The bacillus of leprosy was discovered by Han sen (q.v.), of Bergen, Norway, in 1871. Neisser, in 1879, after extended researches, confirmed Hansen's claims. The bacillus is a straight or slightly curved thin rod, non-motile, occurring singly or in pairs attached end to end, but not in chains. When stained, it appears like the bacillus of tuberculosis, but often takes stain in such a way as to suggest that the protoplasm is fragmented, the bacilli then appearing like cocci in short rows, darkly stained points alter nating with unstained points. The bacilli appear in very large numbers in the leprous tissue, espe cially in the tubercular form, lying in bundles of several bacilli arranged parallel to each other. the bundles lying in various directions. Under the influence of the bacillus, nodules of new tissue arc formed in the skin or subcutaneous tissue. These nodules resemble granulation tis sue. being made up of a fibrous stroma, in which are cells of various shapes. Bacilli are present in the tissue in large numbers, both in and be tween the cells. The nodules arc most common in the exposed parts of the skin, face, hands, etc., but may occur in any part of the skin. The mucous membrane of the eyes, nose, and mouth may be affected. More rarely nodules develop in deeper parts of the body. The nodules may be large or small. There may be extensive ulcera tion with later eieatrization. sometimes produc
ing in the face the so-called `facies leontina.' Deep ulcers affecting the fingers or toes may result in extensive loss of substance. lepra mu tilans! in the form of leprosy known as anes thetic leprosy the lesion seems to he a peripheral neuritis, due to the presence of the bacilli in the nerves.
Some authorities mention three forms of leprosy: the macular, characterized by dark red or black stains; the anwsthetic, characterized by loss of sensation in patches of the integument and flesh; and the tubercular, characterized by nodules of tubercular granulation tissue, or a diffuse infiltration in skin and mucous tissue. Some cases unite all three varieties. In the macular-anwsthetic type the chief changes are in the nerves, leading to destruction of nerve fibres with consequent. anaesthesia, paralysis of muscles, and trophic disturbances. The period of incubation of leprosy is from three to seven or ten years, the patches first appearing on the unexposed parts of the body, with ulcers on the upper part of the nasal passages, thus render ing detection difficult. Heredity of leprosy is considered a mistake. Consult: Morrow, "Lep rosy," in Atlas of Skin and Venereal Diseases (New York, 1890) ; Ashmead, Suppression and Prevention of Leprosy (Norristown, Pa., 1897). See HANSEN.