NationalLibraryOfScotland/medical-history-of-british-india huggingface dataset:
419
APP. VI. ] Measures in the Bombay Presidency and Sind.
No. 6.
General Remarks on the disinfection of Houses.
EXPERIMENTS MADE BY MR. HANKIN.
No. 430, dated Agra, the 15th July 1897.
From—E. H. HANKIN, Esq., Chemical Examiner and Bacteriologist,
North-Western Provinces and Oudh,
To—SURGEON-COLONEL WARBURTON, Inspector-General of Civil
Hospitals, North-Western Provinces and Oudh.
I have the honour to forward for the information of Government
an account of experiments I have recently carried out in Hardwar on
methods of disinfecting plague infected houses.
2. It will be convenient to preface my remarks by a short
résumé of the work I have carried out in Bombay on the action of
disinfectants on the microbe of bubonic plague. A full account of
this work has been already communicated to the Surgeon-General
with the Government of Bombay. The method employed was that
that is most ordinarily used in testing the action of disinfectants on
microbes. The results obtained may be tabulated as follows :—;
A.—Action of the Phenols and their Allies.
The bubonic microbe was found to be somewhat resistant to the
action of carbolic acid, a one per cent, solution not being always
sufficient to kill it under the condition of the experiment. Phenyle,
Lysol, and Izal were found in all cases to destroy the microbe when
in a quarter per cent, solution. The limit of dilution of the solutions
of these substances necessary to destroy the microbe was not
however found. Naphthaline, both pure and impure, and a patent
preparation '' naphtho-sublimate " were found to exert no disinfect-
ant action although tested in solutions containing an undissolved
excess of these substances.
B.—Action of Corrosive Sublimate and Copper Sulphate on the
Plague Microbe.
Sublimate was found to destroy the microbe in a strength of one
in five thousand, but the lower limit of its action was not investigated.
Copper sulphate was found to be efficient in a strength of one in a
thousand. A five per cent, solution of this substance was used by the
French Government in 1892 in combating cholera. It is easily
obtainable in India, and might under certain conditions be used
against the plague as shown by the above result.
C.—Action of Alkalies on the Bubonic Microbe.
This microbe appears to be relatively resistant to the action of
alkalies including ammonia, caustic potash, and freshly slaked lime.
Under the conditions under which lime washing must be carried out
b53
420
Measures in the Bombay Presidency and Sind. [ APP. VI.
in India, it must not be regarded as a disinfectant for the infection of
bubonic plague.
D.—Action of Acids on the Microbe of Bubonic Plague.
The microbe of plague is extremely sensitive to the action of
acids. Even certain organic acids were found to be capable of
destroying it rapidly. The results obtained with these substances
were as follows :—
It is destroyed under the conditions of my experiments within
five minutes by—•
Formic acid of a strength of I in 100.
Acetic acid of a strength of I in 142,
Lactic acid of a strength of I in 333.
In view of the fact that most articles of diet either possess an
acid reaction or rapidly acquire it on the onset of decomposition owing
to the appearance of the above acids or their allies, it seems scarcely
probable that food-stuffs should retain for long the microbe of bubonic
plague. In the case of milk this speculation has been put to an
extended test by Dr. Srinivasa Rau in my laboratory in Bombay.
He found that as soon as milk has been kept long enough to acquire
a well marked acid reaction, that is to say, within a few hours of milk-
ing under ordinary conditions, it has the power of destroying the
bubonic microbe within an hour. If on the other hand the milk is
made faintly alkaline, it is incapable of so doing, and appears to be a
good food medium for the bubonic microbe. Dr. Rau has also carried
out experiments on the vitality of the bubonic microbe in rotten
grain. This substance nearly always has an acid reaction, and is
then capable of rapidly destroying the bubonic microbe. I propose
to describe his experiments at length in another report, The tissues
of animals after death acquire an acid reaction owing to the develop-
ment of an ally of lactic acid. Dr. Rohak under my direction has
found that this acid reaction appears in the bodies of animals dead of
plague. This point, though it has no bearing on the admitted
danger of handling and washing plague corpses, may if worked out,
be found to have an important bearing on the old idea that graveyards
may be a lasting source of infection,
As may be expected, inorganic acids were found to have a still
more potent action on the microbe of plague. The results were as
follows :—
The bubonic microbe was found to be destroyed within five
minutes by—
Nitric acid in a strength of I in 333.
