John Snow - Father of Epidemiology - Bicentennial

John Snow

Twenty-two years ago I started working on the problem of presentation of adequate proof of causation of disease.  I was prompted by a question from the New Jersey Supreme Court.  Should we have a different standard of proof of causation in "increased risk cases"?  They ordered briefing and re-argument of a pair of cases in which plaintiffs alleged that their gastro-intestinal cancer was caused by exposure to asbestos.  I wrote a friend of the court brief for the Association of Trial Lawyers  of America - New Jersey chapter.  In the companion case Landrigan v. Celotex (1992) Justice Stewart Pollock wrote for the court that so long as the evidence was relevant and sound methods were used to reach a conclusion scientific opinion testimony should be admitted into evidence.

One year  later the U.S. Supreme Court reached the same conclusion - though the court's use of the term "gatekeeper" emboldened hundreds of Reagan-appointed federal judges to sweep hundreds of cases from the dockets, citing Daubert v. Merrell Dow Pharmaceuticals (1993).  The question which was presented by the defense in Daubert was whether a scientific theory had to achieve "general acceptance" before it could be admitted into evidence.  That absurd proposition - popularized by ideological conservatives like the propagandist/lawyer Peter Huber in his screed Galileo's Revenge - was rejected by the Supreme Court.

I initiated and co-authored  a friend of the court brief which a group of scientists embraced, including the late great paleontologist Stephen Jay Gould - whose clever columns in Natural History had introduced me to the history of science.  It was, in essence, a recitation of the thesis of Thomas Kuhn's The Structure of Scientific Revolutions.  It recognised that scientific ideas contend, that one "paradigm" replaces another, and that progress is imperfect because no single model explains all.  Kuhn used the example of the slow embrace of the helio-centric Copernican model of astronomy that replaced the geo-centric Ptolemaic theory.  
John Snow, the father of modern epidemiology, presents a different and compelling example.  His pioneering work as anesthesiologist led him to reject the then-prevailing "miasma" theory which asserted that cholera spread via the gases of decomposing organic matter.  
Snow was also a pioneer of mapping - an important tool in epidemiology.  Snow  correctly identified the source of the disease in fecal contamination of the London water supply, famously persuading the City to close the Broad Street pump.  
At his death the great scientist got short shrift from The Lancet, which has on the 200th anniversary of his 1813 birth  published  a new obituary and an article titled The Singular Science of John Snow, an excerpt from which follows.  - GWC

Snow's ether inhaler

"The step to becoming a cholera scientist is not so obvious. Snow had treated cholera as a teenage apprentice, assigned to the coal mines near Newcastle in the epidemic of 1831. But he wrote nothing about cholera until 1849, during the world's second cholera pandemic. Although then occupied intensely in experiments with anaesthetics and the clinical practice of anaesthesia, Snow published that year his theory of the faecal-oral transmission of the cholera agent, and the extension of that transmission when water supplies became contaminated with cholera evacuations.

The connection between the two fields was a negative one. Snow's understanding of how substances in gaseous form affected human physiology made it impossible for him to accept the reigning theory of how epidemic diseases arose and spread through miasmatic gases emanating from decaying animal or vegetable material, assisted by atmospheric changes that led to epidemics. This scepticism is muted in his cholera works, where his emphasis is nearly entirely on argument and evidence for his own theory, but found sharp expression in 1855, when he was called on to give parliamentary evidence in relation to the health risks of the “nuisance trades”, the bone boiling and hide tanning businesses in London. His argument, scathingly dismissed by The Lancet, and met with incredulity by several Members of Parliament, was that these trades, foul though they were, simply did not cause epidemic disease. The effects of gaseous emanations, as he knew well from his anaesthesia work, dropped off by the square of distance from the source. That gases carrying the cholera agent could affect people miles away was to Snow nonsensical."