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Full text of "Pathogenic Bacteria"

444                  PATHOGENIC BACTERIA.

most beautifully by Gram's method, by which it can be
best demonstrated in tissues.

Upon gelatin plates small white colonies are produced
in from twenty-four to forty-eight hours. Under the
microscope they are found to be spherical or elongate
(lemon-shaped), finely granular, and lobulated like a
raspberry or a mulberry. When superficial they form
white, elevated, rather thick masses 1-2 mm. in diameter
(Fig. 124). ^

In   gelatin   punctures a large white surface-growth

FIG. 124.—Micrococcus tetragenus: colony twenty-four hours old upon the sur-
face of an agar-agar plate; x 100 (Heim).

takes place, but very scant development occurs in the
puncture, where the small spherical colonies generally
remain isolated.

Upon the surface of agar-agar spherical white colonies
are produced. They may remain isolated or may become
confluent.

Upon potato a luxuriant thick, white growth occurs.

The growth upon blood-serum is also abundant, espe-
cially at the temperature of the incubator. It has no
distinctive peculiarities.

The introduction of tuberculous sputum or of a most
minute quantity of a pure culture of this coccus into
white mice generally causes a fatal septicemia.