PASTEUR, FATHER OF PREVENTIVE MEDICINE.
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]
[Footnote 12: Heureux celui qui porte en soi un dieu, un idéal de beauté et qui lui obéit; idéal de l'art, idéal de la science, idéal de la patrie, idéal des vertus de l'Evangile.]
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]
[Footnote 13: Ce sont les sources vives des grandes pensées et des grandes actions. Toutes s'éclairent des reflets de l'infini.]
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.
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."
[Footnote 14: L'Histoire d'un esprit, par M. Duclaux, Paris, 1896.]
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.
Most of Pasteur's work, after this first thrilling discovery and its possible significance, is very well known. His meditations on the distinction between material derived from living and non-living sources led him to investigate certain processes called fermentations--before his time considered merely chemical. It is well known that if a dilute solution of sugar be exposed to the air anywhere in the world it will ferment--that is, certain changes will take place in the liquid, some gas will escape from its surface and alcohol will be formed. There are changes that take place in other organic substances--milk, meat solutions, butter, etc.--that resemble quite closely alcoholic fermentations, though the end-product of the process is not alcohol. Pasteur showed that all these supposed chemical changes are really due to the presence of minute living cells, called ferments. During the growth of these cells they split up the substances contained in the material in which they occur, using parts of them for their nutrition. He proved this very clearly for the lactic acid and butyric acid fermentations. Milk was supposed to become sour and butter rancid because they are unstable organic compounds, liable to change in the presence of the oxygen of the air. These changes were now shown to be due to minute living things that grow in the milk and the butter.
When Pasteur offered the same explanation of the origin of vinegar he found a strenuous opponent in Liebig, the great chemist. Liebig admitted the existence of specific substances, [{305}] called ferments, but said that they were nitrogenous compounds in unstable equilibrium as regards their composition, and with a marked tendency to undergo alteration when exposed to the air or free oxygen. These alterations, once begun, affect also the liquids in which the ferments are contained--milk, blood, sugar solutions and the like. Theodore Schwann had shown the existence of certain yeast-like bodies in fermenting liquids, but these were considered to be effects, not causes, of the fermentation, and even Schwann, himself, believed that they originated in the liquids in which they were found. It remained for Pasteur to demonstrate, as he did by a brilliant series of ingenious and conclusive experiments, that ferments are living cells, that they never originate except from previous cells of the same species, and that no fermentation takes place unless they are present.
The changes that take place in organic liquids when exposed to the air and the frequent development in such liquids of moving bodies evidently possessed of life constituted, before Pasteur's time, the principal reason for believing that life might originate from some special combination of chemical forces, and without the necessity for preceding life of the same species as its efficient cause. The new explanation of fermentation greatly weakened the position of those who believed in spontaneous generation--that is, the origin of life from dead matter under certain specially favorable circumstances. Pasteur proceeded to show, by rigid demonstration, that if all life were destroyed in organic substances, living beings never originated in them unless living seeds from the air gained access to them. After a meat solution has been thoroughly boiled nothing living develops in it, even though the air is allowed free access, if the air admitted has been previously filtered through cotton, He showed that even the [{306}] bending of the neck of the tube into the shape of an "S," so as to prevent the entrance of dust particles, suffices to protect the most changeable organic material from the growth of micro-organisms in it. His teaching was not accepted at once. Details of his experiments were impugned. Apparently complete counter-demonstrations were made, but Pasteur knew how, by his marvellous intuition, to detect the fallacy of supposed demonstration, and to invent new crucial tests of the proof of biological succession.
These studies in minute life and in fermentation led him almost naturally to the study of disease. Two centuries before, Robert Boyle, of whom his notorious descendant the great bullster, Sir Boyle Roche, had said that he was the father of chemistry and the brother of the Earl of Cork, made use of an expression wonderfully prophetic in its accurate penetration of the future. "He that thoroughly understands the nature of ferments and fermentations," said Boyle, "shall probably be much better able than he that ignores them to give a fair account of divers phenomena of certain diseases (as well fevers as others) which will perhaps be never properly understood without an insight into the doctrine of fermentations." The marvel is that the very first man who understood the nature of fermentation proved to be the one destined to unlock the mystery of contagious disease and its origin.
