“There is another factory of tartaric acid in Vienna. We go there; I repeat through M. Redtenbacher my string of questions. They have seen nothing. I ask to see their products, and I come upon a barrel full of tartaric acid crystals, on the surface of which I think I perceive the substance. A first test made with dirty old glasses then and there confirms my doubts; they become a certainty a few moments later at M. Redtenbacher’s laboratory. We dine together; then we go back to the factory, where we learn, miraculous to relate, that they are just now embarrassed in their manufacturing process, and, almost certainly, the product which hinders them—though it is in a very small quantity, and they take it for sulphate of potash—is no other than racemic acid. I wish I could give you more details of this eventful day. I was to have left Vienna to-day, but, as you will understand, I shall stay until I have unravelled this question. I have already in the laboratory three kinds of products from the factory. To-morrow night, or the day after, I shall know what to think....

“You remember what I used to say to you and to M. Dumas, that almost certainly the first operation which tartar goes through in certain factories causes it to lose all or nearly all its racemic acid. Well, in the two Viennese factories, it is only two years since they began to operate on crude tartar, and it is only two years since they first saw the supposed sulphate of potash, the supposed sulphate of magnesia. For, at M. Seybel’s, they had taken for sulphate of magnesia the little crystals of racemic acid.

“Shortly, this is as far as I have come—I spare you many details:—

1. “The Naples tartar contains racemic acid.

2. “The Austrian tartar (neighbourhood of Vienna) contains racemic acid.

3. “The tartars of Hungary, Croatia, Carniola contain racemic acid.

4. “The tartar of Naples contains notably more than the latter, for it presents racemic acid even after one refining process, whilst that from Austria and Hungary only presents it when in the crude state.

“I believe it now to be extremely probable that I shall find some racemic acid in French tartars, but in very small quantities; and if it is not detected it is because all the circumstances of the manufacture of tartaric acid are unknown or unappreciated, or because some little precaution is neglected that would preserve it or make it visible.

“You see, dear Marie, how useful was my journey.”

“Vienna, September 30, 1852. I am not going to Trieste; I shall start for Prague this evening.”

“Prague, October 1, 1852. Here is a startling piece of news. I arrive in Prague; I settle down in the Hôtel d’Angleterre, have lunch, and call on M. Rochleder, Professor of chemistry, so that he may introduce me to the manufacturer. I go to the chemist of the factory, Dr. Rassmann, for whom I had a letter from M. Redtenbacher, his former master. That letter contained all the questions that I usually make to the manufacturers of tartaric acid.

“Dr. Rassmann hardly took time to read the letter; he saw what it dealt with, and said to me: ‘I have long obtained racemic acid. The Paris Pharmaceutical Society offered a prize for whoever manufactured it. It is a product of manufacture; I obtain it with the assistance of tartaric acid.’ I took the chemist’s hand affectionately, and made him repeat what he had said. Then I added: ‘You have made one of the greatest discoveries that it is possible to make in chemistry. Perhaps you do not realise as I do the full importance of it. But allow me to tell you that, with my ideas, I look upon that discovery as impossible. I do not ask for your secret; I shall await the publication of it with the greatest impatience. So that is really true? You take a kilogramme of pure tartaric acid, and with that you make racemic acid?’

“‘Yes,’ he said; ‘but it is still’ ... and as he had some difficulty in expressing himself, I said: ‘It is still surrounded with great difficulties?’

“‘Yes, monsieur.’

“Great heavens! what a discovery! if he had really done what he says! But no; it is impossible. There is an abyss to cross, and chemistry is yet too young.”

Second letter, same date. “M. Rassmann is mistaken.... He has never obtained racemic acid with pure tartaric acid. He does what M. Fikentscher and the Viennese manufacturers do, with slight differences, which confirm the general opinion I expressed in my letter to M. Dumas a few days ago.”

That letter, and also another addressed to Biot, indicated that racemic acid was formed in varying quantities in the mother-liquor, which remained after the purification of crude tartars.

“I can at last,” Pasteur wrote from Leipzig to his wife, “turn my steps again towards France. I want it; I am very weary.”

In an account of this journey in a newspaper called La Vérité there was this sentence, which amused everybody, Pasteur included: “Never was treasure sought, never adored beauty pursued over hill and vale with greater ardour.”

But the hero of scientific adventures was not satisfied. He had foreseen by the examination of crystalline forms, the correlation between hemihedral dissymmetry and rotatory power; this was, to his mind, a happy foresight. He had afterwards succeeded in separating the racemic acid, inactive on polarized light, into two acids, left and right, endowed with equal but contrary rotatory powers; this was a discovery deservedly qualified as memorable by good judges in those matters. Now he had indicated the mother-liquor as a source of racemic acid, and this was a precious observation that Kestner, who was specially interested in the question, confirmed in a letter to the Académie des Sciences (December, 1852), sending at the same time three large phials of racemic acid, one of which, made of thin glass, broke in Biot’s hands. But a great advance, apparently unrealizable, remained yet to be accomplished. Could not racemic acid be produced by the aid of tartaric acid?

Pasteur himself, as he told the optimist Rassmann, did not believe such a transformation possible. But, by dint of ingenious patience, of trials, of efforts of all sorts, he fancied he was nearing the goal. He wrote to his father: “I am thinking of one thing only, of the hope of a brilliant discovery which seems not very far. But the result I foresee is so extraordinary that I dare not believe it.” He told Biot and Senarmont of this hope. Both seemed to doubt. “I advise you,” wrote Senarmont, “not to speak until you can say: ‘I obtain racemic acid artificially with some tartaric acid, of which I have myself verified the purity; the artificial acid, like the natural, divides itself into equal equivalents of left and right tartaric acids, and those acids have the forms, the optical properties, all the chemical properties of those obtained from the natural acid.’ Do not believe that I want to worry you; the scruples I have for you I should have for myself; it is well to be doubly sure when dealing with such a fact.” But with Biot, Senarmont was less reserved; he believed the thing done. He said so to Biot, who, prudent and cautious, still desirous of warning Pasteur, wrote to him on May 27, 1853, speaking of Senarmont: “The affection with which your work, your perseverance and your moral character have inspired him makes him desire impossible prodigies for you. My friendship for you is less hastily hopeful and harder to convince. However, enjoy his friendship fully, and be as unreserved with him as you are with me. You can do so in full security; I do not know a stronger character than his. I have said and repeated to him how happy I am to see the affection he bears you. For there will be at least one man who will love you and understand you when I am gone. Farewell; enough sermons for to-day; a man must be as I am, in his eightieth year, to write such long homilies. Fortunately you are accustomed to mine, and do not mind them.”

At last, on the first of June, here is the letter announcing the great fact: “My dear father, I have just sent out the following telegram: Monsieur Biot, Collège de France, Paris. I transform tartaric acid into racemic acid; please inform MM. Dumas and Senarmont. Here is at last that racemic acid (which I went to seek at Vienna) artificially obtained through tartaric acid. I long believed that that transformation was impossible. This discovery will have incalculable consequences.”

