When long voyages in sailing vessels were commonplace, scurvy was a major health hazard in mariners of all nations. The observations of James Lind (1716-94) and others indicated that citrus fruits had both a preventive and curative role in this disease. In the light of this work, by 1800 the disease had been virtually eliminated from Britain's Royal Navy. However, it continued in the merchant navies of all nations until the latter half of the 19th century. In 1867, the Merchant Shipping Amendment Act was passed by the British Parliament largely as a result of a concerted effort by the Seamen's Hospital Society (SHS), one of whose physicians, Harry Leach (1836-79) was the major proselytiser for improved conditions in the merchant service. Examination of the SHS records before and after this event demonstrate a marked reduction in the prevalence of scurvy in the Port of London. Although other factors-such as the introduction of steam ships, which resulted in faster voyages-were clearly important, the compulsory administration of genuine lime juice under supervision in the merchant service seems to have exerted a significant effect.