95
that a strength of 1 in 1,000 is probably sufficient, but it presupposes the plague germs to lie
on the surface of the floor. Seeing, however, the porous nature of the material of which it
is composed and the possibility of infective material being carried by insects or otherwise
some distance into its substance, and in view of the fact that it has been found necessary, on
occasion to use Perchloride solution of a strength of 1 in 75 to kill all the germs in an
earthen floor, I would much prefer that the double strength solution be used. I may say in
this connection that it has been found that re-infection has been found to occur much
oftener in houses with earthen floors than in those with stone or wooden floors.
Dr. O'Brien then recounts the method o£ disinfection work
generally :—
Our practice has been to disinfect the room or group of rooms inhabited by the family
of which the plague patient was a member, and all rooms directly communicating with them.
The results of this method of working have been generally good so far as the rooms actually
disinfected are concerned. They have, as a rule, remained free from infection for a consider-
able time after disinfection, with the exception of the cases which have occurred within ten
days and which we may regard as having imbibed the poison before the rooms were disin-
fected. However, the fact remains that Ave have met with some houses in which plague has
persisted in spite of repeated disinfections of rooms or groups of rooms. The cause of this
persistence of the disease in certain houses, it is difficult to be certain of. In my opinion it
is due to a variety of causes, chief of which are : (1) The fact that they are infested by rats,
which carry the infection to the different rooms : (2) the dirty condition of the houses ; (3)
I think it has often occurred that infective material has reached many different rooms of the
same house at or about the same time, but has not caused the disease in the inmates of all
the infected rooms at the same time. Latterly our method of dealing with these houses in
which the disease has persisted for some time has been to thoroughly disinfect them from top
to bottom and the results have been very good indeed.
He gives instances showing the good results obtained by disinfection
of entire houses when they are found to be very badly infected. Accord-
ingly he argues that the worst infected houses, since they are well known
to have become so in every epidemic in the past, should be thoroughly
disinfected from top to bottom before the next epidemic sets in as a
precautionary measure.
As examples of the good effect of this method of working, I may mention the
following :—
(1) In house No. 20, 1st Nowroji Hill, North (B Ward, North), 12 cases of
plague occurred between the 1st and 17th March this year. On the 18th of that month
it was disinfected from top to bottom. No case of plague had occurred in it from that
date upto 15th April which is the last date on which I have seen its record.
(2) In house No. 45, Coorla Street, 11 cases of plague occurred between 1st and
22nd March. It was evacuated and disinfected from top to bottom on 23rd of that
month. It was re-occupied on 2nd April. One suspicious death occurred on 6th of
that month, and no other cases up to the end of April, beyond which date I have not seen
the records.
In house No. 65, De Souza Street, 8 cases of plague occurred between 1st and 27th
February. Three floors of the house were thoroughly disinfected on 28th February.
No cases have occurred in it up to the end of April.
Equally good results have been obtained in the case of several other houses which it is
not necessary to mention. As a rule Ave have found that a house, which has been disinfected
from top to bottom, remains free from infection for a subsequent period of two months. In