Page:Popular Science Monthly Volume 30.djvu/883

Rh principles are cited, the grouping of which makes it evident to the author that symptoms of alcoholic poisoning can not be trusted as evidence of the immediate use of alcohol; and that the excessive use of alcohol leaves a permanent defect or impress on the brain, which will go down into the future with great certainty. It may be concealed for a lifetime in the child of a drinking parent, but may come to the surface at any moment, from the application of its special exciting cause; or it may appear in some other form of defect, which can be traced back to the injury from the toxic action of alcohol.

Potable Water.—The unsatisfactory character of all purely chemical examinations to determine the wholesome potability of water has long been tacitly admitted. It has more recently been demonstrated that such examinations do not go to the root of the matter, for the quality of water is dependent on the presence or absence of certain bacterial growths. Frankland's combustion process, Wanklyn's ammonia process, and Schützenberger's permanganate of potash method, were all attempts to estimate the organic matter, and, to some extent, its qualities; but they, and all chemical processes, deal with dead matter only, or, rather, fail to draw any distinction between the living and the dead; and, judged by these standards, the water in which vegetables have been boiled, or a cup of meat-broth, or of coffee, would rank far worse than water containing a small quantity of enteric or choleraic stools, or even than the anthrax-bearing waste from a mohair-factory. Bacterioscopic examination of water, the object of which is to determine the bacterial life, or the disease-germs and their activity, has been employed for some years in Germany, and is making headway in England. By this method we are enabled to ascertain the number of living bacteria in a cubic centimetre of water. Koch's results showed the relation between this number and the purity of waters, as well as the effect of filtration, when he was able to announce that the numbers were, for Berlin sewage, 38,000,000; for the waters of the Spree, 118,000; for the effluent from sewage-farms, 18,000; from the Rummelsberger See, 32,000; from the Stralau water-works, before filtration, 125,000, and after filtration, 120. In the best well-waters it is from 30 to 60, and in boiled distilled water from 4 to 6. From this it appears that any number under 100 indicates an irreproachable water, and under 200 a potable one; while polluted rivers count their thousands and sewage its millions. Still, this method fails to distinguish between innocent and pathogenic organisms. Some of them can be identified by their mode of growth in tubes of nutrient gelatin, by their behavior with coloring reagents, and by other methods, even when in themselves morphologically alike and indistinguishable under the microscope. Dr. Dupre suggests an easier and speedier plan, dependent on the fact that some microbes can and others can not survive exposure to certain degrees of heat, and that while dead matter rapidly absorbs oxygen from permanganate of potash, it does so to a very slight extent, if at all, from the water itself, at least within a limited space of time. He is directing his attention to the points that the amount of oxygen taken from the water in its natural condition may be contrasted with that taken from the permanganate; that it may be contrasted with that taken up after any living organisms in the water have been killed by the application of heat; that a degree of heat may be applied sufficient to kill developed organisms or certain germs and spores, but insufficient to kill other kinds of germs and spores, and if this degree of heat be known for the several kinds of germs and spores, a judgment may be formed as to the nature of the germs and spores present; and that some substances, sterile in themselves, but capable of nourishing any living organisms contained in the water, may be added, and the increase in the amount of oxygen absorbed may be noted. Among the practical results to which Dr. Dupre has come, are: A water which does not diminish in its degree of aëration, or, in other words, which does not consume any oxygen from the dissolved air, may or may not contain organic matter, but presumably does not contain growing organisms. Such organic matter, therefore, as on analysis it may be found to contain, need not be considered as "dangerous organic impurity"; a water which,