The British physician John Snow (1813 - 1858) was a leader in the adoption of anaesthesia and medical hygiene, and a pioneer of epidemiology. He was voted in a poll of British doctors in 2003 as the greatest doctor of all time.
Snow was a believer in the germ theory of cholera, as opposed to the then-dominant miasma theory. He was the author of the study of an 1854 outbreak of cholera in London's Soho district. According to an apocryphal story, he mapped and identified the cause of the outbreak as the public water pump on Broad Street, and disabled it, thus ending the outbreak. Whether or not the story of the pump is true, the study was a major event in the history of public health, and can be regarded as the founding event of the science of epidemiology.
There is still a water pump on Broad Street, opposite what is now the John Snow public house. However, it is non-functional, and exists only as a memorial to John Snow.