Page:Popular Science Monthly Volume 30.djvu/801

Rh spores of the micro-organisms discovered in cases of splenic fever have been found to be absolutely unaffected after lying for upward of three months in a five-per-cent solution of carbolic acid in oil. It has been also found that vaccine matter mixed with carbolic acid in solution still retains its efficacy, and the question may therefore well be asked whether the highly diluted carbolic vapor used for purposes of aërial disinfection is not powerless to deal with an atmosphere saturated with the germs of infectious diseases.

When compelled to make use of water of a suspicious class, filtration and boiling constitute the most reliable methods of purification. Spongy iron is upon the whole the most efficacious filtering material. The water, especially if passed through sand afterward, comes out quite clear and pure, and may be kept for a long time without showing any signs of the production of living organisms. Charcoal filters, on the other hand, certainly sometimes allow spores or germs to pass through unchanged, and, when they are employed, boiling should always be superadded. It is not sufficient to bring the water once to the boiling-point; in order to be efficacious, repeated boilings are necessary, for the reasons given in a preceding paragraph. Milk of a suspicious character should always be thus thoroughly boiled. Travelers on the Continent do well to provide themselves with small portable filters, now easily procurable, for in many places the drinking-water is highly charged with impurities. It is satisfactory to know than the tannin contained in tea is a purifying agent of some value as regards organic matter present in water.

It would take up too much space and would be foreign to the purpose I had in view to describe all the methods of using the various disinfectants which are now offered to the public. With regard to many of them it is sufficient to say that their power has been absurdly overestimated. It can not be too strongly insisted, upon that deodorization is by no means equivalent to disinfection. My object has been to indicate in the first place what in the present state of our knowledge seems to be the true theory as to the causation of infectious diseases, and to show how obstacles are presented to more rapid scientific progress by the extreme minuteness of the organisms with which we have to deal. With regard to disinfection, I have striven to prove how entirely it must depend for its success on the specific action exercised upon the disease-germs by the means employed. The realization of this necessary relation can not fail to dispel many a fond belief with regard to disinfectants; but it will leave us with a more intelligent and useful appreciation of their true properties, and, by revealing how far we still are from the goal of complete knowledge, may even stimulate the investigator to explore paths of science which are yet unknown. Virgil says, "Felix qui potuit rerum cognoscere causas," and to nothing is this aphorism nowadays more applicable than to a knowledge of those agencies which produce infectious diseases.—Fortnightly Review.