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It is to be noted that B. prodigiosus retained its vitality in the crude sewage for sixteen
days. Afterwards it could not be found in any of the cultures. During the sixteen days B.
prodigiosus remained alive it was noted that whereas at the start an abundant red growth showed
itself in the agar cultures towards the end of this period the number of red colonies developing was
very small, and in cultures (12), (13), and (14) the number of red growths was only three, one, and
one respectively. Speaking in general terms it may be said that the number of B. prodigiosus
decreased rather rapidly, and usually each successive culture showed less red growth than the one
immediately preceding it.
Experiment 4, November 2nd, 1898.
This experiment was a repetition of experiment 3, 10 c.c. of Crossness crude sewage being
inoculated with a platinum loopful of a recent growth of B. prodigiosus on agar.

In this experiment the B. prodigiosus remained alive for 10 days, but was not discoverable
on the 12th, 14th, 16th, 22nd, or 31st day after inoculation.
Speaking of both the experiments it may be said that B. prodigiosus either dies or becomes
so reduced in numbers as to be no longer capable of being isolated in from about 10 to 16 days in
Crossness crude sewage under the above laboratory conditions of experiment.
It would seem from these experiments as if the cholera bacillus was capable of existing in
sewage for a longer time than the B. prodigiosus. Assuming, of course, that the two different
methods used for detecting these microbes were of equal delicacy, which is probably not quite the
case.
(c) Vitality of Staphylococcus Pyogenes Aureus in Crossness Crude Sewage.
Experiment 5, November 9th, 1898.
In this experiment 10 c.c. of Crossness crude sewage were inoculated with a platinum
loopful of a young agar culture of staphylococcus pyogenes aureus. This pathogenic microbe has
been described as being occasionally present in raw sewage. My own experience leads me to
believe that it is only very rarely present in sewage. Certainly it is to be regarded as a microbe
foreign to the bacterial flora of ordinary sewage.
The tube containing the raw sewage († St. pyogenes aureus) was kept in a dark cupboard •
at the room temperature.
In seeking to determine the viability of this micro-organism in the sewage the following
plan was adopted. Prom time to time a loopful of the sewage († St. pyogenes aureus) was taken
and rubbed over the sloping surface of oblique agar tubes. These were incubated at 37° C., and
the presence of St. pyogenes aureus was readily ascertained by the golden orange-yellow colour
produced by the growth of this germ in agar cultures.

In cultures made subsequent to December 17th, no colonies of St. pyogenes aureus could be found.