“I congratulate you,” answered Biot on the second of June. “Your discovery is now complete. M. de Senarmont will be as delighted as I am. Please congratulate also Mme. Pasteur from me; she must be as pleased as you.” It was by maintaining tartrate of cinchonin at a high temperature for several hours that Pasteur had succeeded in transforming tartaric acid into racemic acid. Without entering here into technical details (which are to be found in a report of the Paris Pharmaceutical Society, concerning the prize accorded to Pasteur for the artificial production of racemic acid) it may be added that he had also produced the neutral tartaric acid—that is: with no action on polarized light—which appeared at the expense of racemic acid already formed. There were henceforth four different tartaric acids:—(1) the right or dextro-tartaric acid; (2) the left or lævo-tartaric acid; (3) the combination of the right and the left or racemic acid; and (4) the meso-tartaric acid, optically inactive.

The reports of the Académie des Sciences also contain accounts of occasional discoveries, of researches of all kinds accessory to the history of racemic acid. Thus aspartic acid had caused Pasteur to make a sudden journey from Strasburg to Vendôme. A chemist named Dessaignes—who was municipal receiver of that town, and who found time through sheer love of science for researches on the constitution of divers substances—had announced a fact which Pasteur wished to verify; it turned out to be inaccurate.

One whole sitting of the Académie, the third of January, 1853, was given up to Pasteur’s name and growing achievements.

After all this Pasteur came back to Arbois with the red ribbon of the Legion of Honour. He had not won it in the same way as his father had, but he deserved it as fully. Joseph Pasteur, delighting in his illustrious son, wrote effusively to Biot; indeed the old scientist had had his share in this act of justice. Biot answered in the following letter, which is a further revelation of his high and independent ideal of a scientific career.

“Monsieur, your good heart makes out my share to be greater than it is. The splendid discoveries made by your worthy and excellent son, his devotion to science, his indefatigable perseverance, the conscientious care with which he fulfils the duties of his situation, all this had made his position such that there was no need to solicit for him what he had so long deserved. But one might boldly point out that it would be a real loss to the Order if he were not promptly included within its ranks. That is what I did, and I am very glad to see that the too long delay is now at an end. I wished for this all the more as I knew of your affectionate desire that this act of justice should be done. Allow me to add, however, that in our profession our real distinction depends on us alone, fortunately, and not on the favour or indifference of a minister. In the position that your son has acquired, his reputation will grow with his work, no other help being needed; and the esteem he already enjoys, and which will grow day by day, will be accorded to him, without gainsaying or appeal, by the Grand Jury of scientists of all nations—an absolutely just tribunal, the only one we recognize.

“Allow me to add to my congratulations the expression of the esteem and cordial affection with which you have inspired me.”

On his return to Strasburg Pasteur went to live in a house in the Rue des Couples, which suited him as being near the Académie and his laboratory; it also had a garden where his children could play. He was full of projects, and what he called the “spirit of invention” daily suggested some new undertaking. The neighbourhood of Germany, at that time a veritable hive of busy bees, was a fertile stimulant to the French Faculty at Strasburg.

But material means were lacking. When Pasteur received the prize of 1,500 francs given him by the Pharmaceutical Society, he gave up half of it to buying instruments which the Strasburg laboratory was too poor to afford. The resources then placed by the State at his disposal by way of contribution to the expenses of a chemistry class only consisted of 1,200 francs under the heading “class expenses.” Pasteur had to pay the wages of his laboratory attendant out of it. Now that he was better provided, thanks to his prize, he renewed his studies on crystals.

Taking up an octahedral crystal, he broke off a piece of it, then replaced it in its mother-liquor. Whilst the crystal was growing larger in every direction by a deposit of crystalline particles, a very active formation was taking place on the mutilated part; after a few hours the crystal had again assumed its original shape. The healing up of wounds, said Pasteur, might be compared to that physical phenomenon. Claude Bernard, much struck later on by these experiments of Pasteur’s and recalling them with much praise, said in his turn—

“These reconstituting phenomena of crystalline redintegration afford a complete comparison with those presented by living beings in the case of a wound more or less deep. In the crystal as in the animal, the damaged part heals, gradually taking back its original shape, and in both cases the reformation of tissue is far more active in that particular part than under ordinary evolutive conditions.”

Thus those two great minds saw affinities hidden under facts apparently far apart. Other similarities yet more unexpected carried Pasteur away towards the highest region of speculation. He spoke with enthusiasm of molecular dissymmetry; he saw it everywhere in the universe. These studies in dissymmetry gave birth twenty years later to a new science arising immediately out of his work, viz. stereo-chemistry, or the chemistry of space. He also saw in molecular dissymmetry the influence of a great cosmic cause—

“The universe,” he said one day, “is a dissymmetrical whole. I am inclined to think that life, as manifested to us, must be a function of the dissymmetry of the universe and of the consequences it produces. The universe is dissymmetrical; for, if the whole of the bodies which compose the solar system were placed before a glass moving with their individual movements, the image in the glass could not be superposed to the reality. Even the movement of solar life is dissymmetrical. A luminous ray never strikes in a straight line the leaf where vegetable life creates organic matter. Terrestrial magnetism, the opposition which exists between the north and south poles in a magnet, that offered us by the two electricities positive and negative, are but resultants from dissymmetrical actions and movements.”

“Life,” he said again, “is dominated by dissymmetrical actions. I can even foresee that all living species are primordially, in their structure, in their external forms, functions of cosmic dissymmetry.”

And there appeared to him to be a barrier between mineral or artificial products and products formed under the influence of life. But he did not look upon it as an impassable one, and he was careful to say, “It is a distinction of fact and not of absolute principle.” As nature elaborates immediate principles of life by means of dissymmetrical forces, he wished that the chemist should imitate nature, and that, breaking with methods founded upon the exclusive use of symmetrical forces, he should bring dissymmetrical forces to bear upon the production of chemical phenomena. He himself, after using powerful magnets to attempt to introduce a manifestation of dissymmetry into the form of crystals, had had a strong clockwork movement constructed, the object of which was to keep a plant in continual rotatory motion first in one direction then in another. He also proposed to try to keep a plant alive, from its germination under the influence of solar rays reversed by means of a mirror directed by a heliostat.

But Biot wrote to him: “I should like to be able to turn you from the attempts you wish to make on the influence of magnetism on vegetation. M. de Senarmont agrees with me. To begin with, you will spend a great deal on the purchase of instruments with the use of which you are not familiar, and of which the success is very doubtful. They will take you away from the fruitful course of experimental researches which you have followed hitherto, where there is yet so much for you to do, and will lead you from the certain to the uncertain.”

“Louis is rather too preoccupied with his experiments,” wrote Mme. Pasteur to her father-in-law; “you know that those he is undertaking this year will give us, if they succeed, a Newton or a Galileo.”

But success did not come. “My studies are going rather badly,” wrote Pasteur in his turn (December 30). “I am almost afraid of failing in all my endeavours this year, and of having no important achievement to record by the end of next year. I am still hoping, though I suppose it was rather mad to undertake what I have undertaken.”

