The Complete Guide to Medicine Through Time

1. Two Thousand Years of the Wrong Answer

Why the humours made sense, and why that made them so hard to kill.

Your doctor examines you, decides you have too much blood, and opens a vein. If you feel worse afterwards, that proves the imbalance was severe and you need more. If you recover, the treatment worked. There is no possible outcome that counts as evidence against it — and that is precisely why the theory lasted for two thousand years.

The idea came from Greek medicine and was systematised by Galen, a physician in the Roman Empire whose writings dominated European and Islamic medicine for well over a millennium. The body contained four humours — blood, phlegm, yellow bile and black bile. Health was balance. Illness was excess, treated by removing the surplus: bleeding, purging, sweating, vomiting.

The four humours: A theory linking bodily fluids to the four elements and four seasons, producing a complete, elegant system that explained personality as well as disease. The words survive in ordinary English: sanguine, phlegmatic, choleric and melancholic are all humoural terms.

It was not stupid. It explained observable things — fevers do produce sweating, and people do have recognisable temperaments — and it gave doctors something definite to do. Galen was also an outstanding anatomist, working carefully on animals because human dissection was forbidden, which is how some confident errors got baked in for centuries.

In 1799 George Washington developed a throat infection. His physicians removed somewhere around 2.4 litres of blood — roughly forty per cent of his blood volume — in about twelve hours. He died the same night. The medicine of the day did not merely fail to help; it was frequently the cause of death.

Challenging Galen was risky, and the first successful challenges were about anatomy rather than disease. In 1543 Vesalius dissected human bodies and published beautiful illustrations showing Galen wrong in dozens of places. In 1628 William Harvey demonstrated that blood circulates in a closed loop, pumped by the heart — refuting Galen directly, and by measurement: the heart pumps far more blood per hour than the body could possibly manufacture from food.

What just happened

• Galen's theory of four humours dominated medicine for around 1,500 years
• Treatment meant removing the supposed excess: bleeding, purging, vomiting
• Vesalius corrected the anatomy in 1543 and Harvey proved circulation in 1628

The humours are the clearest example of a theory that explains everything and predicts nothing. Harvey's argument beat it the way science does beat things: with a measurement it could not accommodate.

Knowing how the body works did not stop patients dying in hospital. For that, someone had to notice something almost nobody wanted to hear.

2. Wash Your Hands

The doctor who worked it out too early, and was destroyed for it.

1847 — The Vienna General Hospital, maternity division

There are two clinics. In the first, staffed by doctors and medical students, about one mother in ten dies of childbed fever. In the second, staffed by midwives, it is about one in twenty-five. Women beg to be admitted to the second clinic. Some give birth in the street rather than be sent to the first, and — this is the detail that torments Ignaz Semmelweis — those women have better survival rates than the ones in his ward.

Semmelweis eliminated every explanation he could think of. Then a colleague died after cutting himself during an autopsy, with symptoms identical to childbed fever. Semmelweis made the connection: the doctors and students came to the delivery room straight from dissecting corpses. The midwives did not.

He ordered handwashing in chlorinated lime before examinations. Mortality in the doctors' clinic fell to roughly the midwives' level within months. He had solved it — twenty years before anyone could explain why it worked, because germ theory did not yet exist.

And that was the problem. He could produce the numbers but not a mechanism, and the implication of his numbers was that respectable physicians had been killing their patients with their own hands. The profession rejected it. Semmelweis grew increasingly angry, publishing open letters calling his critics murderers, was committed to an asylum in 1865, and died there at forty-seven of an infected wound, possibly from a beating by the guards.

This case has a name now — the Semmelweis reflex, the tendency to reject evidence that contradicts an established belief or a professional self-image. He was right, he had the data, and being right was not enough, because he could not explain the mechanism and was asking a profession to accept guilt.

What just happened

• Two maternity clinics in Vienna had wildly different death rates
• Semmelweis traced the difference to doctors arriving from the dissection room
• Handwashing cut deaths dramatically; the profession rejected him and he died in an asylum

Evidence alone does not persuade. A finding usually needs a mechanism, an advocate with standing, and an audience willing to hear that it has been doing harm.

The explanation came from a French chemist who had never intended to work on disease at all — he had been asked to find out why wine went sour.

3. The Enemy Is Alive

Pasteur, Koch, and proving that disease has a cause you can see.

Louis Pasteur (1822–1895)

A chemist who was asked why beer spoiled and answered why people die.

French brewers and winemakers wanted to know why fermentation sometimes went wrong. Pasteur showed that microorganisms in the air were responsible, and that gentle heating killed them — pasteurisation. From there he made the leap that mattered: if microbes spoil wine, microbes might also be what spoils bodies.

