CHAPTER  XII.
TETRAGBNUS.
there can sometimes be found in the normal saliva,
more commonly in tuberculous sputum, and still more
commonly in the cavities of "tuberculosis pulmonalis, a
large micrococcus grouped in fours and known as the
Micrococcus tetragenus (Fig. 123). It was discovered by

FlG. 123.—Micrococcus tetragenus in pus from, a white mouse ; x 615 (Heim).
GafFky, and subsequently carefully studied by Koch and
GafFky. It sometimes occurs in the pus of acute ab-
scesses, and may be of importance in connection with
the pulmonary abscesses which so often complicate tu-
berculosis.
The cocci are rather large, measuring about i // in
diameter. In cultures they show no particular arrange-
ment among themselves, but in the blood and tissues of
animals they commonly appear arranged in groups of
four surrounded by a transparent gelatinous capsule.
The organism stains well by ordinary methods, and
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