John Snow

This article is about the physician. For other uses, see John Snow (disambiguation).
John Snow
Born (1813-03-15)15 March 1813
York, United Kingdom
Died 16 June 1858(1858-06-16) (aged 45)
London, United Kingdom
Citizenship British
Nationality English
Fields Epidemiology
Alma mater University of London
Known for Anesthesia, locating source of a cholera outbreak, thus establishing the disease as water-borne.

John Snow (15 March 1813 – 16 June 1858) was an English physician and a leader in the adoption of anesthesia and medical hygiene. He is considered one of the fathers of modern epidemiology, in part because of his work in tracing the source of a cholera outbreak in Soho, London, in 1854. His findings inspired fundamental changes in the water and waste systems of London, which led to similar changes in other cities, and a significant improvement in general public health around the world.

Early life and education

Snow was born 15 March 1813 in York, England. He was the first of nine children born to William and Frances Snow in their North Street home. His neighbourhood was one of the poorest in the city and was always in danger of flooding because of its proximity to the River Ouse. His father was a labourer [1] who may have worked at a local coal yard, by the Ouse, probably constantly replenished from the Yorkshire coalfield by barges, but later was a farmer in a small village to the north of York.[2] Snow was baptised at All Saints' Church, North Street, York

All Saints, North Street

Snow studied in York until the age of 14, when he was apprenticed to William Hardcastle, a surgeon in Newcastle upon Tyne. It was there, in 1831, that he first encountered cholera, which entered Newcastle via the seaport of Sunderland and devastated the town.[3] Between 1833 and 1836 Snow worked as an assistant to a colliery surgeon, first in Burnopfield, County Durham, and then in Pateley Bridge, West Riding of Yorkshire. In October 1836 he enrolled at the Hunterian school of medicine on Great Windmill Street, London.[4]


In 1837, Snow began working at the Westminster Hospital. Admitted as a member of the Royal College of Surgeons of England on 2 May 1838, he graduated from the University of London in December 1844 and was admitted to the Royal College of Physicians in 1850. In 1850 he was also one of the founding members of the Epidemiological Society of London, formed in response to the cholera outbreak of 1849.[5]

In 1857, Snow made an early and often overlooked[6] contribution to epidemiology in a pamphlet, On the adulteration of bread as a cause of rickets.[7]


John Snow was one of the first physicians to study and calculate dosages for the use of ether and chloroform as surgical anaesthetics, allowing patients to undergo surgical and obstetric procedures without the distress and pain they would otherwise experience. He designed the apparatus to safely administer ether to the patients and also designed a mask to administer chloroform.[8] He personally administered chloroform to Queen Victoria when she gave birth to the last two of her nine children, Leopold in 1853 and Beatrice in 1857,[9] leading to wider public acceptance of obstetric anaesthesia. Snow published an article on ether in 1847 entitled On the Inhalation of the Vapor of Ether.[10] A longer version entitled On Chloroform and Other Anaesthetics and Their Action and Administration was published posthumously in 1858.[11]


Map of a later cholera outbreak in London, in 1866
Legend for the map above

Snow was a skeptic of the then-dominant miasma theory that stated that diseases such as cholera and bubonic plague were caused by pollution or a noxious form of "bad air". The germ theory of disease had not yet been developed, so Snow did not understand the mechanism by which the disease was transmitted. His observation of the evidence led him to discount the theory of foul air. He first publicised his theory in an 1849 essay, On the Mode of Communication of Cholera, followed by a more detailed treatise in 1855 incorporating the results of his investigation of the role of the water supply in the Soho epidemic of 1854.[12]

By talking to local residents (with the help of Reverend Henry Whitehead), he identified the source of the outbreak as the public water pump on Broad Street (now Broadwick Street). Although Snow's chemical and microscope examination of a water sample from the Broad Street pump did not conclusively prove its danger, his studies of the pattern of the disease were convincing enough to persuade the local council to disable the well pump by removing its handle. This action has been commonly credited as ending the outbreak, but Snow observed that the epidemic may have already been in rapid decline:

There is no doubt that the mortality was much diminished, as I said before, by the flight of the population, which commenced soon after the outbreak; but 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.
Original map by John Snow showing the clusters of cholera cases in the London epidemic of 1854, drawn and lithographed by Charles Cheffins.

