346

PATHOGENIC BACTERIA.

position to occur in pairs, and not infrequently forms
chains of five or six members, so that some have been
disposed to look upon it as a streptococcus (Gamaleia).
In tlie fibrinous exudate from croupous pneumonia, in
the rusty sputum, and in the blood of rabbits and mice
containing them the organisms are arranged in pairs,
exhibit a distinct lanceolate shape, the pointed ends
generally approximated, and are usually surrounded by
a distinct halo or capsule of clear, colorless, homogeneous
material, thought by some to be a swollen cell-wall, by

FIG. 98.__Diplococcus pneumoniae, from the heart's blood of a rabbit; x 1000

(Frankel and Pfeiffer).

others a mucus-like secretion given off by the cells. When
grown ordinarily in culture-media, and especially upon
solid media, the capsules are absent.

The organism is without motility, has no spores, and
does not seem to be able to resist any unfavorable con-
ditions when grown artificially. It stains well with the
ordinary solutions of the anilin dyes, and gives most