Pasteur's first investigations in the field of disease concerned a mysterious malady that affected the silkworm and was ruining the silk industry of France. This disease was first noted seriously about 1850. When a colony of silkworms had been attacked it was useless to try to do anything with them. The only resource for the silk farmers was to get the eggs of an unaffected race of worms from some distant country. These became infected after several generations, [{307}] and untainted eggs had to be brought from a distance once more. Soon the silkworm plague invaded most of the silk-growing countries of Europe. In 1864, only the races of silkworms in China and Japan were surely not infected. Great suffering had been entailed on many departments of France by the failure of the silk industry. The most careful investigation failed to reveal any method of combating the disease. Acute observers had been at work and some very suggestive observations on the affected worms had been made, but the solution of the problem of the prevention of the disease seemed as far off as ever. In 1863 the French minister of agriculture formally agreed to pay 500,000 francs (about $100,000) to an Italian investigator who claimed to have found a remedy for the disease, if his remedy proved efficient. The offer was to no purpose. In 1865 the weight of cocoons of silk had fallen to 4,000,000 kilos. It had formerly been nearly 30,000,000 kilos. This involved a yearly loss of 100,000,000 francs (about $20,000,000).
Pasteur showed that the failure of the silkworm was not due to one disease, but to two diseases--pebrine and flacherie. These diseases are communicated to the eggs of the worms, so that the young begin life handicapped by the maladies. The crawling of the worms over leaves and stems makes these liable to communicate the diseases. The prevention of the diseases is accomplished by procuring absolutely healthy eggs and then never letting them come in contact with anything that may have been touched by diseased worms. If, at the egg-laying period, worms show any signs of disease their eggs are to be rejected. These simple suggestions were the result of rigid experimental demonstration of the spread of the diseases from worm to worm, including the demonstration of the microbic causes of the two diseases. These precautions proved effective, [{308}] but their introduction met with opposition. The strain of the work and the worry of controversy brought Pasteur to the brink of the grave by a paralytic stroke. From this he never entirely recovered and was always afterward somewhat lame. After the severest symptoms had passed off he was given the opportunity to make a crucial test of preventing the silkworm diseases at the villa of the French Prince Imperial. The products obtained from the silkworms on the estate had, for years, not sufficed to pay for the fresh supplies of eggs obtained from a distance. Pasteur was given full charge of the silk industry on the estate. The sale of the cocoons at the end of the year gave a net profit of 26,000,000 francs (over $5,000,000). This decisive demonstration effectually ended all opposition.
His attention was next naturally directed to the diseases of animals and human beings. His studies in fermentations and in silkworm diseases had taught him the use of the microscope for such investigations. Splenic fever--known also as anthrax--a disease that attacks most species of domestic animals and may also prove fatal to man, was the first to yield the secret of its origin. The cause proved to be a bacterium--that is, a small, rod-shaped plant. This was but the first of a series of similar discoveries, until now the science of bacteriology has become one of the most important branches of knowledge. Pasteur's investigations included much more, however, than the mere discovery of the germ of the disease. He showed that a series of diseases which passed under different names in different animals were all due to the same cause. Further, he discovered one of the methods of distributing the disease. When the carcasses of animals that have died from the disease are not buried deeply below the surface of the ground, animals grazing above may become infected with the disease. [{309}] The germs of the disease can be shown to occur in the grass above the graves. It is carried to the surface in the bodies of earth-worms. This important observation was the first hint of the methods of disease distribution by some living intermediary. Modern medicine has come to understand that these biological distributing agents are far more important than the fabled transmission through the air.
Pasteur overturned the notion of spontaneous generation of life. Then his work eradicated the idea of the spontaneous generation of disease. It opened up a new era by showing that the origin of many diseases is not due to changes in the atmosphere nor to some morbid productivity of soil or water under favoring circumstances, but to minute living organisms whose multiplication is encouraged by the conditions that were supposed to produce disease. Finally, came the precious suggestion that living things always convey and distribute disease; man to man, for epidemics travel not with the velocity of the wind but only as fast as the means of communication between distant points; animal to man, as is well known, for many diseases now; and, lastly, insects, worms and the like were also shown to be real carriers of disease.
In investigating chicken cholera Pasteur discovered another great basic principle in the knowledge of disease, especially of its treatment. After considerable difficulty he succeeded in finding the germ of this disease which was causing great losses in the poultry industry of France and other European countries. This germ was cultivated for a number of generations on artificial media and never failed to produce the disease when fowls had been inoculated. During the course of his studies in the malady Pasteur was called away to a distant part of France in connection with his investigation of anthrax. He was away from his laboratory for several months. When he returned he inoculated [{310}] some fowls with the cultures of chicken cholera which he had left behind. To his surprise and annoyance the inoculations failed to produce the typical symptoms of the disease. The fowls suffered from some slight symptoms and then recovered. When he left his laboratory inoculations had been invariably fatal. It took considerable time and trouble to procure fresh cultures of the chicken-cholera microbe. Meantime, the fowls which had been only slightly affected by the old cultures were carefully preserved. When these birds were inoculated with the fresh virulent cultures they failed to take the disease. Other fowls promptly died, exhibiting all the characteristic symptoms of chicken cholera. Those that had suffered from the mild form of the disease produced by the old cultures were protected from further attacks of the disease.
