Technology & Medicine › Industrial revolution › Germ theory of disease
Louis Pasteur
1822–1895; swan-neck flasks 1859–62· Person· Germs, drugs & genetics
Well documentedSolid records, physical evidence or scientific consensus.
French chemist who showed microbes cause fermentation and disease, invented pasteurization, and made the first laboratory-weakened vaccines.
See it on the Technology & Medicine map →How it works
Pasteur began as a chemist studying crystals. In 1857 he showed that fermentation is the work of living microbes. His swan-neck flasks (1859–62) proved broth stays sterile when airborne germs cannot reach it. Gentle heating to kill spoilage microbes, pasteurization, saved wine and later milk. He traced silkworm diseases to microbes, made vaccines for chicken cholera and anthrax, and in 1885 treated nine-year-old Joseph Meister, bitten by a rabid dog. The Pasteur Institute opened in 1888.
Why it mattered
He made germs central to biology and medicine, saving industries and lives, and turned vaccine-making into a laboratory science.
Legacy and how we know
His papers, original flasks at the Pasteur Institute, and private notebooks opened in the 1970s; historian Gerald Geison's 1995 study found gaps between them and his public claims.
Still unknown or debated
Meister was treated after limited animal testing; whether the boy would have developed rabies at all is unknown, and the ethics are debated.
Connections (3)
▸Vaccination (Jenner's smallpox vaccine) was generalised by Louis PasteurWell documented
The connection
Jenner's vaccine relied on a lucky natural cousin, cowpox. Pasteur found a general method: weaken the disease germ itself in the laboratory, by ageing cultures, heat or chemicals. He made vaccines for chicken cholera, anthrax and rabies, and proposed calling them all 'vaccines' in Jenner's honor.
When and how
Paris, 1879–85; public anthrax trial at Pouilly-le-Fort, May 1881; rabies treatment of Joseph Meister, July 1885.
How we know
Pasteur's 1881 papers, the press-covered Pouilly-le-Fort trial, and his explicit tribute to Jenner at the London medical congress of 1881.
Debates and open questions
Pasteur's notebooks show his anthrax vaccine was made by a chemical method like rival Toussaint's, not the oxygen method he described; credit to Toussaint and Roux is debated.
▸Louis Pasteur championed and helped prove the Germ theory of diseaseWell documented
The connection
Pasteur showed that fermentation and decay are caused by living microbes, and his swan-neck flasks showed broth stays sterile if airborne germs cannot reach it, undermining belief in spontaneous generation. His work on silkworm diseases and anthrax tied specific microbes to specific diseases, while Koch supplied the rigorous laboratory methods.
When and how
Lille and Paris, 1857–1881; swan-neck flask experiments, 1859–62; silkworm studies in southern France, 1865–70.
How we know
His published papers, repeatable experiments, and original flasks at the Pasteur Institute, still free of growth after more than 150 years.
Debates and open questions
How to divide credit between Pasteur and Koch, rivals whose French–German feud was sharpened by the 1870–71 war, is still discussed.
▸Louis Pasteur inspired Lister's antiseptic surgeryWell documented
The connection
In 1865 Lister read Pasteur's papers showing that microbes from the air cause putrefaction. He reasoned that wound infection was the same process, so killing germs in and around the wound with carbolic acid should prevent it. He credited Pasteur openly and wrote to thank him in 1874.
When and how
Glasgow, 1865, after chemistry professor Thomas Anderson pointed Lister to Pasteur's work.
How we know
Lister's 1867 Lancet papers cite Pasteur, and his 1874 letter thanking Pasteur survives.
Debates and open questions
Lister focused on airborne germs, but hands and instruments mattered more; how this emphasis shaped methods like his later-abandoned carbolic spray is discussed.