The life of Pasteur

by René Vallery-Radot

“I am arriving at this result that there is no silkworm disease. There is but an exaggeration of a state of things which has always existed, and it is not difficult, in my view, to return to the former situation, even to improve on it. The evil was sought for in the worm and even in the seed; that was something, but my observations prove that it develops chiefly in the chrysalis, especially in the mature chrysalis, at the moment of the moth’s formation, on the eve of the function of reproduction. The microscope then detects its presence with certitude, even when the seed and the worm seem very healthy. The practical result is this: you have a nursery full; it has been successful or it has not; you wish to know whether to smother the cocoons or whether to keep them for reproduction. Nothing is simpler. You hasten the development of about 100 moths through an elevation of temperature, and you examine these moths through the microscope, which will tell you what to do.

“The sickly character is then so easy to detect that a woman or a child can do it. If the cultivator should be a peasant, without the material conditions required for this study, he can do this: instead of throwing away the moths after they have laid their eggs, he can bottle a good many of them in brandy and send them to a testing office or to some experienced person who will determine the value of the seed for the following year.”

The Japanese Government sent some cases of seed supposed to be healthy to Napoleon III, who distributed them in the silkworm growing departments. Pasteur, in the meanwhile, was stating the results he had arrived at, and they were being much criticized. In order to avoid the pébrine, which was indeed the disease caused by the corpuscles so clearly visible through the microscope, he averred that no seed should be used that came from infected moths. In order to demonstrate the infectious character of the pébrine he would give to some worms meals of leaves previously contaminated by means of a brush dipped in water containing corpuscles. The worms absorbed the food, and the disease immediately appeared and could be found in the chrysalides and moths from those worms.

“I hope I am in the right road—close to the goal, perhaps, but I have not yet reached it,” wrote Pasteur to his faithful Chappuis; “and as long as the final proof is not acquired complications and errors are to be feared. Next year, the growth of the numerous eggs I have prepared will obviate my scruples, and I shall be sure of the value of the preventive means I have indicated. It is tiresome to have to wait a year before testing observations already made; but I have every hope of success.”

While awaiting the renewal of the silkworm season, he was busy editing his book on wine, full of joy at contributing to the national riches through practical application of his observations. It was, in fact, sufficient to heat the wines by the simple process already at that time known in Austria as pasteurisation, to free them from all germs of disease and make them suitable for keeping and for exportation. He did not accord much attention to the talk of old gourmets who affirmed that wines thus “mummified” could not mellow with age, being convinced on the contrary that the most delicate wines could only be improved by heating. “The ageing of wines,” he said, “is due, not to fermentation, but to a slow oxidation which is favoured by heat.”

He alluded in his book to the interest taken by Napoleon III in those researches which might be worth millions to France. He also related how the Imperial solicitude had been awakened, and acknowledged gratitude for this to General Favé, one of the Emperor’s aides de camp.

The General, on reading the proofs, declared that his name must disappear. Pasteur regretfully gave in to his scruples, but wrote the following words on the copy presented to General Favé: “General, this book contains a serious omission—that of your name: it would be an unpardonable one had it not been made at your own request, according to your custom of keeping your good works secret. Without you, these studies on wine would not exist; you have helped and encouraged them. Leave me at least the satisfaction of writing that name on the first page of this copy, of which I beg you to accept the homage, while renewing the expression of my devoted gratitude.”

Another incident gives us an instance of Pasteur’s kindness of heart. In the year 1866 Claude Bernard suffered from a gastric disease so serious that his doctors, Rayer and Davaine, had to admit their impotence. Bernard was obliged to leave his laboratory and retire to his little house at St. Julien (near Villefranche), his birthplace. But the charm of his recollections of childhood was embittered by present sadness. His mind full of projects, his life threatened in its prime, he had the courage, a difficult thing to unselfish people, of resolutely taking care of himself. But preoccupied solely with his own diet, his own body now a subject for experiments, he became a prey to a deep melancholia. Pasteur, knowing to what extent moral influences react on the physique, had the idea of writing a review of his friend’s works, and published it in the Moniteur Universel of November 7, 1866, under the following title: Claude Bernard: the Importance of his Works, Teaching and Method. He began thus: “Circumstances have recently caused me to re-peruse the principal treatises which have founded the reputation of our great physiologist, Claude Bernard.

“I have derived from them so great a satisfaction, and my admiration for his talent has been confirmed and increased to such an extent that I cannot resist the somewhat rash desire of communicating my impressions....”

Amongst Claude Bernard’s discoveries, Pasteur chose that which seemed to him most instructive, and which Claude Bernard himself appreciated most: “When M. Bernard became in 1854 a candidate for the Académie des Sciences, his discovery of the glycogenic functions of the liver was neither the first nor the last among those which had already placed him so high in the estimation of men of science; yet it was by that one that he headed his list of the claims which could recommend him to the suffrages of the illustrious body. That preference on the part of the master decides me in mine.”