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Snow, John

John Snow

British physician John Snow (1813–1858) is called the "father of epidemiology" (the prevention and control of disease) because of his innovative investigative methods. Living in England's Victorian era, he gained prominence as one of the first physicians to use anesthesia. During a cholera epidemic of 1854, he revealed that the disease was caused by water–borne microorganisms.

John Snow was born in York, England on March 15, 1813, the oldest of nine children. His father, William Snow, was an unskilled laborer, and his family lived in one of the poorest sections of York, which was an industrial shipping area located on the River Ouse. Until he was 14, Snow was educated at a common day school for poor families. In 1827, he traveled to Newcastle–upon–Tyne, 80 miles from his home, where he began serving a six–year apprenticeship in medicine under surgeon William Hardcastle. From Hardcastle, Snow learned the daily realities of running a medical practice. The apprenticeship included attending lectures at the Newcastle Infirmary. During this apprenticeship, which lasted until 1833, Snow became a vegetarian as well as a total abstainer of alcohol.

Advanced Medical Education

While in Newcastle, Snow was employed as one of three surgeon apothecaries at the Lying–In Hospital. He also worked as a secretary. In addition, he held an appointment as mining doctor at the Killingworth Colliery. Through this appointment, he came to know George and Robert Stephenson, the father and son team of locomotive engine designers who hailed from the area. In 1827, they were listed as patients in Snow's practice.

During the cholera epidemic that lasted from 1831 to 1832 that hit a coal mining region near Newcastle, Snow worked as a colliery surgeon and unqualified assistant, treating victims. Cholera caused diarrhea and vomiting and, at the time, was fatal in about fifty percent of all cases. Victims usually died within two or three days, from dehydration. From the 1830s through the 1850s, Snow would come in close contact with the devastation the disease caused, and later in his career he would become keenly interested in preventing its outbreak.

Between 1833 and 1836 he was an assistant in practices in Burnopfield, Durham, and in Pateley Bridge, North Yorkshire. In addition, he often returned to his home town of York, where he was involved in the temperance movement, which sought to restrict the consumption of alcohol. Also in York, Snow joined the practice of Joseph Warburton.

In 1836, Snow decided to advance his medical education. In October, he moved to London, where he began advanced studies at the Hunterian School of Medicine at Great Windmill Street. Snow made the journey on foot, following a path that took him through Liverpool, Wales, and Bath. His initial research involved the toxicity of arsenic. The following year, he attended the medical practice at the Westminster Hospital and, in May 1838, he was admitted as a member of the Royal College of Surgeons of England. In October of that year he became a licentiate of the Society of Apothecaries and then set up his own practice at 54 Frith Street, in the Soho district of London. Still, he continued his medical education, regularly attending the meetings of the Westminster Medical Society (which would later become known as the Medical Society of London), where he would present results of his own research on various scientific issues.

Published Articles

Snow also wrote up his research as articles that were published in medical journals in the late 1830s and early 1840s. In this way, his name became well known in English medical circles. His topics of interest included toxicology and respiratory physiology. Specific subjects included the danger of candles incorporating arsenic, postscarlatinal anasarca, and haemorrhagic smallpox. His first published paper, "Arsenic as a Preservative of Dead Bodies," appeared in the prestigious British medical journal The Lancet in 1838. But his best–known paper, "On Asphyxia, and on the Resuscitation of Still–born Children," was published in 1842. His research in this area would later lead to his interest in anesthesia.

In November 1843, he earned a bachelor of medicine degree from the University of London and, on December 20, 1844, he graduated with a doctorate of medicine from the institution. However, all of Snow's hard work took a toll, and he experienced a physical breakdown. In 1844, he suffered health problems, including an attack of tuberculosis and kidney disease. Health problems would trouble him all through his life after this.

In 1845, he was appointed lecturer on forensic medicine at the Aldergate Street School of Medicine. He held the position until 1849, when the school closed down. In June 1850, he became a Licentiate of the Royal College of Physicians of London.

