William Guy is the Victorian statistician after whom the Royal Statistical Society’s Guy Medal and William Guy Lecturers are named. In an era of poor public health, his insistence that statistics and probability be applied to medicine helped change minds and lives
Up until the 19th century, ‘statists’ were fact-gathering statesmen; ‘statistics’ merely the facts and figures they collected to describe their nations’ resources. But, during that century, statistics began to find a broader meaning: facts and figures that could be valuable not just to politicians but to the public.
This was an age of cholera, smallpox and tuberculosis, as well as health problems brought on by industrialisation, and poor living and working conditions. As the work of early epidemiologists and members of the new Statistical Society of London (SSL) showed, statistics were a way of keeping tabs on disease. But they were also facts and figures that could help usher in new treatments and interventions, as well as new legislation to improve public health.
William Guy, one of the founders of the SSL (later the Royal Statistical Society, RSS), was a 19th-century champion for medical statistics and public health. His contributions are recognised by the RSS’s Guy Medals, awarded since 1892.
Guy was a tireless promoter of what he called “the numerical method” – often preferring this term to the “barbarous” term “statistics” – who used figures to illustrate his investigations of everything from cholera to arsenic poisoning. He wrote numerous papers for the Journal of the SSL and gave important lectures explaining the nature of statistics.
The cathedral in William Guy’s birthplace of Chichester; Guy’s surgeon grandfather had a family vault built in the cathedral. Photo: Dan Edwards/Unsplash
“I think he was the one Victorian statistician who thought most about methodology – how to conduct statistical investigations – and about statistics as a discipline,” says University of Oxford historian, Lawrence Goldman. In his 2022 book, Victorians and Numbers, Goldman calls him “one of the chief propagandists for statistics, a writer of manifestos and interpreter of the work of others”.
Born into Regency era Chichester, in 1810, Guy came from three generations of medics. Chichester was then a clean, elegant market town supplying wool to London and the north of England. Guy’s grandfather, an “eminent surgeon”, lived near its tall-spired cathedral and had a family vault built there. The family was well-situated, it seems, but the young Guy and his work would come to benefit a wider cross-section of society.
After his mother died, Guy was sent to school at Christ’s Hospital in Hertford, presumably with one career path in mind. He graduated from a medical degree at age 27, having already studied at Guy’s Hospital, London (no connection to his own family), as well as, crucially, in Paris. It was here that a revolution in medical statistics had already begun.
Guy contended that doctors should be describing the effects of diseases and treatments using hard figures
“Paris was really the epicentre for these new ideas and the application of statistics and probability to medicine,” says Penny Reynolds, a medical statistician at the University of Florida. “Guy was there …with a lot of other really famous doctors.” One of whom was the French ‘Father of Epidemiology’, Pierre Charles-Alexandre Louis, who became a mentor to Guy.
Doctors of that time treated based on experience, but Louis thought the best treatments could be established by looking at what worked on average, across groups of patients. In the 1830s, his reports on bloodletting as a treatment sparked debate among the Paris medical elite for their use of numbers. As Edward Huth wrote in 2008, “Louis’s reports stimulated advocacy of la methode numérique (the numeric method) for formal judgments on the efficacy of treatments, rather than simply accepting physicians’ opinions.”
Back in England, Guy took up a post as professor of forensic medicine at King’s College London – one he would hold for over 30 years – and, as a subscriber to Louis’s methods, began arguing the case for applying statistics to medicine. He had already cofounded the SSL with William Farr, a lapsed doctor who became well-respected for his work at the General Register Office on statistics, population censuses and classifying disease. In an 1839 paper Guy wrote for the Society’s journal, he contended that doctors should be describing the effects of diseases and treatments using hard figures, contrasting “the numbers 1, 10, 100, 1000”, which “have but one meaning for all mankind”, to terms more commonly used by doctors, like “sometimes” and “occasionally”.
This paper was what Goldman calls Guy’s “manifesto” for medical statistics, in which he suggested that statistics collected by doctors could provide the foundations for new laws to improve standards of hygiene and reduce preventable diseases. Scientists’ understanding of infectious disease was still rudimentary at this time; “germ theory” was on the way in, but in the mid-century, the “miasma” (bad air) theory of the Middle Ages still had to be overturned.
Guy challenged the prevailing view that dirt led to disease led to poverty – that being poor was “your own fault”, for being dirty
Meanwhile, the work of Louis, and Belgian mathematician Adolphe Quetelet (whom Guy often quoted), as well Louis Denis Jules Gavarret – whose book, General Principles of Medical Statistics (1840), was considered pivotal – contributed to a growing sense that averages and patterns distilled from large enough quantities of data could make the practice of medicine more predictable. Gavarret also drew from Poisson’s probability calculations to explain why Louis’ bloodletting studies were flawed, arguing that larger numbers of cases would be needed to reach reliable conclusions on medical treatments.