Whilst he was thus struggling, an experiment, which for others would have been a mere chemical curiosity, interested him passionately. Recalling one day how his first researches had led him to the study of ferments: “If I place,” he said, “one of the salts of racemic acid, paratartrate or racemate of ammonia, for instance, in the ordinary conditions of fermentation, the dextro-tartaric acid alone ferments, the other remains in the liquor. I may say, in passing, that this is the best means of preparing lævo-tartaric acid. Why does the dextro-tartaric acid alone become putrefied? Because the ferments of that fermentation feed more easily on the right than on the left molecules.”

“I have done yet more,” he said much later, in a last lecture to the Chemical Society of Paris; “I have kept alive some little seeds of penicillium glaucum—that mucor which is to be found everywhere—on the surface of ashes and paratartaric acid and I have seen the lævo-tartaric acid appear....”

What seemed to him startling in those two experiments was to find molecular dissymmetry appear as a modifying agent on chemical affinities in a phenomenon of the physiological order.

By an interesting coincidence it was at the very moment when his studies were bringing him towards fermentations that he was called to a country where the local industry was to be the strongest stimulant to his new researches.

CHAPTER IV

1855—1859

Built at the expense of the town, the Faculté was situated in the Rue des Fleurs. In the opening speech which he pronounced on December 7, 1854, the young Dean expressed his enthusiasm for the Imperial decree of August 22, which brought two happy innovations into the Faculties of Science: (1) The pupils might, for a small annual sum, enter the laboratory and practise the principal experiments carried out before them at the classes; and (2) a new diploma was created. After two years of practical and theoretical study the young men who wished to enter an industrial career could obtain this special diploma and be chosen as foremen or overseers. Pasteur was overjoyed at being able to do useful work in that country of distilleries, and to attract large audiences to the new Faculty. “Where in your families will you find,” he said, to excite indolent minds—“where will you find a young man whose curiosity and interest will not immediately be awakened when you put into his hands a potato, when with that potato he may produce sugar, with that sugar alcohol, with that alcohol æther and vinegar? Where is he that will not be happy to tell his family in the evening that he has just been working out an electric telegraph? And, gentlemen, be convinced of this, such studies are seldom if ever forgotten. It is somewhat as if geography were to be taught by travelling; such geography is remembered because one has seen the places. In the same way your sons will not forget what the air we breathe contains when they have once analysed it, when in their hands and under their eyes the admirable properties of its elements have been resolved.”

After stating his wish to be directly useful to these sons of manufacturers and to put his laboratory at their disposal, he eloquently upheld the rights of theory in teaching—

“Without theory, practice is but routine born of habit. Theory alone can bring forth and develop the spirit of invention. It is to you specially that it will belong not to share the opinion of those narrow minds who disdain everything in science which has not an immediate application. You know Franklin’s charming saying? He was witnessing the first demonstration of a purely scientific discovery, and people round him said: ‘But what is the use of it?’ Franklin answered them: ‘What is the use of a new-born child?’ Yes, gentlemen, what is the use of a new-born child? And yet, perhaps, at that tender age, germs already existed in you of the talents which distinguish you! In your baby boys, fragile beings as they are, there are incipient magistrates, scientists, heroes as valiant as those who are now covering themselves with glory under the walls of Sebastopol. And thus, gentlemen, a theoretical discovery has but the merit of its existence: it awakens hope, and that is all. But let it be cultivated, let it grow, and you will see what it will become.

“Do you know when it first saw the light, this electric telegraph, one of the most marvellous applications of modern science? It was in that memorable year, 1822: Oersted, a Danish physicist, held in his hands a piece of copper wire, joined by its extremities to the two poles of a Volta pile. On his table was a magnetized needle on its pivot, and he suddenly saw (by chance you will say, but chance only favours the mind which is prepared) the needle move and take up a position quite different from the one assigned to it by terrestrial magnetism. A wire carrying an electric current deviates a magnetized needle from its position. That, gentlemen, was the birth of the modern telegraph. Franklin’s interlocutor might well have said when the needle moved: ‘But what is the use of that?’ And yet that discovery was barely twenty years old when it produced by its application the almost supernatural effects of the electric telegraph!”

The small theatre where Pasteur gave his chemistry lessons soon became celebrated in the students’ world.

The faults had disappeared with which Pasteur used to reproach himself when he first taught at Dijon and later at Strasburg. He was sure of himself, he was clear in his explanations; the chain of thought, the fitness of words, all was perfect. He made few experiments, but those were decisive. He endeavoured to bring out every observation or comparison they might suggest. The pupil who went away delighted from the class did not suspect the care each of those apparently easy lessons had cost. When Pasteur had carefully prepared all his notes, he used to make a summary of them; he had these summaries bound together afterwards. We may thus sketch the outline of his work; but who will paint the gesture of demonstration, the movement, the grave penetrating voice, the life in short?

After a few months the Minister wrote to M. Guillemin, the rector, that he was much pleased with the success of this Faculty of Sciences at Lille, “which already owes it to the merit of the teaching—solid and brilliant at the same time—of that clever Professor, that it is able to rival the most flourishing Faculties.” The Minister felt he must add some official advice: “But M. Pasteur must guard against being carried away by his love for science, and he must not forget that the teaching of the Faculties, whilst keeping up with scientific theory, should, in order to produce useful and far-reaching results, appropriate to itself the special applications suitable to the real wants of the surrounding country.”

A year after the inauguration of the new Faculty, Pasteur wrote to Chappuis: “Our classes are very well attended; I have 250 to 300 people at my most popular lectures, and we have twenty-one pupils entered for laboratory experiments. I believe that this year, like last year, Lille holds the first rank for that innovation, for I am told that at Lyons there were but eight entries.” It was indeed a success to distance Lyons. “The zeal of all is a pleasure to watch (January, 1856). It reaches that point that four of the professors take the trouble to have their manuscript lessons printed; there are already 120 subscribers for the course of applied mechanics.

“Our building is fortunately completed; it is large and handsome, but will soon become insufficient owing to the progress of practical teaching.

“We are very comfortably settled on the first floor, and I have (on the ground floor immediately below) what I have always wished for, a laboratory where I can go at any time. This week, for instance, the gas remains on, and operations follow their course whilst I am in bed. In this way I try to make up a little of the time which I have to give to the direction of all the rather numerous departments in our Faculties. Add to this that I am a member of two very active societies, and that I have been entrusted, at the suggestion of the Conseil-Général,[24] with the testing of manures for the département of the Nord, a considerable work in this rich agricultural land, but one which I have accepted eagerly, so as to popularize and enlarge the influence of our young Faculty.

“Do not fear lest all this should keep me from the studies I love. I shall not give them up, and I trust that what is already accomplished will grow without my help, with the growth that time gives to everything that has within it the germ of life. Let us all work; that only is enjoyable. I am quoting M. Biot, who certainly is an authority on that subject. You saw the share he took the other day in a great discussion at the Académie des Sciences; his presence of mind, high reasoning powers, and youthfulness were magnificent, and he is eighty-four!”

