THE BACTERIA IN DIFFERENT MEDIA. cap 
§ 1.— Rote or BacTerta IN FERMENTATIONS. 
We say that a liquid is fermenting whenever 
modifications occur in its chemical constitution, as 
a result of the nutrition of organized beings. 
Two kinds of fermentation are commonly distin- 
guished. In the first group (false fermentations) 
are arranged those which are produced by soluble 
quarternary substances (diastase, soluble ferments) 
secreted by living cells, from which they may be 
separated in order to study their action upon fer- 
mentable liquids. This action is comparable to that 
of certain mineral acids, which operate in the same 
manner, either by the breaking up of molecules 
with addition of water or by the phenomena of 
hydration. Veritable chemical reagents, when 
these substances are once precipitated from their 
solutions, purified and dried, they preserve their 
properties indefinitely. A sufficient elevation of tem- 
perature seems to destroy the edifice of their mol- 
ecule; for they lose all their specific power after 
having been subjected to a temperature more or less 
elevated, but always inferior to 100° (212° Fah.). 
In the second group (true fermentations) are 
joined all the phenomena of chemical modifica- 
tion which appear intimately united to the devel- 
opment of inferior organisms, —algz or fungi 
(figured ferments). Compressed oxygen by kill- 
ing these ferments, and chloroform by suspending 
their vital functions, arrest the progress of these 
fermentations, while the same agents do not mod- 
