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 Microses oF DENTAL CARIES. 
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 affection. These acids begin by scttening 
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 