Became Interested in Anesthesia

In the late–1840s, Snow became interested in anesthesia, particularly ether, which was starting to be used as an anesthetic in America. In England, the use of anesthesia was first demonstrated by dentist James Robinson in 1846. Snow investigated the medical efficacy of ether as an anesthetic, and then he made improvements on how the drug was administered by designing his own inhaler. He was granted permission to demonstrate the results of his research in the dental out–patient room at St. George's Hospital. In 1847, after he published a textbook on the administration and effects of anesthetic vapors, Snow became a recognized leader in anesthesiology in London, and he investigated the use of other anaesthetizing agents, including chloroform. On April 7, 1853, Snow made news in England when he administered chloroform to Queen Victoria when she gave birth to Prince Leopold. He used the agent on the Queen once again during the birth of Princess Beatrice on April 14, 1857.

As a physician, Snow treated patients from a range of social backgrounds, and he frequently practiced medicine in the poorest sections of London, providing good medical care to those who could least afford it. In 1852, the Medical Society of London (previously the Westminster Medical Society), chose Snow to be its orator for the coming year. In 1853, he moved his home and practice to 18 Sackville Street. On March 10, 1855, he was inducted as the Medical Society's president. Snow also was a member of the Royal Medical Chirurgical Society and the Pathological Society. In 1854, he served as president of the Physiological Society. In 1857, he was president of the Epidemiological Society.

Investigated Cholera Epidemic

Along with anesthesiology, Snow's major interest included cholera. For a period of 20 years, London was ravaged by outbreaks of cholera epidemics. Snow became very interested in the cause and transmission of the disease in 1832, while he was still a medical apprentice and treated cholera victims.

In 1849, he published a pamphlet, "On the Mode of Communication of Cholera," which countered the conventional thinking regarding the disease. In the pamphlet, Snow remarked how the disease had a tendency to occur in the late summer, most often in the poorest sections of England, and in localized and isolated areas. He determined that cholera was a contagious disease caused by a poison that reproduces in the human body and is found in the vomitus and stools of cholera patients. Further, he suspected that cholera was spread through the microorganism contamination of food and water, but the foremost manner of transmission, he stated, was water contaminated with the poison. According to the prevailing theory, diseases such as cholera were transmitted by breathing in "miasmas," or contaminated vapors.

Despite contradicting the commonly held theory, Snow's pamphlet did not generate any great controversy, as many other theories about cholera were being advanced at the time. Still, he received a good deal of positive notoriety for his work, even though he had no way to prove his theory. However, another outbreak provided Snow the opportunity to prove that his ideas were indeed correct. In 1854, another severe cholera epidemic struck London, in a small area in Soho, where more than six hundred people died. Snow immediately began investigating water sources in the area. He was able to demonstrate—by thoroughly documenting, correlating, and comparing locations of cholera cases among the customer's of London's two water companies—that a higher concentration of incidents occurred among customers of one water company, the Southwark and Vauxhall. The company got its water from the downstream part of the Thames river, an area that was contaminated with London sewage. The other company got its water upstream from the main part of the city, where it was less likely to be contaminated. Snow's evidence was very strong, and it changed many minds.

One situation in particular underscored the soundness of Snow's theory. By mapping the location of cholera–related deaths, Snow found that in one area of the city, at the intersection of Cambridge Street and Broad Street, there was a higher concentration of cholera cases: more than 500 deaths occurred in only ten days. After investigating the situation, Snow determined the cause of so many deaths was due to a water pump on Broad Street. Before the outbreak, the pump had been reportedly discharging a foamy brown water that smelled like raw sewage. The cause of the odor soon became understandable. Further investigation revealed the that well of the pump was about 28 feet deep. At 22 feet, and only yards from the well, was a sewer. Snow was now certain that sewage had contaminated the water.

Snow strongly encouraged officials to remove the pump. The officials were doubtful but followed Snow's advice anyway. The epidemic was soon contained. Moreover, publicity from this part of this investigation drew a great deal of attention to the extremely poor sanitation conditions in London. Officials began a complete renovation of the city's water and sewage systems. As a result, there were no more outbreaks of cholera.

Snow's original 1849 pamphlet, "On the Mode of Communication of Cholera," was awarded a monetary prize from the Institute of France. A second edition of the pamphlet was published in 1855. This one contained a more detailed investigation into the effects of water supplies on certain districts of South London during the 1854 epidemic. Snow's insights and innovative methods led to widespread recognition.

