Simpson's paper was published in the _Edinburgh Medical and Surgical Journal_ in three parts in 1841 and 1842, and to this day is the most valuable contribution to the interesting and important history of the disease. Some of the information had been collected in his student days. In his antiquarian researches he had frequently met with references to the dirty and unwholesome habits and surroundings of Scots towns in early days. The thought that dirt and disease were directly connected--a new thought even so recently as fifty years ago--led to his investigations. He found that leprosy was most prevalent at the time when his country was most dirty; but he was not able to establish his supposition that the cause of the disease lay in the insanitary surroundings of the people; indeed his researches proved that, on the contrary, leprosy had declined and practically disappeared from the country long before any material improvement in sanitary conditions took place. Simpson's conduct when Professor Thomson resigned the Chair of Pathology illustrates the vigour with which he entered into quite casually arising incidents where he saw that strength and a fight were necessary to conquer an evil or prevent an abuse. Thomson resigned in 1841 owing to ill-health. The Chair had been established by William IV. in 1831 on the representations of Thomson himself, who succeeded in satisfying Lord Melbourne that the subject was worthy of the dignity of a separate Chair, in spite of the protests of the Senatus Academicus, who throughout the history of the medical faculty generally appear to have been actuated more by personal considerations and professional jealousies, where new developments were in process, than by zeal for their _Alma Mater_. Professors Syme and Alison actively led an agitation that with Thomson's resignation the separate teaching of pathology should be brought to an end. Without a moment's hesitation, in the midst of his hard work, and suffering from indifferent health, Simpson plunged into a controversy with these colleagues, in which he silenced at once and for ever the detractors who had sneered at him as an ignorant, uncultured man-midwife. The controversy as usual was followed with intense interest by Edinburgh folks, and Simpson received a first taste of that popular approval which undoubtedly was one of the enjoyments of his life. The Crown avoided the difficulty of deciding between the rival petitioners for and against the Chair by transferring its patronage to the Town Council, who showed the same foresight which had led them to appoint Simpson, in deciding to maintain its existence. Unfortunately their wisdom failed when they elected as Thomson's successor a man who, although of brilliant attainments, subsequently brought discredit upon his University and himself by becoming a convert to homoeopathy. Simpson, who was indirectly instrumental in securing the Chair of Pathology for this man became his bitterest opponent when he declared