Hydrochloric acid in a strength of I in 500,,
Sulphuric acid in ä strength of I in 1,429.
421
APP. VI, ] - Measures in the Bombay Presidency and Sind.
A mixture of four parts of sulphuric acid and one part of nitric
acid was found to be as efficient as sulphuric acid in destroying the
plague microbe. The waste acids from the Kirkee Cordite Factory
consists of sulphuric acid with a slightly less proportion of nitric, and
might therefore be used in combating plague, Sulphuric acid is
recommended as a disinfectant by its great cheapness.
E.—Action of Reducing Agents on the Bubonic Microbe,
The microbe was found to be extremely resistant to the action
of ferrous sulphate, a substance that has been frequently recommended
for the treatment of sewage and filth.
The bubonic microbe appears generally to die out when evapo-
rated to dryness in a thin film on glass in the presence of the air.
I found it still alive after five days when evaporated to dryness in
glass bulbs in a current of. hydrogen gas.
F.—Action of Oxidising Agents on the Microbe of Plague.
The bubonic microbe was found to be destroyed by a solution of
one in ten thousand of chloride of lime, but the lower limit of the
action of this substance was not detected. Permanganate of Potash
o
was found to be capable of destroying it, under the artificial condi-
tions of my experiments, in a dilution of I in 50,000, that is to say, in
a solution in which the pink colour is but faintly marked. In certain,
cases it appeared that the organic matter present was sufficient to
destroy all the permanganate used, after the lapse of some hours.
In these cases the microbes were first destroyed and afterwards the
permanganate was reduced. It was shown however by experiment
that the quantity of readily reducible organic matter present on a
cow-dung floor is so great that probably a four per cent, solution of
permanganate would be necessary to produce a safe disinfection.
3. The conditions under which the above experiments were
carried out were probably more favourable to the disinfectant than
would be the case in practice. This fact, while tending to justify
the condemnation of a disinfectant from the results of such experi-
ments, necessitates caution in using such experiments to recom-
mend a disinfectant. The fact that a disinfectant can destroy a
microbe suspended in water, as was the case in my experiments,
does not prove that it would be capable of destroying the microbe
when contained in human dejecta soaked into a cowdung floor.
Hence it appeared to me to be advisable to carry out some experi-
ments in which practical conditions would be more closely imitated.
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
422
Measures in the Bombay Presidency and Sind. . [ APP. VI.
such excreta are likely in some, but not in all, cases, to contain
the plague microbe, and owing further to the probability that the
infection of plague gains entrance to the human body in the major-
ity of cases through the skin of the feet and legs, it is probably the
floor of the house that is most in need of disinfection. 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 cowdung floor with the microbe of plague,
and then to test for its presence after the application of the disin-
fectant. 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 in decreasing the numbers of harmless microbes
present on an ordinary floor.
