Pathogenic Bacteria

PNEUMONIA. 347

beautiful pictures in blood and tissues when stained by
Grain's method. The capsule does not stain.

To demonstrate the capsule, the glacial acetic acid
method may be used. The cover-glass is spread with a
thin film of the material to be examined, which is dried
and fixed as usual. Glacial acetic acid is dropped upon
it for an instant, poured (not washed) off, and at once fol-
lowed by anilin-water, gentian-violet, in which the stain-
ing.continues several minutes. Finally, the preparation
is washed in water, and may be examined at once in water
or mounted in balsam after drying. The capsules are
probably more distinct when the examination is made in
water.

The pneumococcus is no stranger to us; it may some-
times be found in the saliva of healthy individuals, and
the inoculation of human saliva into rabbits frequently
causes a septicemia in which the bacillus is found abun-
dantly in the blood and tissues. Because of its frequent
presence in the saliva it was described by Fliigge as the
Bacillus septicus sputigenus.

When desired for purposes of study, it may be obtained
by inoculating rabbits "with pneumonic sputum and re-
covering the organisms from their heart's blood, or it may
be secured from the rusty sputum of pneumonia by the
method employed by Kitasato for securing tubercle ba-
cilli from sputum. A single mouthful of fresh sputum
is secured, washed in several changes of sterile water to
free it from bacteria of the mouth and pharynx, carefully
separated, and a central portion transferred to an appro-
priate culture-medium.

The organism grows upon all the culture-media except
potato, but only between the temperature-extremes of
24° and 42° C.; the best development is at 37° C. The
growth is always limited, probably because the formic
acid produced serves to check it. The addition of an
unusual amount of alkali to the culture-medium favors
the growth.

The organisms readily lose their virulence in culture-