Louis Pasteur

The Boy on the Table

On July 6, 1885, an aging chemist with no medical degree and a body half-crippled by stroke made a decision that, by any modern standard, he had no right to make.

The patient was Joseph Meister, nine years old, brought to Paris from Alsace by his mother two days after a rabid dog had knocked him down and bitten him fourteen times. Rabies, once its symptoms appeared, was then a sentence with no appeal: fever, thrashing terror, an inability to swallow, death by suffocation or exhaustion. The boy had no symptoms yet. He had, at most, a few weeks before he might.

Louis Pasteur had spent three years chasing a rabies vaccine — attenuating the unseen agent of the disease by drying strips of infected rabbit spinal cord until they lost their power to kill. He had protected dogs with it. He had never tried it on a human being. He was not licensed to practice medicine, and could not legally hold the syringe; physicians Jacques-Joseph Grancher and Alfred Vulpian would have to do that. His closest collaborator, the physician Émile Roux, is said to have wanted no part of treating a child on evidence this thin.

Over the next ten days, Meister received a graded series of thirteen injections, each more virulent than the last — a protocol that, in its final doses, carried the theoretical risk of giving the boy the very disease it was meant to prevent. Then Pasteur waited to see whether he had saved a child or killed one.

The whole of his life pointed at that table. It is also the moment where the gap opens widest between the story Pasteur told the world and the one his notebooks quietly kept.

The Wrong-Handed Molecules

He was born on December 27, 1822, in Dole, in the Jura hills of eastern France, and raised in nearby Arbois. His father, Jean-Joseph, was a tanner who had marched under Napoleon and come home with the Légion d’honneur and a fierce, unglamorous patriotism he passed to his son. The household was modest, hard-working, and provincial. Young Louis was an unhurried, careful student, better known in Arbois for his skill with a pastel crayon than for any flash of genius; his baccalauréat examiner marked him only “mediocre” in chemistry, a verdict history has enjoyed ever since.

He clawed his way to the École Normale Supérieure in Paris — admitted, characteristically, on a second attempt after a disappointing first — and trained under the chemists Antoine Balard and Jean-Baptiste Dumas, whose lectures lit something in him. He took his doctorate in 1847. And then, in 1848, a twenty-five-year-old assistant bent over a microscope made a discovery that would have secured his name even if he had never touched a microbe.

The puzzle was a substance called paratartaric, or racemic, acid, a chemical twin of the tartaric acid that crusts inside wine casks. The two were identical in composition, yet tartaric acid rotated a beam of polarized light and racemic acid did not. Peering at crystals of a racemic salt, Pasteur saw that they came in two shapes — mirror images of each other, like left and right hands. Painstakingly, with a fine needle, he sorted them into two piles. One pile rotated light to the left; the other, to the right; mixed back together, they cancelled out. Molecules, he had shown, could be handed — the founding insight of stereochemistry, and a hint that the chemistry of life itself runs on that asymmetry. The revered physicist Jean-Baptiste Biot, who had been skeptical, made Pasteur repeat the experiment before his eyes and, convinced, is said to have taken the young man’s arm with emotion. It was 1848, the year revolution swept Europe and the year Pasteur’s mother died. He was launched.

Appointed professor at Strasbourg in 1849, he promptly fell in love with Marie Laurent, the rector’s daughter, and married her. She would become far more than a wife: for forty-six years she was his secretary, his note-taker, his sounding board, and the keeper of his records — arguably the most important and least credited collaborator of his career.

The Living Cause

In 1854 Pasteur moved to Lille, an industrial city, as professor and dean, and there he pivoted from crystals toward the messier world of industry and life. In his inaugural address he offered the line that would follow him forever: “In the fields of observation, chance favours only the prepared mind.” Lille’s distillers had a practical problem — their fermentations kept going sour — and Pasteur, investigating, arrived at a radical claim. Fermentation was not, as the great German chemist Justus von Liebig insisted, a purely chemical decomposition. It was the work of living microorganisms: yeasts turning sugar to alcohol, other microbes spoiling the batch. He distinguished creatures that lived with air from those that lived without it, coining “aerobic” and “anaerobic.” Life, invisibly small, was doing chemistry.

