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634 Many apparently unsuccessful attempts have been made to cultivate the lepra bacillus. I use the word " apparently " because some modern leprologists consider that probably a proportion of these attempts were successful, although at the time not regarded as being so. Mycotic forms developed in the culture media, but as these forms were not acid-fast they were regarded, at the time, as contaminations and not growths of the lepra bacillus.* A modern view is to the effect that Bacillus leprœ is really a streptothrix like the actinomyces, or, according to^some, the tubercle bacillus, that it is pleomorphic to a high degree, and that at a certain stage of growth and under certain conditions the mycelia break up into short rods, many of which are now acid-fast. There is great discrepancy of opinion among bacteriologists on the subject, each observer having his special lepra germ grown on his special culture medium; this germ he regards as the only true one, conforming, he claims, to the proper agglutination and complement-fixation tests, and its products possessing a therapeutic value comparable to that of tuberculin, and giving rise to a local and a general reaction when injected into lepers. Other bacteriologists, though following the methods that have succeeded in the hands of their authors, have generally failed to obtain similar results.

The discovery that rats (5 per cent, in Paris) are subject to a disease clinically resembling human leprosy may lead to a better knowledge of the lepra bacillus, seeing that the lesions of the "rat leprosy," as it is called, are intimately associated with an acid- fast bacillus resembling that of human leprosy, and that it is communicable to other rats by association. The leproma.— The young leproma presents a smooth, white, glistening section. When the leproma is older the cut surface has a brown tint, and the morbid tissue may become, from fibrotic changes,