DENTAL CARIES. 



ITS EELATIONS TO THE GERM THEORY OF 

 DISEASE. 



Many theories have been advanced, in times past, to account 

 for caries of the teeth. Most of these have been vague and 

 indefinite, and have passed away with the advance of time. 

 About the beginning of the present century the vital theory, 

 as it was called, was prominent. By those who held this 

 theory, caries was supposed to result from an inflammation of 

 the structure of the dentine, which terminated in the final 

 breaking down of the part ; and as this structure is incapable 

 of physiological repair, a cavity was the inevitable result. 

 This theory seems to have been very thoroughly disproved by 

 the following considerations. It was observed that artificial 

 teeth, constructed of ivory, bone, sheep's teeth and human 

 teeth, were as liable to caries as the<natural teeth ; and that 

 this decay was, to all appearance, the result of similar, if not 

 precisely the same causes. This, of course, could not be the 

 result of vital forces existing in the structure undergoing the 

 process of decay. The conditions of the decaying portions 

 were very closely studied, to see whether or not anything 

 could be discovered that would show that these processes were 

 essentially different from each other. Some differences were 

 found, but the more they were studied the more evident did 

 it seem that these differences were not of such a nature as to 

 show that the processes were in any wise distinct from each 

 other. These studies caused the abandonment of the vital 

 theory; for, if dead substances decayed the same as living 

 ones, the forces which bring about the result must be other 



149 