If tiny organisms drove fermentation, where did they come from? The reigning answer was spontaneous generation — the ancient belief that life arose of its own accord from decaying matter. Pasteur’s assault on that doctrine, waged from around 1859, produced his most elegant experiment. He boiled broth in flasks whose necks he drew out into long, curving “swan necks.” Air could reach the liquid, but dust and the microbes it carried settled in the bends and never arrived; the broth stayed clear indefinitely. Tip the flask so the broth touched the trapped dust, and it swarmed with life within days. He won the Académie des sciences’ Alhumbert Prize in 1862, and at a celebrated Sorbonne soirée in 1864 declared spontaneous generation mortally wounded.

Here, though, the modern reader should slow down. Pasteur’s chief opponent, the naturalist Félix-Archimède Pouchet, was not a crank. Pouchet’s experiments with hay infusions really did keep producing life — because, unknown to either man, hay carries heat-resistant bacterial spores that survive boiling. Pasteur was right that life does not spring from nothing in his broths, but he won the public contest partly through rhetorical command, powerful allies, and a friendly Académie commission, while privately encountering some of the same stubborn anomalies Pouchet reported. The clean, purely empirical rout of legend is too tidy.

The 1860s brought both triumph and grief. At Napoleon III’s request Pasteur studied the “diseases” of wine, and later beer and milk, and showed that gentle heating killed the spoilage microbes without wrecking the product — the process the world now calls pasteurization. Sent south to Alès, he rescued France’s collapsing silk industry by identifying the microbial and parasitic causes of two silkworm plagues. But between 1859 and 1866, three of his five children died young of typhoid fever, and his father died during the silkworm campaign. Biographers have often read his later war on disease as driven by these losses; it is a plausible and human reading, but an interpretive one, and Pasteur himself left the connection unspoken. In 1868, at forty-five, a cerebral hemorrhage left him partly paralyzed on his left side. He would work, often one-handed, for another twenty-seven years.

The Franco-Prussian War of 1870–71 and France’s humiliating defeat marked him deeply. A conservative patriot, he nursed a bitter anti-German feeling that would color his coming rivalry with the German bacteriologist Robert Koch — an irony, given his own insistence that science, unlike scientists, has no homeland.

The Sheep of Pouilly-le-Fort

By the late 1870s Pasteur had turned germ theory toward disease itself, working on anthrax — whose bacillus Koch had described in 1876 — and on fowl cholera. Then came one of those accidents that favour the prepared mind. A culture of chicken-cholera bacteria, left to age over a summer, had lost its virulence; chickens injected with it not only survived but proved immune when later given a fresh, deadly dose. Pasteur grasped the general principle: a weakened, or attenuated, live microbe could train the body to resist the real thing. In homage to Edward Jenner’s cowpox inoculations, he extended the words “vaccine” and “vaccination” to cover all such preparations.

The public apotheosis came in 1881. Challenged by a skeptical veterinarian and the agricultural society of Melun to prove his anthrax vaccine in the open, Pasteur staged a demonstration at the farm of Pouilly-le-Fort with a showman’s flair for the decisive test. Some two dozen sheep were vaccinated and two dozen left unvaccinated; then all were injected with lethal anthrax. On June 2, before a crowd of farmers, veterinarians, and journalists, the results were read out: the vaccinated sheep stood healthy in the field while the unvaccinated lay dead or dying. It was a sensation, and it made vaccination a public cause across the world.

It is also where Pasteur’s private science and his public account part company most sharply. Pasteur presented the triumph as vindication of his own method of weakening anthrax by exposing it to oxygen. But his laboratory notebooks — opened to scholars only after 1971 and studied most closely by the historian Gerald Geison — indicate that the vaccine actually used at Pouilly-le-Fort was a chemically attenuated preparation, treated with potassium dichromate, developed largely by his collaborators Charles Chamberland and Émile Roux. That method was conceptually close to one already published by a rival veterinarian, Jean-Joseph-Henri Toussaint, whose work Pasteur had publicly disparaged. The experiment was real and it succeeded; but the account of whose method had won, and how, was misleading. How to judge this is itself contested: Geison reads it as deliberate misrepresentation, while Pasteur’s biographer Patrice Debré reads it as ordinary scientific improvisation dressed up for the public. The safest verdict is that the science was sound and Toussaint was denied his due.

The Boy Who Lived

Which returns us to the table in July 1885, and to rabies — the disease that would make Pasteur immortal and pose the hardest moral question of his life.