Snow later used a dot map to illustrate the cluster of cholera cases around the pump. He also used statistics to illustrate the connection between the quality of the water source and cholera cases. He showed that the Southwark and Vauxhall Waterworks Company was taking water from sewage-polluted sections of the Thames and delivering the water to homes, leading to an increased incidence of cholera. Snow's study was a major event in the history of public health and geography. It is regarded as the founding event of the science of epidemiology.

Snow wrote:

On proceeding to the spot, I found that nearly all the deaths had taken place within a short distance of the [Broad Street] pump. There were only ten deaths in houses situated decidedly nearer to another street-pump. In five of these cases the families of the deceased persons informed me that they always sent to the pump in Broad Street, as they preferred the water to that of the pumps which were nearer. In three other cases, the deceased were children who went to school near the pump in Broad Street...

With regard to the deaths occurring in the locality belonging to the pump, there were 61 instances in which I was informed that the deceased persons used to drink the pump water from Broad Street, either constantly or occasionally...

The result of the inquiry, then, is, that there has been no particular outbreak or prevalence of cholera in this part of London except among the persons who were in the habit of drinking the water of the above-mentioned pump well.

I had an interview with the Board of Guardians of St James's parish, on the evening of the 7th inst [7 September], and represented the above circumstances to them. In consequence of what I said, the handle of the pump was removed on the following day.

John Snow, letter to the editor of the Medical Times and Gazette
John Snow memorial and public house on Broadwick Street, Soho

Researchers later discovered that this public well had been dug only 3 feet (0.9 m) from an old cesspit, which had begun to leak fecal bacteria. The cloth nappy of a baby, who had contracted cholera from another source, had been washed into this cesspit. Its opening was originally under a nearby house, which had been rebuilt farther away after a fire. The city had widened the street and the cesspit was lost. It was common at the time to have a cesspit under most homes. Most families tried to have their raw sewage collected and dumped in the Thames to prevent their cesspit from filling faster than the sewage could decompose into the soil.

Thomas Shapter had conducted similar studies and used a point-based map for the study of cholera in Exeter, Devon years before John Snow, although this did not identify the water supply problem that was later held responsible.[13]

Political controversy

After the cholera epidemic had subsided, government officials replaced the Broad Street pump handle. They had responded only to the urgent threat posed to the population, and afterward they rejected Snow's theory. To accept his proposal would have meant indirectly accepting the fecal-oral route of disease transmission, which was too unpleasant for most of the public to contemplate.[14]

It wasn't until 1866 that William Farr, one of Snow's chief opponents, realized the validity of his diagnosis when investigating another outbreak of cholera at Bromley by Bow and issued immediate orders that unboiled water was not to be drunk.[15]

Farr denied Snow's explanation of how exactly the contaminated water spread cholera, although he did accept that water had a role in the spread of the illness. In fact, some of Farr's statistical data that he collected helped promote John Snow's views.[16]

Public health officials recognise the political struggles in which reformers have often become entangled.[17] During the Annual Pumphandle Lecture in England, members of the John Snow Society remove and replace a pump handle to symbolise the continuing challenges for advances in public health.[18]

Later life

In 1830 Snow became a member of the Temperance Movement, and lived for a decade or so as a vegetarian and teetotaler. In the mid-1840s his health deteriorated, and he returned to meat-eating and drinking wine. He continued drinking pure water (via boiling) throughout his adult life. He never married.[19]

Snow lived at 18 Sackville Street, London, from 1852 to his death in 1858.[20]

Snow suffered a stroke while working in his London office on 10 June 1858. He was 45 years old at the time.[21] He never recovered, dying on 16 June 1858. He was buried in Brompton Cemetery.[22]

