Part 5

Pausing before this house, Pasteur recalled the image of his father and mother--of those whom he called his dear departed ones--and from the far-off depths of his childhood came so many memories of affection, devotion, and paternal sacrifices that he burst into tears.

The life of his father had been a rough one. An old soldier, decorated on the field of battle, on returning to France, where he had no longer a home, he was obliged to work hard to earn his bread. He took up the trade of a tanner. Soon afterwards, having made the acquaintance of a worthy young girl, he joined his lot with hers, and together they entered courageously on the labours of their married life--he calm, reflective, and more eager, whenever he had a moment of repose, for the society of books than for the society of his neighbours; she full of enthusiasm, her heart and spirit agitated by thoughts above the level of her modest life. Both of them watched with ceaseless solitude over their little Louis, of whom, with mingled pride and tenderness, they used to say, 'We will make of him an educated man.'

In 1825 the Pasteur family quitted Dôle and established themselves at Arbois, where, on the borders of the Cuisance, the father of our hero had bought a small tanyard. At this town, and in this yard, Louis Pasteur spent his childhood. As soon as he was old enough to be received as a half-pay scholar he was sent to the communal college. He, the smallest of all the pupils, was so proud of passing under the great arched doorway of this ancient establishment, that he arrived laden with enormous dictionaries, of which there was no need.

In the midst of his laborious occupations the father of Pasteur took upon himself the task of superintending his son's lessons every evening. This was at first no sinecure. Louis Pasteur did not always take the shortest road either to reach his class or to return to his work at home. Some old friends still living remember having made with the little Pasteur fishing parties, which proved so pleasant that they have been continued to the present day. The boy, moreover, instead of applying himself to his lessons, often escaped and amused himself by making large portraits of his neighbours, male and female. A dozen of these portraits are still to be seen in the houses of Arbois, all bearing his signature. Considering that his age at the time was only thirteen, the accuracy of the drawing is astonishing.

'What a pity,' said an old lady of Arbois a short time since, 'that he should have buried himself in chemistry! He has missed his vocation, for he might by this time have made his reputation as a painter.'

It was not until he reached the third class that Louis Pasteur, beginning to realise the sacrifices which his father imposed upon himself, determined to abandon his fishing implements and his crayons, feeling aroused within him that passion for work which was to form the foundation of his life. The Principal of the college, who followed with watchful interest the progress of a pupil who, in his first effort, had outstripped all his comrades, used to say, 'He will go far. It is not for the chair of a small college like ours that we must prepare him; he must become professor in a royal college. My little friend,' he would add, 'think of the great École Normale.'

The College of Arbois having no professor of philosophy, Pasteur quitted it for Besançon. There he remained for the scholars' year, received the degree of bachelier ès lettres, and was immediately appointed tutor in the same college. In the intervals of his duties he followed the course of mathematics necessary to prepare him for the scientific examinations of the École Normale. He must have been already endowed with a singular maturity of character, for the director confided to him the superintendence of the quarters of the older pupils, who during class time were his comrades. In the class room his table was in the midst of them; and never had so young a master so much authority, and at the same time so little need for its exercise.

His first taste for chemistry manifested itself by frequent questions addressed during class time to an old professor named Darlay. This questioning was so often repeated that the good man, quite bewildered, ended by declaring that it was for him to interrogate Pasteur and not for Pasteur to interrogate him. His pupil pressed him no further, but having heard that at Besançon there lived an apothecary who had once distinguished himself by a paper inserted in the 'Annales de Chimie et de Physique,' he sought this man, with a view of ascertaining whether, on holidays, he would consent to give him lessons secretly.

At the examination for the École Normale, Pasteur passed as fourteenth in the list. This rank, however, did not satisfy him. Notwithstanding the censure of his fellow candidates he declared that he would begin a new year of preparation. It was in Paris itself that he chose to work--in one of the silent corners of the city, amid the seclusion of preparatory schools and convents.

In the Impasse des Feuillantines, there lived a schoolmaster, M. Barbet by name, or rather le père Barbet, as the Franc-Comtois, with provincial familiarity, used to call him. Pasteur begged to be allowed to enter his institution, not as an assistant, but as a simple pupil. Knowing how slender were the means of his young compatriot, M. Barbet reduced the fees of his pupil by one-third. Such kindness was customary with the père Barbet, who did not like to be reminded of his generosity. This, however, gives double pleasure to him who records it.

