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APPENDIX II.
THE BACTERIOLOGICAL EXAMINATION OF INDIAN WATERS.
By the SUPERINTENDENT and Assistant Surgeon T . SEETHAPATHY IYER, L.M.S.,
Senior Bacteriological Assistant.
The existence of pollution in water is generally deduced from the presence of
one or more of the following organisms :-
(1) Bacillus coli communis.
(2) Bacillus sporogenes enteritidis.
(3)
Streptococci.
Unfortunately none of these can with absolute certainty be relied upon as
necessarily having a faecal source. Of the three the significance of the presence
of the b. sporogenes is perhaps generally considered the most certain, though even
the presence of this organism is by some not considered necessarily to denote
fæcal pollution. The significance of b. coil communis depends on its relative
abundance, and there is also, in this case, the question of varieties to be taken into
account ; the significance of the presence streptococci depends on what other
organisms are present. A further point of no small moment is the reliability and
practicability of the tests for the detection of the organisms in question. The
test for the b. sporogenes is definite, easily carried out, and within certain limits
precise ; those for the b. coil communis to be precise need the initial isolation of
the organism.
w
h e r e s k i l l e d a s s i s t a n c e i s l i m i t e d a n d w h e r e o n l y a l i m i t e d t i m e c a n b e g i v e n t o t h e e x a m i n a t i o n o f e a c h s a m p l e t h e i m m e d i a t e p r a c t i c a b i l i t y o f t h e t e s t s
employed is desirable, provided these can be made to give the information
required.
With such an object it is intended year by year to gauge the value of different
bacteriological tests and the present report confines itself to what has been ascer-
tained during the past year in regard to the value of the " sporogenes" test as
ordinarily performed and the conclusions which may legitimately be drawn from the
presence or absence of this reaction in Indian waters.
Under present conditions the examination of water samples cannot be supple-
mented by personal inspection of the conditions at the source from which the
samples are taken, and accurate and detailed information regarding the possibility
of pollution is rarely available. It has been found necessary therefore to depend
for evidence of pollution mainly upon data forthcoming from the examination of the
total sediment collected in the method used by Rideal and Walker. In cases where
the same water has been examined at different times the presence of previous gross
pollution has also often helped one to form an opinion as to the value of purely
bacteriological tests. The apparatus used has been a slightly modified form of
that described by the above mentioned authors. After 1,000 c.c. of the sample
have been passed through the sand this is washed into a test glass with 2 c.c. of
carefully collected, recently made, distilled water, and the fluid which carries with
it all the organic sediment is decanted off and examined under a low power ; portions
of it being afterwards examined under higher powers.
In many waters the procedure suffices to demonstrate the grossest possible
pollution, the most common evidence being the presence of short fragments of blue
and red cotton fibres, no doubt a result of the Indian habit of washing clothes in
whatever water is available. In other samples where such direct evidence of
human pollution is absent organic matter consisting of living and dead animal and
vegetable forms shows the water to be, at any rate, organically impure. A high
degree of this kind of impurity often gives rise to difficulties in the interpretation
of the results of the bacteriological tests. In the case of open waters of this
character it is almost certain that fish, frogs and other animals are abundant and