The life of Pasteur

by René Vallery-Radot

This shows us once more the strange duality of this inspired man, who associated in his person the faith of an apostle with the inquiring patience of a scientist.

He was often disturbed by tiresome discussions from the researches to which he would gladly have given his whole time. The heterogenists had not surrendered; they would not admit that alterable organic liquids could be indefinitely preserved from putrefaction and fermentation when in contact with air freed from dusts.

Pouchet, the most celebrated of them, who considered that part of a scientist’s duty consists in vulgarizing his discoveries, was preparing for the New Year, 1872, a book called The Universe: the Infinitely Great and the Infinitely Small. He enthusiastically recalled the spectacle revealed at the end of the seventeenth century by the microscope, which he compared to a sixth sense. He praised the discoveries made in 1838 by Ehrenberg on the prodigious activity of infusories, but he never mentioned Pasteur’s name, leaving entirely on one side the immense work accomplished by the infinitely small and ever active agents of putrefaction and fermentation. He owned that “a few microzoa did fly about here and there,” but he called the theory of germs a “ridiculous fiction.”

At the same time Liebig, who, since the interview in July, 1870, had had time to recover his health, published a long treatise disputing certain facts put forward by Pasteur.

Pasteur had declared that, in the process of vinegar-making known as the German process, the chips of beech-wood placed in the barrels were but supports for the mycoderma aceti. Liebig, after having, he said, consulted at Munich the chief of one of the largest vinegar factories, who did not believe in the presence of the mycoderma, affirmed that he himself had not seen a trace of the fungus on chips which had been used in that factory for twenty-five years.

In order to bring this debate to a conclusion Pasteur suggested a very simple experiment, which was to dry some of those chips rapidly in a stove and to send them to Paris, where a commission, selected from the members of the Académie des Sciences, would decide on this conflict. Pasteur undertook to demonstrate to the Commission the presence of the mycoderma on the surface of the chips. Or another means might be used: the Munich vinegar maker would be asked to scald one of his barrels with boiling water and then to make use of it again. “According to Liebig’s theory,” said Pasteur, “that barrel should work as before, but I affirm that no vinegar will form in it for a long time, not until new mycoderma have grown on the surface of the chips.” In effect, the boiling water would destroy the little fungus. With the usual clear directness which increased the interest of the public in this scientific discussion, Pasteur formulated once more his complete theory of acetification: “The principle is very simple: whenever wine is transformed into vinegar, it is by the action of the layer of mycoderma aceti developed on its surface.” Liebig, however, refused the suggested test.

Immediately after that episode a fresh adversary, M. Frémy, a member of the Académie des Sciences, began with Pasteur a discussion, which was destined to be a long one, on the question of the origin of ferments. M. Frémy alluded to the fact that he had given many years to that subject, having published a notice on lactic fermentation as far back as 1841, “at a time,” he said, “when our learned colleague—M. Pasteur—was barely entering into science.”... “In the production of wine,” said M. Frémy, “it is the juice of the fruit itself, which, put in contact with air, gives birth to grains of yeast by the transformation of albuminous matter, whilst M. Pasteur declares that the grains of yeast are produced by germs.” According to M. Frémy, ferments did not come from atmospheric dusts, but were created by organic bodies. And, inventing for his own use the new word hemiorganism, M. Frémy explained the word and the action by saying that there are some hemiorganized bodies which, by reason of the vital force with which they are endowed, go through successive decompositions and give birth to new derivatives; thus are ferments engendered.

Another colleague, M. Trécul, a botanist and a genuine truth-seeking savant, arose in his turn. He said he had witnessed a whole transformation of microscopic species each into the other, and in support of this theory he invoked the names of the three inseparables—Pouchet, Musset and Joly. Himself a heterogenist, he had in 1867 given a definition to which he willingly alluded: “Heterogenesis is a natural operation by which life, on the point of abandoning an organized body, concentrates its action on some particles of that body and forms thereof beings quite different from that of the substance which has been borrowed.”

Old arguments and renewed negations were brought forward, and Pasteur knew well that this was but a reappearance of the old quarrel; he therefore answered by going straight to the point. At the Académie des Sciences, on December 26, 1871, he addressed M. Trécul in these words: “I can assure our learned colleague that he might have found in the treatises I have published decisive answers to most of the questions he has raised. I am really surprised to see him tackle the question of so-called spontaneous generation, without having more at his disposal than doubtful facts and incomplete observations. My astonishment was not less than at our last sitting, when M. Frémy entered upon the same debate with nothing to produce but superannuated opinions and not one new positive fact.”

In his passion for truth and his desire to be convincing Pasteur threw out this challenge: “Would M. Frémy confess his error if I were to demonstrate to him that the natural juice of the grape, exposed to the contact of air, deprived of its germs, can neither ferment nor give birth to organized yeasts?” This interpellation was perhaps more violent than was usual in the meetings of the solemn Academy, but scientific truth was in question. And Pasteur, recognizing the old arguments under M. Frémy’s hemiorganism and M. Trécul’s transformations, referred his two contradictors to the experiments by which he had proved that alterable liquids, such as blood or urine, could be exposed to the contact of air deprived of its germs without undergoing the least fermentation or putrefaction. Had not this fact been the basis on which Lister had founded “his marvellous surgical method”? And in the bitterness given to his speech by his irritation against error, the epithet “marvellous” burst out with a visible delight in rendering homage to Lister.