Page 45 - My FlipBook

VITAL MANIFESTATIONS OF BACTERIA. 19

different phenomena, viz. acid reaction and total absence of bad
smell.
AVe cannot therefore draw a sharp line between putrefactive
and fermentative bacteria. According to m}^ observation there
are but a limited number of bacteria which will, under all circum-
stances, produce putrefaction. These might be called obligatory
saprogenic bacteria, in contradistinction to those which produce
putrefaction only under certain specified conditions ; these latter
might be called facultatively saprogenic.
Bacteria produce a series of well-characterized fermentations,
whose nature has, however, in many points not yet been fully
explained. These fermentations are, according to Fliigge's classi-
fication :^^
A. Fermentation of carbohydrates.
B. Fermentation of the polyvalent alcohols.
C. Fermentation of fatty acids.
D. Putrefaction,
E. Oxidation of alcohol to acetic acid. To these we add :
F. Ammoniacal fermentation.
G. Diverse processes of oxidation and reduction first observed
in the soil, but probably going on under various other conditions.

A. Fermentation of Carhoh/drates.

Carbohydrates, when acted upon by difiterent bacteria, undergo
a series of fermentations which may be considered under the
following heads :
a. Lactic acid fermentation.
h. Mannite, or mucous fermentation.
c. Dextrane fermentation.
d. Butyric acid fermentation.
e. Diverse fermentations which cannot be classed under the
above heads.
Among the carbohydrates, the sugars in particular are ferment-
able in a high degree ; other carbohydrates, however, as dextrine,
starch, cellulose, etc., may also undergo fermentation under the
action of certain micro-organisms. Tappeiner (Fliigge ^') observed
a fermentative decomposition of cellulose in the alimentary canal