Part 27

Louis Pasteur is the most striking figure in nineteenth century science. In biology, in chemistry, in physics, in medicine and surgery, and in the important practical subjects of fermentation, spontaneous generation and sanitation, he has left landmarks that represent great advances in science and starting-points for new explorations into the as yet unmapped domain of scientific knowledge. His was a typically scientific mind. His intuitions were marvellous in their prophetic accuracy, yet were surpassed by his wonderful faculty for evolving methods of experimental demonstrations of his theories. His work has changed the whole aspect of biology and medicine, and especially the precious branches of it that refer to the cure and treatment of disease.

To such a man our generation owes a fitting monument. It has been given him. He was modest in life with the sincere modesty of the true man of science, who knows in the midst of great discoveries that he is only on the edge of truth, who realizes that "abyss calls to abyss" in the world of knowledge that lies beyond his grasp. Pasteur's monument, very appropriately for a man of his practical bent, is no idle ornamental memorial. It is a great institution for the perpetual prosecution of his favorite studies and for the care of patients suffering from the diseases to whose investigation the best part of his life was devoted.

In this Institut Pasteur repose his ashes. They find a suitable resting-place in a beautiful chapel. Situate just below the main entrance a little lower than the ground floor, {294} of the institute proper, this chapel seems to form the main part of the foundation of the building. It is symbolic of the life of the man in whose honor it was erected. He who said, "The more I know the more nearly does my faith approach that of the Breton peasant. Could I but know it all my faith would doubtless equal even that of the Breton peasant woman." On a firm foundation of imperturbable faith this greatest scientific genius of the century raised up an edifice of acquisitions to science such as it had never before been given to man to make.

Above the entrance of this chapel-tomb, and immediately beneath the words "Here lies Pasteur," is very fittingly placed his famous confession of faith:

"Happy the man who bears within him a divinity, an ideal of beauty and obeys it; an ideal of art, an ideal of science, an ideal of country, an ideal of the virtues of the Gospel." [Footnote 12]

When we turn to the panegyric of Littré in which the words occur we find two further sentences worth noting here: "These are the living springs of great thoughts and great actions. Everything grows clear in the reflections from the infinite." [Footnote 13]

These words are all the more striking from the circumstances in which they were uttered. When a vacant chair (fauteuil) in the French academy is filled by the election of a new member of the Forty Immortals, the incoming academician must give the panegyric of his predecessor in the same chair. Pasteur was elected to the fauteuil that had been occupied by Littré. Littré, who by forty years of unceasing toil made a greater dictionary of the French language than {295} the Academy has made in the nearly two hundred years devoted to the task, was the greatest living positivist of his day. He and Pasteur had been on terms of the greatest intimacy. Pasteur's appreciation of his dead friend is at once sincere and hearty, but also just and impartial. Littré had been a model of the human virtues. Suffering had touched him deeply and found him ever ready with compassionate response. His fellow-man had been the subject of his deepest thoughts, though his relationship to other men appealed to him only because of the bonds of human brotherhood. Pasteur called him a "laic" saint. For many of us it is a source of genuine consolation and seems a compensation for the human virtues exercised during a long life that the great positivist died the happy death of a Christian confident in the future life and its rewards.

But Pasteur himself rises above the merely positive. The spiritual side of things appeals to him and other-worldliness steps in to strengthen the merely human motives that meant so much for Littré. Higher motives dominate the life and actions of Pasteur himself. In the midst of his panegyric of the great positivist the greatest scientist of his age makes his confession of faith in the things that are above and beyond the domain of the senses--his ideals and his God.

There is said to exist a constant, unappeasable warfare between science and religion. Perhaps it does exist, but surely only in the narrow minds of the lesser lights. In no century has science developed as in the one that has just closed. Faraday the great scientific mind of the beginning of the century, said, at one of his lectures before the Royal Academy of Sciences of England, when the century was scarcely a decade old: "I do not name God here because I am lecturing on experimental science. But the notion of respect for God comes to my mind by ways as sure as those {296} which lead us to physical truth." At the end of the century the monument of a great man of science is a chapel with an altar on which the sacrifice of Him that died for men is commemorated on Pasteur anniversaries.

