paper dealing with the question in which a reliable test for the cholera microbe was described. The test depends on the fact first noted by Dunbar that the cholera microbe flourishes luxuriantly in a solution of peptone. If this substance is added to water containing the microbe of cholera besides other bacteria the former will reproduce in most cases more rapidly than others; and in twelve to twenty-four hours will form a fine pellicle on the surface of the liquid, from which the cholera microbe may be isolated in a pure culture with facility. Soon after the publication of this paper, Metschnikoff, Sanarelli, and others, published accounts of the finding in water, at places where no cholera existed at the time, of microbes practically undistinguishable from that of cholera. Large numbers of persons using this water were in perfect health ; these microbes therefore were completely harmless. These discoveries threw no doubt on the authenticity of the cholera microbe as the cause of cholera ; but they threw great doubts on the tests for the cholera microbe described by Koch. The discoverers came to the conclusion that there existed in nature a number of harmless microbes that could not be distinguished from that of cholera by any known test ; and that therefore it was impossible to say whether a specimen of water contained the microbe of cholera, or whether it merely contained a harmless microbe that has a similarity to it. It was, however, also suggested that these cholera-resembling microbes were in reality the true cholera microbe, but in a state of degeneration. So far as I know no proof has hitherto been given of the truth of this suggestion. I propose in this paper to attempt to fill this hiatus. Commonly, in an European town, there are at most two or three sources of water in use. In an Indian town, on the contrary, there are usually hundreds of sources. In some places, as Cawnpore, there may be a well in almost every house. Each of these wells may contain the cholera microbe under different conditions. This peculiarity no doubt complicates the questions connected with the distribution of cases in a cholera epidemic, and makes their explanation more difficult. But for the present purpose this was an advantage, for in a single outbreak in a town it was possible to meet with the cholera microbe in a state of degeneration under a hundred different conditions, and to see in each case whether it continued to exist in the well water, in a degenerated condition, after the epidemic had passed away. If the above-described view is correct, namely, " that the cholera-resembling vibrios," discovered by several authors, are really nothing more than cholera microbes in a state of degeneration, then one would expect to find that during cholera epi" vibrio" would be present in well water ; demics a and that, after the cessation of the epidemic, the vibrio would be found showing various characters

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OBSERVATIONS

ON CHOLERA IN INDIA.

By E. H.

IIankin,

lion of St. John's College, Cambridge, Chemical Examinci and Bacteriologist to the JY. W. P.

Observations on Cholera in India.

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