In a mere study on Pasteur as a scientific man, the way in which he understood his duties as Dean would only be a secondary detail. It is not so here, the very object of this book being to paint what he was in all the circumstances, all the trials of life. Besides his professional obligations, his kindness in leaving his laboratory, however hard the sacrifice, bears witness to an ever present devotion. For instance, he took his pupils round factories and foundries at Aniche, Denain, Valenciennes, St. Omer. In July, 1856, he organized for the same pupils a tour in Belgium. He took them to visit factories, iron foundries, steel and metal works, questioning the foremen with his insatiable curiosity, pleased to induce in his tall students a desire to learn. All returned from these trips with more pleasure in their work; some with the fiery enthusiasm that Pasteur wished to see.

The sentence in his Lille speech, “in the fields of observation, chance only favours the mind which is prepared,” was particularly applicable to him. In the summer of 1856 a Lille manufacturer, M. Bigo, had, like many others that same year, met with great disappointments in the manufacture of beetroot alcohol. He came to the young Dean for advice. The prospect of doing a kindness, of communicating the results of his observations to the numerous hearers who crowded the small theatre of the Faculty, and of closely studying the phenomena of fermentation which preoccupied him to such a degree, caused Pasteur to consent to make some experiments. He spent some time almost daily at the factory. On his return to his laboratory—where he only had a student’s microscope and a most primitive coke-fed stove—he examined the globules in the fermentation juice, he compared filtered with non-filtered beetroot juice, and conceived stimulating hypotheses often to be abandoned in face of a fact in contradiction with them. Above some note made a few days previously, where a suggested hypothesis had not been verified by fact, he would write: “error,” “erroneous,” for he was implacable in his criticism of himself.

M. Bigo’s son, who studied in Pasteur’s laboratory, has summed up in a letter how these accidents of manufacture became a starting point to Pasteur’s investigations on fermentation, particularly alcoholic fermentation. “Pasteur had noticed through the microscope that the globules were round when fermentation was healthy, that they lengthened when alteration began, and were quite long when fermentation became lactic. This very simple method allowed us to watch the process and to avoid the failures in fermentation which we used so often to meet with.... I had the good fortune to be many times the confidant of the enthusiasms and disappointments of a great man of science.” Young Bigo indeed remembered the series of experiments, the numerous observations noted, and how Pasteur, whilst studying the causes of those failures in the distillery, had wondered whether he was not confronted with a general fact, common to all fermentations. Pasteur was on the road to a discovery the consequences of which were to revolutionize chemistry. During months and months he worked to assure himself that he was not a prey to error.

In order to appreciate the importance of the ideas which from that small laboratory were about to inundate the world, and in order to take account of the effort necessitated to obtain the triumph of a theory which was to become a doctrine, it is necessary to go back to the teachings of that time upon the subject of fermentations. All was darkness, pierced in 1836 by a momentary ray of light. The physicist Cagniard-Latour, studying the ferment of beer called yeast, had observed that that ferment was composed of cells “susceptible of reproduction by a sort of budding, and probably acting on sugar through some effect of their vegetation.” Almost at the same time the German doctor Schwann was making analogous observations. However, as the fact seemed isolated, nothing similar being met with elsewhere, Cagniard-Latour’s remark was but a curious parenthesis in the history of fermentations.

When such men as J. B. Dumas said that perhaps there might be a sequel to Cagniard-Latour’s statement, they emitted the idea so timidly that, in a book On Contagion published at Montpellier in 1853, Anglada, the well known author, expressed himself thus—

“M. Dumas, who is an authority, looks upon the act of fermentation as strange and obscure; he declares that it gives rise to phenomena the knowledge of which is only tentative at present. Such a competent affirmation is of a nature to discourage those who claim to unravel the mysteries of contagion by the comparative study of fermentation. What is the advantage of explaining one through the other since both are equally mysterious!” This word, obscure, was to be found everywhere. Claude Bernard used the same epithet at the Collège de France in March, 1850, to qualify those phenomena.

Four months before the request of the Lille manufacturer, Pasteur himself, preparing on a loose sheet of paper a lesson on fermentation, had written these words: “What does fermentation consist of?—Mysterious character of the phenomenon.—A word on lactic acid.” Did he speak in that lesson of his ideas of future experiments? Did he insist upon the mystery he intended to unveil? With his powers of concentration it is probable that he restrained himself and decided to wait another year.

The theories of Berzelius and of Liebig then reigned supreme. To the mind of Berzelius, the Swedish chemist, fermentation was due to contact. It was said that there was a catalytic force. In his opinion, what Cagniard-Latour believed he had seen, was but “an immediate vegetable principle, which became precipitated during the fermentation of beer, and which, in precipitating, presented forms analogous to the simpler forms of vegetable life, but formation does not constitute life.”

In the view of the German chemist Liebig, chemical decomposition was produced by influence: the ferment was an extremely alterable organic substance which decomposed, and in decomposing set in motion, by the rupture of its own elements, the molecules of the fermentative matter; it was the dead portion of the yeast, that which had lived and was being altered, which acted upon the sugar. These theories were adopted, taught, and to be found in all treatises on chemistry.

A vacancy at the Académie des Sciences took Pasteur away from his students for a time and obliged him to go to Paris. Biot, Dumas, Balard and Senarmont had insisted upon his presenting himself in the section of mineralogy. He felt himself unfit for the candidature. He was as incapable of election manœuvres as he was full of his subject when he had to convince an interlocutor or to interest an audience in his works on crystallography. (These works had just procured the bestowal on him of the great Rumford medal, conferred by the London Royal Society.) During this detested canvassing campaign he had one happy day: he was present on February 5, 1857, at the reception of Biot by the Académie Française.

Biot, who had entered the Académie des Sciences fifty-four years earlier, and was now the oldest member of the Institute, took advantage of his great age to distribute, in the course of his speech, a good deal of wise counsel, much applauded by Pasteur from the ranks of the audience. Biot, with his calm irony, aimed this epigram at men of science who disdained letters: “Their science was not the more apparent through their want of literary culture.” He ended by remarks which formed a continuation of his last letter to Pasteur’s father. Making an appeal to those whose high ambition is to consecrate themselves to pure science, he proudly said: “Perhaps your name, your existence will be unknown to the crowd. But you will be known, esteemed, sought after by a small number of eminent men scattered over the face of the earth, your rivals, your peers in the intellectual Senate of minds; they alone have the right to appreciate you and to assign to you your rank, a well-merited rank, which no princely will, no popular caprice can give or take away, and which will remain yours as long as you remain faithful to Science, which bestows it upon you.”

