Louis Pasteur (1822-1895) in 1886.

Paul Bert, Physiologist and Minister of Public Instruction, demonstrates, in 1883, during a brilliant expose to the Academie on Pasteur, the main lines of the scholar’s work:  he says that Pasteur’s work can be classed in three series which constitute three great discoveries.  The first can be formulated like this:

Each fermentation is the product of the development of a special microbe.”

The second affirms:

“Each infectious illness is produced by the development in the organism of a special microbe.”

The third can be said like this:

“The microbe of an infectious illness, cultivated in certain determined conditions, is attenuated in its nocive activity;  from virus, it has become vaccine.”

Beyond Pasteur’s impressive scientific rigour, as his laboratory notebooks attest, a rigour doubled with a prodigious power for work, also beyond his very great intellectual flexibility, his faculty of being able to ceaselessly manipulate a collection of interchangeable hypotheses, it is his “ecological philosophy” which distinguishes him, his understanding of the connection between living beings and their natural environment, the ties between Man and Nature.  He elaborates this philosophy by stages, each of his works bringing him another stone to build it.  His studies on beer make him understand that the activity of microbes is influenced by their environment, and that microbian life is responsible for the permanent recycling of chemical substances in natural conditions, each bacterium has a role in the organization of the chain of life on Earth:

“If the microscopic beings disappeared from the surface of the Earth, it would be encumbered by animal and vegetal cadavers, by dead organic matter.  It is principally they who give its combustive properties to oxygen.  Without them, life would become impossible, because the work of death would be incomplete.”

The study of the silkworms and, later, human illnesses, made him understand that

“the nature of the life of all living beings is to resist the causes of destruction with which it is naturally surrounded”,

which introduces the notion of the possible coexistence of Man, Animal and microbes, as long as infection cannot declare itself, in particular environmental conditions.  Or, a pacific coexistence.


Louis Pasteur, Chemist.

Pasteur was neither Galileo, nor Newton, who attempted to explain the mysteries of the Universe, but he harmonised his activities with the preoccupations of his epoch, by submitting Nature to Science.  Until the XIXth Century, Society hadn’t had much to ask of the Man of Science, that Science that was the fief of the philosophical mind.  Pasteur would conciliate theory and practice throughout his whole life, his works would find their applications on the ground, in Industry, in the hospital, at home, in the city and in the country.  One could say, along with Claire Salomon-Bayet, that after Pasteur

“the whole of everyday life is kneaded with Pasteurism:  vaccinated children, boiled milk, sterilized rubber nipples, interdiction to spit on the ground, washed hands, controlled waters, disinfections, cut hair, short fingernails, municipal drains.”

One could add Pasteurized beer, Pasteurized butter, Pasteurized cheese, Pasteurized milk.  The list goes on and on…

Pasteur is also the judicious choice of men, of disciples whom he forms to his methods, and on whom he relies to transpose the laboratory researches everywhere.  According to Anne-Marie Moulin’s formula,

“the Pasteurians are perhaps Pasteur’s most impressive work”.

Chamberland, Duclaux, Roux, Grancher, Yersin, Loir, Calmette, Nicolle, Metchnikoff are all his direct heirs, who would in turn form the Pasteurians of the second generation, spreading throughout the world the scholar’s methods and doctrine.  Under its impulse, Doctor Calmette would create a Pasteur Institute in Lille, Adrien Loir would direct a Pasteur Institute in Tunis, Yersin would go to track down the plague in China, Nicolle would organize a bacteriological laboratory in Constantinople, Le Dantec would go to Brazil to study Yellow Fever.  The Pasteurian revolution has conquered the whole Earth.  The ideas and methods of Microbiology, by progressively changing the comportments of Medical Doctors and researchers, have changed the social comportments around illness.  By taking the microbe into the laboratory, and the laboratory into the hospital, Pasteur and the Pasteurians invented modern medical research.

If, today, we no longer die from diphtheria, rabies or tuberculosis, it is in great part thanks to this man who was passionate about Science, and to his everyday methodical application to his work.