Dr. Dougall considers that his experiments prove that putrefaction and fermentation are not identical processes; that putrefaction is more difficult to prevent than fermentation; that fermentation frequently subsides into putrefaction, but that the latter is seldom intensified into the former. The best antiseptics are acids, for it is apparently impossible for marked putridity and acidity to go together; and we mentioned above the only substances which, preventing putrefaction, also prevented fermentation.

The next portion of Dr, Dougall's pamphlet deals with the far more important branch of his subject - the relative aerial antiseptic powers of different volatile bodies; in other words, the power of purifying an atmosphere contaminated with zymotic virus or emanations found in hospital wards. The substances experimented on - putrescents - were milk, beef-juice, urine, egg-albumen, hay solution, and a mixture of all five. 4 dr. of each were placed on a stand 6 in. high, at the bottom of which was an ordinary saucer filled with the supposed antiseptic. The whole was covered with a bell-jar of 1 cub. ft. capacity, so that the roof was 6 in. above the putrescent. The antiseptic was put under the jar 12 hours previous to submitting the substances to its vapour. The "smoking " was continued for 6 days, unless fungi or microzymes appeared, and afterwards the substances unaffected were exposed to ordinary air for 12 days. All the solutions, when merely exposed to the air, contained either fungi or animalculse after the lapse of 12 hours (hay) to 4 days (milk). Carbolic acd prevented the appearance of eitheri in milk, beef-juice, urine, and egg-albumen; but in the hay solution and in the "mixture," animalcule and fungi appeared in 2 to 3 days, with an "abundance of vertical bacteria in 12 hours," and in 48 hours abundance of free life.

Chloroform, camphor, sulphuric ether, all failed to prevent the appearance of either fungi or animalcules, or both; but no putrefaction or fermentation took place in the solutions submitted to iodine, glacial acetic acid, and hydrochloric acid. Chloride of lime acted as an atrial antiseptic to all the substances except beef-juice, which exhibited animalcule on the 15th day, and Penicillia and Torulcet on the 11th. With sulphurous acid, Penicillium appeared on the 15th day in the beef-juice and the hay solution; and animalcule appeared in 15 days in the hay solution submitted to nitrous acid. The results of these experiments show that camphor and sulphuric ether favour putrefaction, that chloroform is inert, but that carbolic acid, sulphurous acid, and chloride of lime are all atrial antiseptics, the latter the best of the three; and that nitrous acid, glacial acetic acid, and hydrochloric acid are the most perfect in their action, the last two being equal and best. Dr. Dougall says: "As the conditions of the experiments infinitely surpassed in severity any produced by their practical application, and seeing that withal putrefaction and fermentation were not entirely prevented, hence aerial antiseption or disinfection in the great majority of cases is fallacious."

Along with the putrescents, and exposed to the different vapours, were separate minims of vaccine lymph, which were afterwards used to vaccinate children, and the summary of results shows that carbolic acid, both vapour and solution, failed to affect the vitality of the vaccine virus, in common with chloroform, camphor, sulphuric ether, and iodine. The vaccinations attempted with the lymph which had been subjected to the action of the vapour of chloride of lime, sulphurous, nitrous, glacial acetic, and hydrochloric acids, were, however, all unsuccessful. "Hence," says Dr. Dougall, "volatile acids, or a volatile body causing acidity by chemical affinity, as the chlorine from chloride of lime, which produces hydrochloric acid and free oxygen, are the best destructives of the active properties of vaccine lymph, and therefore, a priori, of variolous matter, and the other zymotica." This, be it observed, is not altogether unexpected: it has been frequently asserted that carbolic acid does not destroy effluvia, but removes them or occludes them for a time.

But here we have a minim of vaccine lymph buried in 1 cub. ft. of carbolic vapour for 36 hours, and yet it is unaffected; what effect, then, will its vapour have on the contagium of the zymotics as applied in ordinary domestic or hospital use? Some experiments by Dr. Cameron, of Dublin, made with ivory points charged with lymph and exposed to the vapour of chloride of lime, confirm those of Dougall; and Dr. Cameron says: "If the ordinary gaseous disinfection sometimes fails to destroy the vitality of vaccine, and has no effect on microzymes, we cannot rely on it as a means of destroying the con-tagiums of zymotic diseases, which certainly are near akin, if not to bacteria, at least to the virus of vaccine." (English Mechanic.)

A paper by Surgeon-Major O'Neil, in the Army Medical Department's Report for 1871, gives the results of experiments as to the relative power of some reputed antiseptic agents. In all the experiments, animalcule having distinct, however feeble motion, were observed on the 2nd day. Chloralum, chloride of aluminium, and chloride of zinc are set down as of little practical value. Permanganate of potassium was found to have considerable power as a deodorant, but hardly any as a germicide. With sulphate of copper, animalculae became abundant on the 16th day, when there were 4 parts of organic matter; and smell was noted on the 21st day, when there were 12 parts. Bisulphite of sodium was ascertained to be of no value. Employing carbolic acid, animalculae became abundant on the 10th day, when there were 8 parts of organic matter, and not till the 23rd, when there were 6 parts. Bichromate of potassium was tried up to 30 parts of organic matter, and was under observation for 39 days, and resisted up to this point. " This," adds the report, " is the most powerful of all the agents tried. It appears quite equal to carbolic acid in preventing the development of the fungi, and much superior to it and all the others in limiting - none of them prevent altogether - the development of animalcule.