René Vallery-Radot

“ The egg comes into existence during that marvellous phase of the life of a silkworm when, after having spun its cocoon, it sleeps within it as a chrysalis, resolving itself, so to speak, into those kinds of albumen and yelk from which the fully-formed moth will emerge, as a chick emerges from its egg. ”

“ While expounding this opinion before the Academy of Sciences, Pasteur, on one occasion, expressed himself thus:—
'The universe is a dissymmetric whole. I am inclined to think that life, as manifested to us, must be a function of the dissymmetry of the universe or of the consequences that follow in its train. The universe is dissymmetrical; for, placing before a mirror the group of bodies which compose the solar system, with their proper movements, we obtain in the mirror an image not superposable on the reality. Even the motion of solar light is dissymmetrical. ”

“ In scientific discussions, it is not as in politics,' he added with a smile, 'where demonstration is often difficult. In the natural sciences, doctrines must be based on an assemblage of results, of observations, and of experiments. If a doctrine is challenged, it seldom happens that its truth or falsehood cannot be established by the application of some crucial test. Even a single experiment will often suffice either to refute or consolidate the doctrine.'
Reviewing the labours of the past forty years, Pasteur then called to mind the numerous controversies in which he had been engaged. ”

“ The great art—and no one practised it better than Pasteur—consists in instituting decisive experiments which leave no room for an inexact interpretation of facts. These decisive proofs of the true part played by the little microscopic fungus, by this flower of vinegar, this mycoderma aceti, are thus formulated by Pasteur. It is but another example of the method which he used in alcoholic, lactic, and tartaric fermentations. The theories of Berzelius, of Mitscherlich, and of Liebig were destined again to receive the rudest shocks by the demonstration of these rigorous facts. ”

“ May we not now in all confidence assert that, if the cultivators choose, splenic fever may soon be a thing of the past among their animals, their shepherds, and among the butchers and the tanners of the towns, because splenic fever and malignant pustule are never spontaneous? The disease exists only where it has been sown, or where it has been diffused by the unconscious instrumentality of the earth-worm. ”

“ Granting the experiment devised by Pasteur to verify that of Pouchet to be irreproachable, is Pasteur's interpretation of it rigorously true? In presence of the problem of the origin of life, all hypotheses are possible as long as the truth has not been clearly revealed. Truly, it might be argued, if fermentation be caused by germs, then the air which has passed through a red-hot platinum tube cannot provoke fermentation, or putrefaction, or the formation of organisms, because the germs of these last, which were suspended in the air, have lost all vitality. ”

“ The only difference is that the parasite of splenic fever can only be seen by means of a rather powerful microscope. Here, then, is a disease in the highest degree virulent, due in its first cause to the infinitely little. Pasteur laid hold of and isolated this terrible virus. It was in a microscopic parasite, and in it alone, that the virulence of splenic fever resided. A great scientific fact had been gained. A virus might consist not of amorphous matter, but of microscopic beings. The virulence was due to their life. ”

“ In causing the microbe of fowl cholera to pass from culture to culture, in an artificial medium, a sufficient number of times to render it impossible that the least trace of the virulent matter from which it originally started should still exist in the last cultivation, Pasteur gave in an absolute manner the proof that infectious microbes are the sole authors of the diseases which correspond to them. This culture may be repeated ten, twenty, a hundred, even a thousand times: in the latest culture the virulence is not extinguished, or even sensibly weakened. ”

“ The secret of attenuation had thus become an open one to Pasteur. He laid hold of the murderous virus of splenic fever, and succeeded in rendering it, not only harmless to life, but a sure protection against the virus in its most concentrated form. No man, in my opinion, can work at these subjects so rapidly as Pasteur without falling into errors of detail. But this [xxxviii] may occur while his main position remains impregnable. Such a result, for example, as that obtained in presence of so many witnesses at Melun must surely remain an ever-memorable conquest of science. ”

“ For we must always allow for a certain resistance in all living creatures to disease and death. No doubt, life to a parasite in the body of an animal would not be as easy as in a cultivating liquid contained in a glass vessel. If the inoculating microbe is aerobic, it can only be cultivated in blood by taking away the oxygen from the globules, which retain it with a certain force for their own life. ”

“ From the little white mice, which hide themselves in a packet of wadding, to the dogs which bark furiously in their iron cages, all are devoted to death. But it is not only the inmates of the laboratory which daily succeed each other upon the operating and dissecting tables. From divers parts of France, hampers full of fowls which have died of cholera, or of some other disease, are sent to Pasteur. Here is an enormous basket packed with straw containing the dead body of a pig which had died of measles. This fragment of lung, packed in a tin box, belonged to a cow which died of peripneumonia. ”

“ It is also to such boards that living animals are fastened when it is necessary to experiment upon them. Certainly when one sees a dog lying with a forlorn look, its feet tied, its body trembling from fright, on the point of undergoing, though in full health, a bloody operation, one cannot suppress the feelings of pity. But a single visit to a physiological laboratory suffices to reveal vivisection in its only [273] and true light; that of the interest it offers to science, and the results it may have in store for the benefit of humanity. ”

“ Whether the fermentation proceeds from germs taken from the exterior surface of the grapes, or from a small quantity of ferment sown in the must under the form of yeast, as in the fermentation of beer, the life of the ferment, its multiplication, the augmentation of its weight, are so many vital actions which to a certainty cannot borrow from the free oxygen of the external air, or from that originally dissolved in the must, an appreciable quantity of this gas. All the life of the cells of the ferment which multiplies itself indefinitely appears then to take place apart from free oxygen gas. ”