Died Young

During his adult life, Snow suffered chronic health problems, including kidney disease, which led to his premature death on June 16, 1858. He was only 45 years old. At the time of his death, he had been engaged in ongoing research and was preparing a manuscript, "Chloroform and Other Anaesthetics." The work eventually was published posthumously by his friend and colleague Sir Benjamin Ward Richardson. Shortly before his death, he suffered a stroke that left him incapacitated. Although the stroke was given as the direct cause of death, an autopsy revealed that his overall health had been negatively affected by earlier attacks of tuberculosis. Snow, who never married, was buried in the Brompton cemetery, where a monument was erected in his memory.


Because of his pioneering work on London's cholera epidemic, Snow became known as the "father of modern epidemiology." His methods forever changed the way illness, on a widespread scale, would be managed. The information he collected and the maps he created during the 1854 epidemic, which showed how the disease was distributed in relation to water sources, essentially became the first–ever epidemiological survey of an illness. Of course, through the years, medical researchers have built upon Snow's methodology, but he led the way. Modern disease prevention and control owes a great deal to Snow.

As a footnote to Snow's illustrious career, the handle from the infamous Broad Street pump still exists, and it is housed at the John Snow Pub, which is located near the former site of the pump. To honor the memory of the man who contributed so much to modern medicine, a John Snow Society was formed. The only requirement for membership is that one visits the John Snow Pub while in London.


World of Health, Gale Group, 2000.


"Biography of John Snow," UCLA Department of Epidemiology, (December 31, 2004).

"John Snow," BBC Online,–figures/snow–john.shtml (December 31, 2004).

"John Snow," Center for Disease Control and Prevention, (December 31, 2004).

"John Snow (1813–1858)," Royal College of Physicians, (December 31, 2004).

"John Snow: The London Cholera Epidemic of 1854," Center for Spatially Integrated Social Science, (December 31, 2004).

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Snow, John


(b. York, England, 15 March 1813; d. London, England, 16 June 1858)

medicine, anesthesiology, epidemiology.

Snow was the eldest son of a farmer. Little is known of his early life, but at the age of fourteen he was apprenticed to William Hardcastle, surgeon, of Newcastle upon Tyne. He is said to have been industrious and studious, and at the age of seventeen became imbued with vegetarianism and temperance, beliefs which he held—almost to the extent of obsession– to the end of his life, and which he carried into his medical practice. (Although it is reported that later in life he occasionally and of necessity took a little wine.)

In 1831 the first cholera epidemic struck England, entering through Sunderland, a seaport near Newcastle, which suffered a disastrous visitation. Snow was sent to the nearby Killingworth colliery, where in appalling conditions he worked indefatigahly and laid the foundations of his interest in, and knowledge of cholera, for which no cure was known, and which was frequently fatal.

Moving to London in 1836, Snow studied at Westminster Hospital and became a member of the Royal College of Surgeons and a licentiate of the Society of Apothecaries. In 1843 he graduated M.B. from the University of London and in the following year proceeded M.D. The only course then open to him was to enter general practice, and to use his own words, Snow “nailed up his colours” at 54 Frith Street, Soho. He never married, and his life in practice consisted in assiduous attention to his patients (mostly of the working classes), to posts such as that of visitor to outpatients in Charing Cross Hospital, and to his two great contributions to medicine. Snow’s friend and biographer, Benjamin Ward Richardson, described him as reserved and lonely with a dry sense of humor.

In 1841 Snow read to the Westminster Medical Society “Asphyxia and the Resuscitation of Newborn Children.” In this paper he described a double air pump and gave some of his ideas on lack of oxygen. Since he had made other similar studies on the physiology of respiration, his knowledge placed him in a favorable position when ether was introduced as an anesthetic in 1846. The first major operation in England in which the new drug was used was an amputation of a leg performed by Robert Liston at University College Hospital, London, on 21 December 1846, with William Squire administering the ether. Snow at once began experimenting with the substance and invented an apparatus for its administration, based on physiological principles. He demonstrated its use at St. George’s Hospital with so much smoothness and success that he was invited to work with Liston, and later with most of the well-known surgeons of London. Rapidly Snow became the premier anesthetist of the country. In September 1847 he published his masterly little book On Ether, which included a description of his apparatus and of the properties of the drug, together with physiological and practical information regarding its administration. His division of the stages of anesthesia into five degrees was not improved upon until the work of Arthur Guedel in 1917.