Guizot, to whom it fell to welcome Biot to the Académie, rendered homage to his independence, to his worship of disinterested research, to his ready counsels. “The events which have overturned everything around you,” he said, “have never turned the course of your free and firm judgment, or of your peaceful labours.” On that occasion the decline of Biot’s life seemed like a beautiful summer evening in the north, before nightfall, when a soft light still envelops all things. No disciple ever felt more emotion than Pasteur when participating in that last joy of his aged master. In Regnault’s laboratory, a photograph had been taken of Biot seated with bent head and a weary attitude, but with the old sparkle in his eyes. Biot offered it to Pasteur, saying: “If you place this proof near a portrait of your father, you will unite the pictures of two men who have loved you very much in the same way.”

Pasteur, between two canvassing visits, gave himself the pleasure of going to hear a young professor that every one was then speaking of. “I have just been to a lecture by Rigault, at the Collège de France,” he wrote on March 6, 1857. “The room is too small, it is a struggle to get in. I have come away delighted; it is a splendid success for the Université, there is nothing to add, nothing to retrench. Fancy a professor in one of the Paris lycées making such a début at the Collège de France!”

Pasteur preferred Rigault to St. Marc Girardin. “And Rigault is only beginning!” But, under Rigault’s elegance and apparent ease, lurked perpetual constraint. One day that St. Marc Girardin was congratulating him, “Ah,” said Rigault, “you do not see the steel corsets that I wear when I am speaking!” That comparison suited his delicate, ingenious, slightly artificial mind, never unrestrained even in simple conversation, at the same time conscientious and self-conscious. He who had once written that “Life is a work of art to be fashioned by a skilful hand if the faculties of the mind are to be fully enjoyed,” made the mistake of forcing his nature. He died a few months after that lecture.

Pasteur’s enthusiastic lines about Rigault show the joy he felt at the success of others. He did not understand envy, ill-will, or jealousy, and was more than astonished, indeed amazed, when he came across such feelings. One day that he had read an important paper at the Académie des Sciences, “Would you believe it,” he wrote to his father, “I met a Paris Professor of chemistry the very next day, whom I know to have been present, who had indeed come purposely to hear my reading, and he never said a word! I then remembered a saying of M. Biot’s: ‘When a colleague reads a paper and no one speaks to him about it afterwards, it is because it has been thought well of....’”

The election was at hand. Pasteur wrote (March 11): “My dear father, I am certain to fail.” He thought he might count upon twenty votes; thirty were necessary. He resigned himself philosophically. His candidature would at any rate bring his works into greater prominence. In spite of a splendid report by Senarmont, enumerating the successive steps by which Pasteur had risen since his first discoveries concerning the connection between internal structure and external crystalline forms, Pasteur only obtained sixteen votes.

On his return to Lille he set to work with renewed energy; he took up again his study of fermentations, and in particular that of sour milk, called lactic fermentation; he made notes of his experiments day by day; he drew in a notebook the little globules, the tiny bodies that he found in a grey substance sometimes arranged in a zone. Those globules, much smaller than those of yeast, had escaped the observation of chemists and naturalists because it was easy to confound them with other products of lactic fermentation. After isolating and then scattering in a liquid a trace of that grey substance, Pasteur saw some well-characterized lactic fermentation appear. That matter, that grey substance was indeed the ferment.

Whilst all the writings of the chemists who followed in the train of Liebig and Berzelius united in rejecting the idea of an influence of life in the cause of fermentations, Pasteur recognized therein a phenomenon correlative to life. That special lactic yeast, Pasteur could see budding, multiplying, and offering the same phenomena of reproduction as beer yeast.

It was not to the Académie des Sciences, as is generally believed, that Pasteur sent the paper on lactic fermentation, the fifteen pages of which contained such curious and unexpected facts. With much delicacy of feeling, Pasteur made to the Lille Scientific Society this communication (August, 1857) which the Académie des Sciences only saw three months later.

How was it that he desired to leave this Faculty at Lille to which he had rendered such valuable service? The Ecole Normale was going through difficult times. “In my opinion,” wrote Pasteur with a sadness that betrayed his attachment to the great school, “of all the objects of care to the authorities, the Ecole Normale should be the first; it is now but the shadow of its former self.” He who so often said, “Do not dwell upon things already acquired!” thought that the Lille Faculty was henceforth sure of its future and needed him no longer. Was it not better to come to the assistance of the threatened weak point? At the Ministry of Public Instruction his wish was understood and approved of. Nisard had just been made Director of the Ecole Normale with high and supreme powers; his sub-director of literary studies was M. Jacquinet. The administration was reserved for Pasteur, who was also entrusted with the direction of the scientific studies. To that task were added “the surveillance of the economic and hygienic management, the care of general discipline, intercourse with the families of the pupils and the literary or scientific establishments frequented by them.”

The rector of the Lille Faculty announced in these terms the departure of the Dean: “Our Faculty loses a professor and a scientist of the very first order. You have yourselves, gentlemen, been able to appreciate more than once all the vigour and clearness of that mind at once so powerful and so capable.”

At the Ecole Normale, Pasteur’s labours were not at first seconded by material convenience. The only laboratory in the Rue d’Ulm building was occupied by Henri Sainte Claire Deville who, in 1851, had taken the place of Balard, the latter leaving the Ecole Normale for the Collège de France. Dark rooms, a very few instruments, and a credit of 1,800 francs a year, that was all Sainte Claire Deville had been able to obtain. It would have seemed like a dream to Pasteur. He had to organize his scientific installation in two attics under the roof of the Ecole Normale; he had no assistance of any kind, not even that of an ordinary laboratory attendant. But his courage was not of the kind which evaporates at the first obstacle, and no difficulty could have kept him from work: he climbed the stairs leading to his pseudo-laboratory with all the cheerfulness of a soldier’s son. Biot—who had been grieved to see the chemist Laurent working in a sort of cellar, where that scientist’s health suffered (he died at forty-three)—was angry that Pasteur should be relegated to an uninhabitable garret. Neither did he understand the “economic and hygienic surveillance” attributed to Pasteur. He hoped Pasteur would reduce to their just proportions those secondary duties. “They have made him an administrator,” he said with mock pomposity; “let them believe that he will administrate.” Biot was mistaken. The de minimis non curat did not exist for Pasteur.

On one of his agenda leaves, besides subjects for lectures, we find notes such as these: “Catering; ascertain what weight of meat per pupil is given out at the Ecole Polytechnique. Courtyard to be strewn with sand. Ventilation of classroom. Dining hall door to be repaired.” Each detail was of importance in his eyes, when the health of the students was in question.

He inaugurated his garret by some work almost as celebrated as that on lactic fermentation. In December, 1857, he presented to the Académie des Sciences a paper on alcoholic fermentation. “I have submitted,” he said, “alcoholic fermentation to the method of experimentation indicated in the notes which I recently had the honour of presenting to the Académie. The results of those labours should be put on the same lines, for they explain and complete each other.” And in conclusion: “The deduplication of sugar into alcohol and carbonic acid is correlative to a phenomenon of life, an organization of globules....”