Legacy and honours

Funerary monument, Brompton Cemetery, London

See also


  1. Wedding Record of William Snow and Frances Empson, Huntington All Saints, 24/05/1812
  2. Census 1841
  3. Markel, H. (2013). "Happy Birthday, Dr Snow". JAMA. 309 (10): 995–6. doi:10.1001/jama.2013.1304. PMID 23483173.
  4. Thomas, KB. John Snow. In: Dictionary of Scientific Biography. Vol 12. New York, NY: Charles Scribner's Sons; 1973:502–503.
  5. "London Epidemiology Society". UCLA. Retrieved 22 October 2012.
  6. Dunnigan, M. (2003). "Commentary: John Snow and alum-induced rickets from adulterated London bread: an overlooked contribution to metabolic bone disease". International Journal of Epidemiology. 32 (3): 340–1. doi:10.1093/ije/dyg160. PMID 12777415.
  7. Snow, J. (1857). "On the Adulteration of Bread As a Cause of Rickets". The Lancet. 70 (1766): 4. doi:10.1016/S0140-6736(02)21130-7.
    Reedited in Snow, J. (2003). "On the adulteration of bread as a cause of rickets" (PDF). International Journal of Epidemiology. 32 (3): 336–7. doi:10.1093/ije/dyg153. PMID 12777413.
  8. John Snow (1813–58).
  9. "Anesthesia and Queen Victoria". John Snow. Department of Epidemiology UCLA School of Public Health. Retrieved 21 August 2007.
  10. Snow, John (1847) On the Inhalation of the Vapor of Ether.
  11. Snow, John (1858) On Chloroform and Other Anaesthetics and Their Action and Administration. London: John Churchill
  12. Gunn, S. William A.; Masellis, Michele (23 October 2007). Concepts and Practice of Humanitarian Medicine. Springer. pp. 87–. ISBN 978-0-387-72264-1.
  13. Shapter, Thomas (1849). The History of the Cholera in Exeter in 1832. London: John Churchill.
  14. Chapelle, Frank (2005) Wellsprings. New Brunswick, New Jersey: Rutgers University Press. ISBN 0-8135-3614-6. p. 82
  15. Cadbury, Deborah (2003). Seven Wonders of the Industrial World. London and New York: Fourth Estate. pp. 189–192.
  16. Eyler, John M. (April 1973). "William Farr on the Cholera: The Sanitarian's Disease Theory and the Statistician's Method". Journal of the History of Medicine.
  17. Donaldson, L.J. and Donaldson, R.J. (2005) Essential Public Health. Radcliffe Publishing. ISBN 1-900603-87-X. p. 105
  18. "Annual Pumphandle Lecture Series". The John Snow Society. 20 October 2013. Retrieved 24 October 2013.
  19. Snow, Stephanie J. (2004) "Snow, John (1813–1858)" in Oxford Dictionary of Biography
  20. JOHN SNOW'S HOMES. UCLA Department of Epidemiology, 2014. Retrieved 6 June 2014.
  21. Johnson, Steven (2006). The Ghost Map. Riverhead Books. p. 206. ISBN 1-59448-925-4.
  22. "List of notable occupants" (HTTP). Brompton Cemetery. Retrieved 21 August 2007.
  23. Punt, Steve (12 May 2014). "Birmingham". The 3rd Degree. Season 3. Episode 6. Event occurs at 7:05. BBC Radio 4. Retrieved 1 December 2016.
  24. "The College Crest". The Royal College of Anaesthetists. 2014. Retrieved 12 September 2014.
  25. Hempel, S. (2013). "John Snow". The Lancet. 381 (9874): 1269. doi:10.1016/S0140-6736(13)60830-2.
  26. S. William Gunn; M. Masellis (2008). Concepts and practice of humanitarian medicine. ISBN 0-387-72263-7.
  27. Couvrier R, Edwards G (July 1959). "John Snow and the Institute of France". Med Hist. 3 (3): 249–251. doi:10.1017/s0025727300024662. PMC 1034490Freely accessible.


External links

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