Being non-gaseous, they are not withdrawn from air in which they may be floating in clouds by liquid or solid disinfectants exposed in vessels, and in these circumstances should be expelled by ventilation or cleansing, or attacked by gaseous disinfectants. Experiments upon vaccine matter, which may be taken as the type of a virulent material, show that disinfectants to be effectual must be used in much larger quantity than is usually considered necessary, and that when the disinfectant is of an acid nature, the virus must be rendered permanently and strongly acid. These experiments show that sulphurous acid is much more potent than chlorine as a gaseous disinfectant, and that though carbolic acid, in quantity equal to 2 per cent, of the virus, completely deprives it of its infective power for the time being, yet it is not permanently abolished, but returns when the carbolic acid has escaped through exposure to the air. Permanganate of potash, though deficient in antiseptic properties, is truly disinfectant when used in such quantities that the colour is retained, but the expense becomes enormous, except for a few purposes.
Though we have no trustworthy light from direct experiment, there is reason to believe that many metallic salts in very strong solution are disinfectant, and at all events many of them are antiseptic (fatal to microzymes). The waste chlorides from the manufacture of chlorine might be used for drains. It should be remembered that agents such as carbolic acid and metallic salts, which in small quantity have a preservative power, may actually prolong the life of con-tagium which would otherwise succumb to natural processes if the agents are used in limited quantity. Experiments upon vaccine matter prove that several lauded and patented " antiseptics and disinfectants " are perfectly worthless so far as any useful influence upon this virus is concerned. It is necessary clearly to understand what is required when selecting an agent for practical use. There are good deodorants which arrest putrefaction and fermentation, and yet completely fail to destroy contagious particles embedded in an epithelial or albuminous envelope, as they usually are. (Dr. Russell.)
Two sets of important researches on disinfection have been lately (1879) going- on at Berlin. In both the test of the efficacy of the particular disinfectant used has been the effect produced by it either in destroying bacteria and vibri-ones in putrid fluids exposed to its action, or in preventing their development in a form of "Pasteur's fluid," in which the objects that had undergone disinfection in various degrees were immersed.
The first experiments, those of Dr. Mehlhausen, Director of the Charite* Hospital, refer chiefly to the disinfection of rooms in which scarlet fever and other infectious cases have been. The result arrived at is that the most energetic and the cheapest disinfectant is sulphurous acid. Chlorine gas has the disadvantage of destroying clothes and furniture exposed to it, while it is less easy to manipulate, and 4 or 5 times as expensive as sulphurous acid. 16 gr. sulphur per cub. yd. of space destroy, when burnt in a closed room, all bacterial life in 16 hours. Besides blocking up the doors and windows, Mehlhausen advises that the room shall be previously warmed, if the weather is cold, in order to prevent the gas finding its way into the neighbouring apartments. It is also advisable to damp the floor before lighting the sulphur, so as to profit by the great solubility of sulphurous acid in water: 8 hours is long enough to keep the room shut up after the sulphur begins to burn, and at the end of that time any clothes or bedding in it will be effectually disinfected. Mere free exposure of an infected room to the air by allowing the windows to stay open several days is not enough to disinfect it.
This has been practically proved at the Charite" Hospital after scarlet fever and measles in several instances. (Medical Times and Gazette,)
The second series of experiments was made by Dr. Wernich, of Breslau, in the chemical laboratory of the Berlin Pathological Institute, upon- the disinfecting power of sulphurous acid and dry heat. The method adopted consisted in preparing an "infecting material" by steeping woollen threads, pieces of linen-rag and cotton-wool, previously proved to be free from atmospheric organisms, in putrid solutions of faeces or meat, and gently drying them. These substances were then tested for their capability of producing bacteria by the means of the modified Pasteur's fluid above mentioned, which consisted of 100 parts distilled water, 10 cane-sugar, 0.5 ammonium, and 0.1 potassium phosphate. This solution was freshly prepared before each set of experiments, filtered, boiled for 1/2 hour, and immediately poured into the test-glasses and preserved with the usual precautions. To test the effect of disinfection, the wool or wadding, after exposure for a definite time to a definite degree of heat in an oven, or to a measurable volume of sulphurous acid in a bell-glass, was immediately transferred to the Pasteur's fluid, and the efficacy of the disinfectant was estimated by the rapidity of development of bacteria, if such appeared, or by their complete absence, as indicated by the fluid remaining perfectly cloudless.
It was thus found that 3.3 per cent, of sulphurous acid by volume failed even after many hours to prevent the development of bacteria, but that if the amount of gas reached 4.0 to 7.15 per cent, by volume of the contents of the bell-jar, and the process had gone on for at least 6 hours, no bacteria at all developed. On the other hand, while exposure to a temperature of 230° to 244° F. (110° to 118° C), even for 24 hours, failed to destroy the bacterial germs, 5 minutes' exposure to one of 257° to 302° F. (125° to 150° C.) invariably succeeded, and the test fluid remained, clear even for 11 days or longer. Dr. Wernich specially reminds us that his results must not be taken as applicable to all forms of bacteria, some of which probably require severer measures for their complete destruction. He also points out that it is easier to disinfect wool than linen, and that cotton wadding is the most difficult of all to free from infectious germs. (Gen-tralblatt Med. \\ iss.)