Pathogenic Bacteria

334 PATHOGENIC BACTERIA.

diate species between the cholera and the Finkler-Prior
spirilla.

The colonies upon gelatin plates appear in about twelve
hours as small whitish points, and rapidly develop, so that
by the end of the third day large saucer-shaped areas of
liquefaction resembling colonies of the Finkler-Prior
spirilla occur. The liquefaction of the gelatin is quite
rapid, the resulting fluid being turbid. Generally there
will be upon a plate of Vibrio Metchnikoff some colo-
nies which closely resemble cholera by occupying small
conical depressions in the gelatin. Under a high power
of the microscope the contents of the colonies, which ap-
pear to be of a brownish color, are observed to be in rapid
motion. The edges of the bacterial mass are fringed with
radiating organisms (Fig. 90).

In gelatin tubes the culture is very much like that of
cholera, but develops more slowly.

Upon the surface of agar-agar a yellowish-brown
growth develops along the whole line of inoculation.
On potato at the room-temperature no growth occurs,
but at the temperature of the incubator a luxuriant
yellowish-brown growth takes place. Sometimes the
color is quite dark, and chocolate-colored potato cultures
are not uncommon.

In bouillon the growth which occurs at the tempera-
ture of the incubator is quite characteristic, and very
different from that of the cholera spirillum. The entire
medium becomes clouded, of a grayish-white color, and
opaque. A folded and wrinkled mycodenna forms upon
the surface.

When glucose is added to the bouillon no fermentation
or gas-production results.

When grown in litmus milk the original blue color is
changed to pink in a day, and at the end of another day
the color is all destroyed and the milk coagulated. Ulti-
mately the clots of casein sediment in irregular masses,
and clear colorless whey is supernatant.

The addition of sulphuric acid to a culture grown in a