The Broad Street Pump

In the late summer of 1854 a few hundred yards of Soho became the most dangerous ground in England. Cholera emptied the houses around Golden Square so fast that the living could scarcely bury the dead, and the physician who solved it never saw the thing that was killing them. John Snow's tests of the water told him little; what he had was a map, a list of the dead, and a single public pump. From these he reasoned his way to the truth medicine had been missing for a generation: that the disease came up out of the water. He persuaded a parish to take the handle off the pump, and the gesture outlived him as the founding act of a science.

The blue death

Cholera was the great Victorian terror, and it earned the fear. A man could be well at breakfast and dead by nightfall, drained to a husk by a diarrhoea like rice-water that ran out of him until his blood thickened and his skin took on the slate-blue colour that gave the disease its common name.¹ It had reached Britain from the delta of the Ganges in the early 1830s and returned in waves; the visitation of 1853 and 1854 was the third time it had swept the country. London had buried tens of thousands and still had no agreed idea what it was burying them from.

The reigning explanation was miasma: bad air, the foul exhalation of rotting matter and filth, breathed in by the crowded poor in their reeking courts. It was not a stupid theory. Cholera did haunt the squalid low-lying districts, and those places did stink, so the link between disease and stench went unquestioned by most of the establishment and the General Board of Health alike.² Against it stood a quiet, Yorkshire-born physician named John Snow, who had argued since 1849 that the poison lay not in the air but in something swallowed, that it bred in the gut and passed out of it to reach its next victim through water fouled by the discharges of the sick.³ For five years this had been a minority view held by a man with no means to prove it. Then the pump on Broad Street began to kill.

The deadliest yards in London

The outbreak began at the end of August 1854 and moved with a speed that frightened even those who thought they knew the disease. Within two hundred and fifty yards of the spot where Cambridge Street joins Broad Street, by Snow's own reckoning, there were upwards of five hundred fatal attacks of cholera in ten days; before it burnt itself out the dead numbered around six hundred.⁴ Whole households went together. Those who could flee fled, the shops put up their shutters, and the district around Golden Square took on the silence of a town under siege.

Snow knew the neighbourhood, and already suspected its water. He went into the emptying streets with the bearing of a man testing a hypothesis rather than counting corpses, and fixed almost at once upon the public pump at Broad Street, a well prized across the district for the coolness and clarity of what it drew. Mothers sent children to it; publicans cut their spirits with it; the coffee-houses served it to a wide custom. If that well were poisoned, the homes it supplied would trace the outline of the dead. Snow set himself to draw that outline.

The map and the count

He did the work on foot, going from house to house among the fatal cases and asking one question above the rest: where did this household draw its water? Death after death traced back to the Broad Street well. He set the cases down as black marks against the street plan, a stacked bar for each death, and the marks massed thickest about the pump and thinned with distance from it, the way iron filings gather on a magnet.⁵

The map persuades, but it was the exceptions that carried the proof, for a cause is tested hardest where you expect it to fail. A workhouse stood in the middle of the stricken streets with more than five hundred inmates and lost only a handful; it had a well of its own and never sent to the pump. Beside the pump stood the Lion Brewery, and of its seventy-odd men not one died in the outbreak; they drank the brewery's own deep water and a daily ration of malt liquor, and never touched the Broad Street well.⁶ Strangest of all were two deaths far from Soho, in districts the outbreak never touched. A widow named Susannah Eley had moved from Broad Street out to Hampstead, yet kept a fondness for the taste of the pump's water, and her sons sent a large bottle of it out to her by cart. She drank it and died of cholera in her clean suburb. A niece who had come from Islington to visit drank the same water, carried the taste home, and died of cholera there in turn.⁷ The poison was not in the Soho air, which neither woman ever breathed. It was in the Soho water, which had been carried to their doors.

The handle

On the evening of the seventh of September Snow laid his evidence before the Board of Guardians of St James's parish and asked them to do the single practical thing his theory allowed: disable the pump. They were not convinced, but they were frightened enough to act upon the chance, and the next day the handle was taken off.⁸ The outbreak subsided.

