Louis Pasteur (1822-1895) in 1886.

Pasteur takes another balloon whose slim glass neck is strangely curved into the form of an horizontal S, and raises it to his eye-level.  The audience is thoughtful.

“Now, suppose that I repeat this experiment, but before boiling the liquid, I stretch the neck of the balloon over the gaz burner, so as to thin it out, leaving however its extremity open.  Having done this, I bring the liquid inside the balloon to the boil, then I leave it to cool.  And, the liquid in this second balloon will remain unaltered, not for two or three days, but for three and four years…  for the experiment of which I am speaking already has this duration!  The liquid remains perfectly limpid like distilled water.”

He slowly puts down the two glass balloons and his serious voice rises to the tiers of seats:

“What difference is there between these two vases?  They contain the same liquid, they both contain air, both are open.  Why does one alter, and the other doesn’t?  Inside the first, the dusts that are in suspension in the air fall into the liquid, and the germs find appropriate food, then develop.  Whence, microscopic beings.  Here, on the contrary,”

and he again raises the balloon with the neck curved into an horizontal S toward his public,

“it is very difficult for the dusts in suspension in the air to penetrate into the liquid.  Where do they go?  They fall inside the curved neck!”

Pasteur points to the trough of the S.

“In this vase, the air enters very slowly in function of the laws of diffusion and temperature variations.  But if I violently shake this vase, within two or three days, it will contain animalcules and moulds.  Why?  Because the air has entered suddenly and taken dusts in with it…  I take from the immensity of creation my drop of water, full of the fecund jelly appropriate for the development of inferior beings.  And I wait.  And I observe.  And I ask it to perform the primitive creation again for me.  It would be such a beautiful spectacle!  But it is mute since these experiments began four years ago!  Because I removed from it the only thing that Man cannot produce:  Life!  That of the germs which float in the air.  The life is the germ, and the germ is the life!  The doctrine of spontaneous generation will never rise again from the mortal blow that this simple experiment gives it!”

Thunderous applause salutes the Man of Science and the Orator.

Pouchet, Joly and Musset will not present themselves before the Commission.  They desisted with the pretext that this Commission would be favourable to Pasteur, thereby condemning themselves by default.  Pouchet leaves the stage, Pasteur definitively takes the leading role, everything he says and does will from now on be followed by the newpapers.


In fact, the different actors are all partly right.  The heterogenists and Pasteur are unaware that there is a well-hidden “mouse” in the decoction of hay:  resistant forms of a bacillus, the “subtle bacillus”, which will only be discovered in 1876, when an English researcher will again take up the question of spontaneous generation.  Unsuspected – and unsuspectable – characteristics favourise Pasteur in his combat.  But, it could be said, spontaneous generation clings to life.  Friends of Pouchet, relayed by the Press, take the debate to the public right after their defeat.  The conflict then leaves the heights of the Sea of Ice and the Academie des sciences to descend into worldly salons.  If everything comes from a germ, they say, where did the first germ come from?  A mystery before which one must incline, replies Pasteur, a question of the origin of all things, a question which remains outside the domain of scientific research.

However, the Roman Catholic scholar is suspected of having concocted his researches to serve as vehicules for philosophical and religious conceptions:  by attacking spontaneous generation, he is attacking Darwin and the Protestant Pouchet.  Pasteur denies these views and modestly answers:

“Researches on the primary cause are not the domain of Science.  Science only acknowledges that which can be demonstrated, facts, secondary causes, phenomena.  The day that a scholar bases his studies on one or the other of the philosophical systems, he abdicates his title of scholar, he pleads a cause, he is no longer seeking the truth for itself.”

At this epoch, Louis Pasteur, a renowned Chemist, has not yet accomplished the pathway which, from experimentations to discoveries, from discoveries to combats, will lead him to transform world health.  A stubborn worker, he sleeps little, and rises at Dawn.  Rene Valery-Radot sketches this rather emphatic portrait of him:

“His wide forehead overflows from his little calotte, his brow is profoundly prominent, his temple is crossed by a vein as if it has swollen under the effort of his thought, his eye prolongs his contemplative gaze into the distance, his whole face reflects both energy and meditation.”


How did this man, whom nothing destined to approach Medicine, arrive here?  To understand it, it is necessary to go back sixteen years, to February 1848, inside the minuscule laboratory of the Rue d’Ulm, in an Ecole normale closet.  There are riots in the streets of Paris.  Inside his study which muffles the sounds of the combats outside, a young Normalien with a serious face is observing minuscule crystals with a curious instrument, which looks a bit like a little copper telescope.  He is seeing something that no-one before him has seen.  On the table, another copper object which is going to become his favourite weapon:  the microscope.  His father, a provincial tanner and former soldier of the Empire, has advised him to stay away from the political troubles which are shaking the country and are going to lead to the creation of the Second Republic.  The preceding year, young Louis Pasteur had defended two theses covering his three domains of interest:  Physics, Chemistry and Crystallography.  His Physics thesis was on Les phenomenes relatifs a la polarisation rotatoire des liquides.  Explanation:  unlike natural light which vibrates in all directions, polarized light is a light which can be made to vibrate in only one level.  The instrument in the form of a little telescope into which Pasteur is looking, is in fact a polarimetre invented by his master and protector Biot, the great Astronomer and Physiologist.  This precious tool polarizes the light captured by an optical lense over the “juice” that one wants to study.  The deviation of the level of polarization of the light, that is to say, the way in which it is directed as it lights matter, indicates a mineral or organic substance;  mineral matter does not deviate the light, unless it is in a crystal state;  with organic matter, such as essence of terebenthine or a sugar solution, the light is deviated.  Biot also uses it to diagnose diabetes, the rotation of the light in the apparatus also indicating the sugar concentration of the studied liquid.

To be continued.