John Snow

John Snow was born in York in 1813, the eldest of nine children of a labourer, in a street beside the river that regularly flooded with sewage. He was apprenticed at 14 to a surgeon in Newcastle, and in 1831 was sent to treat miners at a colliery during the first cholera epidemic to reach Britain. He saw dozens die and could do nothing.

In 1836 he walked to London, via Wales and Bath, to continue his training. He qualified, set up in practice, and made his name in the new field of anaesthesia, working out safe doses of ether and chloroform when others were killing patients with guesswork. In 1853 he gave chloroform to Queen Victoria for the birth of Prince Leopold, which did more than any argument to make pain relief in childbirth respectable.

Cholera remained his obsession. The accepted explanation was miasma, poisonous air rising from filth. Snow reasoned that a disease which attacked the gut must be swallowed, and in 1849 proposed that it spread through water contaminated by sewage. In the 1854 outbreak around Broad Street in Soho, which killed more than 500 people in ten days, he plotted the deaths on a map and showed they clustered around one pump. The parish removed the handle. He also compared households supplied by two water companies, one drawing from the sewage-laden Thames, and found the death rate was many times higher.

The medical establishment remained unconvinced, and an official inquiry rejected his conclusions. He died of a stroke in 1858, aged 45, before Pasteur's work proved him right.