The prevailing view was spontaneous generation — that life simply arose from decaying matter. Pasteur destroyed it with a beautifully designed experiment. He boiled broth in flasks with long S-shaped necks, open to the air but curved so dust and microbes settled in the bend. Air reached the broth; microbes did not; nothing grew. Break the neck, and the broth clouded within days.

That single flask is the birth of modern medicine. Disease was no longer a mysterious imbalance or a bad smell; it was caused by specific living organisms that could be identified, blocked and killed. Everything after this — antiseptics, vaccines, antibiotics, public health — follows from it.

Robert Koch in Germany turned the insight into a discipline, developing methods for growing bacteria in pure culture, staining them and photographing them. He identified the organisms causing anthrax, tuberculosis and cholera, and set out rules — Koch's postulates — for proving that a particular microbe causes a particular disease. Pasteur and Koch loathed each other, and the Franco-German rivalry drove both to work faster.

In Britain, Joseph Lister read Pasteur and asked the obvious surgical question. If microbes cause infection, they must be what kills patients whose operations succeed. He began spraying carbolic acid on wounds, instruments and hands. Deaths after amputation in his ward fell from around 45% to about 15%. Surgery changed from a last resort with a coin-flip survival rate into something a doctor could recommend.

Pasteur's rabies vaccine was first given to a human in 1885, to a nine-year-old boy mauled by a rabid dog. It had only been tested on animals, Pasteur was not a physician and was risking prosecution, and rabies was invariably fatal. The boy lived. He later worked as caretaker at the Pasteur Institute.

What just happened

• Pasteur showed microbes cause fermentation and spoiling, and disproved spontaneous generation
• Koch developed the techniques to identify specific disease-causing bacteria
• Lister applied germ theory to surgery, cutting post-operative deaths dramatically

Germ theory is the single most consequential idea in the history of medicine. It turned treatment from guesswork into a search for a specific, identifiable cause.

Meanwhile, in a military hospital in the Crimea, a woman with no laboratory was proving something with numbers that nobody could argue with.

4. The Woman with the Data

Nightingale's real weapon was not the lamp.

Florence Nightingale (1820–1910)

A superb statistician who is remembered, irritatingly, for carrying a lamp.

Born into wealth and expected to marry, Nightingale trained as a nurse against her family's wishes and took a team to the military hospital at Scutari during the Crimean War in 1854. She found soldiers dying in numbers nobody could explain, and began recording everything.

The hospital was built over a blocked sewer. Water was contaminated; there was no ventilation; men lay in filth. Nightingale's team scrubbed, opened windows, organised laundry and food. Death rates fell dramatically — though later analysis suggests the decisive change came when a sanitary commission flushed the sewers and improved the water supply, which she came to accept and then argued for relentlessly.

The important part happened after she came home. She had the numbers, and she knew that a table of figures would be ignored, so she invented a way of drawing them. Her polar area diagram shows deaths month by month as coloured wedges, with the area representing the number of deaths and the colours separating wounds from preventable disease. One glance shows that far more soldiers died of preventable infection than of the enemy.

She sent that diagram to ministers, generals and Queen Victoria, and she designed it precisely because, as she put it, it would 'affect through the eyes what we fail to convey to the brains'. She was elected the first female member of the Royal Statistical Society in 1858. She is the reason data visualisation exists as a tool of persuasion.

She then used the evidence to rebuild army medical administration, reform hospital design — with ventilation, space between beds and sanitation built in — and found a training school for nurses at St Thomas's in 1860 that turned nursing from casual, unrespected work into a trained profession. She did most of this from her bed, chronically ill, for decades.

What just happened

• Nightingale took nurses to Scutari and recorded mortality systematically
• Sanitation reforms cut deaths, most of which were from preventable disease
• Her polar area diagrams persuaded government to reform army medicine and hospital design

She proved that presentation is part of evidence. The data would have been ignored; the picture could not be.

Even with clean hospitals and known germs, doctors still had almost nothing to give a patient whose infection had already started. That changed because someone went on holiday and left a mess.

5. The Accident and the Work

Penicillin: the true version, in which Fleming does about a fifth of it.

September 1928 — St Mary's Hospital, London

Alexander Fleming returns from holiday to a famously untidy laboratory. On a stack of petri dishes he had left uncleaned, one is contaminated with a blue-green mould — and around the mould, the ring of staphylococcus bacteria has dissolved. He photographs it, identifies the mould as a Penicillium, publishes a paper in 1929, and cannot find a way to extract enough of the substance to be useful.

Then almost nothing happens for a decade. The paper was barely noticed. Fleming was a bacteriologist, not a chemist; purifying penicillin was a formidable chemical problem, and he moved on to other work.

