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640 by inoculation or otherwise, the cultivated bacillus to the lower animals, or, perhaps, to man himself.

Many attempts have been made to communicate leprosy to man by inoculation; hitherto, with one questionable exception, all have failed. A Sandwich Islander, apparently at the time free from leprosy, was inoculated from a lepra nodule. Within a month he had symptoms of leprous neuritis; two years later he was a confirmed leper; and in six years from the date of the inoculation he died of leprosy. Unfortunately the subject of the experiment was a native of a country in which leprosy was extensively endemic, and, besides, he had lived among lepers; in fact, members of his family were lepers. However possible it may be that the bacillus in this instance had been communicated by the inoculation, the circumstances in which the experiment was made, and the unusual shortness of the incubation period, are against its being regarded as conclusive evidence of the inoculability of the disease.

To bridge over this important gap in the evidence, we have to fall back on the close analogy that subsists between Bacillus lepræ and Bacillus tuberculosis, the leproma and the tubercle, leprosy and tuberculosis. In consideration of this and other circumstances, it is generally conceded that Bacillus lepræ, is the cause of leprosy, just as Bacillus tuberculosis is the cause of tubercle. Authorities differ, however, as to the way in which the bacillus is acquired.

How acquired.—It is absurd to suppose that an organism, no matter how humble its place in the scale of life, can originate de novo. Disregarding this, we have to consider two principal views as to the way in which the bacillus is acquired—heredity and contagion.

Heredity.—From the fact that it tends to run in families and that in certain instances it assumes the appearance of atavism, leprosy, until the Bacillus lepræ was discovered, was almost