although this bacteriological action might be connected with the corpuscles of the blood, it was not confined to them, as the serum of freshly coagulated blood was found to contain some proteid substance which undoubtedly exerted a powerful bactericidal effect. In July, 1889, Babes and Lepp recorded a number of experiments in which they had found that the blood of dogs which had been vaccinated against rabies exerted a distinctly protective action when injected into susceptible animals, either previous to or along with the virus procured from a rabid animal. Ferran appears to have been the next observer to accentuate this point. He was followed by Bouchard in France, while Behring and Kitasato in Germany, and then Roux in Paris, and others in rapid succession pointed out that there was in the serum of the blood of animals vaccinated against diphtheria and tetanus a distinct prophylactic and curative agent which, however, it was difficult to separate from the serum. In 1891 patients were treated in Berlin with a serum prepared by Behring, and since then this serum has been prepared and used in nearly all civilized countries."
Infected Drinking Water.—There is a growing tendency among physicians to belittle the purely chemical examination of potable water, and to rely solely upon the results of the bacteriological tests. A recent episode, the result of which seems at first sight to strengthen this view, occurred during the trials undertaken by the London Local Government Board, in which water samples, purposely inoculated with typhoid germs, were sent for analysis to one of England's leading chemists, and were by him pronounced pure. The obviously weak point in drawing such a conclusion from the above occurrence lies in the fact that such a sample of water would not be found in practice. The mere fact that it contained no sewage, to detect which is the chief purpose of the chemical analysis, would almost certainly in practice preclude the typhoid bacillus, the pure culture being only a laboratory product. The same is practically true with all the pathogenic micro-organisms which are liable to occur in drinking water. The chemical ingredients which the sewage supplies are quite essential for the rapid growth and multiplication of the bacteria. In fact, a favorable breeding ground is perhaps not second in importance to the presence of the germ itself, as the number of individual microbes, up to a certain point, which gain access to the human body, is probably of much more importance than the kind of germ. "The chemist," says Prof. W. P. Mason, in an article in the Journal of the American Chemical Society, "is unable to say whether or not a sewage-laden water is disease-bearing on any particular date, for to him all sewage is alike, but be condemns the water for the reason that, although it may be harmless to-day, it is impossible to predict what may be its condition to-morrow. Within the week I have been requested to make a bacteriological examination of the water of a certain well, in order to determine if it be affected by neighboring cesspools. The physician who made the request was impressed with the belief in the paramount value of such an examination and the comparative uselessness of chemical analysis. I am quite convinced that, had I followed his suggestions, I should have sought in vain for any specific microbe, but inasmuch as, upon chemical analysis, I found that the chlorine ran twenty-four parts per million, which is about ten times the local 'normal,' and the 'nitric nitrogen' read nine parts per million in place of 0·116, I condemned the water offhand without going further. . . . As Dr. Dupré has pointed out, chemistry in such cases anticipates what may happen in the future, and by timely advice may prevent an outbreak of disease; while, on the other hand, the discovery of disease germs in a water is only possible after the water has become infected."
A New Low-Temperature Apparatus.—A most interesting and important demonstration of the efficiency of the process of self-intensification of cold produced by expansion alone without the aid of any extraneous artificial refrigeration is described in a recent issue of Nature. The apparatus consisted of three coils of narrow copper tubing arranged concentrically in a metal case, and connected successively together. The gas, say oxygen, enters the outer coil at a pressure of one hundred and twenty atmospheres, passing from this into the second, and from
