JMS Pearce
Hull, England

John Snow (1813–1858) (Fig 1) was a pioneer of modern epidemiology who almost eradicated cholera from London when, before bacteria were discovered, he showed that cholera was a waterborne infection. His vital part in ether and chloroform anesthesia is often forgotten. And, as an accomplished physician, he wrote many clinical articles about retained placenta, hydrophobia, lead poisoning, smallpox, pericarditis, rickets, and bladder stones.

A more humble start to life than John Snow’s would be hard to find. He was the eldest of nine children. His father William was a laborer who lived in North Street, York; he later became a smalltime farmer in nearby Rawcliffe. After an elementary education, John was apprenticed to William Hardcastle, a surgeon apothecary in Newcastle upon Tyne. In 1831, Hardcastle treated the poor during a cholera epidemic, and the youthful Snow treated affected miners at Killingworth colliery, making observations that influenced his later work.

He attended the Newcastle School of Medicine in 1832–3, and though without formal qualifications, became assistant to general practitioners in Durham and rural Pateley Bridge in Yorkshire. To advance his career, in October 1836 he walked the 400 miles via Liverpool and Bath to London. He enrolled in the Hunterian School of Medicine at Great Windmill Street for a fee of ₤34 and lived in a Soho alley in Bateman buildings. He served at Westminster Hospital and qualified as a member of the Royal College of Surgeons and a licentiate of the Society of Apothecaries in 1838.

He practiced from 54 Frith Street, Soho, at the same time attending the Charing Cross Hospital outpatient department and dispensary. He graduated MB in 1843 and MD in 1844 at the University of London and became a member of the Royal College of Physicians (MRCP) in 1850. He was a founding member of the Epidemiological Society of London, which he served with the distinguished Thomas Addison, Richard Bright, Benjamin Brodie, and Charles Hastings.

Early in his career, he started to investigate respiratory function, which would later be of importance in his use of anesthesia. He published papers “On the effects of carbonic acid” (1839) and “On asphyxia and the resuscitation of newborn children” (1841) in the London Medical Gazette. He devised a pump used for artificial respiration in 1841.

Anesthesia

On 16 December 1846, the Royal Mail steamship Acadia docked in the Mersey estuary bringing a letter from Jacob Bigelow, surgeon at the Massachusetts General Hospital (MGH), to Francis Boott, an American expatriate physician in London. It related how William Thomas Green Morton had given the first public demonstration of ether anesthesia,¹ during which JC Warren ligated a congenital lymphovascular malformation from Edward Abbott’s jaw on 16 October 1846 at the later famous MGH ether dome.²

Only three days later on 19 December, in Boott’s home at 24 Gower Street, a dental surgeon James Robinson administered ether to a young woman undergoing a molar tooth extraction—the first use of general anesthesia in England. A few days later, Snow witnessed the use of ether and immediately extended his work to study the effects of the inhalation of ether. He quickly developed an anesthetic practice in many London hospitals with eminent surgeons, including Robert Liston, William Fergusson, and Caesar Hawkins.

He presented “Comments on inhalation of ether” to the Westminster Medical Society on 16 January 1847, published in the London Medical Gazette six days later. In August 1847, Snow produced his original ether inhaler (Fig 2) and in October 1847 published “On the Inhalation of the Vapour of Ether in Surgical Operations…and the results of nearly eighty operations in which ether has been employed in St George’s and University College hospitals.”

Favorable reviews encouraged him to publish a series of papers between 1848 and 1851 in the Lancet and London Medical Gazette,^3,4 in which he described his experiences using several anesthetic agents. He importantly described five identifiable stages of the anesthetic process, which enabled doctors to interpret the patient’s physiological signs and to adjust the anesthetic accordingly.⁵

He advanced the use of chloroform, which had been first administered in November 1847 by the Scottish obstetrician James Young Simpson. Snow’s reputation for safety and experience led to his successful administration of anesthesia to Queen Victoria during the births of Prince Leopold (1853) and Princess Beatrice (1857).⁶ Given the controversy about the safety of chloroform and its justification in childbirth, Snow’s attendance exposed both the queen and his reputation to considerable risk.

Cholera and the Broad Street pump

Despite the originality and importance of this anesthetic work, Snow is better known for eradicating a cholera outbreak in London (Fig 3). A major outbreak of cholera with some six hundred deaths swept through Soho, London, in 1854; previous epidemics had occurred in 1832 and 1849. At the time, cholera was considered an airborne infection or miasma arising from foul smells or from decaying animal flesh in knacker’s yards. But Snow thought this unlikely and set out to map cholera death rates in selected London districts.

