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XXVIII] peptone solution, so that in twenty-four hours pure cultures and the cholera-red reaction can be obtained in secondary peptone tubes. Also, a positive result may be obtained by this method in cases in which the microscopical examination has failed to give definite evidence of the presence of vibrios. In addition to these methods the agglutination test is frequently employed. The serum of a rabbit immunized against a known cholera vibrio by frequent and massive intraperitoneal injections, and therefore having a high agglutinating power, affords a very rapid means of differentiation of pathogenic from non-pathogenic vibrios. In case of doubt as to the identity of a suspected cholera vibrio, Pfeiffer's reaction might be employed with advantage. An emulsion of the organism, to which a small amount of the patient's serum had been added, is injected into the peritoneal cavity of a normal guineapig. Half to one hour later the peritoneal fluid is examined. If the case be one of cholera the bacteria will be found to be degenerated and mostly spherular. The first two methods are applicable to those instances in which microscopical examination of the stools shows crowds of comma bacilli. Method 3 is specially applicable to those stools in which comma bacilli are in very small numbers.

As an agglutination reaction is not obtainable from the blood serum during the acute stage of the disease, this means of diagnosis is not available in cholera.

Mortality.— The average case-mortality in cholera amounts to about 50 per cent. Some epidemics are more deadly than others. As already mentioned, the mortality is greater at the earlier than at the later stages of an epidemic. To the old, the very young, the pregnant, the subjects of grave organic disease— particularly of the liver, kidneys, and heart —the dissipated, the underfed, and the feeble, the danger is very great. Quarantine prevention.— Theoretically, quarantine should be "an efficient protection against the introduction of cholera into a community; practically, it has proved a failure. Unless they are stringent and thoroughly carried out, quarantine regulations can be of little use. Unfortunately, the temptation to evade such regulations is in proportion to their stringency. It is impossible to secure the absolute honesty and efficiency of every individual in a large