The year passes, the time of the examination arrives, and Pasteur is received as fourth on the list. Thus at last, in the month of October 1843, he finds himself in that École Normale in which he was destined to take so great a place. Pasteur's taste for chemistry had become a passion which he could now satisfy to his heart's content. Chemistry was at this time taught at the Sorbonne by M. Dumas and at the École Normale by M. Balard. The pupils of the École attended both courses of lectures. Different as were the two professors, both of them exercised great influence on their pupils. M. Dumas, with his serene gravity and his profound respect for his auditory, never allowed the smallest incorrectness to slip into his exposition. M. Balard, with a vivacity quite juvenile, with the excitement of a southerner in the tribune, did not always give his words time to follow his thoughts. It was he who once, showing a little potash to his audience, exclaimed with a fervour which has become celebrated, 'Potash, which--potash, then--potash, in short, which I now present to you.'

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. Pasteur rushed forward, and, presenting his handkerchief, received the snow. He returned triumphant, and running forthwith to the École Normale, repeated the principal experiments which the illustrious chemist had just exhibited to his audience. He preserved religiously the handkerchief which had been touched by M. Dumas.

Pasteur usually spent his Sundays with M. Barruel, the assistant of M. Dumas. He thought of nothing but experiments. For a long time in one of the laboratories of the École Normale was exhibited a basin--perhaps it is still shown--containing sixty grammes of phosphorus obtained from bones bought at the butcher's by Pasteur. These he had calcined, submitted to the processes known to chemists, and finally reduced, after a whole day's heating, from four in the morning to nine in the evening, to the said sixty grammes. It was the first time that the long manipulations required in the preparation of this simple substance were attempted at the École Normale.

Isolated in laboratory or library, Pasteur's only thought was to search, to learn, to question, and to verify. As the rule of the school leaves much to individual initiative, he devoted himself to his work with a joyful heart. This daily liberty constitutes the charm and the honour of the École Normale. Not only does it permit but it encourages individual effort; it allows the student to visit at his will the library, and to consult there the scientific journals and reviews. This free system of education develops singularly the spirit of research. There is in it an element of superiority over the École Polytechnique. Influenced by its military origin, constrained, moreover, by the number of its pupils to impose on all an exact discipline, and to introduce into their exercises a strict regularity, the École Polytechnique is, perhaps, less calculated than the École Normale to awaken in the minds of its pupils a taste for speculative science. It is certain that Pasteur owed to the freedom of work, and to the facilities for solitary reading which he there enjoyed, the first occasion for an investigation which was the starting-point to a veritable discovery.

Unlike the old professor of physics and chemistry at Besançon, one of the lecturers in the École Normale often took pleasure, not only in answering Pasteur's questions, but in leading him on to talk over scientific subjects. M. Delafosse, whose memory remains dear to all his pupils, was one of those men who fail to do themselves justice, or who, according to the expression of Cardinal de Retz, do not fulfil all their merit. Not that circumstances have been unfavourable to them, but that an invincible modesty, and a natural nonchalance which finds in that modesty a shield against latent self-reproach, leave them in a sort of twilight in which they are content to dwell. Pupil, and afterwards fellow worker, of the celebrated crystallographer Haüy, M. Delafosse had devoted himself to questions of molecular physics. Pasteur, who had read with enthusiasm the works of Haüy, conversed incessantly with Delafosse about the arrangements of molecules, when an unexpected note from the German chemist Mitscherlich, communicated to the Academy of Sciences, came to trouble all his scientific beliefs. Here is the note:--

'The paratartrate and the tartrate of soda and ammonia have the same chemical composition, the same crystalline form, the same angles, the same specific weight, the same double refraction, and consequently the same inclination of the optic axes. Dissolved in water, their refraction is the same. But while the dissolved tartrate causes the plane of polarised light to rotate, the paratartrate exerts no such action. M. Biot has found this to be the case with the whole series of these two kinds of salts. Here (adds Mitscherlich) the nature and the number of the atoms, their arrangement, and their distances apart are the same in the two bodies.'

Imbued as he was with the teachings of Haüy and Delafosse, and full of the ideas of M. Dumas in molecular chemistry, Pasteur asked himself this question: 'How can it be admitted that the nature and number of the atoms, their arrangement and distances apart, in two chemical substances are the same; that the crystalline forms are equally the same, without concluding that the two substances are absolutely identical? Is there not a profound incompatibility between the identity affirmed by Mitscherlich and the discrepancy of optic character manifested by the two compounds, tartaric and paratartaric, which form the subject of his note?'

