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work this micro-organism would be searched for in the effluents from the coke-beds. It was also pointed
out that its presence in such an effluent might be considered as showing a derivation of the liquid from
sewage, and hence as indicating the possible presence of other and, perhaps, dangerous bacteria which had
survived the biological processes at work in the coke-beds, but did not signify that the liquid was
necessarily of a degraded, offensive, and putrescible character.
Although it has been long known that 11. coli is an organism characteristic of faecal discharges,
no accurate record exists of the determiation of the number of these germs in samples of crude sewage
periodically examined. The importance of establishing such a record will be understood when it is
remembered that sewage is the chief and most dangerous source of pollution of potable waters. If, then,
we know the number of germs of B. coli in crude sewage, and if we find that pure waters do not contain
this organism, or contain it only in few numbers, we are in a position to judge of the importance of
its presence in a given sample of water. It is true that B. coli is widely distributed in nature, is capable
under certain circumstances of multiplying outside the animal body, and is present in other excreta
besides those of human beings. These facts no doubt to some extent lessen the value of the mere
demonstration of B. coli in water, but sink into comparative insignificance when the relative abundance of
this micro-organism is considered. It has already been shown that B. coli may be present in crude sewage
in numbers exceeding 100,000 per c.c., and it may safely be affirmed that in a water free from any likelihood of
pollution B. coli is not discoverable, or is present in very few numbers. A minimal quantity of sewage
gaining access to a large bulk of water would increase the number of B. coli in water very greatly; and it
is difficult to conceive of any substance other than sewage producing a result in any way comparable.
It is particularly difficult to conceive of a substance of an unobjectionable nature producing this result.
No doubt in certain cases the presence of B. coli in water may arise from indirect pollution with sewage,
as, for example, where the surface drainage from manured or polluted soil gains access to a supply. Yet,
even here, the danger so far as potability is concerned could hardly be considered remote. It is not the
presence of B. coli in water, but its relative abundance, which entitles the bacteriologist to assume pollution
direct or indirect with sewage, or to avoid all controversial points with a substance of an objectionable
nature. Certainly, in view of the fact that this organism is not discoverable in waters free from any
likelihood of sewage pollution, and is found to be present in great numbers in waters which are known to
be fiscally contaminated, and is present in crude sewage in numbers vastly exceeding any other substance
at all likely to contaminate a water supply; it seems justifiable to conclude that its presence in
considerable numbers in a given sample of water indicates pollution of an objectionable kind, and,
in all probability, points to contamination with sewage.
Enough, at all events, has been made out to show the importance of a large number of observations
having for their object the collection of data dealing not only with the presence, but with the relative
abundance of B. coli in sewage. Of the importance of experiments having for their aim the estimation of
the number of B. coli in the effluents from the biological coke-beds as compared with the number in the crude
sewage applied to the coke-beds there cannot be a doubt. And here it may be stated that much that has been
said in the above sentences applies with perhaps even greater force to B. enleritidis sporogenes. B coli.
is an example of an aerobic, and B. enteritidis sporogenes of an anaerobic micro-organism, the former
being peculiarly abundant in crude sewage, and the latter less abundant, but perhaps more characteristic. The
estimation of their numbers in the effluents as compared with the crude sewage needs no comment to show
its importance.

These results are shown in graphic form in Diagram 9.