Rabies had no visible germ; the agent was too small for any microscope of the age. Working with Roux, Chamberland, and the young Louis Thuillier — who would die of cholera in Egypt in 1883 on a Pasteur-team mission, a reminder of what the work cost — Pasteur learned to propagate the infection through rabbits and to weaken it by drying their spinal cords over days. A series of injections, from most-dried and harmless to freshest and most virulent, seemed to build protection in dogs faster than the disease itself could take hold after a bite.

Then Joseph Meister’s mother appeared at his laboratory. Pasteur’s published justification implied that he had already established the treatment’s safety and effectiveness in a substantial number of dogs. Geison’s reading of the notebooks suggests the animal trials were fewer and less conclusive than that account claimed, and that the exact protocol given to Meister did not match any fully validated animal experiment. In plain terms, the nine-year-old was, in effect, an early human trial, undertaken without anything a modern ethicist would recognize as informed consent, on evidence Pasteur overstated to the world. And it worked. Meister never developed rabies. In October a second child, a shepherd boy named Jean-Baptiste Jupille, bitten while shielding smaller children from a rabid dog, was treated and also survived; his statue still stands at the Institut Pasteur.

The gamble is usually judged vindicated, and fairly so — the treatment went on to save many. But honesty requires holding both halves at once: the lives saved and the corners cut, the courage and the control of the story. It also requires remembering the failures the legend omits, such as young Louise Pelletier, brought to Pasteur too late, who died. Post-exposure treatment could not raise a defense faster than an advanced infection.

The Crypt Beneath the Institute

Meister’s survival made Pasteur one of the most famous men alive. Money poured in from around the world by public subscription, and on November 14, 1888, the Institut Pasteur was inaugurated in Paris with Pasteur as its first director — a fortress of microbiology and immunology that would spread into a global network of research institutes still bearing his name. Further strokes progressively disabled him through his last years. He died on September 28, 1895, aged seventy-two, and after a state funeral at Notre-Dame his body was placed, where it remains, in an ornate crypt beneath the Institut rather than in the Panthéon that France offered him. He never won a Nobel Prize; he died six years before the first was awarded.

For most of the century that followed, Pasteur was a secular saint — his face on French banknotes, his name on streets and thousands of schools, his life told and retold in the adoring biography his son-in-law René Vallery-Radot published in 1900, the source of much of the popular imagery. Then, after 1971, the notebooks came out, and Geison’s 1995 study made Pasteur the standard case study in how heroic science is manufactured: the public demonstrations polished, the private doubts and borrowed methods and uncredited collaborators quietly edited out. Roux, Chamberland, Thuillier, and above all Marie Pasteur did far more of the hands-on work than the singular legend allowed.

None of this overturns the science. Pasteur was, with Koch, a founder of microbiology; he gave the world a usable germ theory, pasteurization, the modern attenuated vaccine, and the principle behind rabies post-exposure treatment still in conceptual use. The revisionist reckoning does not make him a fraud, and it is worth saying plainly that the real, documented controversies are sometimes seized upon by anti-vaccine and germ-theory-denial movements — heirs to Pasteur’s embittered rival Antoine Béchamp — to peddle pseudoscience. The honest conclusion resists both the myth and its inversion. Pasteur was frequently right, occasionally cut corners, and always controlled the narrative.

A last image, offered as legend rather than fact: Joseph Meister grew up to be a caretaker at the Institut, guarding the crypt of the man who saved him, and died in June 1940 as German troops entered Paris. The often-repeated story that he killed himself rather than open Pasteur’s tomb for them is disputed by historians. It is a fitting coda all the same — the boy on the table, keeping the gate to the end, and a life whose truth turned out to be more complicated, and more human, than the monument.

Sources & Further Reading

1. Institut Pasteur — history pages on Louis Pasteur and the founding of the Institut (pasteur.fr/en/institut-pasteur/history)
2. Geison, Gerald L. — The Private Science of Louis Pasteur (Princeton University Press, 1995)
3. Debré, Patrice — Louis Pasteur, trans. Elborg Forster (Johns Hopkins University Press, 1998)
4. Science History Institute — “Louis Pasteur” scientific biography (sciencehistory.org)
5. Vallery-Radot, René — The Life of Pasteur (1900; English translation 1902)
6. Œuvres de Pasteur, 7 vols., ed. Pasteur Vallery-Radot (1922–1939); Pasteur’s papers in the Comptes rendus of the Académie des sciences, digitized via Gallica (BnF)