Louis Pasteur

• 1. Introduction

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  On the 6th of July 1885, Louis Pasteur faced a choice that could have ended in his prosecution. A 9-year-old boy named Joseph Meister had been badly mauled by a rabid dog. Pasteur held a rabies vaccine he had tested in dogs, but he held no medical license. Treating the boy was a personal risk. He could have faced legal action for practicing medicine he was not authorized to perform. He consulted physicians and went ahead. Over 11 days, Meister received 13 inoculations. Three months later, the boy was in good health, and Pasteur was hailed as a hero. This was the same Pasteur who had been an average student, drawn more to fishing and sketching than to books, dyslexic and dysgraphic, who once earned a mediocre grade in chemistry. How did a poor tanner's son from the Jura become a man of whom one Academician would say no one had done as much for medicine? And why did this celebrated figure instruct his family, in 1878, to never reveal his laboratory notebooks to anyone? The answers run from the shape of crystals to the souring of wine, from dying silkworms to a vault covered in Byzantine mosaics.

• 2. The Twist In Crystals

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  Tartaric acid posed a puzzle that Pasteur resolved in 1848. The compound drawn from living things rotated the plane of polarized light passing through it. Yet tartaric acid made by chemical synthesis had no such effect, even though its reactions and elemental composition were identical. Pasteur noticed something small under examination: the crystals of tartrates carried tiny faces. In racemic mixtures, he observed that half the crystals were right-handed and half were left-handed. In solution, the right-handed compound bent light one way and the left-handed one bent it the other. Pasteur concluded that optical activity came from the shape of the crystals. An asymmetric internal arrangement of the molecules was twisting the light. The two forms were non-superposable mirror images of each other. This was the first demonstration of molecular chirality and the first explanation of isomerism. Some historians regard this as his most profound and most original contribution to science, his greatest scientific discovery. His investigation of sodium ammonium tartrate opened the field of optical isomerism early in his career.

• 3. Wine, Yeast, And Souring

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  In 1856, a local wine manufacturer named M. Bigot, whose son studied under Pasteur, came to him at Lille for advice on making beetroot alcohol and on souring. The request pulled Pasteur into fermentation. He began by repeating and confirming the work of Theodor Schwann, who a decade earlier had shown that yeast were alive. Jöns Jacob Berzelius and Justus von Liebig had argued that fermentation was caused by decomposition. Pasteur showed they were wrong: yeast was responsible for turning sugar into alcohol. When a different microorganism contaminated wine, lactic acid formed, and the wine soured. In 1861, he noticed that less sugar fermented per part of yeast when the yeast met air, a slowing later called the Pasteur effect. The discovery that microbes spoiled beverages led him to a practical method. He heated liquids such as milk to a temperature between 60 and 100 degrees Celsius, killing most bacteria and moulds within them. Pasteur and Claude Bernard completed tests on blood and urine on the 20th of April 1862. He patented the process to fight the diseases of wine in 1865, and the method became known as pasteurization. He published Etudes sur le Vin in 1866 and Etudes sur la Biere in 1876.

• 4. Life From Dust

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  Felix Archimede Pouchet, director of the Rouen Museum of Natural History, delivered Pasteur a particularly stern criticism. Pouchet held that air everywhere could spark spontaneous generation of living organisms in liquids. To settle the dispute between the two scientists, the French Academy of Sciences offered the Alhumbert Prize, carrying 2,500 francs, to whoever could experimentally demonstrate for or against the doctrine. Francesco Redi and Lazzaro Spallanzani had offered earlier evidence against spontaneous generation in the 17th and 18th centuries. Spallanzani's experiments in 1765 suggested that air contaminated broths with bacteria. Pasteur built on this with a sequence of careful tests. He boiled liquid, let hot air enter a flask, then sealed it, and nothing grew. When he opened flasks of boiled liquid to dust, organisms grew in some of them. At higher altitudes, fewer flasks grew organisms, since that air held less dust. His swan neck flasks were the decisive design. Air entered through a long curving tube that trapped dust particles, and nothing grew unless the flask was tilted so the broth touched the contaminated neck. He gave five presentations to the academy in 1881, published in 1882. He declared that the doctrine of spontaneous generation would never recover from the mortal blow of this simple experiment, that no microscopic being came into the world without parents similar to itself.

