Cholera in 1849 and the Biopsychosocial Model: Historical Analysis or Anachronism? The Snowflakes of MSU: Peter Vinten-Johansen Howard Brody Nigel Paneth Steve Rachman Michael Rip
The Argument • One can draw useful analogies between: • Today’s biopsychosocial model of human health, and • The scientific approaches used by John Snow to study both cholera transmission and inhalation anesthesia in 1846-56?
The Argument--II • The BPS model • John Snow and his career • Methods of studying anesthesia • Methods of studying cholera transmission • Snow’s theoretical synthesis (“continuous molecular changes”)
Engel, 1977: BPS Model • Systems (part-whole relations) • Multilevel hierarchy (atoms to biosphere) • “Ripple effects” among levels • Patterns of information flow (feedback loops) • Anti-reductionistic
BPS: Sources • General systems theory (von Bertalanffy, Laszlo) • Cybernetics (von Neumann), information theory, game theory • “Holistic” biology (Dubos, Mayr) • All grounded in mid-20th-century thought
John Snow: Early Life • Born 1813, York • Father: Laborer/farmer • Mother: Illegitimate • Apprentice in Newcastle, 1827-32 • Cared for coal miners in 1831-32 cholera epidemic
John Snow: Life (cont.) • Newcastle medical school, 1832-34 • Assistant, Newcastle and Yorkshire, 1834-36 • Walked to London (via Bath), 1836 • Hunterian school and Westminster Hospital, 1836-38 • MRCS/LSA, 1838 • General practice, Soho, 1838
John Snow: Later life • Active in Westminster Medical Society • MD, Univ. of London, 1844 • Begins anesthetic research and practice, 1847 • On the Mode of Communication of Cholera, 1849 • Attends Queen Victoria, 1853, 1857 • Broad Street Pump, 1854 • President, Medical Society of London, 1855 • Completes On Chloroform, 1858 • Death of apoplexy, 1858
Snow on Ether • Dec. 1846: Sees ether used in London • Jan. 1847: Displays data on relation between concentration and temperature; working on apparatus • September 1847: Publishes On Ether, 80 cases, describes degrees of anesthesia
How? • Snow’s research, 1838-46, ideally prepared him for ether: • Studies of respiration and asphyxia • Studies of chemistry and physics of gases • Properties of inhaled medications and poisons • Design of new apparatus
Snow’s Approach to Ether • Chemical level: problem in defining physics and chemistry e.g. concentration-temperature relationships • Physiological level: animal experiments with different concentrations of gases • Clinical level: correlate bedside observations with animal experiments to predict degrees of anesthesia
Ether and Chloroform • Define a class of agents with similar properties (“narcotism”), of which anesthesia only one effect • Calculate precise serum concentrations of agent when inhaled at given concentration in air • Correlate serum concentration with clinically observed effects • Hardly anyone else doing this work in 1847-58
Snow and Cholera: 1848-9 • Cholera must be communicable person-to-person based on geographic distribution • A local affection of alimentary canal; dehydration produces systemic symptoms • Assumed to be inhaled by lungs– why must this be true?
Snow’s Theory • Causal agent of cholera ingested • Multiplies in gut • Causes symptoms of disease by irritating mucous membrane • Shed in evacuations • Household spread: dirty hands • Area spread: drinking water
Budd, Brittain, Swayne 1849 • Microscopic particle must cause cholera • Therefore must search for evidence at microscopic level • Identified “cholera fungus” • Identification quickly refuted
Snow, 1849 Community Spread by contaminated drinking water Household Spread by poor hygiene Organ/System Irritation > Diarrhea > Dehydration Cellular Can’t identify agent; analogy to ova of intestinal worms Molecular “Continuous molecular changes” (self-replication of vital processes)
Snow on Cholera, 1849 • Move from levels where “collateral sciences” least developed to levels allowing better tools for investigation • Ova of worms: analogy of functional properties • Cf. “Cholera fungus”: identified a structure but had no idea of function
Cholera Deaths per 10,000 Households (Snow, 1855) (first weeks of epidemic) Lambeth Co. Southwark & Vauxhall Co.
Snow’s Method, 1849-1855 • Ultimately discovered that statistics was a sounder basis for investigation than microscopy • Reasoned across levels to deduce likely effects at neighborhood and community levels • Then gathered data to confirm or disconfirm hypotheses
CMC, 1853 • Annual oration to Medical Society of London • Rare opportunity to speak at theoretical-speculative level • Opportunity to link (successful) anesthesia research with (so far rejected) cholera theory
CMC, 1853-- II • “Molecular” = smallest level of organization, “insensible” (very small) distances between particles acting on each other • “Change” = constant flux at molecular level in either living or non-living matter (common chemical basis of vital and non-vital)
CMC, 1853--III • “Continuous” = molecular processes peculiar to living things; never commence anew without continuity with previous processes of same type • Combustion/oxidation– a bridging process, exists in both living and non-living matter
Anesthesia: Counter-Affinity A B C exerts pull on A and prevents A from combining with B, without itself combining C
Anesthesia Theory • C = anesthetic agent • A <-> B = oxidation process responsible for maintaining consciousness and sensation • Reversible interference with normal bodily process
CMC and Epidemic Diseases • Causative agent of disease enters body • By CMC, replicates itself inside body • Hijacks normal body processes of oxidation, etc. to support its own replication • Disruption of normal body processes causes symptoms of disease (irreversible in extreme cases)
“Communication” • “Mode of Communication” of epidemic diseases • “Communication” among molecules accounting for continuity of vital processes– infections agents as packets of information (computer viruses?) • Social and cultural communication as analogous flows of information
The communication of certain molecular changes taking place in the brain is by no means confined to…parents and offspring, but extends collaterally in all directions, by means of vibrations in the air… If the brain of an animal is in a particular state of molecular action, from any object that excites fear or joy, it may cause a similar state in the brain of others of the species, by uttering a cryor merely assuming a particular demeanour.
The faculty of speech gives man a power of communicating his complex feelings and ideas, far exceeding that of lower animals; and the invention of literature has greatly increased this power in civilized nations. By speech, not only can fresh sensations and ideas be communicated, but also that continuation of them called remembrance, by which they revive after, it may be a long interval of suspended animation.
Snow’s Social Vision • According to Snow, his oration “On Continuous Molecular Changes” was itself an example of continuous molecular change in human organisms and human society • Both chemical and social processes viewed as governed by patterns of information flow (“communication”)