The walls of the chapel are inscribed with the scientific triumphs of the master whose ashes repose here. It is a striking catalogue. Each heading represents a great step forward in science:

1848, Molecular Dissymmetry. 1857, Fermentations. 1862, So-called Spontaneous Generation. 1863, Studies in Wine. 1865, Diseases of Silk Worms. 1871, Studies in Beer. 1877, Virulent Microbic Diseases. 1880, Vaccinating Viruses. 1885, Prophylaxis of Rabies.

Apparently these various subjects are widely separated from one another. It might seem that Pasteur was an erratic genius. As a matter of fact, each successive subject follows its predecessor by a rigid logic. Pasteur's life-work can be best studied by a consideration of these various topics and an appreciation of the advance made in each one.

Pasteur was first of all and always a chemist! He was interested in chemistry from his early years. In the decade from 1840 to 1850 organic chemistry--or as we prefer to call it now, the chemistry of the carbon compounds--was just opening up. Great discoveries were possible as they were not before or since. Pasteur, with a devotion to experimental work that amounted to a passion, was a pupil at the Ecole Normale, in Paris. Bruited about he heard all the suggestive questions that were insoluble problems even to the great men around him. He was especially interested in the burning {297} question of the day, the internal constitution of molecules and the arrangement of atoms in substances which, though they are composed of exactly the same constituents, exhibit very different physical and chemical qualities. The subject is, almost needless to say, a basic problem in chemistry and remains to our own day the most attractive of scientific mysteries.

Mitscherlich, one of the greatest chemists of the time, had just announced that certain salts--the tartrates and paratartrates of soda and ammonia--"had the same chemical composition, the same crystalline form, the same angles in the crystalline condition, the same specific weight, the same double refraction and, consequently, the same inclination of the optic axes. Notwithstanding all these points of similarity, if the tartrate is dissolved in water it causes the plane of polarized light to rotate while the paratartrate exerts no such action." Pasteur could not believe that all the chemical and physical qualities of two substances could be identical and their action to polarized light be so different. Mitscherlich was known, however, as an extremely careful observer. For several years Pasteur revolved all the possibilities in Mitscherlich's observations and, finally, came to the conclusion that there perhaps existed in the paratartrates, as prepared by Mitscherlich, two different groups of crystals, the members of one of which turned the plane of polarization to the right, the other to the left. These two effects neutralized each other and apparently the paratartrates have no influence on the polarized beam of light.

Pasteur found that the paratartrates were composed of crystals that were dissymmetrical--that is, whose image reflected in a mirror cannot be superposed on the crystal itself. This idea Pasteur makes clear by reference to the mirrored image of a hand. The image of the right hand as {298} seen in a mirror is a left hand. It cannot be superposed on the hand of which it is the reflection any more than the left hand can be superposed on the right and have corresponding parts occupy corresponding places. Pasteur found that the paratartrates were not only dissymmetrical, but that they possessed two forms of dissymmetry. The mirrored image of some of the crystals could be superposed on certain of the other crystals just as the mirror image of the right hand can be superposed on the actual left hand. He concluded that if he separated these two groups from each other he would have two very different substances, and so the mystery propounded by Mitscherlich would be solved.

