Medieval Medicine: Humours, Galen and the Doctor's World
A World Where Doctors Already Had All the Answers
Imagine being ill in a Norfolk village in 1300. The physician who visits is highly trained, well paid, and entirely confident in his diagnosis — yet almost everything he believes about your body is wrong. To understand the medieval doctor, you have to understand the system he worked inside. That system was Greek, ancient, and held together by two names: Hippocrates and Galen.
Medieval medicine rested on Galen’s Theory of the Four Humours: blood, phlegm, yellow bile and black bile. Illness was caused by an imbalance, and treatment aimed to restore balance through opposites — bleeding a fevered patient, warming a cold one.
The Hippocratic Foundation
Hippocrates lived in Greece in the fifth century BC. His writings, the Hippocratic Corpus, taught doctors to observe patients carefully — checking pulse, urine and breathing — and to record what they saw. This was a major step away from explanations that blamed angry gods. Crucially, Hippocrates also gave doctors an ethical code: act in the patient’s interest, do no harm. Six centuries later Galen, working in Rome, built on this foundation and added his own grand theory of how the body worked. Because Galen’s explanations were complete, confident and Christian-friendly, his ideas dominated medical training for the next 1,500 years.
The Four Humours and the Theory of Opposites
Galen taught that the body contained four fluids, or humours. When the four were balanced, you were well. When one was in excess, you were ill. A fever meant too much blood (linked to summer and heat), so a doctor would bleed the patient using a knife or leeches. A cold, runny illness meant too much phlegm, so the patient would be warmed and given dry foods. This was the ‘theory of opposites’ — treat hot with cold, wet with dry. It was logical, internally consistent, and almost completely wrong.
The physician would inspect a urine sample (uroscopy), comparing its colour against a wheel-shaped chart with around twenty shades. He would feel the pulse and check the patient’s star sign. The ‘zodiac man’ diagram showed which planet ruled which body part — the moon was thought to control the brain, Mars the blood, and bleeding was avoided when the moon was ‘in’ the relevant body part. None of this involved touching a wound or examining the patient’s internal organs.
Treatments matched the diagnosis. Bleeding (phlebotomy) was the most common. Purging with laxatives, sweating in hot baths, or cupping with heated jars all aimed to remove the excess humour. Herbal remedies prescribed in the Theriac — a recipe of dozens of ingredients including viper flesh and opium — were also widespread.
Natural and Supernatural Causes Side by Side
A medieval villager did not see ‘science’ and ‘religion’ as opposites. Most people accepted multiple explanations of illness at the same time. Miasma — bad air from rotting waste — was a natural cause. Imbalance of humours was a natural cause. But sin, divine punishment for breaking God’s law, and unfavourable star alignments were also normal explanations. A patient with a fever might be bled by a physician, prayed over by a priest, and given a herbal posy to ward off bad smells, all in the same week.
Galen survived because his system fit the medieval world: it matched Christian belief in a divinely-ordered body, it was preserved in Latin texts copied by monks, and there was no rival framework. Communication and religion together kept his theory alive.
Training the Medieval Doctor
Becoming a physician took up to a decade. Universities at Salerno, Bologna, Montpellier and from the thirteenth century Oxford and Cambridge taught medicine, but training was based on reading classical texts in Latin, debating them, and memorising Galen. Dissection was rare and tightly controlled by the Church.
When dissection did happen, the senior physician read aloud from Galen while a barber-surgeon did the cutting and a junior pointed at the organs — if the body did not match Galen’s description, the body was assumed to be abnormal, not the book. Below the university-trained physician sat barber-surgeons (who pulled teeth, set bones and bled patients), apothecaries (who prepared herbal remedies), and wise women in the village who delivered babies and treated everyday complaints. Most ordinary people never saw a physician — the cost was beyond them.
Why This Matters for the 16-Mark Essay
The big 16-mark factor essay asks students to weigh one factor against others over a thousand years. This first lesson plants two factors firmly. Communication: Galen’s ideas spread because they were written down and copied; without books and the Latin Church, his system would have died with Rome. The role of the individual: Hippocrates and Galen are textbook examples of single thinkers shaping centuries of practice. When the Renaissance arrives in Lesson 4, you will see those same two factors flip — printed books and individuals like Vesalius will be what finally crack Galen’s grip.