The method I have employed was to remove as much of the
material of the floor as could be taken up on the end of a flattened
needle. This was put into a test tube containing melted agaragar,
mixed up well with the food medium, and the mixture was then
allowed to solidify. On the following day the number of colonies
that had developed was counted. It is needless to say that this
method does not give results of any absolute value. If for ins-
tance the material of the floor was dry, it is likely that most of
the microbes present in the specimen removed for examination
would adhere to the particles of sand and dirt, and that each par-
ticle would produce only a single colony. If on the other hand the
particles were damp, it is likely that the microbes adhering to them
would more readily become suspended and distributed in the
agaragar and thus produce a large number of colonies. Though
the method has no absolute value, it has some relative value, if re-
peated sufficiently often. If a specimen taken before disinfection
produced a great number of colonies and a specimen taken after dis-
infection produced no colonies after 24 hours, we may infer that some
disinfectant action has been exerted. It would not be safe to conclude
that the specimen taken after disinfection was absolutely sterile,
i
423
APP. VI. ] Measures in the Bombay Presidency and Sind.
for microbes might be, and as a matter of fact were always, present
that could not produce colonies after 24 hours, but that did so
after a longer interval.
, The following results were obtained in some preliminary obser-
vations :—
Number of colonies
developed after
24 hours.
Earthen floor of my laboratory in Hardwar (a grass hut)
before " lepoing "
...
...
...
Earthen floor of my laboratory in Hardwar (a grass hut)
before " lepoing "
...
...
...
,,.
Floor of dhobie's house, (mixed mud and cow-dung)
...
Floor of dhobie's house, (mixed mud and cow-dung) -1/2 inch from
surface
...
...
...
...
,,.
Floor of dhobie's sleepingroom
...
,,,
.,,
Mud floor of grass cutter's room
...
...
...
Mud floor of grass cutter's room 1/2 inch from surface
...
Floor of bearer's room recently lepoed
...
...
Floor of bearer's room recently lepoed 1/4 inch from surface
...
Fresh cow-dung
...
...
...
...
Ditto
Earth (out of doors exposed to sun)
...
...
...
Ditto
\...
...
800
584
19,000
1,400
28,000
13,400
640
10,500
6,700
7.500
11,500
7,000
4,000
Experiments to test the action of different disinfectants were carried
out on the mud floor of the grass hut that served me for a laboratory
in Hardwar in the following manner. The floor had been covered
with the ordinary mixture of mud and cowdung some days before.
Areas about a foot square were divided off from each other by ridges
of earth. Two specimens of the mud mixture of each area were ex-
amined bacteriologically as described above before pouring on the
disinfectant. The disinfectant to be tested was then poured on
to the surface, so that the whole of it was wetted, but no attempt
was made to rub it in. After this at different intervals other speci-
mens were taken and tested. In every case two specimens were
taken from different parts of the area. The figures in the follow-
ing table give the average of the two results. For the sake of
clearness I have not given the actual number of colony producing
microbes found, but I have given the relative numbers that developed
for every hundred colonies found in the control observations. For
instance, for every hundred colonies present before treatment with
sublimate, half an hour afterwards only 60 were present, and 24
424
Measures in the Bombay Presidency and Sind. [APP. VI.
hours later the relative number had risen to 130 as shown by the
first line in the table.
Disinfectant.
A. Sublimate I in 1,000
,,,
B. Sublimate I in 1,000 plus Hydro-
chloric acid 2 in 1,000
...
C. Chloride of lime 1 percent.
...
D. Potassium permanganate 1 per
cent.
...
,,.
E. Sulphuric acid I per cent.
,.,
F. Permanganate and Sulphuric
acid each I per cent.
G. The same mixture diluted ten
times
. .
...
H. Sulphuric acid I in 250
I. Sulphuric acid I in 500
...
J. Sulphuric acid I in 500 plus per-
manganate 1 in 1,000
K. Phenyle I per cent.
...
L. Lysol 1 per cent.
...
Before treat.
ment.
100
100
100
100
100
100
IOO
100
IOO
100
100
100
After \
hour.
60
O
O
98
o
17
31
87
91
68
o
o
After 1
hour.
55
43
112
55
79
12
49
63
140
72
248
72
After a
hours.
40
O
63
76
57
II
131
45
142
63
1 66
67
After 24
hours.
