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BIOLOGICAL STUDIES ON THE BACTERIA OF THE MOUTH. 87

cultures on beef-water-peptone-sugar agar-agar, certain bacteria
will develop with tolerable regularity. Of these I think the
following worthy of mention :
1. A micro-organism occurring in somewhat irregular cocci
or diplococci, singly or in chains (Fig. 45). It produces small,
prominent, shining colonies resembling in older cultures tiny
glass beads ; these colonies are further charac-
terized by their cartilaginous consistency, and Fig. 4 5.
by the fact that they cannot be taken up with the
€*
point of the needle, but run ahead of it on the \
s
surface of the plate. Under a low power the , &^
colonies appear roundish, very dark, lustrous, <*
frequently having a villous margin and a black
Ascococcus BUCC.XLIS,
pattern within (Fig. 46). These two last char-
ncH3 : 1.
acteristics are not, however, constant.
2. A bacterium which appears in the form of unequally large
cocci (Fig. 47). It forms small round or roundish, very thin colo-

FiG. 46. FiQ. 47. Fig. 48.

-^-^'*-''
Cells of the Mouth-Bacte-
CoLOSY OF Ascococcus bT-c- eiu-M described rXDEE 2.
CALIS 3 DAYS OLD. UUO : 1.
70:1.
Sector of a Coloxy of the
Mouth-Bactericm de-
scribed rXDER 2.
3 DATS old. 200 : 1.
nies, without a distinct margin, which are quite colorless or tinged
but faintly yellowish-gray when examined under the microscope.
The separate cocci are visible under a power of about 200 diam-
eters, the whole colony appearing coarsely granular, and the short
chains of cocci or separate cocci protruding over the margin.
Fig. 48 shows the sector of a colony under about 200 diameters.
3. A third bacterium appears as oval cocci, mostly in pairs
It also forms thin, small colonies, hardly
or chains (Fig. 49).