240 Measures in the Bombay Presidency and Sind. [CHAP. VIII.
summary of its advantages is taken from a report by Surgeon-
Captain Dyson, Deputy Sanitary Commissioner, Gujarat:-
Its advantages.
(a) It is simple, cheap and efficient, and secures a great saving
of time and labour. Further experience will probably show
that a weaker solution (1 to 2,000) is sufficiently strong.
(b) It ensures almost complete immunity from infection to
labourers.
(c) It entails a minimum of discomfort and inconvenience on the
occupants of a house.
(d) Perchloride of mercury is odourless and non-volatile.
The former quality recommends it to natives, and the second
gives a greater chance of a permanently good effect.
Mr. Hankin's
experiments on
the floors of
houses.
Mr. Hankin conducted a series of important experiments on the
action of different disinfecting agents under the ordinary conditions of
an Indian dwelling. The following is a summary of his method and
conclusions:-
The floor the
portion of the
house most in
need of
disinfection.
Principle of the
experiments.
"Owing to the fact that the excreta of men and rats suffering from
plague are likely to fall on to the floor of houses, and that
such excreta are likely in some, but not in all, cases, to
contain the plague microbe, and owing further to the prob-
ability that the infection of plague gains entrance to the human
body in the majority of cases through the skin of the feet and legs,
it is probably the floor of the house that is most in need of disinfec-
tion. The floors of houses of the lower classes in India are usually
covered with a mixture of mud and cow-dung. My experiments
therefore have been in the first place directed to examining the means
of disinfecting such floors. The most satisfactory way of carrying
out such a test would be to impregnate a cow-dung floor with the
microbe of plague, and then to test for its presence after the applica-
tion of the disinfectant. Unfortunately, however, this is at present
impossible as no reliable test exists for the presence of the plague
microbe when mixed with others. Hence I have had to experiment with
floors that had not been infected. By estimating the numbers of ordinary
microbe present before and after the application of the disinfectant
some idea can be formed of the activity of the latter on a cow-dung
floor. No doubt some of the microbes present are more resistant
than the plague microbe to the action of disinfectants; others, on the
other hand, are likely to be as sensitive, and hence it would probably
not be safe to employ a disinfectant against plague that had no action