In 1938 a team at Oxford — Howard Florey, Ernst Chain and Norman Heatley — went looking through the literature for antibacterial substances and found Fleming's paper. Heatley designed the extraction process, using improvised equipment including bedpans, milk churns and a bath. In May 1940 they injected eight mice with a lethal dose of streptococci and treated four with penicillin. The next morning, the four treated mice were alive and the four untreated were dead.

The first human patient, in 1941, was a policeman with an infection from a scratch. He improved dramatically — and then the supply ran out. The team recovered penicillin from his urine to reuse it, and still ran out. He died. It is one of the most painful near-misses in medical history, and it proved the drug worked.

Britain was being bombed and had no capacity for industrial production, so Florey and Heatley flew to the United States, where the war effort, deep-tank fermentation and a strain of mould found on a mouldy cantaloupe melon in a Peoria market turned a laboratory curiosity into mass production. By D-Day in June 1944 there was enough penicillin to treat every wounded Allied soldier who needed it.

Commonly believed: Fleming discovered penicillin and it saved millions of lives.

Actually: Fleming made the observation and deserves great credit for noticing and publishing it. But the drug exists because Florey, Chain and Heatley did twelve years of extremely difficult chemistry and organisation. The Nobel Prize was shared between Fleming, Florey and Chain — Heatley, who solved the extraction, received nothing at the time and an honorary doctorate fifty years later.

“It is not difficult to make microbes resistant to penicillin in the laboratory by exposing them to concentrations not sufficient to kill them.”

He warned about antibiotic resistance in the same speech in which he accepted the prize — before most doctors had ever prescribed the drug.

What just happened

• Fleming noticed and published the mould's antibacterial effect in 1928–29, then stalled
• The Oxford team purified it, proved it in mice in 1940 and in humans in 1941
• American industrial fermentation made mass production possible by 1944

The penicillin story is the best correction available to the myth of the lone genius. Discovery is one step; making a discovery usable is usually the longer and harder half.

One last thread ties all of it together, and it is not about drugs at all.

6. What Actually Saved Us

Drains, data and vaccines — the unglamorous answers.

Ask what caused the great fall in death rates and most people say medicine. The historical evidence points somewhere less exciting. Life expectancy in industrial countries rose enormously between about 1850 and 1950 — mostly before antibiotics existed — and the main causes were clean water, sewers, better food, less crowded housing and the systematic collection of health statistics.

1854 — Broad Street, Soho, London

Cholera is killing people street by street, and everyone knows it is caused by bad air. John Snow does not believe this. He maps every death and finds them clustering around one water pump, and interviews the exceptions: a brewery whose workers drank beer and were untouched, a widow who had water carted from Broad Street because she liked the taste and died miles away. He persuades the parish to remove the pump handle.

The outbreak was already declining, so the handle did not end it — but the map did something more important. It made a scientific case with geography, and modern epidemiology starts there. London's sewer system, built by Joseph Bazalgette after the 'Great Stink' of 1858 forced Parliament to act, then removed cholera from the city permanently. He deliberately doubled the pipe diameters his calculations required, which is why the system still works.

What changed the numbers most

Smallpox killed an estimated 300 million people in the twentieth century alone. It was declared eradicated in 1980 after a global vaccination campaign, and now exists only in two secure laboratories. It is the only human disease we have ever deliberately driven to extinction.

The final lesson of this story is that medicine's biggest wins came from public systems: drains, water treatment, vaccination programmes, health statistics, trained nurses. None of it makes a good film. All of it is why you expect to live past forty.

And the gains are not permanent. Fleming's warning has arrived: bacteria resistant to most available antibiotics now kill well over a million people a year, driven by over-prescription, agricultural use and a drug pipeline that has nearly dried up because antibiotics are unprofitable to develop. The problem in this chapter is the only one in the guide that is still open.

What just happened

• Sanitation, nutrition and housing drove most of the fall in death rates before antibiotics
• Snow's cholera map founded epidemiology; Bazalgette's sewers ended cholera in London
• Smallpox was eradicated by vaccination in 1980; antibiotic resistance is now rising

The most effective medicine has usually been infrastructure and organisation rather than a heroic individual cure — which is exactly why it is so easy to neglect until it fails.

Now you know the story

You live in the first period in human history in which a bacterial infection is usually a minor inconvenience. That window is about eighty years old, and antibiotic resistance means it is not guaranteed to stay open. The people in this guide bought it for us; keeping it is a live problem, not a solved one.

• Explain why the theory of the four humours survived for two thousand years
• Describe germ theory and why it took decades to be accepted
• Tell the true story of penicillin, including the part Fleming did not do
• Say how Nightingale used statistics to save more lives than her nursing did

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The assessed version of this material is Pearson Edexcel International GCSE History breadth study B2 — Changes in medicine, c1848–c1948 — which has fixed dates, five prescribed key topics and a specific question format. If you are taking that exam, use the course rather than this enrichment version.