One of the great mysteries of medicine, the varying virulence of disease, had been thus solved by what seemed an accident. There are no accidents in the lives of great investigators. There are surprises, but genius knows how to reconcile their occurrence with the principles they are working out. Pasteur understood at once the wonderful utility there might be in this discovery for the protection of men and animals from disease. He proceeded to practical applications of the new theory by providing old cultures for the inoculation of fowls in districts where chicken cholera produced serious ravages. Then, working on the same lines as for chicken cholera, he proceeded to elaborate vaccine material for anthrax.
Vaccine was the name deliberately selected for the inoculating substance in order to honor the genius of the English physician Jenner, who had discovered the power of vaccination to protect from smallpox. The weakening of the germs of anthrax, so as to produce only a mild form of the disease, was a much more intricate problem than for chicken cholera, [{311}] because the anthrax bacillus does not weaken with age, but enters a resting or spore stage, resembling the seed stage in large plants. After a patient series of investigations Pasteur accomplished his object by some ingenious methods that served to show, perhaps better than any other details of his career, how thoroughly practical was his inventive genius.
Unfortunately the absorption in his work proved too much for his health. He was seized by a series of apoplectic attacks which for a time threatened to put an end to his invaluable career. When he did begin to recover his health one of the most serious problems in his regard was to keep him from hindering his convalescence by a return to his old-time absorption in the important problems of the cure and the prevention of disease, at which he had been so happily engaged. The keynote of Pasteur's life was to prevent human suffering as far as possible, and any time not given to this important duty seemed to him to be utterly wasted. With regard to this unfortunate break in Pasteur's work Dr. Christian Herter, in his address on the "Influence of Pasteur in Medical Science," delivered before the Medical Society of Johns Hopkins University, [Footnote 15] has an interesting passage, in which he discusses the significance of the master's work up to this time, and the interest that his illness awakened among all the distinguished medical scientists of Europe at the time:
[Footnote 15: New York: Dodd, Mead & Co., 1904.]
"It is likely that excessive work and mental stress in some degree contributed to the onset of the series of paralytic seizures which in October, 1868, threatened the life of Louis Pasteur. During the critical period of his illness, many of the most distinguished scientific men of France vied with each other to share with Mme. Pasteur the privilege of nursing the man they loved so well and of rescuing the life [{312}] that had already placed science and a nation under enduring obligation through discoveries which were either of the greatest practical utility or appeared susceptible of almost unlimited development. Had Pasteur died in 1868, he would have left a name immortal in the annals of science. Others would in some degree have developed his ideas. Already inspired by the researches on fermentation, Lister would have continued to develop those life-saving surgical methods which will forever be associated with his name. But we may well question whether investigations in biology and medicine would not have been for a time at least conducted along less fruitful paths. Who shall say how soon the great principle of experimental immunity to pathogenic bacteria, the central jewel in the diadem of Pasteur's achievements, would have been brought to light?"
When Pasteur recovered sufficiently to resume work, it was soon clear to apprehensive friends that he had no intention of leaving his ideas to be worked out by other men. The miseries of the Franco-Prussian War deeply affected him, and could not fail to inhibit his productiveness, but after a time the unquenchable love for experimental research was once more ascendant and there began a new epoch, the epoch of great discoveries relating to the origin and cure or prevention of the infectious diseases of man and the domestic animals. As in the case of Ignatius Loyola, it seems as if the lamp of the genius shone with a larger and more luminous flame after the onset of bodily infirmity in defiance of the physical mechanism which is too often permitted to master the will.
After his illness Pasteur devoted himself even more than before to the study of the various biological problems connected with human diseases. There was one exception to this, in his series of studies on beer, undertaken shortly after [{313}] the Franco-Prussian War. Pasteur was an ardent patriot, so much so, indeed, that after the war he sent back to the German government certain decorations and diplomas that had been conferred upon him. He thought that his country had been overreached by a scheming, political statesman, bent on the aggrandizement of the kingdom of Prussia. To the end of his life this feeling of hostility never entirely vanished. It was his hope, then, that by improving the character of French beer it might not only be made more wholesome in the best sense of the word, but also that the French brewing industry might be made a serious rival of its German competitors. Pasteur's discoveries are the most important for the brewing industry that have ever been made. The Germans proved, however, even more capable of taking advantage of them than his French compatriots.