When chloroform was introduced into anesthesia by James Young Simpson in November 1847, Snow was quick to appreciate the advantages and disadvantages of the new drug. Snow’s expertise in apparatus led him to construct new pieces for the administration of chloroform. He laid emphasis on the use of such apparatus as a means of delivering low and exact percentages of chloroform in air; this was in direct contrast to Simpson’s “open method” of dropping chloroform on the corner of a towel or handkerchief. The controversy between protagonists of the two methods lasted for the remainder of the century, but Snow was the pioneer in raising the art and practice of English anesthesia and anesthetic apparatus to its subsequent heights.

Simpson’s goal had been the prevention of the pangs of childbirth, and he fought valiantly against religious and medical prejudice. Anesthesia, however, became respectable on 7 April 1853, when Snow administered chloroform to Queen Victoria at the birth of Prince Leopold, the so-called “chloroform à la reine.” Snow continued his work in anesthesia for the remainder of his short life. He introduced amylene in 1856, and his great book On Chloroform, completed a few days before his death, was edited by B. W. Richardson, who added a definitive biography.

During these years Snow was occupied also with investigations of cholera, which many will consider as giving him an even greater claim to recognition as a benefactor of humanity. Since his interest in the disease had been aroused by his earlier work in the colliery near Newcastle, recurrent outbreaks in London gave him opportunity and experience, and in 1849 he wrote the first of many papers and published his book On the Mode of Communication of Cholera. Many physicians still believed in the ancient view that infectious diseases such as cholera and smallpox were carried by “miasmas” or evil humors arising from mud, sewage, or other noxious sources. Snow’s theory and proof of transmission by water infected with fecal matter was to provoke controversy between supporters of Snow, such as William Budd, and the “miasmatists.” Even workers in the Board of Health were slow to alter their ideas.

In the great London epidemic of 1854, Snow’s genius as an epidemiologist and statistician reached fruition. By meticulous survey he established that the areas supplied by water from the Southwark and Vauxhall Water Company, obtained from the fecal-contaminated Thames, were infected nine times more fatally than the areas supplied by the Lambeth Company, which supplied water from an upstream source.

Even more dramatic was the affair of the Broad Street pump, which he showed by careful plotting to be in the center of a cholera outbreak in his own parish of Soho. Within a few hundred yards of this pump, some five hundred fatal cases occurred in ten days. Snow found that a sewer pipe passed within a few feet of the well, and his belief that contaminated water was the source of infection was vindicated when he persuaded the parish councillors to remove the pump handle.

Pasteur and Lister had not yet published their work on microorganisms and infection, and the vibrio of cholera was not to be described by Koch till 1884. Snow’s reasoned argument was that cholera was propagated by a specific living, waterborne self-reproducing cell or germ. He recommended sensible precautions such as decontamination of soiled linen, washing hands, and boiling water. In treatment, he believed in the use of saline fluids, given intravenously, although techniques were hardly sufficiently advanced to make full use of this advice, which is now the basis of modern treatment. Snow’s writings and practice were a very considerable influence upon the great sanitary reformers such as Sir John Simon and Sir Edwin Chadwick in the later part of the century. He was a founder of the Epidemiological Society.

Tired and worn by overwork, and perhaps undermined by too ascetic a way of life, Snow died of a cerebral hemorrhage at the age of forty-five. He was buried in Brompton churchyard, where his tumbstone, originally erected by Richardson, was reconstructed in 1947 by the Association of Anaesthetists of Great Britain and Ireland.


I. Ooriginal Works. Snow wrote over 30 papers on cholera and matters of public health, and a similar number on ether, chloroform, other anesthetics, and respiratory physiology. Among the most important works on cholera, are On the Mode of Communication of Cholera (London. 1849; 2nd ed.,1855); “On the Pathology and Mode of Communication of Cholera,” in London Medical Gazette, 44 (1849), 730, 745, 923: “On the Communication of Cholera by Impure Thames Water,” in Medical Times and Gazette, n.s. 9 (1854), 365–366; “On the Chief Cause of the Recent Sickness and Mortality in the Crimea,” ibid., n.s. 10 (1855), 457–458; and “Drainage and Water Supply in Connection With the Public Health.” ibid., n.s. 16 (1858), 161, 189.