The reports of the Académie des Sciences for 1858 show how Pasteur recognized complex phenomena in alcoholic fermentation. Whilst chemists were content to say: “So much sugar gives so much alcohol and so much carbonic acid,” Pasteur went further. He wrote to Chappuis in June: “I find that alcoholic fermentation is constantly accompanied by the production of glycerine; it is a very curious fact. For instance, in one litre of wine there are several grammes of that product which had not been suspected.” Shortly before that he had also recognized the normal presence in alcoholic fermentation of succinic acid. “I should be pursuing the consequences of these facts,” he added, “if a temperature of 36° C. did not keep me from my laboratory. I regret to see the longest days in the year lost to me. Yet I have grown accustomed to my attic, and I should be sorry to leave it. Next holidays I hope to enlarge it. You too are struggling against material hindrances in your work; let it stimulate us, my dear fellow, and not discourage us. Our discoveries will have the greater merit.”

The year 1859 was given up to examining further facts concerning fermentation. Whence came those ferments, those microscopic bodies, those transforming agents, so weak in appearance, so powerful in reality? Great problems were working in his mind; but he was careful not to propound them hastily, for he was the most timid, the most hesitating of men until he held proofs in his hands. “In experimental science,” he wrote, “it is always a mistake not to doubt when facts do not compel you to affirm.”

In September he lost his eldest daughter. She died of typhoid fever at Arbois, where she was staying with her grandfather. On December 30 Pasteur wrote to his father: “I cannot keep my thoughts from my poor little girl, so good, so happy in her little life, whom this fatal year now ending has taken away from us. She was growing to be such a companion to her mother and to me, to us all.... But forgive me, dearest father, for recalling these sad memories. She is happy; let us think of those who remain and try as much as lies in our power to keep from them the bitterness of this life.”

CHAPTER V

1860—1864

“After I had finished, M. Dumas, who occupied the chair, rose and addressed me in these words. After praising the zeal I had brought to this novel kind of teaching at the Society’s request, and the so great penetration I had given proof of, in the course of the work I had just expounded, he added, ‘The Académie, sir, rewarded you a few days ago for other profound researches; your audience of this evening will applaud you as one of the most distinguished professors we possess.’

“All I have underlined was said in those very words by M. Dumas, and was followed by great applause.

“All the students of the scientific section of the Ecole Normale were present; they felt deeply moved and several of them have expressed their emotion to me.

“As for myself, I saw the realization of what I had foreseen. You know how I have always told you confidentially that time would see the growth of my researches on the molecular dissymmetry of natural organic products. Founded as they were on varied notions borrowed from divers branches of science—crystallography, physics, and chemistry—those studies could not be followed by most scientists so as to be fully understood. On this occasion I presented them in the aggregate with some clearness and power and every one was struck by their importance.

“It is not by their form that these two lectures have delighted my hearers, it is by their contents; it is the future reserved to those great results, so unexpected, and opening such entirely new vistas to physiology. I have dared to say so, for at these heights all sense of personality disappears, and there only remains that sense of dignity which is ever inspired by true love of science.

“God grant that by my persevering labours I may bring a little stone to the frail and ill-assured edifice of our knowledge of those deep mysteries of Life and Death where all our intellects have so lamentably failed.

“P.S.—Yesterday I presented to the Academy my researches on spontaneous generation; they seemed to produce a great sensation. More later.”

When Biot heard that Pasteur wished to tackle this study of spontaneous generation, he interposed, as he had done seven years before, to arrest him on the verge of his audacious experiments on the part played by dissymmetrical forces in the development of life. Vainly Pasteur, grieved at Biot’s disapprobation, explained that this question, in the course of such researches, had become an imperious necessity; Biot would not be convinced. But Pasteur, in spite of his quasi-filial attachment to Biot, could not stop where he was; he had to go through to the end.

“You will never find your way out,” cried Biot.

“I shall try,” said Pasteur modestly.

Angry and anxious, Biot wished Pasteur to promise that he would relinquish these apparently hopeless researches. J. B. Dumas, to whom Pasteur related the more than discouraging remonstrances of Biot, entrenched himself behind this cautious phrase—

“I would advise no one to dwell too long on such a subject.”

Senarmont alone, full of confidence in the ingenious curiosity of the man who could read nature by dint of patience, said that Pasteur should be allowed his own way.

It is regrettable that Biot—whose passion for reading was so indefatigable that he complained of not finding enough books in the library at the Institute—should not have thought of writing the history of this question of spontaneous generation. He could have gone back to Aristotle, quoted Lucretius, Virgil, Ovid, Pliny. Philosophers, poets, naturalists, all believed in spontaneous generation. Time went on, and it was still believed in. In the sixteenth century, Van Helmont—who should not be judged by that one instance—gave a celebrated recipe to create mice: any one could work that prodigy by putting some dirty linen in a receptacle, together with a few grains of wheat or a piece of cheese. Some time later an Italian, Buonanni, announced a fact no less fantastic: certain timberwood, he said, after rotting in the sea, produced worms which engendered butterflies, and those butterflies became birds.

Another Italian, less credulous, a poet and a physician, Francesco Redi, belonging to a learned society calling itself The Academy of Experience, resolved to carefully study one of those supposed phenomena of spontaneous generation. In order to demonstrate that the worms found in rotten meat did not appear spontaneously, he placed a piece of gauze over the meat. Flies, attracted by the odour, deposited their eggs on the gauze. From those eggs were hatched the worms, which had until then been supposed to begin life spontaneously in the flesh itself. This simple experiment marked some progress. Later on another Italian, a medical professor of Padua, Vallisneri, recognized that the grub in a fruit is also hatched from an egg deposited by an insect before the development of the fruit.

The theory of spontaneous generation, still losing ground, appeared to be vanquished when the invention of the microscope at the end of the seventeenth century brought fresh arguments to its assistance. Whence came those thousands of creatures, only distinguishable on the slide of the microscope, those infinitely small beings which appeared in rain water as in any infusion of organic matter when exposed to the air? How could they be explained otherwise than through spontaneous generation, those bodies capable of producing 1,000,000 descendants in less than forty-eight hours.

The world of salons and of minor courts was pleased to have an opinion on this question. The Cardinal of Polignac, a diplomat and a man of letters, wrote in his leisure moments a long Latin poem entitled the Anti-Lucretius. After scouting Lucretius and other philosophers of the same school, the cardinal traced back to one Supreme Foresight the mechanism and organization of the entire world. By ingenious developments and circumlocutions, worthy of the Abbé Delille, the cardinal, while vaunting the wonders of the microscope, which he called “eye of our eye,” saw in it only another prodigy offered us by Almighty Wisdom. Of all those accumulated and verified arguments, this simple notion stood out: “The earth, which contains numberless germs, has not produced them. Everything in this world has its germ or seed.”

Diderot, who disseminated so many ideas (since borrowed by many people and used as if originated by them), wrote in some tumultuous pages on nature: “Does living matter combine with living matter? how? and with what result? And what about dead matter?”