After this Pasteur devoted himself without further interruption to the study of the microbic diseases of man. His greatest practical triumph was undoubtedly with regard to hydrophobia, or, as it is more properly called, rabies. The mystery of the disease was most illusive. Pasteur could not succeed in finding the germ of the disease. Even down to our own day it has not been satisfactorily demonstrated. In spite of this lack of an important element of knowledge, which might be supposed absolutely essential for the successful therapeutics of rabies from a biological standpoint, Pasteur succeeded in producing material that would protect those bitten by rabid dogs from developing the affection.
Long and bitter was the opposition to the introduction of his method of treatment. The greatest living German bacteriologist said that it was idle to provide "remedies of which we know nothing for diseases of which we know less." The reference was to the failure to find the germ of the disease and the claim, nevertheless, of having discovered [{314}] a cure. Wherever the Pasteur treatment for rabies was introduced, however, the number of deaths following the bites of mad animals fell off. In Russia, where the mad wolves of the Steppes so often inflict fatal bites, the power of the new treatment was soon recognized. In Hungary its value was appreciated without delay. Then the British government, after a most careful investigation, introduced it into the Indian army. Then Austria took it up officially. At the International Medical Congress at Moscow, in 1897, Americans, who expressed doubts as to the efficiency of the Pasteur treatment for rabies, were laughed at by the medical representatives of nations who have the most opportunities for studying the disease. Shortly after the Moscow congress the German government officially announced its intention of treating all persons bitten by rabid animals by the Pasteur method. A Pasteur institute for the treatment was opened in connection with the University of Berlin. With this the last serious opposition disappeared. The Germans are now enthusiastic advocates of the value of the Pasteur treatment. The statistics of the Berlin Pasteur Institute are pointed to as demonstrating beyond doubt the possession of power to cope with one of the most fatal diseases man is liable to. Alas, that this should not have come during the master's lifetime! It would have been the happiest moment of Pasteur's life to have had his ideas triumphant in Germany. Unlike the generality of great men, however, Pasteur enjoyed the meed of almost unstinted appreciation during life.
Geniuses are often said to be neglected by their contemporaries. The expression is exemplified much less frequently in our own time than formerly. The rapid diffusion of ideas, and the consequent control and confirmation of scientific claims by many minds, enable the present generation to recognize merit before its possessor has starved. [{315}] Pasteur's career was certainly an exemplification of the fact that true genius, though it may meet with opposition, will be well rewarded. The son of the poor tanner of Dole, by the mere force of his intellectual energy, lifted himself to the level of earth's great ones. His funeral obsequies were a pageant in which French officialdom felt itself honored to take part. The President of the French Republic, the members of both houses of the legislative department, the officials of the city of Paris, the members of the faculty of the university, of the French Academy, and of the various scientific societies of the French capital, gathered to honor their mighty dead. Never has it been given to anyone without family prestige or political or ecclesiastical influence to have a great world-capital and a great nation accord such glorious obsequies, while all the world extended its sympathy and added paeans of praise.
Nor was it only at the moment of death that the expression of sincere respect and merited honor was paid. When there was question of erecting a Pasteur institute, in which the master's great work could be carried on more effectually, contributions poured in from every part of France and from all over the civilized world. Two of the world's greatest hereditary rulers made it a point to visit the humble laboratory of the great scientist whenever they came to Paris. Alexander II, the Czar of the Russians, was the intimate friend of the tanner's son, who became the world's benefactor. Dom Pedro II, the late Emperor of Brazil was another royal visitor to Pasteur. In the library of the Institut Pasteur at Paris, the busts of these two and of two other great friends of his, scarcely less in worldly importance and greater in their beneficence, keep watch above the ashes of the dead scientist. They are Baroness Hirsch, the world benefactress, and Baron Albert Rothschild, the head of the French branch of the great banking family.
