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THERE is a marked tendency to regard and diagnose all fevers occurring in tropical countries, or in individuals who have returned from tropical countries, as malarial. Such slovenliness in diagnosis must be strenuously avoided by the practitioner. It is apt to become a habit which, sooner or later, is bound to have disastrous consequences.

At the same time the opposite error of overlooking malarial infection must be equally guarded against. In many tropical and sub- tropical localities practically every European is, or may be, the subject of active or latent malaria. The tropical practitioner therefore should approach the diagnosis of all his cases, no matter what, with the idea ever present to his mind that they may be malarial or complicated with malaria.

The three pathoguomonic signs of malaria.—— These are—— periodicity; the effect of quinine; the presence of the malaria parasite.

The diagnosis of malarial disease, if all the means at our disposal be employed, is usually not a difficult matter. Formerly, periodicity and the effect of quinine were the tests principally relied on. In certain circumstances they are fallible. Nowadays, in all doubtful and serious cases, it behoves the practitioner to have recourse to the least fallible test—— the microscopical examination of the blood. When such an examination yields a positive result, when the parasite in any of its forms, or its characteristic product—— hæmozoin—— either free in the liquor sanguinis or enclosed in leucocytes, is found, the diagnosis of malaria is securely established. Negative results from a single microscopical examination are not so trustworthy as