130
I
315
86
35
7
112
112
300
161
138
220
After addition of the disinfectants the treated areas were pro-
tected from dust by means of covers placed over them. It will be
noted that the only substance tried that produced anything approach-
ing a complete disinfection was corrosive sublimate in an acidulated
solution. Chloride of lime, phenyle, and lysol appear to be without
much action on the microbes of a cow-dung floor, although as is known
they are energetic disinfectants of microbes suspended in test tubes
of bouillon. A comparison of experiments D, E, and F, shows that
a mixture of permanganate and sulphuric acid acts more strongly
than either of these substances alone. The same deduction can be
drawn from experiments I. and J. As already explained, moistening
a cow-dung floor is likely to lead to an increase of the number of
colonies that will appear in these experiments. The specimens
taken before treatment were obtained from the floor while it was
dry. Those taken after treatment were taken when it had for
some time been moistened with the disinfectant solution. This is
the most probable cause of the increase in the number of colonies
developed after addition of the solution of phenyle in experiment
K,
The following observations were made in houses in course of
disinfection in Hardwar and in the neighbouring village, Kankhal.
The first case investigated was in a large two-storied pucca
built house near Hurki-Pairi Ghat in Hardwar. This house had been
ApP, VI. ] Measures in the Bombay Presidency and Sind.
435
evacuated about two weeks before my visit, and the inhabitants had
cleaned it up and had most of the rooms whitewashed. On the first
floor I found a small room that the coolies had not thought notice-
able enough to whitewash. One or two of them appear to have used
it as a latrine. This is referred to below as room A. The small
numbers of microbes or rather colonies met with before disinfection
is probably due to the room being pucca built and thoroughly dried.
This room was treated with a neutral solution of sublimate of a
strength of 1 in 1,000. Room B was a badly smelling place on the
ground floor. It had not been previously cleaned. It was treated
with sulphuric acid of a strength of 1 in 250 with about half the quan-
tity of permanganate. The specimens were taken about a quarter
of an hour and again 24 hours after disinfection. The following are
the results :—
Locality,
1
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
Dirt from floor of room A
Do.
do.
Do.
do.
Do.
do.
Dirt from floor of room B.
...
Do.
do.
Do.
do.
Do.
do.
Dirt from wall of room B.
...
Do.
do.
. Cow-dung floor of cook-room..
Do.
do.
Do.
do.
Do.
do.
Number of colonies in specimen taken.
Before.
2,980
960
1,280
640
1,100
2,000
0
0
400
0
1,200
0
0
0
1 hour after.
5
6
256
o
44
24
171
25
1
88
0
0
0
0
24 hours after.
11
19
1,440
30
117
35
29
340
34
1,280
544
640
12,000
768
The cook-room had been previously whitewashed. On the day
of my visit it was treated with sublimate solution.
Other observations were carried out in Kankhal, a village near
Hardwar. No local cases of plague had occurred here, but some
rats had been dying of plague in the house of one of the leading
inhabitants. This was a large pucca-built ill-ventilated and dirty
house. A large quantity of grain was stored in one of the rooms on
the ground floor. The owner told me that the doors of the rooms
had to be kept shut owing to the depredations of monkeys. . The
upper stories of the house seemed in great part to be given up to
the use of these animals. Acidulated sublimated solution was used
to disinfect this house, and I noticed that the disagreeable smell of
dirt was still present in each room after the disinfection had been
carried out.
426
Measures in the Bombay Presidency and Sind. [ APP. VI.
The following results were obtained :—
Number of Colonies developed in specimens taken.
Locality.
I.
2.
3.
4.
5.
6.
7.
8.
9.
Brick Courtyard
...
,,.
Do.
do.
Outer-room South side, cut cha floor ,,,
Do.
do
do.
Cutcha stable floor, outside granary ...
Do.
do.
do.
...
Pucca living room
....
Do.
do.
Cook-room
Before
disinfection.
9,600
28,000
1,800
2,500
25,000
3,5000
1,900
3,560
0
Quarter hour after
disinfection.
