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270 THE MICRO-ORGANISMS OF THE HUMAN MOUTH. :

ti-rtiiuTCROus pul])s is more dangerous than inoculation with pure
euhures ti'om the same pulps, which is as we should naturally
expect it to be. I intend, however, later (Chapter XT) to discuss
the question of infection through foul i)ulps at length, and pass
the subject here with this brief mention.
The mixed infections invarial)ly resulted in the death of the
animal.
During these studies I have found in the oral cavity a number
of bacteria which possess more or less pathogenic action, four of
which I have examined more in detail, and named as follows
Micrococcus gingivae pyo-
Fig. 114. genes.
Bacterium gingivae pyogenes.
Bacillus dentalis viridans.
Bacillus pulpee pyogenes.

i. Micrococcus gingivce pyogenes.
• •J
• '#.?
I found this organism in a case
of pyorrhoea alveolaris three
times in the same mouth, at
intervals of three months ; also
in a very filthy mouth, in the
deposit around the teeth. It
Micrococcus gingiv.e pyogenes. appears as irregular cocci, or
Culture in gelatine, 8 days old. n, separate
very plump rods, singly or in
cells. 1100 : 1.
pairs (Fig. 114, a). In gelatine
plate-cultures it grows rapidly at room temperature, forming
round colonies, with a distinctly sharp margin. At first the
colonies appear very slightly colored under the microscope; as
they become older they grow very dark, especially where they
lie far apart. Line-cultures on agar-agar present a moderately
thick, grayish growth, having a tinge of purple by transmitted
light. Under the microscope they appear as a homogeneous,
nearly colorless matrix, interspersed with darker figures of vari-
ous irregular shapes.
Puncture- (stick) cultures in gelatine have, when eight days
old, the appearance seen in Fig. 114. The gelatine does not be-
come liquefied. Cultures in beef-extract-peptone-sugar solutions