Appearance
3.3 — The Chemists, Biologists and Doctors
The people on this page worked out what things are made of and what makes us ill. Several of them were disbelieved for years by people who were washing their hands in the same room.
What matter is made of
Who was Lavoisier and why was he executed?
Antoine Lavoisier (1743–1794) turned chemistry from a collection of recipes into a science, mainly by weighing things.
The prevailing theory held that burning released a substance called phlogiston. Lavoisier weighed materials before and after burning in sealed vessels and found the total mass never changed — and that metals gained weight when they burned, which phlogiston could not explain unless it had negative mass. He identified what was actually happening: burning is combination with a gas in the air, which he named oxygen. He did the same for respiration, showing that breathing is a slow version of the same reaction.
He established the law of conservation of mass — matter is neither created nor destroyed in a chemical reaction — and wrote the first modern chemistry textbook with a systematic naming scheme, which is why compounds are named the way they are.
He was also a tax collector, a member of the deeply unpopular Ferme générale that collected indirect taxes for the crown, and in 1794 the Revolutionary Tribunal condemned him along with the other farmers-general. The story that the judge said "the Republic has no need of scientists" is probably apocryphal. The mathematician Lagrange's remark the next day is documented: it took a moment to cut off that head, and a hundred years may not produce another like it.
How did Mendeleev arrange the elements?
By weight, and then by trusting the pattern more than the data — which is the part that made him right.
The full account is in 2.4. What belongs here is the man. Dmitri Mendeleev (1834–1907) was the youngest of a very large family in Siberia; his mother reopened a glass factory to support them, and when it burned down she travelled over a thousand miles with him to get him educated.
He was a serious public figure in Russia — he worked on the metric system, the oil industry, and agricultural policy — and a genuine eccentric, cutting his own hair and beard once a year regardless of occasion. He never received a Nobel Prize, losing by one vote in 1906 partly through the opposition of a chemist he had publicly doubted; he died the following year.
What did Mendel do with peas, and why did nobody read it?
Gregor Mendel (1822–1884), an Augustinian friar in Brno, spent eight years breeding pea plants and counting the results — around 28,000 plants.
He chose seven traits that come in two clear versions with nothing in between: tall or short, round or wrinkled seeds, green or yellow pods. Crossing a tall with a short gave all tall. Crossing those offspring with each other gave tall and short in a ratio close to 3:1. The shortness had not been destroyed and then recreated; it had been carried invisibly through a generation.
That is the whole foundation of genetics: inheritance is particulate, not a blending of fluids. Each parent contributes one factor of a pair, one version can mask the other, and the pairs sort independently.
His 1866 paper was read to a local natural history society, printed in its proceedings, and essentially ignored for thirty-four years. Darwin, who needed exactly this mechanism, never saw it. Three separate botanists rediscovered the same laws in 1900 and found Mendel's paper when searching the literature.
He gave up research after being made abbot of his monastery, spending his last years in an administrative dispute over taxes.
The germ theory, and the people who were not believed
What did Pasteur actually prove?
That living things do not appear from nothing, which sounds obvious and was the central scientific dispute of his time.
The accepted view was spontaneous generation: leave broth out and micro-organisms arise from it. Pasteur's decisive experiment used a flask with a long S-shaped neck. Air could reach the broth freely, but dust and airborne organisms settled in the bend and never arrived. The broth stayed sterile indefinitely — and spoiled within days if the neck was snapped off or the flask tilted so the liquid touched the bend.
From that came pasteurisation, the germ theory of disease, and vaccines for anthrax and rabies. The rabies vaccine was first given to a human in 1885, to a nine-year-old boy bitten fourteen times by a rabid dog. Pasteur was a chemist, not a physician, and was risking prosecution. The boy lived, and later became the caretaker of the Pasteur Institute.
His laboratory notebooks, opened to historians only in the 1970s, show he was less scrupulous than his public account: the anthrax vaccine he demonstrated publicly was prepared by a rival's method, not his own.
Why is Semmelweis the saddest story in medicine?
Ignaz Semmelweis (1818–1865) worked in a Vienna maternity hospital with two clinics. In one, staffed by doctors and medical students, roughly ten per cent of women died of childbed fever. In the other, staffed by midwives, it was around four. Women begged to be admitted to the second, and some gave birth in the street rather than enter the first.
Semmelweis worked through the differences and found the answer when a colleague died after cutting himself during an autopsy, with symptoms identical to childbed fever. The doctors and students were coming to the delivery room directly from dissecting corpses. The midwives were not.
He instituted handwashing with chlorinated lime in 1847 and mortality in the doctors' clinic fell to around one per cent.
He was rejected, and the reasons are worth naming. He had no theory — germs had not been discovered, so his explanation involved vague "cadaverous particles". He published late and badly. And the claim carried an unbearable implication: that respectable physicians had been killing their patients with their own hands. He became increasingly aggressive, writing open letters calling obstetricians murderers, was committed to an asylum in 1865, was beaten by guards, and died at 47 of an infected wound.
The germ theory arrived within two decades and proved him right about everything except the mechanism.
Who was Florence Nightingale, and why is she in a statistics textbook?
Because she was one of the first people to win a political argument with a picture of data.
Nightingale (1820–1910) went to the Crimean War in 1854 with 38 nurses. What she found was that far more soldiers were dying of typhus, cholera and dysentery in the hospitals than of wounds. She kept records.
Back in London she needed to persuade a government that was not going to read a table. So she invented — or at least perfected — the polar area diagram, a circular chart in which each month is a wedge whose area shows the deaths, split by cause. The picture made one thing impossible to miss: the blue wedges, deaths from preventable disease, dwarfed the red ones from wounds.
