Medical Officers of the Army of India.
13
cultivation had developed large numbers of yellowish, almost odourless colonies
of considerable size, consisting of straight Bacilli. No commas ever appeared
in it. Subsequent cultivations from this sample of soil also failed to produce
any commas.
In the above experiments we find that very large quantities of comma-bacilli
introduced into fæcally contaminated soil and exposed to conditions similar
to those to which the Bacilli entering the soil in Calcutta are normally liable
during the period of year dealt with, failed to multiply, and, on the contrary, rapidly
and completely disappeared. In dealing with any case in which the possibility of
the existence of resting forms is present, it is, of course, necessary to exercise
caution in concluding that an organism has finally disappeared because it fails
to manifest its presence under conditions in which the active form flourishes.
The resting stage by no means necessarily is replaced by the active one on the
mere incidence of conditions favourable to the latter and at certain times cer-
tainly serving to bring the resting stage to a close. The element of time is often
an important factor in the result. This is very conspicuously evident in the case
of many teleutospores of uredinal fungi, and also in the resting cells of some
of the unicellular algæ. In the present case, however, it may, I believe, be safely
assumed that the phenomenon of failure of appearance corresponded with
actual death of the commas, because the period of observation was sufficiently
prolonged to extend beyond that at which, if the phenomenon of temporary
subsidence of the prevalence of cholera in the cold weather be so interpreted,
there is a tendency to the assumption of a resting condition on the part of the
Schizomycetes which are related to it.
Allowing that the experiments seemed to show that the choleraic commas
rapidly and completely died out in these portions of soil, the possibility remain-
ed that this result was due, not to any incapacity on their part for continued life
in soil apart from any adverse agencies represented by other organisms, but was
due to the presence of the Schizomycetes and Fungi of the fæcal matter with
which the soil was contaminated. This point was so far, at all events, settled
by means of the following experiment, which was carried out sumultaneously
with those which have just been considered. In it a beaker was filled with
common clean garden-earth, and a considerable quantity of a fresh chole-
raic evacuation was then poured over the latter, so as to saturate it thorough-
ly. This was done on the 17th December 1886, and the beaker was then set
aside beneath a bell-glass. The earth gradually dried up and soon was ap-
parently nearly dry. On the 26th January 1887 a plate-cultivation was set
of materials derived from it. An extremely abundant development of Schizo-
mycete colonies of various kinds resulted, but no commas were to be found
among them. On the 23rd March the earth appeared to be thoroughly dry
throughout, and some freshly-boiled distilled water was poured over it, so as
to flood it and form a surface layer of standing water. The earth was now