THE MICROBES OF HUMAN DISEASES. 177 



over Bacterium termo, which appears to be fatal to 

 the former when present in any number. ... In 

 my culture flasks, a small drop of blood from an in- 

 fected rabbit gave birth within a few hours to such 

 a number of microbes that the liquid contained in the 

 flask was completely filled with them, and it was 

 deprived of the nutriment necessary for any further 

 development." 



The exceptional virulence of this microbe must 

 therefore be ascribed to its vital and reproductive 

 energy, and to the rapidity with which it multiplies ; 

 at any rate, until we know more on the subject. 



IV. The Microbes of Dental Caeies. 



Miller's recent researches (1884) tend to show that 

 dental caries is chiefly due to the development of one 

 or more species of bacteria. The presence of acids 

 introduced into the mouth, or developed by certain 

 diseases (ulcers, thrush, etc.) which are themselves 

 produced by microbes, appears to be the predisposing 

 cause of this aflection. These acids begin by softening 

 the dentine, deprived at some point of its superficial 

 coating of enamel, and through this the bacteria enter. 

 Saliva can be rendered experimentally acid by mixing 

 it for four hours, at a temperature of 20°, with sugar 

 and starch (Cornil). Hence the injuriousness of sugar- 

 plums and other sweetmeats, long and correctly 

 9 



