DENTAL CAEIES. 151 



informed men on this important subject; and that it is still 

 very uncertain that any of the theories in regard to the matter 

 are correct. It is proper that I should say, however, that 

 more than one of these explain the phenomena with sufficient 

 accuracy to be of great value, both in the prevention and 

 treatment of this affection. It must not be supposed that a 

 theory must be absolutely correct to be of use. Theories are 

 usually contrived in the effort to explain phenomena, and it 

 often happens that a false theory leads to as good an applica- 

 tion of means to ends as the true one would do. Of this, 

 however, we can never have any assurance; therefore, as long 

 as there is a reasonable doubt the search for the truth should 

 continue. 



The theory for the explanation of caries which has received 

 the greatest attention and the widest recognition in modern 

 times, is what is known as the acid theory. This theory seems 

 to account for the phenomena more perfectly than any other 

 that has as yet attained prominence in the minds of thinking 

 men. As a working theory, a basis upon which to found 

 principles of treatment, it has undoubtedly been the means of 

 good. Yet, in the scientific aspect of the subject, there is 

 much objection to be urged against it. A very large amount 

 of work has been done with the view of demonstrating the 

 absolute truth of this theory, all of which must be regarded 

 as a failure, so far as the attainment of that particular object 

 is concerned. The labor has not been lost, however; but, on 

 the other hand, has been of immense value. It is this labor, 

 the basis of fact which it has brought to light, that will be of 

 most service to us in the building up of other theories for the 

 explanation of the phenomena, which may serve us usefully, 

 until such time as theories shall be displaced by demonstra- 

 tion, the goal to which we are all looking forward. 



According to the chemical theory, the substance of the 



