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VITAL MANIFESTATIONS OF BACTERIA. 35

ing matter, with the exception, perhaps, of Bacterium chlorinum
(Engelmann) and Bacillus virens (van Tieghem). Access of
atmospheric air is essential to the production of pigment fer-
mentation.
II. Kronecker first called attention to a liquefying bacillus
whose cultures in bouillon showed no color when the access of
air was limited, but when shaken with air an intensely green
color instantly appeared. I have noted a similar
result in the case of other bacteria. Liborius^^ Fig. 8.
proved for a large number of pigment bacteria
" that all these coloring- matters are formed only
where there is free access of air."
Chromogenic bacteria are widely distributed in
nature. Whea a plate of nutritive agar-agar is
exposed to the air for some time, and then kept in
a moist chamber, colonies of various kinds of
chromogenic bacteria generally develop upon it.
They have their representatives among the patho-
genic, as well as the non-pathogenic organisms.

3. Aerogerdc Bacteria.

Various kinds of gases, C0^„ H, N", SHo, CH^,
NH3, etc., are often formed as waste products of
bacteria, as well as of fungi in general. Accord-
ing to Fliigge, the functional activity of the lower
fungi must always be accompanied by the develop-
ment of CO^. ^Nevertheless the quantity of CO2
evolved from many cultures is excessively small, Culture op a
Gas-foemixg
and is to be considered as a product of intermolec-
Bacterium
FROM THE
ular respiration only (see also page 20).
Stomach, in
In fermentations of carbohydrates, lactic and Bread-Sugar
butyric acid, mannite and cellulose fermentations, Gelatine.
One day old.
and various others, COj, H, and CH^ are princi-
pally or exclusively formed, the former often in
such quantities that the course of the fermentation is exceed-
ingly violent (Fig. 8).
The fermentation of albuminous substances (putrefaction) is