On anesthesia, see “Asphyxia and the Resuscitation of New-born Children,” in London Medical Gazette, n.s. I (1842), 222–227; On the Inhalation of the Vapour of Ether in Surgical Operations (London, 1847); “On the Use of Ether as an Anaesthetic ...,” in London Medical Gazette, n.s. 4 (1847), 156–157; “On the Inhalation of Chloroform and Ether,” in Lancet (1848), I , 177–180: “On Narcotism by the Inhalation of Vapours,” in London Medical Gazette, in 16 parts from n.s. 6 (1848) to n.s. 12 (1851); “Death From Inhalation of Chloroform,” in Association Medical Journal, I (1853), 134; “On the Administration of Chloroform During Parturition,” ibid., I (1853), 500–502; and On Chloroform and Other Anaesthetics (London, 1858).

II. Secondary Literature. The chief biographical source on Snow is Benjamin W. Richardson’s memoir in On Chloroform and Other Anaesthetics. An obituary is in Medical Times and Gazette, n.s. 16 (1858), 633–634; and reviews (written almost as obituaries) of Snow’s posthumous book are in Lancet (1858), 1 555–556: and in British Medical Journal (1858), II , 1047–1049.

See also Lord Cohen of Birkenhead, “John Snow— the Autumn Loiterer?” in Proceedings of the Royal Society of Medicine, 62 (1969), 99–106; B. Duncum. The Development of Inhalation Anaesthesia (Oxford, 1947), with an extensive discussion of Snow’s work on anesthesia: J. Edwards, “John Snow, M.D. , 1813–1858,” in Anaesthesia, 14 (1959), 113–126; and K. B. Thomas. “John Snow, 1813–1858,” in Journal of the Royal College of General Practitioners, 16 (1968), 85–94.

Snow MSS are in the Clover/Snow Collection of the Woodward Biomedical Library, University of British Columbia (annotated by K. B. Thomas, in Anaesthesia, 27 [1972], 436–449).

K. Bryn Thomas

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Snow, John


John Snow (18131858) was a London physician and a founding father of modern epidemiology. He was a pioneer anesthetist who invented a new kind of mask to administer chloroform, which he used on Queen Victoria to assist at the births of her two youngest children. He was an astute clinician and kept meticulously detailed notes about his patients and their diseases. His work on cholera was of lasting value because it demonstrated several fundamental intellectual steps that must be part of every epidemiologic investigation. He began with a logical analysis of the then available facts, which demonstrated that cholera could not be due to a "miasma," a theory that was then popular. It could only be caused, Snow determined, by a transmissible agent, most probably in drinking water.

Having arrived at this logical conclusion, Snow conducted two epoch-making epidemiological investigations in the great cholera epidemic of 1853 to 1854. One was a study of a severe, localized epidemic in Soho, using analysis of descriptive epidemiologic data and spot maps to demonstrate that the cause was polluted water from a pump in Broad Street. His investigation of the more widespread epidemic in South London involved him in an inquiry into the source of drinking water used in some seven hundred households. Snow compared the water source in houses where cholera had occurred with that in houses where it had not. His analysis showed beyond doubt that the cause of the epidemic was water that was being supplied to houses by the Southwark and Vauxhall water company, which drew its water from the Thames downriver, from London, where many effluent discharges polluted the water. Snow found that very few cases occurred in households supplied with water by the Lambeth company, which collected water upstream from London, where there was little or no pollution. Snow's work was remarkable in that it was completed thirty years before Robert Koch identified the cholera bacillus. Snow published his work in a monograph, On the Mode of Communication of Cholera (1855). This classic book has been reprinted in several modern editions and is still used as a teaching text in courses of epidemiology.

John M. Last

(see also: Filth Diseases; Miasma Theory )


Snow, J. (1855). On the Mode of Communication of Cholera. Reprint. New York: Haffner, 1965.

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