John Snow

person · earth · London, England

English physician (1813–1858), a pioneer of anaesthesia and the author of the argument that cholera is spread by contaminated water rather than by foul air. During the 1854 Soho outbreak he mapped deaths against the water pumps that served them and identified the Broad Street pump; he also assembled the larger and stronger natural experiment of the South London water supply, comparing mortality among households served by the Lambeth company, which had moved its intake upstream of the sewage outfalls, with those served by the Southwark and Vauxhall company, which had not. The second study is the better epidemiology and the first is the better story. Snow died in 1858, four years before Pasteur's work and long before the cholera vibrio was accepted as its cause; his conclusion was correct and his mechanism was unproven in his lifetime.