It is the most famous gesture in the history of public health, and Snow was too honest to let it carry more weight than it could bear. By the eighth of September the epidemic was already in steep decline, partly because so much of the population had fled, partly for reasons no one could name. Snow said so himself: the attacks had so far diminished before the water was stopped that it was impossible to decide whether the well still held the poison in an active state or had somehow become free of it.⁹ The handle did not break the back of the outbreak; the outbreak was already breaking. What the act demonstrated was quieter than a rescue and far more lasting. A physician had found the source of a plague by reasoning, and had been believed enough to be let act on it, before anyone alive could see the agent or say what it was.

Whitehead and the child

The proof of the source came from a sceptic. Henry Whitehead, a young curate who had nursed the dying, set out to refute Snow by the same door-to-door method. The inquiry made a convert of him, and gave Snow the one thing the map could not: a beginning. Whitehead found the first case in an infant at number forty Broad Street, a few feet from the pump. The Lewis child, five months old, had fallen ill with diarrhoea on the twenty-eighth of August, days ahead of the general outbreak, and her mother had rinsed the soiled napkins in pails and emptied the water into the cesspool at the front of the house.¹⁰

That cesspool sat barely three feet from the well. When the drains were at last opened, the brickwork was found decayed and the earth between cesspool and well sodden through, so that the filth of the one seeped steadily into the water of the other.¹¹ The chain was complete, and unbearable in its smallness: one sick child, one mother's washing-water, one crumbling course of brick, and a well the whole district trusted had become the deadliest object in London. The organism itself was seen by none of them. That very year, in Florence, the anatomist Filippo Pacini examined the gut of cholera victims and described under his microscope the comma-shaped bacillus he found massed there, naming it Vibrio cholerae; the age believed in bad air and paid him no heed, and the cause Snow had inferred went unconfirmed until Robert Koch isolated the same organism in 1883-84, a quarter of a century after Snow was in his grave.¹²

Read from the Ward

I have stood at the bedside of a patient in the kind of shock cholera brings, though the cause that night was something else, and the body at that edge tells the same story whatever empties it: the thready pulse, the pressure falling out from under your hands, the cold slack skin, the blood chemistry tipping toward the place from which people do not return. What strikes me is how little it asks to reverse, caught in time. Salt and water in the right proportions, run back faster than they leak away, and the patient who looked as good as dead sits up and asks for tea. The cure for the thing that killed five hundred souls around Golden Square is, at root, clean fluid given correctly, whether by the drip in my unit or the oral rehydration salts that now spare millions of children a year. The simplicity is almost an insult, and it is the second thing I think of when I read Snow.

The first is that he was right without being able to prove why, and that this is the true birth of my trade. Snow never saw the vibrio. Pacini saw it the same year and was ignored, because the age could not yet hear him. Snow had no agent and no culture in a dish; he had a pattern of deaths in space and the discipline to ask, of every one, where the water had come from, and from that alone reached a conclusion no laboratory would confirm until he had lain a quarter of a century underground. We teach it as a triumph of the map, yet the map was drawn largely to persuade men who already doubted him, and the celebrated handle came off an outbreak already dying. The real achievement is harder to picture than a pump: that a cause can be found, and acted against, through the shape of the evidence, before it consents to be seen. I live by that, treating the septic patient before any culture returns, hunting the shared source of a ward's infections before the laboratory can name it.

The honest part of his story, the part the legend files away, is the part I need most. He did not wait for a certainty he could not have. He took the handle off on the strength of a pattern, knowing the epidemic might already be passing and that he could not prove the well still held its poison, judging the cost of being wrong to be a dry pump for a week and the cost of waiting to be counted in the dead. That is the plain arithmetic of acting under uncertainty, which is most of what medicine is. So the pump handle keeps its hold on the imagination, though not for the reason the story gives. It is not the relic of a single saving stroke; it is the first time a doctor traced an unseen killer to its route and chose to cut the route rather than wait to meet the killer. The well at Broad Street is paved over now, and a pump without a handle stands near the spot. I have come to think that missing handle the truest monument we have: the shape of a decision made in time, on evidence that did not yet amount to proof.

