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possibility of the entrance of the fœcal contamination, can be obtained by taking samples
from the wells shortly after heavy rain and, in case the well water is the sole drinking
supply of a community, such as a jail or school, a series of analyses of samples taken
under different meteorological conditions should always be made in doubtful cases,
before giving a definite opinion.
Of course these remarks apply mainly to surface wells. Deep wells are
comparatively rare in India. There is no doubt that the surface well is an extremely
bad source of water-supply, and that it is probably responsible for a large proportion
of the water-borne disease in this Presidency. Unfortunately in many places i.t is the
only supply available.
In samples of water that have been taken from pipes, a comparison should always
be made between these and that of the original source of the supply, or, if filter beds are
present, between both the original source, and the water immediately after filtration.
Thus, one would not expect to find other organisms in the water, than those obtained
from the river or lake, whence the water came, unless the pipe line were defective.
Therefore it is a safe rule to pay particular attention to the natural water, and if any
deterioration goes on, either in filtration or in the pipes, to look to these for the cause.
We have some instances in Madras, where pipes containing silt, add organisms to
what otherwise is very fairly satisfactory supply. This accident will easily be recognised
by comparing the results of analyses of samples taken before the IN ater enters the
pipes, with those taken from hydrants.
A few words are perhaps necessary on the other points of the analysis :-
The total colonies on acar. —The estimate of the total number of organisms is of
no more value in India than it is in Europe,. its main use being in comparing a series
of samples derived from one supply. We do not recommend that any great stress be
laid upon it, for we have found many waters of fair purity contained close on 10,000
colonies per cc., and, on the other hand, it is not unusual to find a well or a spring
water, with comparatively few organisms, the majority of these being highly
objectionable. Most rivers and lake waters contain between two to five hundred.
Sporogenes enteritidix test.—On the value of this test we have not yet come to
any conclusion. When the organisms are present in 20 cc. it is an additional reason
for considering the water to have been highly polluted. Unfortunately it gives us no
indication of the date of such pollution, and it will be observed that this organism
is much more prevalent during the dry weather months than the wet ones.
We are submitting the following standards for the various kinds of waters as the
result of our experience :—
Lake Waters.
Good lake water should contain less than 100 colonies per cc. (on agar at 37°C.).
No lactose fermenters in 20 cc.
No organism of class I in 50 cc.
The few faecal organisms isolated should belong to class II and lactis ærogenes
should be plentiful.
A fair or usable lake water should. not contain more than 200 organisms (on
agar at 37°C .).
Lactose fermenters should not be present in more than, 5 cc.
No organisms of class I should be present in less than 20 cc.
Lactis ærogenes should very largely predominate.
A lake water should be condemned—
If it contains organisms of class 1 in 1 cc. or less.
If foetal organisms are present in the characteristic proportions seen in
fresh faeces.
If lactis ærogenes are absent or scarce.
It should, however, be remembered that 48 hours will make an enormous
difference in the purity of a lake water.
The lake water should be looked upon as suspicious if it contains more f œ cal
organisms than 1. in a cc., even though these may be entirely confined to class 3 ..as