Louis Pasteur (1822-1895) in 1886.

For the moment, Pasteur leaves Arbois for Ales:  he is called there by Jean-Baptiste Dumas, Senator of the Gard and former Minister of Agriculture.  This gentleman is also Pasteur’s first Professor, and his scientific protector.  A famous Chemist, he guided the young scholar’s first steps at the Sorbonne.  Pasteur has replied:

“I am at your service.”  [“Disposez de moi.”]

So he goes to the bedside of strange patients.  These are not yet children bitten by enraged dogs, they are fat, pale, voracious worms which devour mulberry leaves and spin silk cocoons.  The Chemist’s mission is to save the Silk Industry, an Industry struck by an illness which is making France lose important sums each year.  Pasteur thinks that he is leaving for four months.  In fact, he is going to study these famous worms – which are really caterpillars – for four years, armed with his microscope and his formidable intuition.

Louis Pasteur’s personality, the methodical researcher and the rather rough man-on-the-ground, is fairly well reflected in an anecdote from these years.  Jean-Henri Favre, a great Naturalist who was to leave immortal pages on the lives and customs of the insects, recounts:

“A few words exchanged on the ill that was raging, without any other preamble:  ‘I want to see the cocoons,’ says my visitor.  ‘I’ve never seen any.  I only know the name.  Could you procure me some?’

‘Nothing could be easier.  My landlord sells cocoons, and we are next-door neighbours.  Will you wait a moment, and I’ll be back with what you want?’

“I rush to my neighbour’s place, where I stuff my pockets with cocoons.  When I get back, I present them to the scholar.  He takes one, turns it around and around in his fingers;  curiously, he examines it as we would a singular object from the other end of the Earth.  He shakes it near his ear:

It’s ringing,’ he says all surprised.  ‘There’s something inside.’

‘Yes there is.’

‘And what is it?’

”  ‘The chrysalis.’

”  ‘What’s the chrysalis?’

‘It’s a sort of mummy into which the caterpillar changes itself before becoming a moth.’

‘And in every cocoon, there is one of these things?’

‘Of course, it is to safeguard the chrysalis that the caterpillar has spun the silk!’


“And without anything more, the cocoons went into the pocket of the scholar who was going to have to teach himself in his own good time about this great new thing, the chrysalis.  This magnificent assurance struck me.  Ignorant about caterpillar, metamorphosis, cocoon, chrysalis, Pasteur was coming to regenerate the silkworm.  A genial fighter against the plague of the Magnaneries – Centres for raising silkworms – he was coming completely naked to the battle.  That is to say, without even simple notions about the insect to be snatched from peril.  I was stunned.  More than that, I was amazed.”

But straight away, more questions from Pasteur:

‘Show me your cellar, please.’

Another problem was worrying the scholar:  that concerning the improvement of wines by heating.

“I pointed to a corner of the kitchen, a chair without straw, and on this chair a dame-jeanne of a dozen litres.  With my Professor’s salary, I could not afford the expense of a little wine, and was making for myself in this jar a sort of piquette by putting in a handful of cassonade [sugar] and grated apples.

That’s my cellar, Monsieur.’

‘That’s all?’

‘Alas, yes, that’s all…’


“Not another word, nothing more from the scholar.  Pasteur, it was obvious, knew nothing about this food with strong spices that the common people call poverty [la vache enragee].  […]  A microbe has escaped him, the most terrible of all:  that of misfortune strangling goodwill.”

But Fabre was wrong to worry about the silkworms.  Pasteur learns very fast.  And very quickly he begins “by collecting facts to get some ideas”, as the Naturalist Buffon used to say.  He knows that another Italian Naturalist, Agostino Bassi, has already observed some “corpuscules”, some “infinitely small things” inside the bodies of sick worms.  He goes straight to work.

Nine days after his arrival in the Gard, he is painfully hit by the death of his father.  He has to leave.  Another drama follows, the death in September 1865 of his daughter Camille, aged two, over whom he watched night after night until the end.  Extremely upset, he takes the little coffin to the Arbois cemetery.  Six months later, death strikes again:  his second daughter, Cecile, is taken by typhoid in her twelfth year.  It is a broken man who settles in Ales with his family and his three pupils:  Desire Gernez, the faithful Emile Duclaux and Eugene Maillot.  He returns to his work in a little Magnanery and does not abandon it again.  Fabre was mistaken about the bearded, unsociable man who had come to see his cellar:  Pasteur, despite his well-known lack of diplomacy, is filled with compassion for the Small Farmers touched by the malediction of the silkworm and threatened with poverty.  This “microbe of misfortune” is far from having escaped him.  When people in Paris smile about this malady of the silkworms, he, who is the least ironic of men, thinks about the ravages of this plague, of the Peasant who puts into the cultivation of the worm his hope for bread, of the big Spinning Factories whose fortunes touch the country’s interests.  He repeats in a tone full of confidence:

“The year 1867 must be the last to hear the complaints of the Silkworm Farmers.”

Three thousand five hundred owners of Centres for raising silkworms are therefore awaiting the results of the research of this Chemist to whom the Government has given the heavy responsibilty of saving their future;  this man, up before the sun, likes to repeat:

“Let us work, that’s the only distraction.”

Faithful to his method, he infinitely varies the conditions of observation and experimentation, he modifies the factors of development so as to produce differences which create questions and make reflection advance.  He passes from one Silkworm Centre to another, questions, takes samples of eggs, caterpillars, moths, sorts them, observes them.  His pupils install a glasshouse for mulberry bushes, submitting the leaves of the plants to chemical analysis.  Could the illness be in the caterpillars’ food?  His bonnet on his head, his eye riveted to the microscope, Pasteur gradually unravels the illness’ secrets.  It is in fact two illnesses, which will be named flachery and pebrina.  He shows that the eggs and the caterpillars can carry these illnesses without the corpuscules being seen under the microscope.  It is in the moth, the result of the worm’s metamorphosis, that it has to be sought.  He then puts together a method for eliminating the propagation of the ill, a simple, efficient, trustworthy method:  one takes a dead moth which has laid eggs, one leaves it to dry out, then one grinds it in a mortar with a drop of water, so as to verify under the microscope the presence of corpuscules in the powder.  If the moth is infected, one destroys its eggs whose products can contaminate the whole production.

And once more, Pasteur is confronted with the incredulity that this very simple method inspires.  And once more, Pasteur the Fighter deploys his eloquence and makes his detractors bite the dust.  Made impatient by the objections opposed to him as to the difficulty of getting the use of the microscope accepted by Peasants, he loses his temper:

“Don’t tell me that we must find something simpler that a preventive method which consists in placing one’s eye to the lense of a microsope, after having ground a dried moth with a few drops of water, real child’s play, which demands an apprenticeship of an hour or two.  Such a refusal would only be ridiculous when one considers that it is a question here of interests which, for France alone, result in an annual loss of 30, 40 and 50 million francs, and for each Farmer Owner, by that of his best, and often his only, revenue!”

He then starts a veritable campaign of propaganda and appeals to the Minister of Agriculture.  But these efforts and his mourning have exhausted him.  A cerebral haemorrhage strikes him, leaving him with a gammy leg and his left hand paralyzed.  He has looked death in the eye, he enters into convalescence.


To be continued.