the production of 

 caries, the tooth presents the lime for the formation of the 

 lactate, and thus furnishes the very conditions necessary to 

 the continuous growth of the organism. 



In this connection, I wish to call attention again to a diffi- 

 culty that has ever existed in the study of the action of 

 organized germs in producing impressions of whatever kind, 



* Since the above was written Dr. Miller has reported the finding of 

 this soluble ferment. 