“ In our age, and at the time when Pasteur was led to the study of the question, one theory held almost undisputed sway. It was a very ancient theory, to which Liebig, in reviving it, had given the weight of his name. 'The ferments,' said Liebig, 'are all nitrogenous substances—albumen, fibrine, caseine; or the liquids which embrace them, milk, blood, urine—in a state of alteration which they undergo in contact with the air.'
The oxygen of the air was, according to this system, the first cause of the molecular breaking up of the nitrogenous substances. ”

“ All that has lived must die, and all that is dead must be disintegrated, dissolved or gasified; the elements which are the substratum of life must enter into new cycles of life. If things were otherwise, the matter of organised beings would encumber the surface of the earth, and the law of the perpetuity of life would be compromised by the gradual exhaustion of its materials. One grand phenomenon presides over this vast work, the phenomenon of fermentation. ”

“ A great scientific theory has never been accepted without opposition. The theory of gravitation, the theory of undulation, the theory of evolution, the dynamical theory of heat—all had to push their way through conflict to victory. And so it has been with the Germ Theory of communicable diseases. Some outlying members of the medical profession dispute it still. I am told they even dispute the communicability of cholera. Such must always be the course of things, as long as men are endowed with different degrees of insight. ”

“ In short, according to Pasteur's observations, the deterioration of wines should not in any case be attributed to a natural working of the constituents of the wine, proceeding from a sort of interior spontaneous movement, which would only be affected by variations of temperature or atmospheric pressure. They are, on the contrary, exclusively dependent on the development of microscopic organisms, the germs of which exist in the wine from the moment of the original fermentation which gave it birth. What vast multitudes of germs of every kind must there not be introduced into every vintage tub! ”

“ There can, I think, be but little doubt that such experiments were suggested by the pregnant discovery of Faraday published in 1845. By both helices and magnets Faraday caused the plane of polarisation in perfectly neutral liquids and solids to rotate. If the turning of the plane of polarisation be a demonstration of molecular dissymmetry, then, in the twinkling of an eye, Faraday was able to displace symmetry by dissymmetry, and to confer upon bodies, which in their ordinary state were inert and dead, this power of rotation which M. Pasteur considers to be the exclusive attribute of life. ”

“ The most strange, assuredly, is that which has been from all time established with a great number of these diseases, that they are non-recurrent. As a general rule, notwithstanding some rare exceptions, man can only have measles, scarlet fever, plague, yellow fever once. What explanation, even hypothetically, can be given of such a fact? Still more difficult is it to explain how vaccination, which is itself a virulent though benign disease, preserves from a more serious malady, the small-pox? ”

“ Time has passed, and opposition has been overthrown. It has been granted to Pasteur to see, everywhere around him, the beneficent results of his discoveries. From all parts, from his own as well as from foreign countries, such proofs of admiration and gratitude have been showered upon him as are usually granted only to those whose death has atoned for their genius. ”

“ The conclusion is simple; the disease can protect from itself. It has evidently that characteristic of all virulent diseases, that it cannot attack a second time.
However curious it may be, this characteristic is not a thing unknown in pathology. Formerly it was the custom to inoculate with small-pox to preserve from small-pox. Sheep are still inoculated to preserve them from the rot; to protect horned cattle from peripneumonia they are inoculated with the virus of the disease. Fowl cholera offers the same immunity; it is an additional scientific acquisition, but not a novelty in principle. ”

“ It is, then, absolutely proved, that if splenic fever germs exist, as they often do, in the light earth which covers the pits in which animals dead of that disease lie buried, these germs result from the disintegration by rain of the little excremental cylinders deposited by the earth-worms. The dust of this disintegrated earth spreads itself over the grasses on a level with the soil, and thus it is that animals come to find on the pasture-field, and in particular kinds of forage, the germs of splenic fever by which they are infected. ”

“ Where, then, does nature find the agents of destruction of these secondary products?
The great fact of the destruction of animal and vegetable matters is accomplished by slow combustion, through the appropriation of atmospheric oxygen. Here, again, one must banish from science the preconceived views which assumed that the oxygen seized directly on the organic matter after death, and that this matter was consumed by purely chemical processes. It is life that presides over this work of death. ”

“ The veterinary surgeons especially, who had received with entire incredulity the anticipations recorded in the programme of the experiments, who in their conversations and in their journals had declared very loudly that it was difficult to believe in the possibility of preparing a vaccine capable of triumphing over such deadly diseases as fowl cholera and splenic fever, could not recover from their surprise. They examined the dead, they felt the living. ”

“ I allude to what he calls 'virus attenuation.' And here it may be well to throw out a few remarks in advance. When a tree, or a bundle of wheat or barley straw, is burnt, a certain amount of mineral matter remains in the ashes—extremely small in comparison with the bulk of the tree or of the straw, but absolutely essential to its growth. In a soil lacking, or exhausted of, the necessary mineral constituents, the tree cannot live, the crop cannot grow. Now contagia are living things, which demand certain elements of life just as inexorably as trees, or wheat, or barley ”

“ The general principles which M. Dumas in his teaching delighted to develop, the multitude of facts which M. Balard unfolded to his pupils, all answered to the needs of Pasteur's mind. If he loved the vaster horizons of science, he was also possessed by the anxious desire for exactitude, and for the perpetual control of experiment. Each of the lectures of the École Normale and of the Sorbonne excited in him a profound enthusiasm. One day M. Dumas, while illustrating the solidification of carbonic acid, begged for the loan of a handkerchief to receive the carbonic acid snow. ”