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i88                 PA THOGENIC BACTERIA.

of color-production, so that the centre of the growth is
distinctly golden ; the edges may be white.

Upon potato the growth is luxuriant, producing an
orange-yellow coating over a large part of the surface.
The potato-cultures give off a sour odor.

When grown in bouillon the organism causes a diffuse

In milk coagulation takes place, and is followed by
gradual digestion of the casein.

The Staphylococcus albus is exactly the same as the
aureus, with the exception that in all media it is con-
stantly colorless.

Experiments have shown that the Staphylococcus
aureus, like its congener, the albus, exists in an atten-
uated form, and there is every reason to believe that in
the majority of instances it inhabits the surface of the
body in that condition.

When virulent the golden Staphylococcus is a danger-
ous and often deadly organism. Its pathogeny among
animals is decided. When introduced subcutaneously,
abscesses almost invariably follow, except in a certain
few comparatively immune species, and not infrequently
lead to a fatal termination. In such cases the organisms
may be cultivated from the blood of the large vessels,
though by far the greater number collect in, and fre-
quently obstruct, the capillaries. In the lungs and
spleen, and still more frequently in the kidneys, infarcts
are formed by the bacterial emboli. The Malpighian
tufts of the kidneys sometimes are full of cocci, and
become the centres of small abscesses.

The coccus is almost equally pathogenic for man,
though the fatal outcome is much more rare. It enters
the system through scratches, punctures, or abrasions,
and when virulent generally causes an abscess, as various
experimenters who inoculated themselves have discov-
ered to their cost. Garre applied the organism in pure
culture to the uninjured skin of his arm, and in four
days developed a large carbuncle with a surrounding