But at the same time he was forced to realise how incomplete and superficial were the observations of the man whom he nevertheless revered as the first among his masters.
How often was he to find occasion for revising the statements of his predecessors! They were not merely incomplete; they were often erroneous, even when they had the greatest names to recommend them.
Must we then ignore all that has been said and written and wholly repudiate the inheritance of the centuries and the scientists of the past? Heaven preserve us from such stupidity! But while it would not be reasonable or even possible to make a clean sweep of all that has been acquired by our [[158]]predecessors, it is none the less prudent not to accept, in blind confidence, the whole heritage of the past, but to subject to the control of facts the statements even of the masters when these appear at all extravagant. Otherwise we run the risk, if not of perpetrating error by repeating it on our own responsibility, at all events of following a false trail on which we may lose much time and which may finally lead us to envy the lot of those who are able to attack their subject, from the very first, with minds empty of all information and any preconceived ideas. This was brought well home to Fabre by the repeated experience of errors which had escaped the most learned authors and erroneous methods suggested by the best books. And the persuasive effect of the highly symptomatic example afforded by an absolutely unrivalled master was even more eloquent.
Unexpectedly, one fine day [writes Fabre], Pasteur rang my door-bell: the Pasteur who was presently to acquire so great a celebrity. His name was known to me. I had read his beautiful essay on the dissymmetry of tartaric acid; I had followed with the keenest interest his researches concerning the generation of the Infusoria.
Every period has its scientific craze; to-day it is evolution; then it was spontaneous generation. By [[159]]his glass bulbs, made sterile or fertile at will, by his experiments, magnificent in their rigorous simplicity, Pasteur exploded for ever the insanity which professed to see life arising from a chemical conflict in a mass of putrescence.
Aware of this dispute, so victoriously elucidated, I gave my illustrious visitor the best of welcomes. The scientist had come to me in the first place for certain information. I owed this notable honour to my quality of colleague as a teacher of physics and chemistry. Ah, but what a humble, obscure colleague!
Pasteur’s tour through the district of Avignon was in connection with sericulture. For some years the silk-worm nurseries had been at sixes and sevens, ravaged by unknown plagues. The silkworms, without appreciable cause, became masses of putrid deliquescence, or hardened into stony lumps. The peasant, in dismay, saw one of his chief sources of income disappearing; after much expense and trouble he had to throw his litters on the dung-heap.
A few words were exchanged concerning the prevailing evil; then, without further preamble:
“I wanted to see some cocoons,” said my visitor; “I have never seen any; I know them only by name. Could you get me some?”
“Nothing simpler. My landlord is himself a dealer in cocoons, and he lives across the road. If you’ll be good enough to wait a moment, I will bring you what you want.” [[160]]
A few long strides and I had reached my neighbour’s house, where I stuffed my pockets with cocoons. On my return I offered them to the scientist. He took one, turned it over and over in his fingers; curiously he examined it, as we should some singular object which had come from the other end of the world. He shook it against his ear.
“It rattles!” he said, quite surprised. “There is something inside!”
“Why, yes!”
“But what?”
“The chrysalis.”
“What’s that, the chrysalis?”
“I mean the sort of mummy into which the caterpillar turns before it becomes a moth.”
“And in every cocoon there is one of those things?”
“Of course; it’s to protect the chrysalis that the caterpillar spins.”
“Ah!”
And without more ado, the cocoons went into the pocket of the scientist, who was to inform himself at leisure concerning this great novelty, the chrysalis. This magnificent assurance impressed me. Knowing nothing of caterpillar, cocoon, chrysalis, or metamorphosis, Pasteur had come to regenerate the silkworm. The ancient gymnasts presented themselves naked for the contest. This ingenious thinker, who was to fight the plague of the silk-worm nurseries, had also hastened to battle wholly naked: that is, devoid of the simplest [[161]]notions of the insect he was to save from danger. I was astounded; more, I was filled with wonder.[14]
The fact is indeed so extraordinary that it may well appear incredible, but it receives authentic confirmation from the wholly concordant account of Duclaux, Pasteur’s pupil and historiographer, as well as from the honesty of the naturalist, who is assuredly incapable of having invented the story for our amusement.
I still remember the day [says Duclaux] when Pasteur, returning to the laboratory, said to me with a touch of excitement in his voice:
“Do you know what M. Dumas has just asked of me? To go to the Midi, to study the silk-worm disease.”
I don’t know what I replied; probably what he himself replied to his illustrious master: Then there is a silk-worm disease? There are provinces that are being ruined by it? All this was happening so far from Paris, and we were so far from Paris in the laboratory!…
Pasteur hesitated. He was not a physiologist. But Dumas’ insistence, the attraction of the unknown, and an inward voice urged him to accept. So he left for the Midi; it was early in June 1865. He was invested with an official mission which confronted him with a plague that had to be conquered [[162]]and obliged him to render an account of the attempts made and the results obtained.
To be sent to fight a fire and not to know what fire is and to have no fire-engine or hose! It needed Pasteur to accept and to shoulder such a responsibility!… To his complaint that he had no knowledge of the matter, Dumas had replied:
“So much the better! You will have no ideas on the subject but those that will come to you as a result of your own observations!”
This reply is not always a paradox, but one has to be careful to whom one makes it![15]
In this case the choice was not mistaken, and the lesson was as profitable to Pasteur as it was to Fabre, to whom he was about to hand it on, all unsuspecting.
When Pasteur was called upon to regenerate sericulture, the silk-worm disease had been known for twenty years. During that period much research had been undertaken and many efforts had been made, in France as well as in Italy, to discover the nature of the affection and to fight it. But “of all this story, a mixture of truth and falsehood, Pasteur knew nothing when he began his researches.” More—and this was what astonished Fabre—he knew nothing of the physiology or the rearing of the silk-worm. “For [[163]]the first time he has seen a cocoon, and has learned that there is something in the cocoon, a rough model of the future moth,” … and he is about to revolutionise the hygiene of the silk-worm nurseries and is preparing to revolutionise medicine and general hygiene in the same way,[16] by showing that the maladies of silk-worms and most of our human maladies arise from the development in the tissues of a microscopic living entity, a microbe, the cause of the malady. And while his other discoveries won for him only fame and the admiration of his contemporaries, this will give him immortality and place him in the front rank of the benefactors of humanity. Decidedly ignorance may have its advantages.
Encouraged by the magnificent example of Pasteur (continues the entomologist), I have made it a rule to adopt the method of ignorance in my investigations of the instincts. I read very little. Instead of turning over the leaves of books, an expensive method which is not within my means, instead of consulting others, I set myself obstinately face to face with my subject until I contrive to make it speak. I know nothing. So much the better; my interrogation will be all the freer, to-day tending in one direction, to-morrow in another, according to the information acquired. And [[164]]if by chance I do open a book, I am careful to leave a section of my mind wide open to doubt.[17]
Beginning with that arising out of Dufour’s memoir, repeated experiences taught Fabre not to be too greatly influenced, in his conceptions of natural objects, by faith in his reading or even in the assertions of his masters. To go still further, Pasteur’s example made him appreciate the advantage of coming fresh to the facts, of confronting them in a state of ignorance, of receiving impressions from them alone, and of having no ideas but those that truly emanate from the reality.