7

Medical Officers of the Army of India.

choleraic commas, for in not a single case was there any evidence of the
presence of any such phenomenon.

V.—On Fungal contamination of the Gelatine and Agar-Agar in
sterilised tubes during the Rains in Calcutta.

     On returning to Calcutta in 1886, after an absence of more than two months
during the rainy season, I found that almost all the sterilised tubes of com-
mon gelatine and agar-agar which I have left in the laboratory showed
manifest signs of contamination, the surfaces of the nutritive media being
covered with conspicuous white growths. As many of these tubes had
remained for months previous to my departure in the end of the hot weather
without showing a trace of any contamination, it appeared at first sight difficult
to account for the phenomenon. Microscopical examination of the nature of the
growths present in the tubes appeared, however, to afford a plausible explanation
of it. It was ascertained that in no case did the growth consist of Schizomy-
cetes, but that they were composed of filamentous mould-fungi. Now, the
conidia of such bodies are very much more abundant in the air in Calcutta
during the rains than at other times, and the general moisture of the surfaces
on which they may be deposited favours their germination. The infected tubes
were closed by two superimposed plugs of sterilised cotton wool, but were
not capped, so that particles of atmospheric dust were free to be deposited on
the upper surfaces of the superior plugs.

     During the cold and hot weather, the number of conidial elements thus
deposited was relatively small and the cotton wool was too dry to favour their
germination, and at this time contamination did not occur. With the rains,
however, new conditions were established: the numbers of fungal elements
liable to deposition became greatly increased and the cotton wool became
gradually moist enough to allow of those which were deposited germinating
and to form a medium in which continuous mycelial filaments could readily
spread. Gradual penetration of the entire thickness of the plugs by mycelium
was therefore liable to occur, and when this had been established, any free
conidial elements arising on the under surface of the inferior plug would of
course be very likely to be deposited on the surface of the nutritive medium
in the lower part of the tube. The plugs remained effective obstacles to the
access of Schizomycetes, because they did not present suitable nutritive mate-
rials to allow of growth of Schizomycetes in such quantities as to penetrate
the thick obstructive strata. The higher fungi were at an advantage because
of the greater amount of store-nutritive materials which their ordinary repro-
ductive elements contain, and because of their mode of growth which permits
of the continuous progress of the protoplasm from one area to another, and
therefore render it possible that the comparatively small amounts of nutritive
materials present at different points should be successively utilised in assimi-
lation.