heights showing unimportant deviations. Experiments were also made as to the power of penetration into plaster, but this was found most irregular. The following table gives results of experiments made with lime paste exposed on glass plates:

Of greater interest is the determinations of amounts of SO,. absorbed by square metres of cloth exposed to the gas.

From these experiments it may be generally gathered that clean things absorb more SO, than dirty, and that moist things absorb more than dry. As might be expected, flannel absorbs more than linen or cotton, and of the latter two, linen is the least absorbent.

The applicability of SO, as a general disinfectant for goods in transit was tested in the following manner :

Two overcoats, a bundle of linen, a bundle of wadding, three envelopes of various thickness, a roll of dark green flannel, and a mass of tow pressed in a cubical shape, the side of which was 70 cm., were exposed to the gas in a room, the volume of the gas being 1 per cent. Litmus paper was placed in suitable positions within these different articles. The duration of the experiment was 24 hours. The gas penetrated through all the articles save through the cubical mass of tow, but a second experiment, in which the amount of the gas was raised to 10 per cent. of the air, was more successful, complete penetration of the tow being effected. This result would, however, not be obtained in practice; therefore Wolfhugel condemns the use of SO2 on a large scale for the disinfection of goods in transit.

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Wolfhugel next turned his attention to the question of the injurious action of SO, on clothing, iron, and other objects. 1 per cent. of SO,, acting for many hours, attacked bright metal objects so slightly that the film deposited was easily rubbed off; woollen fabrics were also not injured. When the percentage volume of the gas was raised to 10 per cent., acting for 24 hours, two overcoats and a roll of flannel exposed were changed to a red colour. Washing with ammonia water imperfectly restored the colour.

Wolfhugel finally made experiments on pathogenic and nonpathogenic micro-organisms, and found that bacilli, such as the bacillus anthracis, were readily destroyed if free from spores by exposure to sulphur dioxide disinfection; but if the microorganisms contained spores, prolonged exposure and concentration of the gas had little effect. By steaming a room first, keeping it at the same time at a high temperature, and then afterwards disinfecting, some of the spore-holding material was destroyed, but not all; likewise infected articles wrapped in tow were not disinfected. Small doses of SO2, acting for long periods of time,

likewise led to no satisfactory result. Wolfhugel's verdict is, renounce disinfection by sulphurous acid gas, for only such agencies should be employed which are fatal to every kind of micro-organism.

(273) Cash's Experiments on Sulphurous Acid.

Dr. Cash, F.R.S., has also made experiments with a view to determine the disinfectant value of sulphurous acid. (Supplement to the 16th Annual Report Local Government Board.)

These experiments are not comparable with Wolfhugel's, for they were made either on solutions of the gas or upon substances suspended in water, and known volumes of the gas passed through the water; nevertheless the information acquired is of the highest value, the acid being made to act upon living infectious material, and the result being tested by inoculation into animals. Solutions of the gas were prepared, the strength of which had some definite relation to the atomic weight of SO,; for example, 64 parts by weight of SO, solution in 1000 grms. of water would be a standard or normal, while 100 c.c. of this solution made up to 2000 would

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be ; 100 of the normal solution made up to 3000 would be 20

Cash found in a strictly quantitative experiment that 00012 grm sulphurous acid destroyed the spore-free anthrax bacillus in min. of anthrax blood in 5 minutes.

That 0001 grm. sulphurous acid did not destroy min. of anthrax blood in 5 minutes.

That 00001 grm. sulphurous acid did not destroy 1 min. of anthrax blood in 5 minutes.

Further that 00002 grm. of sulphurous acid did not destroy min. of anthrax blood in 5 minutes.

With regard to spores, he found that 0004 grm. (i.e. ‘4 mgrm.) sulphurous acid, acting for 24 hours on min. of a minim of an anthrax spore cultivation, destroys it; but if only acting for an hour, the spores are still active.

Experiments were made as to the effect of sulphurous acid solution on the disinfection of tuberculous matter.

A grumous fluid obtained by pounding the tuberculous lungs of a guinea-pig which had died from tuberculosis, in a glass mortar, was diluted with distilled water to 10 c.c. This was found to be disinfected thoroughly when acted upon in an incubator at 37°, in

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the proportion 0041 SO, to 1c.c.; but equal parts of 100 acid solution and a strong infusion could act for 28 hours without destroying the virus.

Other experiments were made with tubercular materials placed in a nitrogen bulb with water, and the gas passed through, the result being tested by direct inoculation. A piece of a tubercular lung treated in this way with 013 SO2, and removed at the end of 1 minute, produced tuberculosis in a guinea-pig; but 18 grm. SO2 and above, acting for 20 minutes, disinfected perfectly.

The writer has also made experiments on the effect of SO, on anthrax bacilli, both with and without spores, and obtained very similar results to those already quoted.

We may presume that the infection of most maladies contains resistant spores, and until we have evidence to the contrary, it is safest to discard sulphurous acid, whether as gas or in solution. It is sufficiently proved that only the best results can be obtained when this agent acts under very strict experimental conditionsconditions which may be met with in the scientific laboratory, but not in the practical application of disinfecting agencies in ordinary life, and on a more or less technical scale.

(274) The Practice of Disinfection. The Disinfection of the Sick-room.

As an example may be a room in which a person has been suffering from small-pox. The first thing that the disinfector should do is to paste up window and chimney and other crevices with brown paper. Bleaching powder is then distributed in three or four lots about the room. It is best to put some at the highest practical level, others on the ground, all in suitable basins or receptacles. The amount may be in the proportion of 1 lb. to 1000 cubic space. The operator having first seen that the door is open so that his retreat will not be cut off,

and that no living creature remains in the room,1 rapidly evolves the chlorine by tipping one after the other the requisite quantity of strong hydrochloric or diluted sulphuric acid on to the chloride of lime, and makes his escape (if he should care to breathe through a cloth well charged with moist lime, he may do matters less hurriedly). On closing the door, the next thing is to paste the keyhole and the space around the door, so as to make the chamber as airtight as possible. The room should now be left for 12 hours, then opened, and well ventilated. The room must be now considered superficially disinfected, and there will only be trifling danger in handling any article of apparel, or in removing matters for "stoving" through the streets. The next operation is to remove all things that can be washed to the wash-tub, and the bed, cushions, pillows, carpets, and the like to a hot air or steam chamber. This done, the walls may be stripped of their paper, or otherwise cleaned, the floor thoroughly scrubbed, and the articles of furniture well cleansed and polished. There are, however, cases in which the bedroom contains such valuable furniture, or pictures, or other articles of vertu, that chlorine fumigation would entail a considerable money loss. In this case some risk may be run, and sulphur fumigation be resorted to, after which the floor may be sprayed with a 1 per cent. solution of corrosive sublimate, all matters which can be disinfected by heat or steam removed, and the room and its furniture very thoroughly cleansed.

(275) Disinfection of House Drains and Closets.

House drains should not require disinfection save when there is sickness in the house. A saturated watery solution of crude carbolic acid, or a 1 per cent. corrosive sublimate solution constantly kept in every closet, and in the bed pans used by the patient, will answer the purpose well. The disinfectant should, of course, be kept in bottles or jars labelled poison, and where there are children the stock should always be under lock and key, and the closets charged by a responsible person.

Other details on practical disinfection will be given when treating of infectious maladies.

1 I have known cats to have been under articles of furniture and to have been killed by chlorine fumigation.