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39
Agar "streak" cultures.
In two days, at 37° C., an abundant creamy white
layer, covering nearly the whole surface, which on close
inspection shows numerous minute circular areas where
the growth, instead of being opaque, is semi-transparent.
In 20 hours, at 20° C., a greyish-white layer, not
specially characteristic. In 48 hours, growth somewhat
dry and granular looking. In four days, curious
wrinkled appearances. Ridges, formed by the unequal
rate of growth, or by the contraction of the bacterial
skin, stand out from the surface of the medium about
one-sixteenth of an inch, and usually are arranged in
more or less transverse folds.*
Gelatine "stab" cultures.
In 2 days, at 20° C., liquefaction has occurred right
down to the foot of the stab. White flocculent masses
of bacteria sink through the liquefied and grey-coloured
gelatine to the foot of the stab. The liquefaction
extends rapidly from the line of inoculation outwards
as well as from the surface downwards. A scum
forms on the surface, but no distinct skin is formed.†
Rapid liquefaction all the way down the stab,
but as the growth proceeds the liquefaction spreads
in cylindrical fashion from above downwards rather than
from within outwards from the region of the line of
inoculation. A distinct skin forms on the surface,
which eventually sinks in the liquefied gelatine.‡
Liquefaction.
Rapidly liquefies gelatine and blood serum.
Liquefies gelatine and blood serum fairly rapidly.
Gas formation.
Forms no gas in gelatine "shake" cultures.
Forms no gas in gelatine "shake" cultures.
Broth cultures.
Diffuse cloudiness in 24 hours at 37° C. A scum
forms on the surface which readily falls to the foot of
the tube on shaking.
Diffuse cloudiness: a skin forms on the surface
which is brittle and sinks on shaking the tube.
Indol.
Forms no indol.
Forms no indol.
Litmus milk cultures.
In 2 days, at 37° C., there is complete discoloration
and a clot has formed; no redness is visible. In 5 days
a white clot occupies about one-third of the bulk of
medium, which appears to be slowly peptonised. The
liquid surrounding the clot is pale yellow in colour,
and semi-transparent without pink coloration.
The purple-blue colour of the litmus milk gradually
fades, but no clotting or redness occurs. In 8 days the
milk is almost transparent and of a pale dirty yellow
colour; on shaking the tube the liquid assumes a faint
pink tinge. By the 21st day the milk has changed to a
semi-transparent dirty yellow liquid; on shaking the
tube the contents assume a reddish tint.
Potato cultures.
In 2 days, at 378 C., a dirty-white layer is formed
with a yellowish tint.
A white, rather dry-looking coat is formed. Later
portions of the growth become upraised, and sometimes
present a worm-like appearance.
Blood serum cultures.
In 24 hours, at 378, a white layer develops, accompanied
with liquefaction of the medium.
In 20 hours, at 20° C., a thin whitish layer is formed.
In 48 hours commencing liquefaction and markedly
wrinkled skin.||
Remarks.—Several varieties of B. subtilis occur in sewage. For the purpoee of description I have named
these two :—Sewage variety A, and sewage variety B. The fact, however, of the latter organism not growing at
37° C. makes it doubtful whether it should be considered a variety of B. subtilis.
8.—Bacillus Membraneus Patulus.
[An aerobic, non-chromogenic, slowly liquefying, spore-forming (?), non-motile bacillus.]
Source.—Crude sewage and effluent from coke-beds.
Optimum temperature.—Grows well at 37° C., and at the room temperature.
Morphology.—A very large bacillus which forms long chains.§
Spore formation.—Old culture resist heating to 80° C. for ten minutes, and the microbe has been found in
cultures made from sewage which had previously been heated to 80° C. for ten minutes. A satisfactory doublestained
preparation, however, has not been obtained.
Motility.—No motility could be made out, even in a 20 hours' broth culture.
Gelatine plates.—The surface colonies appear as coarsely granular greyish-white films of somewhat
irregular shape. From the spreading edge of the colonies processes extend in a tortuous fashion over the
surface of the mediums often forming patterns of great delicacy and beauty. Beneath the surface film-like growth,
slow liquefaction of the gelatine occurs. The growth is rapid. Under a low power of the microscope the
colonies present a characteristic granular and striated appearance.¶
Oblique gelatine cultures.—In less than two days, at 20° C., a coarsely granular film forms on the surface of
the gelatine which spreads rather rapidly and may extend nearly to the walls of the tube. From the spreading
edge processes are given off which wind over the surface of the gelatine in a characteristic way. Soon a
longitudinal pitting of the bacterial film along the line of inoculation is observed, and later on as liquefaction
proceeds, the growth slips down to the foot of the tube, and all delicate details are lost. The growth is like an
elongated surface colony in gelatine plate culture. **
Oblique Agar cultures.—In one night, at 37° C., the growth appears as a coarsely granular, semi-transparent,
greyish - white film. By the second day the growth is less transparent and less granular looking. In old
cultures the surface assumes a tuberculated appearance.
Gelatine "stab" cultures.††—The growth varies, as sometimes there is liquefaction down the line of the stab
with tuft-like processes extending into the solid medium, and at other times there is almost no liquefaction along
the line of inoculation, and the processes extend nearly to the walls of the tube, giving rise to an appearance of
great beauty. The growth on the surface is like the growth of a surface colony in a gelatine plate culture.
Liquefaction.—Liquefies gelatine, but not rapidly. Produces only very slight liquefaction of blood serum
even in cultures kept at 37° C. for 16 days.
Gas formation.—Forms no gas in gelatine "shake" cultivations.
* Fig. 20, Plate V.
§ Fig. 21, plate VI.
† Fig. A, plate VII.
¶ Fig. F, plate VIII
‡ Fig. C., plate VII., and Fig. 19, plate V.
** Fig. 22, plate VI., and Fig. E, plate VIII.
|| Fig. D., plate VII.
†† Fig. 23, Plate VI.