"The general method followed when solutions were employed was to take for example 1 part of the blood of an animal just dead from anthrax, to mix it with 49 parts of the standard chlorine water, or a dilution of it, mix in a watch glass, draw it up in a pipette, seal the pipette for a definite time, at the end of which the end of the pipette was broken off and an animal inoculated. In this way it was found that 00035 grm. chlorine disinfected in five minutes one fiftieth of its bulk anthrax blood, but that a dilution to one half was not certain in its action. The blood from an animal dying of anthrax is always spore free, so that this statement only applies to the bacilli. With regard to anthrax spores it was found that chlorine solution of, mixed in the proportion of 20 to 1 of a strong solution of anthrax spores, destroyed them within 24 hours. With regard to tubercular material, one twentieth of a drop of strong infusion of a tuberculous spleen, mixed with one drop of 100 chlorine solution kept in a pipette respectively for 1 hour and for 24 hours, did not disinfect within the shorter time but did in the longer time: the quantity of chlorine in this case was 000035 grm. In another experiment in which a similar dosing took place, and it was submitted to the action of a disinfectant for 28 hours, the result was not so good, for the inoculated animal died from tuberculosis. Using a strong solution of a tubercular lung, Cash found that 4 minims of a chlorine solution containing 0008 grm. of chlorine destroyed the virus in one drop of such infusion within one hour and a half.

"In the second method, air from a gas-holder was passed slowly through strong chlorine solution and thus charged with the gas passed through nitrogen bulbs containing a solution of the pathogenic substance to be acted upon. From time to time, usually at the beginning and end of an experiment, this bulb was replaced by another, which contained fresh acidulated solution of iodide of potassium, in order that the amount of escaping gas might be estimated for a given time by the liberation of iodine as calculated by subsequent titration with a standard hyposulphite solution."

One point Dr. Cash endeavoured to obtain information on, viz. "If a stream of air laden with a certain ascertained amount of disinfectant gas be passed with a given speed through a solution containing pathogenic micro-organisms, how soon will the disinfectant's action make itself felt as evidenced in the destruction

of such pathogenes? If we bring two nitrogen bulbs containing iodide of potassium into connexion distally with a bottle containing chlorine solution through which air is slowly forced to them from a Pepy's gas-holder, we observe that in the bulb nearer to the gas supply the iodide of potassium is rapidly decomposed, iodine being set free, but in the second bulb no decomposition whatever occurs, at any rate for a considerable time, the fluid remaining perfectly colourless.

"If now we substitute for the proximal bulb another containing say, an infusion of tubercular lung, and continue the circulation of air charged with chlorine through this and through the distal KI bulb, we notice almost immediately a liberation of iodine in the latter; this simple experiment shows us that an escape of the gaseous disinfectant takes place before its maximal action has been attained (as demonstrated by experiment), the maximal action for our purpose being death of all micro-organisms, coagulation of albuminous bodies, and other actions. Whilst in its passage through the bulb a portion of the chlorine acts on the contents causing certain effects by liberation of oxygen, a portion remains behind in general solution having a potentiality for further action, and still another portion passes away without having produced any disinfectant action. Small portions of the nascent oxygen are probably lost in the same manner."

The following are the details of an experiment by Dr. Cash :"Took one tubercular lung of a guinea-pig killed when suffering from human tuberculosis. The lung was studded with translucent pearls, the spleen enlarged, and the liver slightly necrotic. The lung was broken up in a mortar with a little distilled water, the fluid strained through muslin, diluted up to 10 c.c. and transferred to a nitrogen bulb.

"Air was passed slowly (10 bubbles per minute) from a Pepy's gas-holder through a bottle with the proximal tube dipping beneath the surface of a considerable volume of chlorine solution.

"The second tube communicated by means of an air-tight joint with the nitrogen bulb. The chlorine coming over was determined by means of liberations of iodine from a slightly acidulated KI solution. 0 min., circulation commenced through the nitrogen bulb containing tubercular material. 10 min., infusion has changed much in colour, is now of turbid appearance, deep brownish red. A

sample was taken and at once inoculated into a guinea-pig. The circulation of the gas was interrupted only for a few seconds and was then continued for 40 minutes more without stoppage. At the expiration of this time the infusion was of a deep muddy brown colour. A second guinea-pig was then inoculated. The total chlorine passed through the solution as estimated by the discharge of colour from the liberated iodine by sodic hypo-sulphite solution was before the first inoculation 016 grm.; before the second, 064 grm. ('064 + 016 = '08 grm.).

"In spite of this relatively large discharge of chlorine both animals became tubercular, and when killed the usual appearances were found in their organs.

In the next two experiments the tubercular virus was successfully destroyed.

"The lung employed was that of a guinea-pig suffering from human tuberculosis, and the preparation of its infusion was the same as in the last experiment.

