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618 infective material comes from another leper. Leprosy has never been shown to arise in a country de novo. There are many facts and arguments to support this statement; their discussion is deferred until the subjects of heredity, contagion, and the hygienic questions connected therewith, come to be considered.

2. The period of incubation.— This is generally, possibly always, long, and has to be reckoned usually in years— two or three at least. There are cases on record in which the period of incubation must have been longer even than this. Danielssen mentions one in which the period was ten years, Leloir describes another in which fourteen years or more, and Höegh one in which twenty-seven years elapsed between the time at which infection was presumed to have occurred and the first manifestations of the disease. On the other hand, cases are on record in which the incubation period was set down at three months or even at a few weeks.

3. Prodromata.— Fever of greater or less intensity and occurring more or less frequently is, almost invariably, a feature of the prodromal stage of leprosy. Febrile attacks may recur off and on during one or two years. It is well to bear in mind that in tropical countries such attacks are apt to be looked on as malarial. Another very common prodromal feature is an unaccountable feeling of weakness, accompanied usually by a sensation of heaviness and a tendency, it may be irresistible, to fall asleep at unusual times. Dyspeptic troubles, associated with diarrhœa in some cases, with constipation in others, and usually attributed to " liver," are also common. Epistaxis and dryness of the nostrils, perhaps symptomatic of the initial lesion, perhaps corresponding to the epistaxis in the prodromal stage of typhoid, tuberculosis, and such as is sometimes met with in early syphilis, are noted by Leloir. Headache; vertigo; perversions of sensation such as localized pruritus, hyperæsthesia, " pins and needles," neuralgic pains— intermittent for the most part, and perhaps very severe and especially common in the limbs and face; general aching, rheumatic-like pains in loins,