DataViz History: The Ghost Map: Dr. John Snow

Dr. John SnowJohn Snow (1813–1858) is revered as a founding father of two medical disciplines. Anesthesiologists remember him as the physician who first made anesthesia scientific by showing how the human body responded to different doses of anesthetic drugs, and how anesthesia affected the human physiology. In addition, Snow the practicing anesthetist is widely known for the inhalers he designed and for administering chloroform to Queen Victoria during the delivery of two of her children. He is also celebrated as a founder of the modern science of epidemiology, and as an exemplar of the notion that physicians should apply their expertise toward the amelioration of public health problems. During the cholera epidemic in London, 1848–49, Snow proposed the unconventional notion that the dread disease was caused by a particle that was ingested orally, rather than by a befouled component of miasmatic air. Then, during the epidemic of 1853–54, he gathered the body of data that others would cite after his death as conclusively supporting his theory that cholera was primarily spread by sewage–contaminated water. These investigations — locally around the Broad Street pump, and more widely into the water supply of South London — are still taught to epidemiology students today as models of scientific reasoning. [SOURCE]

Snow formulated his theory of cholera transmission and undertook shoe–leather epidemiological investigations a decade before Pasteur’s ground–breaking experiments on microbes. His ability to reason among events occurring at different levels of organization — from the molecular to the physiological, from clinical observations on individual patients to data drawn from entire populations — presage the “biopsychosocial model” of health and disease developed in the 1970s.

John Snow was the oldest child of a laboring–class family in York. His father eventually became a farmer and landlord, with sufficient property value to make him eligible to vote after the first Reform Bill of 1832. Snow, himself, undertook a parallel path in social mobility, from medical apprentice to separate qualifications as a surgeon, apothecary, and physician. He was apprenticed at the age of fourteen to a surgeon–apothecary in Newcastle for six years. Thereafter, he served as an uncertified assistant apothecary for a year in rural Durham and two years in rural West Yorkshire. In the late summer of 1836, he walked from York to London, via Liverpool, Wales, and Bath. He attended lectures at the Hunterian School of Medicine and “walked the wards” at the Westminster Hospital. He qualified as a surgeon and as an apothecary in 1838, as a physician in 1844. He lived and practiced in metropolitan London until his death in 1858.

Jeffrey's Vaporizer
Adapted from LMG 29 (1841-42): 821-22. Snow had used Julius Jeffrey’s vaporizer in his clinical practice. In January 1847 Snow designed an inhaler in which the volute and ether chamber were modeled on Jeffreys’ construction.

During his apprenticeship, he converted to vegetarianism. The book that influenced him toward adopting that diet stressed the disease–causing properties of impure drinking water, which may partly explain his attraction to a water–borne theory of cholera transmission almost two decades later. At this time, he also made a pledge to advance temperance, a cause in which he was joined by several family members and which he would support for the rest of his life.

Snow’s life and work are gateways into the social and intellectual history of medicine, particularly that of England during the early and middle years of the nineteenth century. A study of Snow reveals important issues of the day in general medical practice, clinical anesthesia, the control of infectious diseases, and the responsibility for sanitation policies — many of which remain of vital concern in science, medicine and public health today.

Sunday, September 3rd, 1854

The Soho neighborhood was eerily quiet. The streets were empty. People had packed up and evacuated or shuttered themselves in. The most common site on the streets were the priests and the doctors making frantic rounds.

Dr. John Snow stopped at the Broad Street pump. He examined it for several minutes. Then, he drew a bottle of water from the pump and started at it a little more. Then, he turned and when back to analyze this water closer at his lab in his home on Sackville Street.

Snow decided to ask William Farr for an early look at the mortality numbers. Perhaps the distribution of deaths would point to a contaminated water supply.

Snow needed to work quickly. The longer he waited, the more difficult his investigation would be. The witnesses were dying.

Next: Miasma Theory

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