This difficulty rested in Pasteur's mind with the tenacity of a fixed idea. Received as agrégé of physical science at the end of his third year at the École, and then keeping near his master, M. Balard, he had begun the study of crystals and the determination of their angles and forms, when his nomination to the professorship of physics in the Lycée of Tournon surprised and distressed him. M. Balard repaired immediately to the bureau of the Minister of Education, and spoke of his assistant in terms which caused the nomination to be cancelled. Pasteur remained in the laboratory of the École Normale.

With a view to mastering the science of crystallography, he took for his guide the extensive work of M. de la Provostaye, resolving to repeat all the measurements of angles and all the other determinations of this author with a view to a comparison of their respective results. The work of M. de la Provostaye, who was distinguished by the exactitude of his researches, had for its subject the tartaric and paratartaric acids and their saline compounds.

* * * * *

Two or three years ago, while we were walking together along a road in the Jura, M. Pasteur, after quoting textually the note of Mitscherlich, described to me with enthusiasm the pleasure he had experienced in crystallising tartaric acid and its salts, the crystals of which, he said, rivalled in size and beauty the most exquisite of crystalline forms.

'I should have great difficulty,' I remarked, 'in following you through the labyrinth of tartaric acid, tartrates, and paratartrates. However much your other studies have attracted me, those which had for their starting-point the note of Mitscherlich and the memoir of M. de la Provostaye have appeared to me, whenever I tried to master them, difficult of access. Ah,' I added, 'you would have done well, out of consideration for those who love to speak of your labours, had you made no discoveries in this field.'

Pasteur, with a mixture of indignation and indulgence, replied:--'Is it possible that you have not discerned the grand horizons that lie behind these researches in physics and molecular optics? If I have a regret, it is that I did not follow out this path. Less rough than it at first sight appears, it would, I am convinced, have led to the most important discoveries. By a sudden turn it threw me unexpectedly upon the subject of fermentation, and fermentation led me to the study of diseases; but I still continue to lament that I have never had time to retrace my steps.'

Then, with a simplicity of exposition in which one recognised the teacher who had always endeavoured to place his ideas within the range of his hearers, he said--

'If you picture to yourself all the bodies in nature--mineral, animal, or vegetable, and consider even the objects formed by the hands of man, you will see that they divide themselves into two great categories. The one has a plane of symmetry and the other has not. Take, for instance, a table, a chair, a playing die, or the human body; we can imagine a plane passing through these objects which divides each of them into two absolutely similar halves. Thus, a plane passing through the middle of the seat and of the back of an arm-chair would have, on its right and left, identical parts; in like manner a vertical plane passing through the middle of the forehead, nose, mouth, and chin of an individual, would have similar parts to the right and to the left. All these objects, and a multitude of similar ones, constitute our first category. They have, as mathematicians express it, one or several planes of symmetry.

'But, as regards the repetition of similar parts, it is far from being the case that all bodies are constituted in the manner here described. Consider, for example, your right hand: it is impossible to find for it a plane of symmetry. Whatever be the position of a plane which you imagine cutting the hand, you will never find on the right of this plane exactly the same as you find on its left. The same remark applies to your left hand, to your right ear and to your left ear, to your right eye and to your left eye; to your two arms, your two legs, and your two feet. The human body, taken as a whole, has a plane of symmetry, but none of the parts composing one or the other of its halves has such a plane. The stalk of a plant whose leaves are distributed spirally round its stem has not a plane of symmetry, nor has a spiral staircase such a plane; but a straight one has. You see this?

'It would have been truly extraordinary, would it not, if the various kinds of minerals, such as sea salt, alum, the diamond, rock crystal, and so many others which illustrate the great law of crystallisation, and which clothe themselves in geometric forms, should not present to us examples of the two categories of which we have just been speaking? They do so in fact. Thus a cube, which has the form of a player's die, has a plane of symmetry; it has indeed several planes. The form of the diamond, which is a regular octahedron, has also several planes of symmetry. It is thus also with the great majority of the mineral forms met with in nature or in the laboratory. They have generally one or several planes of symmetry. There are, however, exceptions. Rock crystal, which is found in prisms, often of large volume, in the fissures of certain primitive rocks, has no plane of symmetry. This crystal exhibits certain small facets, distributed in such a manner that in their totality they might be compared to a helix, or spiral, or screw, which are all objects not possessing a plane of symmetry.

'Every object which has a plane of symmetry, when placed before a looking-glass, has an image which is rigorously identical with the object itself. The image can be superposed upon the reality. Place a chair before a mirror; the image faithfully reproduces the chair. The mirror also reproduces the human body considered as a whole. But place before the mirror your right hand and you will see a left hand. The right hand is not superposable on the left, just as the glove of your right hand cannot be fitted to your left, and inversely.'