Questions to ask Louis Pasteur

Pasteur's work at a glance

Louis Pasteur was born on 27 December 1822 in Dole, in eastern France, the son of a tanner, and trained as a chemist at the École normale supérieure in Paris. He was not a medical doctor, which matters for several questions below. He died on 28 September 1895 near Paris and is buried in a crypt at the Institut Pasteur. Each row of this table is a good starting point for an interview question.

How to use this list

Most students only ask about milk and vaccines. You will stand out if you ask about one experiment in detail and about the gap between his public claims and his notebooks. For a wax museum, the flask and Meister questions are clear and dramatic. Treat everything about vaccines as history: this page, and any interview based on it, says nothing about the safety of modern vaccines.

You can practise the interview with an AI recreation of Louis Pasteur on Yuga, by voice or text. It is built from his writings and the record, but it is a recreation that can be wrong, so cite Pasteur's papers or a biography, not the app.

Early life and the first discoveries

Record: he was an average pupil who liked drawing; his pastel portraits of his parents survive. In 1848 he found that crystals of a form of tartaric acid came in two mirror image shapes, which he separated by hand under a magnifying glass. In 1854 he became dean of the new science faculty at Lille, where local industry brought him fermentation problems.

1. You were good at drawing. Why did you choose chemistry?
2. How did you separate the left handed and right handed crystals?
3. Why did a beetroot alcohol factory in Lille send you to study fermentation?
4. What did you mean when you told your Lille students that chance favours the prepared mind?

Germs, flasks and wine

Record: many scientists believed microbes arose by themselves from rotting matter. Pasteur boiled broth in flasks with long curved necks that let air in but trapped dust. The broth stayed clear unless the neck was broken or tipped. He presented the results in a famous lecture at the Sorbonne on 7 April 1864. His heating process was first for wine and beer; heating milk this way was developed later, by others.

1. Why did you bend the necks of your flasks into an S shape?
2. Who was Félix Pouchet, and why did you argue with him?
3. Why did you take flasks up a glacier near Chamonix?
4. How did heating wine save French winemakers money?
5. Why did you want French beer to beat German beer?
6. Silkworms were not your field. Why did you agree to study their disease in 1865?

Vaccines, rabies and Joseph Meister

Record: in May 1881 at Pouilly-le-Fort he vaccinated 25 sheep against anthrax and left 25 unvaccinated, then infected all of them; by 2 June the unvaccinated sheep were dead and the vaccinated ones alive. On 6 July 1885 Joseph Meister, a boy from Alsace bitten by a rabid dog two days earlier, was brought to him. Because Pasteur was not a physician, doctors gave the boy a series of injections of dried rabbit spinal cord over about ten days. Joseph survived. A few months later a 15 year old shepherd, Jean-Baptiste Jupille, bitten while protecting younger children from a rabid dog, was also treated. The vaccine idea itself had come from chicken cholera cultures left standing over the summer of 1879, which turned out to protect rather than kill. Pasteur used the word vaccine in honour of Edward Jenner's cowpox work.

1. Why did you make the anthrax trial a public event with journalists watching?
2. What happened to the chicken cholera cultures you left over the summer of 1879?
3. What did you feel the night before the first injection into Joseph Meister?
4. Why did doctors have to give the injections and not you?
5. Why did you call your treatments vaccines?
6. Why is there a statue of the shepherd boy Jean-Baptiste Jupille at your institute?

The notebooks and the man

Record: Pasteur asked his family not to show his laboratory notebooks. His grandson gave them to the Bibliothèque nationale de France in 1964. The historian Gerald Geison studied them and argued in The Private Science of Louis Pasteur (1995) that the anthrax vaccine used in 1881 was made by a chemical method close to a rival's, not the method Pasteur described in public, and that the rabies treatment had less animal testing behind it than he implied. Other historians accept parts of this and dispute others. Pasteur also lost three of his five children to illness, had a stroke in 1868 at 45, and returned his honorary degree from the University of Bonn in 1871 after Prussia shelled Paris.

1. Why didn't you tell the public how the Pouilly-le-Fort vaccine was really made?
2. How sure were you that the rabies treatment was safe before you tried it on Joseph?
3. How did losing your daughters affect your work on disease?
4. How did you keep working after your stroke?
5. Why did you send back your degree from Bonn?

Pasteur answers, in his own words

Q: How did your experiments end the idea of spontaneous generation?

Q: What did research feel like when you were young?

Q: Is discovery a matter of luck? His answer, from his inaugural lecture as dean at Lille on 7 December 1854, is usually translated as: in the fields of observation, chance favours only the prepared mind.

Q: Does science belong to one country? At the opening of the Institut Pasteur on 14 November 1888 he said, in substance, that science has no country because knowledge belongs to humanity, but the scientist has a country and must serve it. The exact wording varies between reports, so paraphrase it.

Questions to leave out

Pasteur could never see the cause of rabies: it is a virus, too small for the microscopes of his day, and viruses were first seen in the 1930s with the electron microscope. He knew nothing of antibiotics (penicillin, 1928). Do not ask him to judge any modern vaccine or medical decision; that turns history into medical advice. A better question is how he decided when an experiment was ready to try on a person, which his notes and letters do address.

Primary sources and where to find them

His collected works, the Œuvres de Pasteur (seven volumes, 1922 to 1939), and many of his Comptes rendus papers are digitised on Gallica, the French national library's site, in French. The Institut Pasteur in Paris has a museum in his apartment and keeps his crypt. In English, Patrice Debré's Louis Pasteur (1998) is a full biography, and Geison's book is the key study of the notebooks. Our list of pioneers of medicine puts him beside Florence Nightingale and others, and the guide to checking quotes helps with the many lines wrongly credited to him.