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Scientific Memoirs by
thoroughly stirred up with a sterilised platinum wire and a plate-cultivation
set from it. A limited number of colonies, became developed in the cultivation
, but none of them contained choleraic commas. The majority of the colonies
consisted of straight Bacilli, and a few of them of peculiar, thick, slightly
curved ones. Repeated cultivations of these were made, lest they might be
a modified form of the choleraic comma-bacillus, but the result was to show
that they were permanently and specifically distinct. Another plate-culti
va-tion of the earth was set on the 29th March. Numerous colonies, all composed
of large straight Bacilli, were developed in it, but, as before, no commas
appeared. The above experiments having clearly shown that choleraic comma
-bacilli rapidly and permanently disappear from portions of soil, whether pure or
fæclly contaminated, exposed to the ordinary conditions prevalent in Calcutta,
an attempt was made to ascertain whether any other materials to which they
are likely to gain access were more favourable to their continued existence. The
material selected for experiment in the first place was cowdung, which, from
the extent to which it enters into the domestic economy of the lower classes of
natives, is constantly at hand to receive choleraic contamination. Some fresh
cowdung was procured on the 23rd of March 1887, and two separate portions
of it were inoculated with masses of agar-agar full of choleraic commas. In
both cases the portions of dung were set in sterilised watch-glasses in moist
chambers, but while the dung in one case was set in its natural condition,
in the other it had been previously mixed with distilled water and subjected
to prolonged boiling. Five days later small portions were removed from each,
at sites far removed from the sites of inoculation, and were used to start plate
-cultivations. In both cultivations a great number of Schizomycete colonies
were developed. In that corresponding to the boiled dung these, in so far as
could be ascertained, all consisted of vigorous, well-developed choleraic commas.
In the cultivation corresponding to the unboiled dung commas were also present.
They were not, however, apparently so vigorous, but were slender and stained
feebly, and they were accompanied by numerous colonies of large, straight,
Bacilli. The boiled dung appeared, therefore, to represent a pure cultivation
of vigorous choleraic commas, the unboiled dung a mixed cultivation of com
-paratively feeble commas and of other Bacilli. The boiled dung was now
removed from the moist chamber and was kept in the incubator for 72 hours at
a temperature of 37°C. At the close of this period it was quite dry throughout
and readily broke up into dust on being disintegrated. A plate cultivation
was inoculated from some sterilised salt solution in which portions of the
dried material had been allowed to soak for some time in a state of fine
division. An abundance of colonies became developed in it, a few consisting of
Micrococci, and the great majority of straight Bacilli. Not a trace of the
presence of any commas could anywhere be detected in it.
A second portion of fresh cowdung was procured on the 3oth March.