With Pasteur to conceive an idea was to think out its experimental demonstration. He manufactured the paratartrates according to the directions given by Mitscherlich, and then proceeded to sort the two varieties of crystals by hand. It was slow, patient work, and for hours Pasteur strove feverishly on alone in the laboratory. At length, the crystals were ready for solution and examination as to their effect upon polarized light. If Pasteur's idea as to the dissymmetry of crystals were confirmed, a great scientific advance was assured. Tremblingly the young enthusiast adjusted his polariscope. He tells the story himself of his first hesitant glance. But hesitation was changed to triumph. His prevision was correct. There were two forms of crystals with different effects on polarized light in Mitscherlich's supposed simple substance. Pasteur could not stay to put his instrument away. The air of the laboratory had become oppressive to him. Drunk with the wine of discovery, as a French biographer remarks, he rushed into the open air and almost staggered into the arms of a friend who was passing. "Ah," he said, "I have just made a great discovery. Come to the Luxembourg garden and I will tell you all about {299} it." It was characteristic of the man all through life to have no doubt of the true significance of his work. He was sure of each step in the demonstration and his conclusions were beyond doubt.

Pasteur's discovery made a profound sensation. The French Academy of Sciences at once proceeded to its investigation. Among the members who were intensely interested, some bore names that now belong to universal science--Arago, Biot, Dumas, De Senarmont. Pasteur told long years afterward of Biot's emotion when the facts were visibly demonstrated to him. Greatly moved, the distinguished old man took the young man's arm and, trembling, said: "My dear child, I have loved science so well that this makes my heart beat." How deeply these men were bound up in their work! How richly they were rewarded for their devotion to science! There were giants in those days.

Pasteur's discovery was much more than a new fact in chemistry and physics. It was the foundation-stone that was to support the new science of stereochemistry--the study of the physiochemical arrangement of atoms within the molecule--that took its rise a few years later. Much more, it was a great landmark in biology. Pasteur pointed out that all mineral substances--that is, all the natural products not due to living energy--have a superposable image and are, therefore, not dissymmetrical. All the products of vegetable and animal life are dissymmetrical. All these latter substances turn the plane of polarization. This is the great fundamental distinction between organic and inorganic substances--the only one that has endured thus far in the advance of science. Dissymmetry probably represents some essential manifestation of vital force. Often there seem to be exceptions to this law; but careful analysis of the conditions of the problem shows that they are not real.

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An apparent contradiction, for instance, to this law of demarcation between artificial products and the results of animal and vegetable life is presented by the existence in living creatures of substances like oxalic acid, formic acid, urea, uric acid, creatine, creatinin, and the like. None of these substances, however, has any effect on polarized light or shows any dissymmetry in the form of its crystals. These substances, it must be remembered, are the result of secondary action. Their formation is evidently governed by the laws which determine the composition of the artificial products of our laboratory, or of the mineral kingdom properly so called. In living beings they are the results of excretion rather than substances essential to life. The essential fundamental components of vegetables and animals are always found to possess the power of acting on polarized light. Such substances as cellulose, fecula, albumin, fibrin, and the like, never fail to have this power. This is sufficient to establish their internal dissymmetry, even when, through the absence of characteristic crystallization, they fail to manifest this dissymmetry outwardly.

It would scarcely be possible to indicate a more profound distinction between the respective products of living and of mineral nature than the existence of the dissymmetry among living beings and its absence in all merely dead matter. It is strange that not one of the thousands of artificial products of the laboratory, the number of which is each day growing greater and greater, should manifest either the power of turning the plane of polarization or non-superposable dissymmetry. Natural dissymmetrical substances--gum, sugar, tartaric and malic acids, quinine, strychnine, essence of turpentine, and the like--may be and are employed in forming new compounds which remain dissymmetrical though they are artificially prepared. It is evident, however, that all these new {301} products only inherit the original dissymmetry of the substances from which they are derived. When chemical action becomes more profound--that is, becomes absolutely analytic or loosening of the original bonds imposed by nature--all dissymmetry disappears. It never afterward reappears in any of these successive ulterior products.