1. On the clinical course of cholera — the rice-water stools, profound fluid loss, hypovolaemic collapse and cyanotic "blue" appearance that gave the disease its epithet — see Christopher Hamlin, Cholera: The Biography (Oxford: Oxford University Press, 2009); Sandra Hempel, The Medical Detective: John Snow, Cholera and the Mystery of the Broad Street Pump (London: Granta, 2006).↩
2. On the dominance of miasma theory and the General Board of Health (under Edwin Chadwick), see Hamlin, Cholera: The Biography; Peter Vinten-Johansen et al., Cholera, Chloroform, and the Science of Medicine: A Life of John Snow (New York: Oxford University Press, 2003).↩
3. John Snow, On the Mode of Communication of Cholera, 1st ed. (London: John Churchill, 1849) — the waterborne hypothesis advanced five years before the Broad Street outbreak.↩
4. "Within two hundred and fifty yards of the spot where Cambridge Street joins Broad Street, there were upwards of five hundred fatal attacks of cholera in ten days": John Snow, On the Mode of Communication of Cholera, 2nd ed. (London: John Churchill, 1855), 38. Total mortality for the outbreak is generally given as around 616 (parish returns).↩
5. On the spot map and its later "nearest-pump" boundary, and the argument that it served to persuade and communicate rather than to discover the source, see Snow, Mode of Communication, 2nd ed. (1855); Howard Brody, Michael R. Rip, Peter Vinten-Johansen, Nigel Paneth and Stephen Rachman, "Map-making and Myth-making in Broad Street: The London Cholera Epidemic, 1854," The Lancet 356 (2000): 64-68.↩
6. On the St James workhouse (its own well, few deaths among more than five hundred inmates) and the Lion Brewery (some seventy men, no cholera deaths, supplied by the brewery's deep well and a malt-liquor ration): Snow, Mode of Communication, 2nd ed. (1855), 42.↩
7. On Susannah Eley, the Hampstead widow supplied by her sons with carted Broad Street water, and her niece who drank the same water and died at Islington: Snow, Mode of Communication, 2nd ed. (1855), 44; Vinten-Johansen et al., Cholera, Chloroform. The Eley family kept a percussion-cap works in Broad Street.↩
8. On Snow's address to the Board of Guardians of St James's parish on the evening of 7 September 1854 and the removal of the pump handle the following day, see Vinten-Johansen et al., Cholera, Chloroform; Snow, Mode of Communication, 2nd ed. (1855).↩
9. "the attacks had so far diminished before the use of the water was stopped, that it is impossible to decide whether the well still contained the cholera poison in an active state, or whether, from some cause, the water had become free from it": Snow, Mode of Communication, 2nd ed. (1855), 51-52.↩
10. The index case — Frances Lewis, the five-month-old infant of 40 Broad Street, taken ill on 28 August 1854 — was identified by the Rev. Henry Whitehead working with the parish Cholera Inquiry Committee: Henry Whitehead, "The Broad Street Pump: An Episode in the Cholera Epidemic of 1854," Macmillan's Magazine 12 (1865): 113-22; Vinten-Johansen et al., Cholera, Chloroform.↩
11. The cesspool roughly three feet from the well, its decayed brickwork and the seepage between them, were established by the surveyor's examination for the parish Cholera Inquiry Committee in 1855: Report of the Cholera Inquiry Committee (St James's, Westminster, 1855); Vinten-Johansen et al., Cholera, Chloroform.↩
12. Filippo Pacini, "Osservazioni microscopiche e deduzioni patologiche sul cholera asiatico" (Florence, 1854), describing and naming Vibrio cholerae; the work was neglected under miasma orthodoxy. Robert Koch identified the cholera bacillus in Egypt in 1883 and isolated it in pure culture in Calcutta the following year. John Snow died on 16 June 1858, aged 45.↩

• Brody, Howard, Michael Russell Rip, Peter Vinten-Johansen, Nigel Paneth, and Stephen Rachman. "Map-making and Myth-making in Broad Street: The London Cholera Epidemic, 1854." The Lancet 356, no. 9223 (2000): 64-68.
• Hamlin, Christopher. Cholera: The Biography. Oxford: Oxford University Press, 2009.
• Hempel, Sandra. The Medical Detective: John Snow, Cholera and the Mystery of the Broad Street Pump. London: Granta, 2006.
• Snow, John. On the Mode of Communication of Cholera. 2nd ed. London: John Churchill, 1855.
• Vinten-Johansen, Peter, Howard Brody, Nigel Paneth, Stephen Rachman, and Michael Rip. Cholera, Chloroform, and the Science of Medicine: A Life of John Snow. New York: Oxford University Press, 2003.
• Whitehead, Henry. "The Broad Street Pump: An Episode in the Cholera Epidemic of 1854." Macmillan's Magazine 12 (1865): 113-22.