He compiled a detailed hand-drawn map, plotting the locations of all reported cholera cases as dots (known as a “dot map”) and correlated them with the places where the public water pumps were sited:

On proceeding to the spot, I found that nearly all the deaths had taken place within a short distance of the [Broad Street] pump.⁷

Evidence suggested to him that cholera was a waterborne infection. Firstly, he noted that houses that drew water from the Lambeth Water Company (free from heavy fecal contamination) had few cases of cholera. In contrast, homes supplied by the Southwark and Vauxhall Water Company (which drew water from the lower reaches of the Thames) had a high incidence of cholera.⁶ Secondly, he observed that workers in a nearby brewery remained healthy because they preferred beer to water from the pump. And local residents told him the Broad Street* water pump (Fig 4) gave off an odious smell. He also identified one woman living far away who died of cholera but drank water from the Broad Street pump because she preferred its taste.

Sydney Smith, the famous Anglican cleric, in an 1851 memoir similarly blamed drinking water: “He who drinks a tumbler of London Water has literally in his stomach more animated beings than there are Men, Women and Children on the face of the Globe.”

Snow persuaded the local authorities to remove the handle of the pump: the cholera outbreak quickly subsided. Ironically, the medical profession for many years did not accept his conclusions. The germ theory of infections had not yet developed, thus Snow did not know the etiological bacterium by which cholera was transmitted. He published his findings “On the pathology and Mode of Communication of Cholera” in 1849.^8,9,10 It cost him £200 to produce, but his income was only £3.12s.

It was subsequently confirmed that the pump’s water had been contaminated by sewage, which contained cholera bacteria from a nearby cesspit. Another crucial factor in eliminating cholera, dysentery, and typhoid was Joseph Bazalgette¹¹ who laboriously created 1,100 miles of street sewers whose noxious effluent was pumped and transported to treatment works sited eastwards of the city into the Thames at high tide.

John Snow was a quiet, reserved but resolute man of great integrity.¹² He was a vegetarian. Aged only forty-five, he had a fatal stroke in June 1858 and was buried in the Brompton Cemetery. A pub near the pump was named the “John Snow” in his honor. The University of Durham founded the John Snow College in 2001, which has seven blocks named after the roads surrounding the Broad Street pump. The John Snow Society promotes his life and works.

End note

* Now named Broadwick Street

References

1. The John Snow Archive and Research Companion. https://johnsnow.matrix.msu.edu/publications.php
2. Firth PG. Ether Day Revisited. The Surgical Records of Edward Gilbert. Ann Surg Open. 2022 May 17;3(2):e166. 
3. Snow J. On the inhalation of chloroform and ether, with description of an apparatus, Lancet 1848;1:177-80.
4. Snow J. On narcotism by the inhalation of vapours. London Medical Gazette 1848;11: 749–54. 1850;12:622-7.
5. Shephard DAE. History of Anaesthesia. John Snow and Research. Can J Anaesth 1989;36(2):224-41.
6. Ramsay, Michael A. E. (6 January 2009). John Snow, MD: anaesthetist to the Queen of England and pioneer epidemiologist. Proceedings Baylor University. Medical Center 2006;19(1):24-28. https://pmc.ncbi.nlm.nih.gov/articles/PMC1325279/
7. Snow J. The cholera near Golden–Square, and at Deptford. The Medical Times and Gazette. 2nd series. 1854;9:321-2.
8. Snow J. On the Mode of Communication of Cholera. London: John Churchill, September 1849.
9. Snow J. On the pathology and mode of communication of cholera. London Medical Gazette 1849;44:745-52. Part 1.
10. Snow J. On the pathology and mode of communication of cholera, London Medical Gazette 1849;44:923-9. Part 2.
11. Pearce JMS. Epidemic cholera and Joseph William Bazalgette. Hektoen Int Fall 2021. https://hekint.org/2021/12/22/epidemic-cholera-and-joseph-william-bazalgette/
12. Sir Benjamin Ward Richardson. John Snow, M.D., A Representative Of Medical Science and Art of the Victorian Era. Brit. J. Anaesth 1952; 24: 267. (Reprinted from The Asclepiad of1866).