"A variation was, however, made in this experiment by generating larger quantities of chlorine from hydrochloric acid and manganese dioxide under gentle heat and conducting the gas through a small wash bottle originally containing water, before leading it through the nitrogen bulb.

"A control animal was inoculated with the lung infusion before the circulation of the disinfectant was commenced. An estimation of the escaping gas was made as before, and then the nitrogen bulb with its contained infusion was put into connexion with the second bottle.

"Inoculations were made after the passage of air laden with chlorine at the rate of 16 bubbles per minute, for (a) 2 minutes, for (b) 6 minutes, and for (c) 10 minutes, respectively. The issuing chlorine was again estimated at the end of the experiment.

"It was calculated that before the first inoculation 0710 grm. of chlorine had been passed. In all before the second (b) 213 grm. In all before the third (c) not more than 335 grm. But a the third estimation of chlorine showed a slight falling off in the evolution of the gas, the total may have been somewhat less.

"The control guinea-pig and the guinea-pig (a) became distinctly tubercular (though some delay in the development of glandular swelling appeared to occur in the latter). The other two (b) and

(c) guinea-pigs escaped infection altogether. There is only one conclusion to be drawn from this experiment, namely, that air strongly laden with chlorine gas can rapidly disinfect or destroy a great mass of tubercular virus by transmission through a solution of the latter.

"In a third experiment an infusion of a tubercular lung was disinfected in 4 minutes, the quantity of chlorine being about 05 grm., and in another, 0355 grm. acting for 2 minutes failed to disinfect, but 0768 acting for 6 minutes disinfected."

Very similar experiments were made with iodine and bromine, the general result being to show that there was no very decided difference between the three, but that in order of disinfecting power when employed in quantities proportional to their atomic weight, iodine was the best, next bromine, and last chlorine.

The value of chlorine as a disinfectant has been strikingly shown by Klein (Thirteenth Annual Report Loc. Gov. Board, Supplement). Klein's experiments were made on swine plague, a disease easily reproduced and highly infectious, for he had already proved (1877-78) that the infection spread from a diseased to a healthy animal living in the same stable with it, this even when the animals were separated by considerable space; and if a diseased and healthy animal were placed in the same building in two different compartments, but both compartments opened into each other, the healthy animal contracted the malady. He found that if the air of the stable was kept pungent with chlorine, healthy and diseased animals might occupy adjoining compartments and also that one good fumigation of a stable infected from animals which had died of the swine fever, was effective.

(258) The Experiments of Fischer and Proskauer.

Fischer and Proskauer1 made some very important researches on the disinfectant action of chlorine and bromine. The substances submitted were sometimes in a large glass vessel of 21-35 litres capacity, and sometimes placed in a cellar which was made into an experimental room. The gas was developed from binoxide of manganese and hydrochloric acid. In some of the experiments.

1 Mittheilungen aus dem Kaiserlichen Gesundheitsamte. Bd. ii. Berlin, 1884.

the air was specially dried by means of strong sulphuric acid, in others the air was saturated with moisture.

The pathogenic substances submitted for disinfection were:(1) Spore-holding micro-organisms such as anthrax in the spore state, the so-called earth bacillus, and dried tuberculous sputum. (2) Spore free micro-organisms such as the bacillus anthracis (spore free), the microbe producing septicemia in mice and rabbits, fowl-cholera, yeast, sarcina, and several others.

The results were tested mainly by ascertaining how far the disinfected bacteria were capable of growing on nutrient soil, but in a few cases inoculation of animals was resorted to. The original paper must be referred to for full details, but the chief results were as follows:

No less percentage than 5:38 chlorine per 1,000 of air in rooms. to be disinfected can be considered efficacious.

It is best to keep the air of the room moist for some time before disinfection.

Disinfection in dry air is uncertain.

Chlorine fumigation carried out under the best conditions may fail to disinfect spore-holding material covered over or lurking in chinks and cracks.

In all cases chlorine is far more efficacious than sulphurous acid gas. In their experiments on the disinfecting power of bromine, they used for the purpose of developing bromine vapour the ingenious process of Dr. Frank-fluid bromine is made to soak into a porous siliceous earth, the earth is preserved in well stoppered bottles ready for use; on removing the stopper the heavy bromine vapour pours over the neck of the bottle and gradually diffuses itself about the room; the bottle should of course be placed as near the ceiling as possible. This process is far above all others in the single point of ease of application.

They found that provided the air of the room was sufficiently moist a good superficial disinfection could be attained with bromine but even with such high quantities as 357 grms. of bromine per cubic metre of air, spore-holding anthrax escaped disinfection. They also found that bromine was more destructive of organic tissues such as cotton or woollen goods than chlorine; these disadvantages and the higher price led them to give the preference to chlorine.