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Full text of "Pathogenic Bacteria"

474                 PA THOGENIC BA CTERIA.

plate. Often from the radiated central part of the colony
peculiar zooglea are formed, having a sausage- or screw-
shape, or wound in spirals like a corkscrew. The '
younger colonies, which have not yet reached the surface
of the gelatin, are more compact, rounded or nodular,
later covered with hair, and then becoming radiated and
like the superficial colonies."

When the culture-medium is more concentrated, or the
culture one that has been frequently transplanted, the
phenomenon is much less marked and sometimes does
not take place at all.

Puncture-cultures in gelatin are not at all character-
istic. They show a rapid stocking-like liquefaction of
the gelatin, extending so as to take in the entire gelatin
in the tube in a few days. Anaerobic cultures do not
liquefy.

Upon agar-agar the bacillus grows with the production
of a moist, thin, transparent, rapidly extending layer
which probably rarely reaches the sides of the tube.
Upon agar-agar plates the wandering of the colonies is
also said to occur.

Upon potato the growth is in the form of a dirty-look-
ing, smeary patch.

In culture-media containing either grape- or cane-sugar
fermentation occurs both  in the presence  and  in  the
absence of oxygen.    Milk-sugar is not decomposed.
When grown in milk the medium is coagulated.
In its growth the bacillus usually produces a strong
alkaline  reaction.    Indol and phenol are formed from
the peptone of the culture-media.    Nitrates are reduced
to nitrites, and then partly reduced to NH3.    In most
culture-media not   containing  sugar  the  bacillus  pro-
duces a very disagreeable odor.

It is a question whether the Bacillus proteus is to be
ranked among the pathogenic bacteria. Small doses of
it are harmless for the laboratory animals; in large doses
it produces abscesses. A toxic substance undoubtedly
results from the metabolism of the organism, and is the