Leprosy is a chronic infectious disease closely allied to tuberculosis, caused by the Mycobacterium Leprae discovered by Hansen in 1871 (usually known as Bacillus Leprae). Leprosy is known to the man from the ancient times, and the first description of the leprosy occurs some thousands of years before Christ. It is true, however, that even at the present time there is occasionally much difficulty with regard to the diagnosis of leprosy from allied diseases, and therefore in the ancient times and in the Middle Ages many skin diseases and syphilis, without doubt, were confused with it.