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35
Gelatine plate cultures.
The growth is not very rapid. The deep colonies
have a somewhat starlike appearance; the superficial
colonies appear as bluish-white, delicate granular
films, which are almost coli-like in character. These
surface colonies are somewhat irregular in shape, and
from the wavy, transparent edge irregular processes
are given off.
Under a lower power of the microscope the deep
colonies show a central darkish yellow spot, from which
root-like processes are given off. The surface colonies
are transparent, granular, and striated, and from the
spreading edge delicate processes are given off, which
spread over the surface of the gelatine, forming often
curious and intricate patterns. The colonies do not
attain a large size, and liquefaction only slowly sets in.
The growth is characteristically rapid. The deep
colonies quickly reach the surface, to form large areas
of liquefied gelatine, which become saucer-shaped, and
are greyish-white in colour and almost translucent.¶
From the edge of these saucer-shaped surface colonies
processes may be given off which are almost of the
nature of "swarming islands." These almost translucent
areas of liquefied gelatine are rendered greyishwhite
by the presence of innumerable bacteria, and
these bacteria may be gathered together in clumps so
as to give rise to a mottled appearance. A thin
bacterial film tends to form on the surface of the
liquefied gelatine. In a very few days the whole
plate is completely liquefied.
Under a low power of the microscope the deep
colonies are dark in colour and granular. The surface
colonies at first may be almost completely translucent
and of an irregular, star-shaped form, but soon form
large circular areas of liquefied gelatine, in which the
extraordinarily rapid movement of the individual
bacilli can be clearly watched.
Gelatine "stab" cultures.
The growth at the surface is slow, and resembles the
growth of a superficial colony in gelatine plate culture.
Growth takes place all the way down the stab, accompanied
by slow liquefaction; delicate tuft-like filaments
are given off all down the line of the inoculation. These
extend more and more deeply into the solid gelatine as
growth proceeds. Gradually at the surface liquefaction
Bets in, showing itself at first merely by a slight central
pitting of the bacterial film. Later, the liquefaction
spreads, and the delicate details of growth are lost.
Rapid liquefaction takes place nearly if not quite to
the foot of the stab and in funnel form.§ Very soon
the liquefaction spreads to the walls of the tube and
increases rapidly from above downwards as well as from
the stab in an outward direction. The liquefied gelatine
has a greyish-white translucent appearance, and has
also a somewhat flocculent appearance due to aggregation
of little masses of bacteria. Very soon the whole
contents of the tube are completely liquefied and converted
into a greyish-white turbid fluid.
Gelatine "streak" cultures.
A delicate granular film forms on the surface of the
gelatine which is of somewhat limited extent. Liquefaction
slowly sets in and shows itself as a longitudinal
furrow. After some days the film changes its appearance
and shows numberless fine processes radiating
outwards and upwards from the central line. Tuft-like
processes also extend into the solid gelatine. As
liquefaction proceeds all the delicate details of growth
become lost.
The growth is not characteristic, as the liquefaction
is so rapid that the peptonised gelatine runs down the
oblique surface to the foot of the tube, and in a few
days the whole of the contents are converted into a
turbid greyish-white liquid.
Gelatine "shake" cultures.
No gas bubbles are formed; the gelatine is slowly
liquefied.
No gas bubbles are formed; the gelatine is rapidly
liquefied.
Agar plate cultures.
In agar plate cultures at 37° C. the growth is so rapid
and the colonies spread so much laterally, that frequently
the whole plate is covered with a granular
dirty yellowish-white film in 24 hours. The spreading
edge is often broken up into processes of most varied
Bhape, and which frequently form tree-like patterns.
In agar plate cultures at 37° C. the growth is so rapid
that it is difficult to obtain discrete colonies. The
growth is yellowish-white, granular, and often of unequal
thickness. The spreading edge has less tendency
to form tree-like patterns than in the case of
B. mesentericus E.
Agar "stab" cultures.
In 24 hours at 37° C. there is growth all down the
stab, and the surface of the medium is covered with a
yellowish-white granular layer, which later may become
wrinkled.
In 24 hours at 37° C. there is growth all down the
stab, and the surface of the medium is covered with a
yellowish-white granular layer, which later may become
wrinkled.
Agar "streak" cultures.
In 24 hours at 37° C. a dirty yellowish-white film has
covered nearly the whole oblique surface. The spreading
edge may extend as irregular processes forming leaf-like
patterns. Later the film darkens in colour and becomes
wrinkled.
In 24 hours at 37° C. a dirty yellowish-white film has
covered nearly the whole oblique surface. The spreading
edge may be lobed or fissured and of unequal thickness.
The film darkens in colour and becomes wrinkled.
Potato cultures.
The growth is extremely characteristic. At 37° C.
in 24 hours the whole surface of the potato is covered
with a thin yellowish-white film, which has a characteristic
folded, creased and wrinkled appearance. There
is an appearance also as of blisters : these dry up,
leaving deeply wrinkled skins. The substance of the
potato takes on a bright pink colour. Later the film
becomes thicker, more deeply pitted and wrinkled, and
the colour becomes brown.
The growth is extremely characteristic. In 24 hours
at 37° C. the whole surface of the potato is covered with
a thick greyish-white moist skin, which is thrown into
multiple folds, creasings and wrinkles.** The colour
rapidly changes from greyish-white to yellow, and then
to brown. The growth, if touched with a platinum needle,
is found to be held to the potato by a viscous substance
which can be drawn out into long threads.
Broth cultures.
The growth at 37° C. is characteristic even in 24
hours. A greyish-white wrinkled film is formed at the
surface, and the liquid below is nearly quite clear.
Later the film thickens and becomes deeply pitted and
wrinkled.
The growth at 37° C. is characteristic even in 24
hours. A greyish-white wrinkled film is formed at the
surface, and the liquid below is nearly quite clear.
Later the film thickens, and the wrinkled appearance
becomes more marked. It acquires a reddish-brown
colour, and the liquid below, which remains nearly
quite transparent, also takes on a reddish-brown colour.
¶ See fig. 7, Plate II.
§ See fig. 8, Plate II.
** See fig. 9, Plate III.