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XXVIII] natural cholera. The modern tendency is to regard the clinical phenomena as the result partly of local irritation and partly of toxæmia; variation in the proportional intensities of the different clinical elements depending on the degree of virulence of the particular strain of microbe introduced, and on the circumstances and idiosyncrasy of the patient.*

Diagnosis.— During the height of an epidemic the diagnosis of cholera is generally an easy matter; the profuse rice-water discharges, the collapse, the cold clammy skin, the cyanosis, the shrunken features the shrivelled fingers and toes, the feeble, husky, hollow voice, the cold breath, the cramps, and the suppression of urine, together with the high rate of mortality, are generally sufficiently distinctive. But in the first cases of some outbreak of diarrhœa, which may or may not turn out to be cholera, and the true nature of which for obvious reasons it is of importance to determine, correct diagnosis, though urgently required, may not be so easily attained. Symptoms resembling true cholera may supervene in the course of an ordinary severe diarrhœa, and are very usual in cholera nostras, in mushroom poisoning, in ptomaine poisoning, in the early stages of trichinosis, and in a certain type of pernicious malarial fever. In none of these, however, is the mortality so high as in cholera. It may be laid down, therefore, that epidemic diarrhœa attended by a case- mortality of over 50 per cent, is cholera.

In other forms of diarrhœa it is rare for the stools to be persistently so absolutely devoid of biliary colouring matter as they are in cholera. A careful inspection of the stools sometimes yields valuable information in other ways. Thus, in mushroom poisoning fragments of the mushrooms which caused the catharsis may be seen; in trichinosis the microscope may detect the adult trichina. In choleraic malarial attacks the presence of the malaria parasite