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260 THE MICRO-ORGANISMS OF THE HUMAN MOUTH.

A. Frankel ^^^ also obtained pure cultures of tlie same organism
from the blood of a rabbit which had just died. He used agar-
ag-ar dissolved in calf's or beef broth, and added h to 1 per cent.
grape-sugar or an equal quantity of the double tartrate ot potas-
sium and sodium. A culture on coagulated beef-blood serum
proved siill more successful. Optimum of temperature, 35° to
37° C.
" Within twenty-four hours, at 35° to 87° C, the culture grew
in the shape of a nearly transparent grayish-white, gelatinous
coating upon the surface. Viewed by reflected light, it resem-
bled a dew-drop.
" When scraped together with the needle, the coating pre-
sents a yellowish-brown appearance."
Flasks of bouillon exposed to a temperature of 30° to 35° C.
become equally clouded throughout twenty-four hours after the
infection; later the culture sinks to the bottom as a peculiar,
granular, sandy precipitate, while the liquid above it becomes
clear.
The coccus of sputum septicpemia grows only between 22° and
42.5° C, no development taking place either below the former or
above the latter temperature.
Its cultivation is difficult un-
Fi(i 1 11.
der all circumstances. Above
i^O all, the nutrient medium must
not be too concentrated (ac-
cording to Weiehselbaum, IJ
per cent, of peptone, 1| per
cent, of grape-sugar, 1\ per
cent, of common salt in IJ
per cent, solution of agar-
agar), and must be exactly
Capsule Cocri
neutralized.
from piieuinonic exudation in inaii (After
This bacterium appears in
Bauingarton.) 1500 : 1.
the form of oval cocci, some-
times single, oftener in pairs, as diplococci, or in short chains (Fig.
111). The separate cells, as well as the chains, are surrounded
by gelatinous capsules, which become visible even under 300
to 400 diameters, and may be stained by the method of Fried-