The life of Pasteur

by René Vallery-Radot

A few months later, on November 17, 1873, he read to the Academy a paper containing further developments of his principles. “In order that beer should become altered and become sour, putrid, slimy, ‘ropy,’ acid or lactic, it is necessary that foreign organisms should develop within it, and those organisms only appear and multiply when those germs are already extant in the liquid mass.” It is possible to oppose the introduction of those germs; Pasteur drew on the blackboard the diagram of an apparatus which only communicated with the outer air by means of tubes fulfilling the office of the sinuous necks of the glass vessels he had used for his experiments on so-called spontaneous generation. He entered into every detail, demonstrating that as long as pure yeast alone had been sown, the security was absolute. “That which has been put forward on the subject of a possible transformation of yeast into bacteria, vibriones, mycoderma aceti and vulgar mucors, or vice versa, is mistaken.”

He wrote in a private letter on the subject: “These simple and clear results have cost me many sleepless nights before presenting themselves before me in the precise form I have now given them.”

But his own conviction had not yet penetrated the minds of his adversaries, and M. Trécul was still supporting his hypothesis of transformations, the so-called proofs of which, according to Pasteur, rested on a basis of confused facts tainted with involuntary errors due to imperfect experiments.

In December, 1873, at a sitting of the Academy, he presented M. Trécul with a few little flagons, in which he had sown some pure seed of penicillium glaucum, begging him to accept them and to observe them at his leisure, assuring him that it would be impossible to find a trace of any transformation of the spores into yeast cells.

“When M. Trécul has finished the little task which I am soliciting of his devotion to the knowledge of truth,” continued Pasteur, “I shall give him the elements of a similar work on the mycoderma vini; in other words, I shall bring to M. Trécul some absolutely pure mycoderma vini with which he can reproduce his former experiments and recognize the exactness of the facts which I have lately announced.”

Pasteur concluded thus: “The Academy will allow me to make one last remark. It must be owned that my contradictors have been peculiarly unlucky in taking the occasion of my paper on the diseases of beer to renew this discussion. How is it they did not understand that my process for the fabrication of inalterable beer could not exist if beer wort in contact with air could present all the transformations of which they speak? And that work on beer, entirely founded as it is on the discovery and knowledge of some microscopic beings, has it not followed my studies on vinegar, on the mycoderma aceti and on the new process of acetification which I have invented? Has not that work been followed by my studies on the causes of wine diseases and the means of preventing them, still founded on the discovery and knowledge of non-spontaneous microscopic beings? Have not these last researches been followed by the discovery of means to prevent the silkworm disease, equally deducted from the study of non-spontaneous microscopic beings?

“Are not all the researches I have pursued for seventeen years, at the cost of many efforts, the product of the same ideas, the same principles, pushed by incessant toil into consequences ever new? The best proof that an observer is in the right track lies in the uninterrupted fruitfulness of his work.”

This fruitfulness was evidenced, not only by Pasteur’s personal labours, but by those he inspired and encouraged. Thus, in that same period, M. Gayon, a former student of the Ecole Normale, whom he had chosen as curator, started on some researches on the alteration of eggs. He stated that when an egg is stale, rotten, this is due to the presence and multiplication of infinitesimally small beings; the germs of those organisms and the organisms themselves come from the oviduct of the hen and penetrate even into the points where the shell membrane and the albumen are formed. “The result is,” concluded M. Gayon, “that, during the formation of those various elements, the egg may or may not, according to circumstances, gather up organisms or germs of organisms, and consequently bear within itself, as soon as it is laid, the cause of ulterior alterations. It will be seen at the same time that the number of eggs susceptible of alteration may vary from one hen to another, as well as between the eggs of one hen, for the organisms to be observed on the oviduct rise to variable heights.”

If the organisms which alter the eggs and cause them to rot “were formed,” said Pasteur, “by the spontaneous self-organization of the matter within the egg into those small beings, all eggs should putrefy equally, whereas they do not.” At the end of M. Gayon’s thesis—which had not taken so long as Raulin’s to prepare, only three years—we find the following conclusion: “Putrefaction in eggs is correlative with the development and multiplication of beings which are bacteria when in contact with air and vibriones when away from the contact of air. Eggs, from that point of view, do not depart from the general law discovered by M. Pasteur.”

Pasteur’s influence was now spreading beyond the Laboratory of Physiological Chemistry, as the small laboratory at the Ecole Normale was called.