About the middle of the eighteenth century the problem was again raised on scientific ground. Two priests, one an Englishman, Needham, and the other an Italian, Spallanzani, entered the lists. Needham, a great partisan of spontaneous generation, studied with Buffon some microscopic animalculæ. Buffon afterwards built up a whole system which became fashionable at that time. The force which Needham found in matter, a force which he called productive or vegetative, and which he regarded as charged with the formation of the organic world, Buffon explained by saying that there are certain primitive and incorruptible parts common to animals and to vegetables. These organic molecules cast themselves into the moulds or shapes which constituted different beings. When one of those moulds was destroyed by death, the organic molecules became free; ever active, they worked the putrefied matter, appropriating to themselves some raw particles and forming, said Buffon, “by their reunion, a multitude of little organized bodies, of which some, like earthworms, and fungi, seem to be fair-sized animals or vegetables, but of which others, in almost infinite numbers, can only be seen through the microscope.”

All those bodies, according to him, only existed through spontaneous generation. Spontaneous generation takes place continually and universally after death and sometimes during life. Such was in his view the origin of intestinal worms. And, carrying his investigations further, he added, “The eels in flour paste, those of vinegar, all those so-called microscopic animals, are but different shapes taken spontaneously, according to circumstances, by that ever active matter which only tends to organization.”

The Abbé Spallanzani, armed with a microscope, studied these infinitesimal beings. He tried to distinguish them and their mode of life. Needham had affirmed that by enclosing putrescible matter in vases and by placing those vases on warm ashes, he produced animalculæ. Spallanzani suspected: firstly that Needham had not exposed the vases to a sufficient degree of heat to kill the seeds which were inside; and secondly, that seeds could easily have entered those vases and given birth to animalculæ, for Needham had only closed his vases with cork stoppers, which are very porous.

“I repeated that experiment with more accuracy,” wrote Spallanzani. “I used hermetically sealed vases. I kept them for an hour in boiling water, and after having opened them and examined their contents within a reasonable time I found not the slightest trace of animalculæ, though I had examined with the microscope the infusions from nineteen different vases.”

Thus dropped to the ground, in Spallanzani’s eyes, Needham’s singular theory, this famous vegetative force, this occult virtue. Yet Needham did not own himself beaten. He retorted that Spallanzani had much weakened, perhaps destroyed, the vegetative force of the infused substances by leaving his vases in boiling water during an hour. He advised him to try with less heat.

The public took an interest in this quarrel. In an opuscule entitled Singularities of Nature (1769), Voltaire, a born journalist, laughed at Needham, whom he turned into an Irish Jesuit to amuse his readers. Joking on this race of so-called eels which began life in the gravy of boiled mutton, he said: “At once several philosophers exclaimed at the wonder and said, ‘There is no germ; all is made, all is regenerated by a vital force of nature.’ ‘Attraction,’ said one; ‘Organized matter,’ said another, ‘they are organic molecules which have found their casts.’ Clever physicists were taken in by a Jesuit.”

In those pages, lightly penned, nothing remained of what Voltaire called “the ridiculous mistake, the unfortunate experiments of Needham, so triumphantly refuted by M. Spallanzani and rejected by whoever has studied nature at all.” “It is now demonstrated to sight and to reason that there is no vegetable, no animal but has its own germ.” In his Philosophic Dictionary, at the word God, “It is very strange,” said Voltaire, “that men should deny a creator and yet attribute to themselves the power of creating eels!” The Abbé Needham, meeting with these religious arguments, rather unexpected from Voltaire, endeavoured to prove that the hypothesis of spontaneous generation was in perfect accordance with religious beliefs. But both on Needham’s side and on Spallanzani’s there was a complete lack of conclusive proofs.

Philosophic argumentation always returned to the fore. As recently as 1846 Ernest Bersot (a moralist who became later a director of the Ecole Normale) wrote in his book on Spiritualism: “The doctrine of spontaneous generation pleases simplicity-loving minds; it leads them far beyond their own expectations. But it is yet only a private opinion, and, were it recognized, its virtue would have to be limited and narrowed down to the production of a few inferior animals.”

That doctrine was about to be noisily re-introduced.

On December 20, 1858, a correspondent of the Institute, M. Pouchet, director of the Natural History Museum of Rouen, sent to the Académie des Sciences a Note on Vegetable and Animal Proto-organisms spontaneously Generated in Artificial Air and in Oxygen Gas. The note began thus: “At this time when, seconded by the progress of science, several naturalists are endeavouring to reduce the domain of spontaneous generation or even to deny its existence altogether, I have undertaken a series of researches with the object of elucidating this vexed question.” Pouchet, declaring that he had taken excessive precautions to preserve his experiments from any cause of error, proclaimed that he was prepared to demonstrate that “animals and plants could be generated in a medium absolutely free from atmospheric air, and in which, therefore, no germ of organic bodies could have been brought by air.”

On one copy of that communication, the opening of a four years’ scientific campaign, Pasteur had underlined the passages which he intended to submit to rigorous experimentation. The scientific world was discussing the matter; Pasteur set himself to work.

A new installation, albeit a summary one, allowed him to attempt some delicate experiments. At one of the extremities of the façade of the Ecole Normale, on the same line as the doorkeeper’s lodge, a pavilion had been built for the school architect and his clerk. Pasteur succeeded in obtaining possession of this small building, and transformed it into a laboratory. He built a drying stove under the staircase; though he could only reach the stove by crawling on his knees, yet this was better than his old attic. He also had a pleasant surprise—he was given a curator. He had deserved one sooner, for he had founded the institution of agrégés préparateurs. Remembering his own desire, on leaving the Ecole Normale, to have a year or two for independent study, he had wished to facilitate for others the obtaining of those few years of research and perhaps inspiration. Thanks to him, five places as laboratory curators were exclusively reserved to Ecole Normale students who had taken their degree (agrégés). The first curator who entered the new laboratory was Jules Raulin, a young man with a clear and sagacious mind, a calm and tenacious character, loving difficulties for the sake of overcoming them.

Pasteur began by the microscopic study of atmospheric air. “If germs exist in atmosphere,” he said, “could they not be arrested on their way?” It then occurred to him to draw—through an aspirator—a current of outside air through a tube containing a little plug of cotton wool. The current as it passed deposited on this sort of filter some of the solid corpuscles contained in the air; the cotton wool often became black with those various kinds of dust. Pasteur assured himself that amongst various detritus those dusts presented spores and germs. “There are therefore in the air some organized corpuscles. Are they germs capable of vegetable productions, or of infusions? That is the question to solve.” He undertook a series of experiments to demonstrate that the most putrescible liquid remained pure indefinitely if placed out of the reach of atmospheric dusts. But it was sufficient to place in a pure liquid a particle of the cotton-wool filter to obtain an immediate alteration.

A year before starting any discussion Pasteur wrote to Pouchet that the results which he had attained were “not founded on facts of a faultless exactitude. I think you are wrong, not in believing in spontaneous generation (for it is difficult in such a case not to have a preconceived idea), but in affirming the existence of spontaneous generation. In experimental science it is always a mistake not to doubt when facts do not compel affirmation.... In my opinion, the question is whole and untouched by decisive proofs. What is there in air which provokes organization? Are they germs? is it a solid? is it a gas? is it a fluid? is it a principle such as ozone? All this is unknown and invites experiment.”

