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Full text of "Pathogenic Bacteria"


make their appearance in plain agar as well as in sugar-
agar, though, of course, less plentifully. They first ap-
pear in the line of growth; afterward throughout the
agar, often at a distance from the actual growth. Any
fluid collecting about the bubbles or at the surface of the
agar-agar may be turbid from the presence of bacilli.
The gas-production is more abundant at incubation- than
at room-temperatures.

The agar-agar is not liquefied by the growth of the
bacillus, but is often broken up into fragments and forced
into the upper part of the tube by the excessive gas-pro-

In its growth the bacillus produces acid in considerable

In bouillon growth does not occur in tubes exposed to
the air, but when the tubes are placed in Buchner's jars,
or kept under anaerobic conditions, it occurs with, abun-
dant gas-formation, especially in glucose-bouillon, with
the formation of a frothy layer on the surface. The
growth is very rapid in its development, the bouillon
becoming clouded in two to three hours. After a few
days the bacilli sediment and the bouillon again becomes
clear. The reaction of the bouillon becomes strongly

In milk the growth is rapid and luxuriant under
anaerobic conditions, but does not take place in cul-
tures exposed to the air. The milk is coagulated in
from twenty-four to forty-eight hours, the coagulum
being either uniform or firm, retracted, and furrowed
by gas-bubbles. When litmus has been added to the
milk it becomes decolorized when the culture is kept
without oxygen, but turns pink when it is exposed to
the air.

The bacillus will also grow upon potato when the tubes
are enclosed in an anaerobic apparatus. There is a
copious gas-development in the fluid at the bottom and
sides of the tube, so that the potato becomes surrounded
by a froth. After complete absorption of the oxygen a