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XXXVI] most part they merge imperceptibly into each other, and, in not a few instances, some of them cannot be recognized.
 * 1. Primary infection.
 * 2. Period of incubation.
 * 3. Prodromata.
 * 4. Primary exanthem or macular stage.
 * 5. Period of specific deposit.
 * 6. Sequelæ ulceration, paresis, trophic lesions.
 * 7. Terminations.

1. Primary infection.— Seeing that leprosy is caused by a specific germ, there must have been a time, in the history of every leper, when the infecting germ entered the body. In many specific diseases, such as syphilis, the site of the primary infection is indicated by a well-marked local lesion, and the time of infection can usually be ascertained. So far as present knowledge goes, this much cannot be affirmed of leprosy; in this disease we know of nothing that indicates precisely either the seat or, with rare exceptions, the time of primary infection. In this respect leprosy resembles tuberculosis. We are equally ignorant as to the condition of the infecting germ, whether it enters the body as spore or as bacillus, and also as to the medium in or by which it is conveyed. We cannot say whether it enters in food, in water, in air; whether it passes in through the unbroken epithelium, or whether it is inoculated on some accidental breach of surface, or, perhaps, introduced by some insect bite. Sticker has found Bacillus leprœ in the nasal mucus in 128 out of 153 lepers examined. He considers that the initial lesion of the disease is a specific ulceration of the cartilaginous septum of the nose; the lesion persists and is an active source for the diffusion of infection. Of the presence of this condition, epistaxis, he maintains, is often an early symptom. Several subsequent observers favour this view.

Although we are in absolute ignorance as to the process of infection, we may be quite sure that in leprosy there is an act of infection, and that the