"What can be the causes of so great a difference?" We quote from Pasteur's life by his son-in-law: "Pasteur often expressed to me the conviction," says M. Radot, "that it must be attributed to the circumstance that the molecular forces which operate in the mineral kingdom and which are brought into play every day in our laboratory are forces of the symmetrical order; while the forces which are present and active at the moment when the grain sprouts, when the egg develops, and when under the influence of the sun the green matter of the leaves decomposes the carbonic acid of the air and utilizes in diverse ways the carbon of this acid, the hydrogen of the water and the oxygen of these two products are of the dissymmetrical order, probably depending on some of the grand dissymmetrical cosmic phenomena of our universe."

For the first few years after this discovery Pasteur endeavored by every possible means to secure experimental modifications of some of these phenomena of dissymmetry. He hoped thus to learn more fully their true nature. Magnetic influences especially would, he hoped, enable him to pierce, at least to some degree, this fundamental mystery of nature. While acting as professor at Strasburg, he procured powerful magnets with the view of comparing the actions of their poles and, if possible, of introducing by their aid among the forms of crystals a manifestation of dissymmetry. At Lille, where he was for several years dean of the scientific faculty, he contrived a piece of clockwork intended {302} to keep a plant in continual rotary motion, first in one direction and then in the other. "All this was crude," he says himself, "but further than this I had proposed with the view of influencing the vegetation of certain plants to invert, by means of a heliostat and a reflecting mirror, the motion of the solar rays which should strike them from the birth of their earliest shoots. In this direction there was more to be hoped for."

He did not have time, however, to follow out these ingenious experiments. He became involved, as we shall see, in labors more than sufficient to take up all his time and all his energy. These labors were of great practical importance for France. Pasteur always insisted, however, that great discoveries will yet be made in following out this order of ideas, and that there is in this subject magnificent opportunity for young men possessed of the genius of discovery and the power of persistent work.

When, only a few years ago, Professor Duclaux, Pasteur's successor as the head of the Pasteur Institute, and himself one of the greatest living authorities on biological chemistry, wrote the story of the mind of the master, [Footnote 14] he said, of this subject of dissymmetry: "A living cell appears to us, then, as a laboratory of dissymmetrical forces, a bit of dissymmetrical protoplasm acting under the influence of the sun--that is to say, under the influence of exterior dissymmetrical forces. It presides over actions of very different kinds. It can manufacture, in its turn, new dissymmetrical substances which add to or take away from its energy. It can, for instance, utilize one of the elements of a paratartrate without touching another. It can manufacture crystalline sugar at one moment and consume it at another, laying by stores for itself to-day using them up to-morrow. In a word, the living cell {303} presents a marvellous plasticity, which exerts itself without the slightest disturbance by minimal deviations of forces due to dissymmetrical influence. Ah, if spontaneous generation were only possible! If we could only create living matter, raise up in the midst of inactive mineral material a living cell, then it would be easy for us to understand something more of vital manifestations and to comprehend better the mystery of dissymmetry."

But spontaneous generation is as far off as ever. Pasteur's discoveries in dissymmetry have brought us closer than ever before to the mystery of life. Scientists still hope, but it is with ever-waning confidence, that they may pluck out the heart of the mystery. Pasteur's own thoughts with regard to dissymmetry rose above even the lofty heights of mere earthly biology. He saw in it the great force that links the universe together. On one occasion, at the Academy of Sciences, he expressed himself as follows:

"The universe 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 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 movement, we obtain in the mirror an image not superposable on the reality. Even the motion of solar light is dissymmetrical. A luminous ray never strikes in a straight line. Terrestrial magnetism, the opposition which exists between the north and the south poles of a magnet, the opposition presented to us by positive and negative electricity, are all the resultants of dissymmetrical actions and motions."

This raising of his thoughts far above the sordid realities he is concerned with into the realms of suggestive theory is typical of Pasteur. His was a true creative mind--poetic {304} in its highest sense. The imagination properly controlled is of as great value to the scientist as to the poet. Pasteur's theories were ever pregnant with truth to be. All his life he kept this question of dissymmetry before his mind and hoped to get back to work at it. But opportunity failed. Other and more practical work was destined to occupy the busy half-century of investigation that followed.