After a year’s study, Pasteur reached this conclusion: “Gases, fluids, electricity, magnetism, ozone, things known or things occult, there is nothing in the air that is conditional to life, except the germs that it carries.”

Pouchet defended himself vigorously. To suppose that germs came from air seemed to him impossible. How many millions of loose eggs or spores would then be contained in a cubic millimetre of atmospheric air?

“What will be the outcome of this giant’s struggle?” grandiloquently wrote an editor of the Moniteur Scientifique (April, 1860). Pouchet answered this anonymous writer by advising him to accept the doctrine of spontaneous generation adopted of old by so many “men of genius.” Pouchet’s principal disciple was a lover of science and of letters, M. Nicolas Joly, an agrégé of natural science, doctor of medicine, and professor of physiology at Toulouse. He himself had a pupil, Charles Musset, who was preparing a thesis for his doctor’s degree under the title: New Experimental Researches on Heterogenia, or Spontaneous Generation. By the words heterogenia or spontaneous generation Joly and Musset agreed in affirming that “they did not mean a creation out of nothing, but the production of a new organized being, lacking parents, and of which the primordial elements are drawn from ambient organic matter.”

Thus supported, Pouchet multiplied objections to the views of Pasteur, who had to meet every argument. Pasteur intended to narrow more and more the sphere of discussion. It was an ingenious operation to take the dusts from a cotton-wool filter, to disseminate them in a liquid, and thus to determine the alteration of that liquid; but the cotton wool itself was an organic substance and might be suspected. He therefore substituted for the cotton wool a plug of asbestos fibre, a mineral substance. He invented little glass flasks with a long curved neck; he filled them with an alterable liquid, which he deprived of germs by ebullition; the flask was in communication with the outer air through its curved tube, but the atmospheric germs were deposited in the curve of the neck without reaching the liquid; in order that alteration should take place, the vessel had to be inclined until the point where the liquid reached the dusts in the neck.

But Pouchet said, “How could germs contained in the air be numerous enough to develop in every organic infusion? Such a crowd of them would produce a thick mist as dense as iron.” Of all the difficulties this last seemed to Pasteur the hardest to solve. Could it not be that the dissemination of germs was more or less thick according to places? “Then,” cried the heterogenists, “there would be sterile zones and fecund zones, a most convenient hypothesis, indeed!” Pasteur let them laugh whilst he was preparing a series of flasks reserved for divers experiments. If spontaneous generation existed, it should invariably occur in vessels filled with the same alterable liquid. “Yet it is ever possible,” affirmed Pasteur, “to take up in certain places a notable though limited volume of ordinary air, having been submitted to no physical or chemical change, and still absolutely incapable of producing any alteration in an eminently putrescible liquor.” He was ready to prove that nothing was easier than to increase or to reduce the number either of the vessels where productions should appear or of the vessels where those productions should be lacking. After introducing into a series of flasks of a capacity of 250 cubic centimetres a very easily corrupted liquid, such as yeast water, he submitted each flask to ebullition. The neck of those vessels was ended off in a vertical point. Whilst the liquid was still boiling, he closed, with an enameller’s lamp, the pointed opening through which the steam had rushed out, taking with it all the air contained in the vessel. Those flasks were indeed calculated to satisfy both partisans or adversaries of spontaneous generation. If the extremity of the neck of one of these vessels was suddenly broken, all the ambient air rushed into the flask, bringing in all the suspended dusts; the bulb was closed again at once with the assistance of a jet of flame. Pasteur could then carry it away and place it in a temperature of 25-30° C., quite suitable for the development of germs and mucors.

In those series of tests some flasks showed some alteration, others remained pure, according to the place where the air had been admitted. During the beginning of the year 1860 Pasteur broke his bulb points and enclosed ordinary air in many different places, including the cellars of the Observatory of Paris. There, in that zone of an invariable temperature, the absolutely calm air could not be compared to the air he gathered in the yard of the same building. The results were also very different: out of ten vessels opened in the cellar, closed again and placed in the stove, only one showed any alteration; whilst eleven others, opened in the yard, all yielded organized bodies.

In a letter to his father (June, 1860), Pasteur wrote: “I have been prevented from writing by my experiments, which continue to be very curious. But it is such a wide subject that I have almost too many ideas of experiments. I am still being contradicted by two naturalists, M. Pouchet of Rouen and M. Joly of Toulouse. But I do not waste my time in answering them; they may say what they like, truth is on my side. They do not know how to experiment; it is not an easy art; it demands, besides certain natural qualities, a long practice which naturalists have not generally acquired nowadays.”

When the long vacation approached, Pasteur, who intended to go on a voyage of experiments, laid in a store of glass flasks. He wrote to Chappuis, on August 10, 1860: “I fear from your letter that you will not go to the Alps this year.... Besides the pleasure of having you for a guide, I had hoped to utilize your love of science by offering you the modest part of curator. It is by some study of air on heights afar from habitations and vegetation that I want to conclude my work on so-called spontaneous generation. The real interest of that work for me lies in the connection of this subject with that of ferments which I shall take up again November.”

Pasteur started for Arbois, taking with him seventy-three flasks; he opened twenty of them not very far from his father’s tannery, on the road to Dôle, along an old road, now a path which leads to the mount of the Bergère. The vine labourers who passed him wondered what this holiday tourist could be doing with all those little phials; no one suspected that he was penetrating one of nature’s greatest secrets. “What would you have?” merrily said his old friend, Jules Vercel; “it amuses him!” Of those twenty vessels, opened some distance away from any dwelling, eight yielded organized bodies.

Pasteur went on to Salins and climbed Mount Poupet, 850 metres above the sea-level. Out of twenty vessels opened, only five were altered. Pasteur would have liked to charter a balloon in order to prove that the higher you go the fewer germs you find, and that certain zones absolutely pure contain none at all. It was easier to go into the Alps.

He arrived at Chamonix on September 20, and engaged a guide to make the ascent of the Montanvert. The very next morning this novel sort of expedition started. A mule carried the case of thirty-three vessels, followed very closely by Pasteur, who watched over the precious burden and walked alongside of precipices supporting the case with one hand so that it should not be shaken.

When the first experiments were started an incident occurred. Pasteur has himself related this fact in his report to the Académie. “In order to close again the point of the flasks after taking in the air, I had taken with me an eolipyle spirit-lamp. The dazzling whiteness of the ice in the sunlight was such that it was impossible to distinguish the jet of burning alcohol, and as moreover that was slightly moved by the wind, it never remained on the broken glass long enough to hermetically seal my vessel. All the means I might have employed to make the flame visible and consequently directable would inevitably have given rise to causes of error by spreading strange dusts into the air. I was therefore obliged to bring back to the little inn of Montanvert, unsealed, the flasks which I had opened on the glacier.”