Sanitary reform in military hospitals followed. She was elected the first female member of the Royal Statistical Society, spent most of her remaining fifty years bedridden with what was probably chronic brucellosis contracted in Crimea, and ran a campaign of reform from her bed by correspondence.
Who was Fleming, and who actually made penicillin a drug?
Alexander Fleming returned from holiday in September 1928 to a laboratory bench of dishes he had left untidy. One was contaminated with a mould, and around the mould the staphylococcus colonies had dissolved.
He published it in 1929 and it went nowhere for a decade. Fleming could not purify the active substance in useful quantity, could not keep it stable, and did not press the case.
The people who turned it into medicine were Howard Florey, Ernst Chain and Norman Heatley at Oxford, from 1939. Chain worked out the chemistry; Heatley designed the production, growing the mould in whatever vessels wartime Britain could supply, including hospital bedpans, and building an extraction apparatus out of scrap. The first patient, a policeman with a facial infection, improved dramatically and then died when the supply ran out — they had been recovering penicillin from his urine to re-use it and still could not make enough.
Production at scale happened in the United States, after a strain was found on a mouldy cantaloupe in a market in Peoria, Illinois that yielded far more than any other. By D-Day in 1944 there was enough for every Allied casualty.
Fleming, Florey and Chain shared the Nobel Prize in 1945. Heatley, who was not a physician or a chemist by title, received nothing at the time and was given an honorary doctorate of medicine by Oxford in 1990 — the first in the university's 800-year history.
Fleming used his Nobel lecture to warn that using too little penicillin, or using it carelessly, would breed resistant bacteria. He was right, and that is now one of the largest threats in medicine.
DNA, and who was left out
What did Rosalind Franklin do?
She produced the experimental evidence that determined the structure of DNA, and she did it by being better at a difficult technique than anyone else working on the problem.
Franklin (1920–1958) was an expert in X-ray crystallography — firing X-rays at a substance and deducing its atomic arrangement from the pattern of scattered rays. Working at King's College London from 1951, she found that DNA takes two forms depending on humidity, separated them, and obtained an image of the wetter B form of extraordinary quality, known as Photograph 51.
From it she determined that the molecule is helical, that the phosphate backbones are on the outside, and the dimensions of the repeat. Her notebooks show she had the essentials and was working towards the structure.
Watson and Crick at Cambridge were building models. In January 1953, Maurice Wilkins showed Watson Photograph 51 without Franklin's knowledge or permission, and a summary of her unpublished data reached them through a research council report. Watson later wrote that seeing the photograph made his mouth fall open. The double helix model followed within weeks.
Three papers appeared together in Nature in April 1953: Watson and Crick's, Wilkins's, and Franklin's. The arrangement made her data look like supporting evidence for their model rather than the basis of it, and Watson and Crick's paper acknowledged her only in a sentence about having been "stimulated by a knowledge of the general nature" of unpublished results.
She died of ovarian cancer in 1958, aged 37, probably related to her X-ray exposure. The Nobel Prize went to Watson, Crick and Wilkins in 1962, and Nobel Prizes are not awarded posthumously — so the honest statement is that we do not know whether she would have been included, and that she was written out of the story long before she died. Watson's own 1968 memoir describes her in terms that damaged her reputation for a generation.
What is HeLa, and who was Henrietta Lacks?
In 1951 a 31-year-old Black woman named Henrietta Lacks was treated for cervical cancer at Johns Hopkins. A sample of her tumour was taken without her knowledge — routine practice at the time — and passed to a researcher who had been trying for years to keep human cells alive in culture.
Her cells did not die. Every previous human cell line had divided a limited number of times and stopped. Hers kept going, and they still are. They were shared freely, then sold commercially, and have been used in tens of thousands of studies: the polio vaccine, cancer research, the effects of spaceflight, HPV, COVID-19 vaccines.
Henrietta Lacks died months after the sample was taken, and her family did not learn of the cells for over twenty years — during which they could not afford health insurance. In 2013 the family reached an agreement with the National Institutes of Health giving them a say in access to the genome data, and in 2023 they settled with a company that had sold the cells.
The case is the reason modern research ethics requires informed consent for tissue, and it is taught as the standard example of how a genuine scientific good and a genuine wrong can be the same event.
Feeding people
What was the Green Revolution, and was it good?
Norman Borlaug spent from 1944 in Mexico breeding wheat that resisted rust fungus and — crucially — grew short. Tall wheat given plenty of fertiliser grows a heavy head, falls over, and rots. Dwarf varieties put the extra growth into grain instead of stem, so they can absorb heavy fertiliser and irrigation and convert it into food.
India and Pakistan adopted the varieties from the mid-1960s, in the middle of a food crisis in which India was importing grain under emergency aid and famine was widely predicted. Indian wheat production roughly quadrupled over the following decades, and the country moved from dependence to self-sufficiency. M. S. Swaminathan led the Indian side of the effort and is the reason the varieties were adapted to local conditions rather than simply imported.
Borlaug received the Nobel Peace Prize in 1970, and is often credited with saving hundreds of millions of lives.
The criticisms are also real, and a book that gives only the first half is doing propaganda. The system depends on fertiliser, pesticide and irrigation, which favoured farmers who could afford them and widened rural inequality. Groundwater in Punjab and Haryana has been drawn down severely. Fertiliser runoff damages rivers. Regional diversity in crop varieties collapsed, which is a risk in itself. And the gains were in wheat and rice, so pulses and millets — nutritionally better and less thirsty — lost ground.
The honest summary is that it prevented a catastrophe that was actually approaching, and created a different set of problems that are now the ones being worked on.
What comes next
The next page is the builders — the engineers and inventors who made things that had to stand up, stay up, or work the first time.