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266 Diagnosis.— The diagnosis of yellow fever is treated of in one of the chapters on malaria and in that on black water fever (see pp. 114, 288). Practically, the only two diseases with which severe yellow fever is likely to be confounded are bilious remittent and hæmoglobinuric fever. The difficulties of diagnosis are often very great; particularly so in the earlier cases of an epidemic. When several deaths, preceded by fever and black vomit, have occurred within a limited area and in quick succession, a suspicion of yellow fever becomes a certainty. There is no clinical feature, so far as is known, which would distinguish a mild attack of yellow fever from an ordinary febricula, nor any pathognomonie clinical sign that would absolutely distinguish a malarial remittent from yellow fever. Probabilities must be weighed in diagnosis when it is based on clinical grounds alone. The only reliable guides are the discovery of the malaria parasite and the characteristic pigment and leucocytic variation in malarial fever, and the determination of their absence in yellow fever ; and, when cases come to the postmortem table, the presence of pigment in the viscera in the former, and of extensive fatty degeneration of the liver cells in the latter.

Treatment.— Formerly a much more active treatment than that in vogue at the present day was the fashion for yellow fever. It is now recognized that, as with most specific fevers, the treatment is more a matter of nursing than of drugs.

Experience has shown that a smart purgative at the very onset of the disease is beneficial. With many castor oil is the favourite drug, but to be of service it has to be given in very large doses 2 to 4 oz. Others use calomel; or calomel combined with quinine— 20 gr. of each. Others, again, prefer a saline. The purgative, whichever be selected, must not be repeated, nor, for that matter, given at all if the patient is not seen until after the second day of the disease. Hot mustard pediluvia, frequently repeated during the first twenty -four hours, the patient and