F. C. MINETT AND M. R. DHANDA
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The behaviour of the anthrax bacillus in these soils is shown in Table V.
It is seen that growth takes place in all cases, except in very acid soils, where
as would be expected, there is a tendency for growth to be inhibited.
Naturally, the saturation capacity of these soils varied greatly but they were
all brought to the water-logged state before being seeded. It may here be
noted that, according to Koci [1934], the extreme pH limits for growth of the
anthrax bacillus are 6.6 and 8.7, with an optimum between 7.2 and 8.1.
B. Natural (unsterilized) soils and water containing same
In experiments with natural soils, a suitable quantity of air-dry Muktes¬
war soil was thoroughly mixed with two-fifths of its weight of tap water and
amounts corresponding to 200 gm. of the dry soil were distributed in 250 c.c.
bottles (bottom diameter 6.3 cm.). Some of the bottles were sterilized to
act as controls and the water content then readjusted to equal roughly that
of the unheated soil. The actual water content of all bottles was taken at
the end of the experiment.
In the water experiments, thin layers of soil (50 gm.) were placed in
rounded 500 c.c. flasks and filled with distilled water. Some were autoclaved
to act as controls.
Anthrax spores were added in known numbers to the bottled soil and
well mixed. Spores were similarly added to the water in the flasks. After
various periods at 25°C. or 30°C., the soil was again mixed, the flasks were
shaken and samples (4.8 gm. soil, 4 c.c. water) withdrawn for making dilu-
tions,—for inoculation of guinea-pigs with the unsterilized medium and for
plating with the sterilized control medium.
The results of several experiments are shown in Tables VI and VII.
In experiments 13 and 14 (Table VI), soil alone was used ; in experiments
15-17, horse manure (in form of 10 per cent watery extract), as well as lime
and superphosphate to give final concentrations of 1.0, 0.1 and 0.02 per
cent respectively, were added to the soil. In experiment 18, defibrinated
ox blood 10 c.c. and water 100 c.c. were added to 200 gm. dry soil ; after 6
days incubation, this medium became highly putrid and gave off abundant
gas. From Tables VI and VII, it can be gathered that there is no evidence
of growth taking place within 7-11 days in natural soil, even with the addi-
tion of substances which should produce a favourable effect. The same is
true of unsterilized water standing over a thin layer of soil. On the other
hand, under identical conditions, except that the media has been sterilized,
growth took place within 5 or 6 days. It is important to note that only one
out of 63 guinea-pigs died of intercurrent disease after inoculation with natural
soil or water.
GROWTH OF CL. CHAUVŒI IN SOIL
Tests were made at 25° or 30°C., usually the latter, using 100-200 gm.
amounts of untreated Mukteswar soil, soil containing lime or ammonium
sulphate to 0.1 per cent, soil containing lime to 0.1 per cent, superphosphate
to 0.02 per cent and watery extract of horse manure to 1.0 per cent, (Table IV,
legend). The water content was set at about 40 per cent. The number
of viable organisms used for seeding the soil or the water in the