Now disinfectants, such as chlorine, permanganate of potash, or Condy fluid, operate by oxidizing not only the gaaeous products given off by putrefaction, but also all organic matters with which they may come into contact ; whilst carbolic acid, on the contrary, merely destroys the causes of putrefaction, and, at the same time, sterilizes the organic matter, rendering it inert as a pabulum for the reproduction or the nutritiou of disease germs. The great difference which dietinguiahes them, therefore, is that the former deal with the effects ; the latter, with the cause. Again, these microscopic ferments are alwaya in email quantities, as compared with the substances on which they act ; aa a very small quantity of carbolic acid suffices to prevent the dec,omposition, its employment is both efficacious and economical. Moreover, carbolic acid is volatile, it meets with and destroys the germs or sporules as they float in the atmosphere ; but this cannot be the case with Candy fluid, nor with chloride of zinc or iron, which are not volatile, act only when in solution, and are mere deodorizers. This is why carbolic acid wee used with euch marked succesa, in England, Belgium, and Holland, during the prevalence of cholera and cattle plague. Professor Crookes did not meet with a single instance in which the plague spread on a farm where the acid was freely used.
The antiseptic properties of carbolic acid are so powerful, that one-thousandth, and even one five-thoueandth, part will, for months,.prevent the decomposition, fermentation, or putrefaction of urine, blood, glue eolution, flour paste, fsecee, &c., &c.; and its vapour alone is sufficient to preserve meat in confined spacee for weeks ; and even a little of its vapour in ordinary atmosphere will pre serve meat for several days, and prevent its being fly-blown. Indeed, one ten-thousandth part has been found sufficient to keep sewage sweet, for Dr. Letheby found that, through the use of such a quantity of carbolic acid in the sewers of London, during the existence of cholera in 1866, the sewers of the city were nearly deodorized.
Some experiments made hy Dr. Calvert, on tho comparative powers of various products ordinarily used as antiseptics, consisted in placing in bottles (not corked) solutions of albumen and flour paste ; to these were added various proportions of some substances patronized as antiseptics ; thb following table shows the tesults obtained :— These figures show clearly that the only true antiseptics are carbolic and cresylic acids, for they continued their action till the albumen solution and paste dried up ; and these results coincide with those obtained by Professor Crookes, and by Drs. Angus Smith and Saneom.
It may be remarked that disinfectants are of two classes, those which act by oxidation, destroying the organic substances which give rise to the infection, such as permanganate of potash, bleaching powder, and nitric acid ; and those which act by their presence, undergoing no decomposition them selves, but appearing to poison, or render innocuous, the germs of disease. To the latter class belong
camphor, and sulphurous and carbolic acids.
If deodorizers am merely intended to remove the noxious odour from any mass of matter in a state of decay or decomposition, they may be used with advantage : such are chloride of manganese, chloride of lime, sulphate of iron, permanganate of potash, chloralum, &c. But if it is desired to pievent the decomposition of organic matter, and to render it inert for the reproduction and nutrition of disease germs, carbolic and cresylic acids seem to be the only two substances to be relied on.
As the products given off from decaying organic matter are well known to facilitate the decom position of similar classes of substances to themselves, if placed in close proximity (the atmosphere, no doubt, conveying the germs), Dr. Calvert made the following experiments, with a view of ascer taining which of the undermentioned products would possess the moat active power in destroying such germs, and thus preserving the animal substance from decay. At the bottom of wide-mouthed pint bottles, he placed a known quantity of each of the antiseptics, and suspended over them, by a thread, a piece of sound meat. By daily examination, it was easily ascertained when the meat became tainted, 8,nd when putrid. The subjoined table indicates the results :— The following account of a series of experiments, undertaken by Hare and Longstaff, with a view of determining the relative merits of a few so-called disinfectants recently introduced, as com pared with others that have beon long before the public, will he of interest. It should be premised that they only deal with the relative values as antiseptics.
A quantity of urine was well mixed with a sufficient quantity of water to prevent the deposition of urates ; 100 c.e. of this mixed urine was placed in each of thirty-four vessels. To two of them, 5 c.o. of tap-water were added ; and to the others, the various antiseptics in the following amounts : —Of the solids, 0' I grin. with 5 c.o. of water ; of the liquids miscible with water, 5 c.c. of a solution containing 0.1 c.c. of the antiseptic ; and, in the case of the liquids not miscible with water, 5 c.c, of a recently agitated emulsion of the same strength. Thus, in each case, the amount of antiseptic usod was 0.1 per cent. of the volume of urine experimented on. All the experiments were in dupli cate (I. and II. in tables). The only phenornena looked for were the appearance of mould, and a dis tinct putrefactive odour :— As regards mould :—Burnett's fluid, ohloralum, borax, cupralum, and sanitas failed to delay its appearance ; terebene, Condy's fluid, sodium salicylate, and McDougall's fluid had hut little effect ; turpentine delayed it four or fivc days ; ferralum was only under observation fourteen days, during which no mould appeare,d ; carbolic acid appeared to prevent it entirely, since, after seventy-five days, the urine had evaporated nearly to dryness, without the slightest trace of mould having been observed.