DISINFECTANTS (ante). The subject of disinfectants is not yet perfectly under stood, and there are many unsettled notions regarding it. There has lately been con siderable skepticism in regard to the disinfeeting powers of chlorine and carbolic acid, and with apparently good reason. Doubtless too much reliance has been placed upon them, or upon an inefficient mode of using them. The mode of action of chloride of lime, or the chlorine or chlorine compounds liberated therefrom, is probably like that in bleaching. The disease-breeding organism is broken up, and consequently its propa gating power destroyed, just as coloring matter is broken up. This explanation does not take into consideration, of course, the theory of bleaching which supposed the abstraction of hydrogen by the chlorine compound and the liberation of oxygen in the condition of ozone. The important fact to bear in mind is that the disinfectant destroys the disease germs. Now, to act in this way, it is necessary to have at least one molecule of th' disinfectant in the presence of one molecule of the disease-producing organism, and probably it requires several, perhaps a hundred to one. The question then arises how many molecules of matter or how many organic compound particles are there in a given number of disease germs. No positive answer can be given. It is a mere matter, not of guess-work, but of estimation, and involves the question as to how many molecules of the disinfecting material are required to produce the death or disorgani zation of the disease germs. After a number of experiments, the question can be, and has been, practically decided. It is found that when an apartment is thoroughly fumi
gated with chlorine, or the compounds liberated by chloride of lime, that disease germs are destroyed. If, however, chloride of lime has simply been strewed about the prem ises, even in considerable quantity, it is found often that the place has not been thor oughly disinfected. If carbolic acid is used in too weak a solution it may not suf ficiently arrest or destroy the vitality of the growing disease germs. To depend upon the fumes of carbolic acid would be a practical fallacy. The substance must be directly applied, as a rule, to have a full sanitary effect. Perhaps chlorine may act by simply killing the germs. Carbolic acid probably does, and some other substances of less power may act upon some disease germs sufficiently, when they are not present in too great quantity, to prevent development of disease. Heat and cold, ,when intense enough, are perfect disinfectants. The continued application of dry air heated to 150' or 200° will generally destroy disease germs. It doubtlessly desiccates them, and they Oie. Moist air must be heated to the boiling point to produce the same effect. A suf ficient degree of cold will also effect the purpose; how great, cannot be stated for every instance. We know that diphtheria and scarlet fever, particularly the latter disease, often flourish in severe cold weather. The application of cold, except in a limited and partial manner, is impracticable. The mode of disinfecting any given locality must depend upon circumstances, and often requires much judgment. Sec CAnnomc Acm, ante.