THE BACTERIA IN DIFFERENT MEDIA. 145 
9Pro 
The most suitable temperature seems to be 35 
(95° Fah.). 
We know but little about this Pee Gton. 
“Tt merits, however, to be better studied. It 
is this which causes the spontaneous coagulation 
of milk: sugar of milk is transformed into lactic 
acid, which coagulates the caseine. We often see it 
occur in beef juice or in sour starch water; it must 
play a part in the formation of sour krout, and 
intervenes very certainly, and perhaps more than 
the alcoholic fermentation, in the preparation of 
bread. Finally, it very easily invades beer, which 
of our domestic drinks is most exposed, because of 
its slight acidity, to become the seat of this fer- 
mentation. All of these facts render it interest- 
ing, so much the more as it is rarely exempt from 
complication, and is frequently accompanied, for 
example, by a commencement of butyric fermenta- 
tion, far more disagreeable in its products” (Du- 
claux). 
2. Butyric Fermentation. — This is, in fact, al- 
ways preceded by a lactic transformation, and it is 
by an ulterior modification that the lactic acid 
produces the butyric acid. The organism which 
accompanies it is a bacterium very nearly allied 
to Bacillus subtilis, Cohn. 
The reaction represented by the phenomena, 
from a chemical point of view, is the follow- 
ing : — 
2C®?H®O? = CtH8O? + 2C0? + Ht. 
—_—_o— —_———" 
lactic ac. butyric ac. 