208
1,100
1,100
78
I2O
43
128
192
352
In drawing conclusions from the above results it must be borne
in mind that the action of acidulated sublimate solution only reaches
its maximum after two hours, as shown by earlier experiments, and
that the specimens in the above experiment were taken only fifteen
minutes after the application of the disinfectant.
Recent work has shown that sulphur fumigation cannot be
relied upon to destroy microbes. Experiments carried out by the
German Health Officer have shown that though gaseous disinfectants
may destroy the microbe in experiments on a small scale, they will
not do so in large rooms as the gases do not show sufficient penetra-
tive power. I carried out the two following experiments to further
test the matter.
In the first experiment a small godown in the Collector's bunga-
low in Hardwar was treated. The room was closed up as well as
was practicable. The men employed to fumigate with sulphur in
Hardwar were called in and told to treat the room with sulphur as
was customary. They first brought in an " ungete " containing a
bright coal fire. On this they put a "degchie" of water to produce
steam. Then another " ungete " with a fire was brought in. On
this they threw a handful of flour of sulphur, which, owing to the
strength of the fire, was almost immediately consumed. Then one
of them rushed into the room and threw a small quantity of methy-
lated spirit on to the fire containing the sulphur. Owing to the
presence of two brisk fires in the room, the greater part of the con-
tained oxygen is likely to have been changed into carbonic monoxide
and dioxide, so that only a fraction of the oxygen would have had a
chance of combining with sulphur had enough of the latter substance
been present. Naturally under such conditions no disinfection took
place. Specimens of dirt taken before fumigation produced from
1,800 to 3,200 colonies. Specimens taken from the same positions
after fumigation produced from 2,400 to 5,000 colonies. Some
APP. VI. ] Measures in the Bombay Presidency and Sind.
427
agaragar plague cultures were placed in different parts of the room,
and after fumigation were inoculated on to fresh agaragar. In all
cases a typical growth was produced.
The second experiment was carried out in a bathroom in the
same bungalow. Before fumigation water was thrown over the walls
and ceiling of the room, so that plenty of aqueous vapour should be
present in the air. The sulphur was burnt in the following manner.
About two seers of flour of sulphur were placed in each of two
earthenware pans. Enough methylated spirit was added to make
the powdered sulphur stick together, so that it could be moulded
into a thick column. The columns were then lighted and the doors
closed. The sulphur burnt for a long time, and a yellowish fog
gradually developed in the air in the room. The following results
were obtained :—
Dirt off floor
Ditto
...
...
Ditto
Ditto
Before fumigation,
370,000
14,400
0
0
After fumigation,.
1,700
6,000
4,8oO
400
The above results show that an incomplete disinfection had
occurred. As in the previous experiment, agaragar plague cultures were
placed in different parts of the room before the fumigation. After
fumigation each culture was inoculated on to fresh agar and in each
case it grew. In two of the tubes, however, the colonies were not
very numerous, suggesting the possibility that some slight effect had
been produced on the microbes present. It may be objected to this
part of the experiment that the bubonic microbes were present in test
tubes closed in each case by a plug of cotton wool, and that thus they
were to some extent protected from the action of the gas. It is im-
possible, however, to conceive that a plug of cotton wool can greatly
hinder the diffusion of a gas. In practice the sulphurous acid gas
would have to penetrate far more serious obstacles than loose cotton
wool if it is to be of any use at all. Another condition was in favour
of the sulphur, that might not always exist in practice, namely, that
the bubonic microbes exposed to its action were moist. Sulphur when
burnt produces sulphur dioxide. This is only disinfectant when it has
combined with water forming sulphurous acid. Hence microbes in a
damp condition are more likely to be affected than if they are dry.
There remains another way of treating an infected floor which
where practicable is likely to give better results than can be obtained
with a chemical disinfectant, namely, by exposing it to the action of
fire. The following experiment was carried out to test this possi-
bility.
b5.4