• 5. The Silkworm Years

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  In 1865, Jean-Baptiste Dumas asked Pasteur to study a disease decimating silkworm farms across the south of France and Europe. The disease was pebrine, marked by black spots and, under the microscope, by Cornalia corpuscles. Pasteur accepted and made five long stays in Ales between the 7th of June 1865 and 1869. He began in error. Pasteur believed that pebrine and a second disease, flacherie, were the same, and even that most known silkworm diseases were identical. Only in letters of the 30th of April and the 21st of May 1867 to Dumas did he first separate pebrine from flacherie. He also began by denying the parasitic nature of pebrine, which scholars such as Antoine Bechamp considered well established. One contemporary remark held that Pasteur would only change his mind during 1867. Before he understood the cause, he found a working remedy. A sample of chrysalises was crushed and searched for corpuscles, and if the proportion was very low, the chamber was judged good for reproduction. This sorting of seeds curbed pebrine and saved much of the silk industry in the Cevennes. Flacherie proved harder. In 1878, at the Congres international sericicole, Pasteur admitted that if pebrine is overcome, flacherie still exerts its ravages, blaming farmers who had not followed his advice.

• 6. Weakening The Enemy

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  In October 1879, a delay changed the course of medicine. Pasteur, kept from the laboratory by his daughter's wedding and ill health, instructed his assistant Emile Roux to start a new chicken cholera culture from bacteria that had sat since July. The two inoculated chickens showed mild symptoms, then recovered completely instead of dying as usual. Roux later inoculated the same two chickens with a fresh culture, and this time they died. The aged culture had not protected them, but it pointed to how bacteria might be weakened in the laboratory. In February 1880, Pasteur presented this to the French Academy of Sciences and introduced the term attenuation for the weakening of virulence. He told the academy he hoped to find a vaccine for all infectious diseases. Anthrax came next. His laboratory found that anthrax bacillus formed spores and was not easily weakened by air, so in early 1881 they grew the bacilli at about 42 degrees Celsius to stop spore production. On the 21st of March, despite inconsistent results, he announced successful vaccination of sheep. The veterinarian Hippolyte Rossignol proposed a public test, and the trial ran at Pouilly-le-Fort. Of 58 sheep, 2 goats, and 10 cattle, half were vaccinated. On the 2nd of June, before more than 200 spectators, the vaccinated animals survived while the unvaccinated had died or were dying. Pasteur named these artificially weakened diseases vaccines, in honour of Edward Jenner.

• 7. Secrets And Rivals

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  A French national hero at age 55, Pasteur in 1878 told his family never to reveal his laboratory notebooks to anyone. His family obeyed, and the documents passed down in secrecy. Pasteur Vallery-Radot, his grandson and last surviving male descendant, donated the papers to the French national library in 1964, though they stayed restricted until his death in 1971. The notebooks held uncomfortable truths. At Pouilly-le-Fort, Pasteur claimed he had used a live vaccine, but his notebooks show he used a potassium dichromate-killed vaccine prepared by Charles Chamberland, a method similar to one Henry Toussaint had developed. Toussaint had presented an attenuated anthrax vaccine to the academy on the 12th of July 1880, and it was Toussaint who had isolated the chicken cholera bacteria later named Pasteurella in Pasteur's honour. Pasteur had contested the discovery on grounds of jealousy. The rabies story carried its own gap. Pasteur wrote that the vaccine had been tested in 50 dogs before Joseph Meister, yet according to the historian Gerald L. Geison, the notebooks show only 11. In 1995, the centennial of Pasteur's death, Geison published The Private Science of Louis Pasteur and argued that Pasteur had given misleading accounts in his most important discoveries. Patrice Debre, examining the same documents, found Pasteur sometimes unfair, combative, arrogant, inflexible, and even dogmatic.

• 8. The Vault And The Faith

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  Pasteur suffered a severe stroke in 1868 that paralysed the left side of his body, and he recovered. A stroke or uremia in 1894 severely impaired his health. He died on the 28th of September 1895, near Paris. He was given a state funeral and buried in the Cathedral of Notre Dame, but his remains were later moved to the Pasteur Institute in Paris, in a vault covered with Byzantine mosaics depicting his accomplishments. His private life had carried heavy loss. He married Marie Laurent in 1849, daughter of the rector of the University of Strasbourg and his own scientific assistant. They had five children, and three died young, three of typhoid. Their daughter Jeanne died at age 9 in 1859, Camille at age 2 of a liver tumour in 1865, and Cecile of typhoid fever at age 12 on the 23rd of May 1866. His faith was disputed even after death. His grandson Louis Pasteur Vallery-Radot wrote that he kept from his Catholic background only a spiritualism without religious practice. The well-known line about having the faith of a Breton peasant is, according to family members, apocryphal, appearing for the first time shortly after his death. The institute he founded outlived him by far. Beginning in 1891 it spread abroad, and today there are 32 institutes in 29 countries, where Roux had taught the first course of microbiology in the world.