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it is not impossible that bacteria from the intestinal canals of these may yield..
results similar to those given by human pollution. In piped supplies such
organi cally impure water almost presupposes massive incrustations largely of organic
material in the pipes and the putrifaction of this at high temperatures may quite.
well give rise to results difficult to differentiate clearly from fæcal pollution,
Where waters are more or loss free from organic impurity it is not unfrequent
to find a few green vegetable cells. In open waters the presence of such cells has
little or no significance, but in filtered waters not exposed to light after filtration
they show filtration to be inefficient, and in a well they argue either imperfect
protection or pollution by the direct entry of surface waters Many samples are
practically free from sediment, and these have to be judged on purely bacteriolo-
gical standards It is obvious that, with the significance of the tests still undecided,
such samples offer the greatest difficulty of all.
To arrive at the clearest results, it is advisable to divide samples into four.
groups as given below, and to discuss each group separately in relation to purely
bacteriological tests.
Group A.—Samples showing gross pollution as evidenced by cotton fibres or
other direct proof of pollution from human sources.
Group B.—Samples not included in Group A, which contain a great deal of
organic matter. In this group are included those samples showing many infusoria,.
since the connection of these with organically impure waters has been very
constant.
Group C.—Samples not included in Groups A and B but showing occasional.
green vegetable cells.
Group D.—Samples with practically no sediment.
Group A.—Of this group 10 samples have been examined. They have all
shown the "sporogenes " reaction in from 25 c.c. to 1.00 c.c. of the sample. Two
of the samples were filtered waters, filtration evidently being ineffective.
Group B.—Of this group 31 samples have been examined, of which 24 have
shown the reaction in quantities varying from 25 c.c. to 100 c.c. of the sample.
The group seems to represent the most frequent condition of water from
fairly good sources in India. There can he no doubt, however, that most of such
waters are open to grave pollution, if not actually so polluted. The chief interest
attaches to the seven samples not showing the reaction. Conjeeveram water-supply
unfiltered, examined on two occasions belonged to this group since it contained
living rotifers, infusoria, diatoms, and green algæ. On one occasion it gave the
reaction in 100 c.c. and on the other did net. Conjeeveram water-supply, filtered,
has twice come under Class D without giving the reaction. It is quite possible
that the source, which is a river, though organically impure, is occasionally also
polluted.
Rajahmundry Central Jail well No. 8 came in the group, but did not give the
reaction when examined on 30th November 1906, but at other times it showed
" sporogenes." A filtered water and a hill water from a pipe also came under this
head without " sporogenes."
Group C.—Only 3 out of 14 samples belonging to this group showed the
" sporogenes " reaction, one being the Conjeeveram unfiltered water already-
referred to. The others were an unfiltered water from Madura, and a well. Pollu-
tion of some sort in each case may be safely inferred. To this group showing green
cells, but no reaction, some filtered waters belonged. The significance of the fact
can only be considered in connection with the exact nature of the local conditions.
Many unfiltered hill waters not showing the reaction belong to this group and
I
are probably pure.
Group D.—Of 33 samples of this class 23 did not give the sporogenes "
reaction 5 being well waters.
Of the ten samples giving the reaction five had at other times belonged either
to class A or B. In the case of Dindigal the unfiltered water showed sporogenes,
4