HPS211! Lecture 12! Germ Theory!

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Samson Rice
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1 HPS211 Lecture 12 Germ Theory Agenda Prior theory: humors Germ theory Alternative theories: spontaneous generation miasma John Snow & epidermiology Louis Pasteur, bacteria, vaccine Robert Koch's work Theory of Four Humours Dominant theory in Western medicine was humour theory Originated from mesopotamian civilization Galen's Humor theory which was most widely accepted Blood Air, Sanguine Pleasure-Seeking Yellow Bile Fire, Choleric Energetic Black Bile Earth, Melancholy Introverted Phlegm Water, Plegmatic Relaxed and Quiet, sometimes lazy These 4 fluids were seen in the body Related to the 4 elements of Aristotle Represents the four personalities

2 Healthy when humors are balanced Ill when humors are not balanced Medical treatments involved balancing the humors Blood letting Challenges to the humor theory Paracelus One specific disease, one particular cause Use mineral chemicals as medicine (iatrochemistry) Specificity of diseases confirmed from pathological anatomy Difficulty of humor theory to account for infectious diseases Black death Massive and contageous Germ Theory Fermentation Putrefaction Infection Microscopic organic agents (germs) were the cause They are transmitted from without (outside the body) Difficulties: No microorganisms observed Even they were observed under microscope, not sure whether they caused the disease or reaction Not sure whether they were transmitted from without Some believed microorganisms could be generated spontaneously from within In early 19th c, more popular theory of infection was miasma Bad air in the infected area Solution was better air circulation and more, brighter light Public health campaign believed miasma theory

3 New Modern Government Mentality To improve the quality of life of individuals, not just to collect taxes and stuff This means policies were drafted around miasma theory Required better air circulation and lighting in public buildings and hospitals John Snow & Cholera Outbreak Pioneer of anesthesia Requested to investigate breakout of cholera in London, 1854 Documented patients' life histories Analyzed their statistical data Plotted the addresses of dead people, and where they died, where they lived Found that it was concentrated around Broad Street All of them drank water from a single water pump on Broad Street Snow identified the source of infection as the water pump on Broad Street Germ theory of Cholera Louis Pasteur Son of a veteran from Napoleon's army Studied chemistry at Ecole Normale Institute to train teachers Interested in fermentation & putrefaction. More interested in biology later on. Tried to demonstrate that the germs causing fermentation and putrefaction were transmitted from without via air, not due to spontaneous generation from within. Staged a sequence of experiments. Swan neck bottle trial Broth did not decay despite air from neck Reason air in, germs trapped gravitationally at lower end of neck.

4 First practical application of Germ Theory Heating milk or wine prevented it from becoming sour Sterilization or "pasteurization" Chicken Cholera, Anthrax & Vaccines Employed germ theory in research on chicken cholera (1879) Isolated and identified the bacteria of chicken cholera under a microscope Injected 2-week-old bacteria to chickens, stayed healthy Germs toxicity decayed Infected those chickens with fresh germs, stayed healthy, while previous uninfected chickens fell ill with same treatment Principle of vaccine Same approach gained success in making anthrax vaccine High-profile demonstration in 1881 Next target: vaccine for rabies Difficult to identify organism under microscope (a virus) But Pasteur managed to use dried spinal cords of infected rabbits as vaccine. Success. Established Institut Pasteur in Paris (1887) Robert Koch Prussian military doctor Identified bacteria of Anthrax Koch's Postulates An organism is the cause of a disease if: 1. The organism is discovered in every instance of the disease 2. Extracted from the body, the germ can be produced in a pure culture and maintained for several generations

5 3. A disease can be reproduced on experimental animals using such cultured germs (after several generations) 4. The organism can be retrieved from the inoculated animals and cultured anew. Developed cholera vaccine using infected animal serum (body fluids) instead of tissues. Massive public health campaign in early 20th century. Universal vaccination of preschool children Early 20th c. was golden age of immunization and vaccine treatment.

Why was there so much change in this period?

Why was there so much change in this period? Germ Theory: Summary? 1) 1861: Germ Theory Bacteria in the air turned things bad (working to find why beer was going sour). Pasteur wondered if this could make