From a practical perspective, Guy wasn’t wholly convinced of Gavarret’s arguments, which he thought called for impossibly large quantities of data. But, while he wasn’t a theorist, or as skilled a mathematician as some of his contemporaries, he helped show the value of their work and of medical statistics. And, as a writer and lecturer, he made extensive use of facts and figures to demonstrate his own points. During his Croonian lectures in 1860 – prestigious talks later published in the British Medical Journal – he often quoted from death data produced by Farr’s colleagues at the General Register Office to discuss the numbers of “facts” that would be needed to approximate trustworthy averages.
According to Reynolds, Guy was also a “superb organiser”. He demonstrated this skill by rigorously organising his figures into neat tables. One on cholera deaths, for example, was cited by John Snow in his 1854 publication on the disease, in which he famously connected London cholera epidemics to the city’s water supply. Guy, who was interested in how people’s jobs affected their risk of certain conditions, had tabulated death ratios for every occupation from ballast-heaver to brass finisher. His table reinforced Snow’s theories by suggesting that those who drank river water at work were more susceptible to cholera. “[One] remarkable circumstance connected with Dr. Guy’s table…” Snow wrote, was that so few brewers died of cholera, probably because, he suggested “they never drink water”.
Much of Guy’s data came from King’s College Hospital, where he was involved with the care of outpatients starting from 1841. Guy was by now living on Bloomsbury Square in London – where he must also have met his wife Georgina Lucinda Wright, the daughter of a retired colonel living on the adjoining street.
William Guy, 1874. National Library of Medicine/Public Domain
In one study, Guy tabulated figures from the hospital to compare tuberculosis deaths across groups of workers in different jobs. The study has been called “the first case-control study”, though this claim, and the validity of Guy’s conclusions – suggesting active jobs protected against the disease – remain contestable. However, as Reynolds points out, “[Guy’s] recognition of the relationship between occupation and disease was really noteworthy.” He went on to conduct detailed studies on the contributions of working conditions to ill health in industries such as printing, which called for long hours spent working with lead type and new steam-powered presses in dusty, crowded, poorly ventilated offices.
Guy challenged the prevailing view that dirt led to disease led to poverty – that being poor was, as Reynold puts it, “your own fault”, for being dirty. By distinguishing between dirt and disease, and questioning whether poor living and working conditions could cause ill health, doctors like Snow and Guy started to change the narrative. Asked, in 1844, for his opinion on the causes of tuberculosis, for example, Guy stated that, “tradesmen in London… are nearly twice as liable to consumption as the gentry”, saying that he accounted for the difference via “their confinement during so many hours of every day in ill-ventilated shops”.
Among other subjects, he studied prison diets, illnesses of “nightmen, scavengers and dustmen”, and deaths in workhouses and asylums
Guy was becoming a public health leader. He was a founder of the Health of Towns Association, which helped bring in the landmark Public Health Act of 1848, and went on to write a popular text on public health. Meanwhile, he carried out work for the Privy Council’s John Simon, who was establishing a more scientific approach to studying it. In 1862, Simon commissioned Guy to investigate illness caused by Scheele’s green, an arsenic-containing pigment used as a colouring for artificial flowers and wallpapers. Guy took the opportunity to promote evidence-based policymaking, gathering enough evidence to suggest a health problem and then advising that the premises making and using the pigment should be registered and inspected.
It was for his book, Principles of Forensic Medicine (1844), though, that Guy had become renowned among medics – the text was often consulted in legal cases. Guy was consulted directly too, but as a rather personal obituary in The Lancet notes, “nothing would induce him to appear publicly”. He was “too sensitive”, the article claims – and sceptical of the legal system when it came to medical cases.
Guy must have kept himself in fine fettle, because he died aged 76 at a time when the average life expectancy for a man in England was 44. While little is written about his personal life, it appears he and Georgina were still together in London in the 1880s, living comfortably with a cook and a housemaid. Yet, during his long career, Guy turned his attention, as Chinese researchers (translated) note, to “the health of every social class, from the nobility to the common people”. Among other subjects, he studied prison diets, illnesses of “nightmen, scavengers and dustmen”, and deaths in workhouses and asylums.
Although Guy may not have been the most famous Victorian statistician, he was admirable, according to Goldman, for trying to figure out the purposes and methods of social statistics. “Many of his contemporaries just piled up the numbers,” Goldman says. “Guy thought hard about what they were doing.” And, it’s clear, whom they might help.
Hayley Bennett is a science writer based in Bristol, UK.
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