All united in honoring the marvellous genius whose work has proved of such practical utility for mankind, and whose discoveries are as yet only beginning their career of pregnant suggestiveness to scientific men. His genius has brought the great ones of earth to his level or raised him to theirs. His own thought on the equality of man is a confession of the faith that was in him. It was expressed in his discourse of reception into the French Academy in the midst of the panegyric on Littré, from which we quoted at the beginning of this sketch: "Where are the true sources of human dignity, of liberty and of modern democracy, if not in the infinite, before which all men are equal? The notion of the infinite finds everywhere its inevitable expression. By it the supernatural is at the bottom of every heart."
Pasteur, the man, is, however, if possible, even more interesting than Pasteur, the greatest of living scientists. In the midst of all his work and his wonderful success, amid the plaudits of the world, Pasteur remained one of the simplest of men and the kindest of friends to those who knew him. Dr. Roux's expression is well known: "The work of Pasteur is admirable; it shows his genius; but one must have lived on terms of intimacy with him in order to know all the goodness of his heart." He was kindness personified, and those who think of him as a cruel vivisector and encourager of experiments upon animals that cause suffering, belie him and his humanity very much. He would never permit animals to be used in experiments without an anesthetic, and even then only when he deemed that use absolutely necessary for the furtherance of projects that promised great benefit to humanity. Nothing was harder for him to do than to walk the hospitals and see human suffering when he was studying the causes of disease in human beings. Even the slight pain inflicted during the [{317}] injections for hydrophobia was a source of great discomfort to him, and his anxiety with regard to these patients was one of the main causes of the breakdown in health that shortened his life.
One of the most beautiful things about Pasteur's personal life is the relation to his family, and especially to his children, and their union in religious simplicity. On the occasion of the death of his father, whom Pasteur loved very deeply and for whom he had instilled the deepest affection into the hearts of his children, he wrote to his daughter, whose first communion was to occur on that day. His letter is that of a man deeply affectionate, sincerely religious, and eminently trustful of the future that faith alone points out. His letter runs:
"He died, my dear Cecelia, the day of your first communion. Those are two memories which will, I hope, never leave your heart, my dear child. I had a presentiment of his death when I asked you to pray particularly on that morning for your grandfather at Arbois. Your prayers will surely be very agreeable to God at such a time, and who knows if grandpa himself did not know of them and did not rejoice with our little Jeanne It is not surprising, then, to find many other expressions of Pasteur's extreme interest in spiritual things, though they might have been little expected from a man so deeply immersed in scientific investigations as he was. After all, it must not be forgotten that his discoveries, by solving the mystery that surrounds the origin of disease, cleared some of the ways of Providence of that inscrutable character which is supposed in shallow minds to constitute the greatest part of their impressiveness. With epidemics explained, not as dispensations of Divine Providence, but as representing the sanction of nature for the violation of natural laws, one of the [{318}] reasons for which mankind worshipped the Deity seemed to be gone. The man who had done most to make clear these mysterious processes of nature was, however, himself far from thinking that materialism offers any adequate explanation of the mysteries of life, or of the relations of man to man, and of man to his Creator. Impatient at the pretensions of such pseudoscientists, Pasteur once said: "Posterity will one day laugh at the sublime foolishness of the modern materialistic philosophy. The more I study nature, the more I stand amazed at the work of the Creator. I pray while I am engaged at my work in the laboratory." For Pasteur, death had no mysteries. He had written to his father, once, on the death of his little daughter Jeanne: "I can only think at this moment of my poor little one so good, so full of life, so happy in living, and whom this fatal year, now drawing to a close, has snatched from us. After a very short time she would have been for her mother and for me, for all of us, a friend, a companion, a helpmate. But I ask your pardon, dear father, for recalling to you such sad memories. She is happy. Let us think of those who remain, and let us try to prevent for them, as far as lies in our power, the bitternesses of life." So, when it came to the hour of his own death, Pasteur faced it with the simple confidence of a sincere Christian, and the undoubting faith of a lifelong son of the Church. For many hours he remained motionless, one of his hands resting in that of Madame Pasteur, while the other held a crucifix. His last conscious glance was for his lifelong companion, his last conscious act a pressure of the image of his Redeemer. Thus, surrounded by his family and disciples in a room of almost monastic simplicity, on Saturday, September 28, 1895, about five in the afternoon, passed peacefully away the greatest of the nineteenth century scientists. Almost needless to say, the life of a man like Pasteur contains the most wonderful lessons for the young scientists of the twentieth century. Few men have lived their lives so unselfishly, and with so much preoccupation for the good that they might accomplish, as he did. To have remained in the midst of it all simple, earnest and faithful to duty, without self-seeking, is a triumph worthy of recording, and makes a career well deserving of emulation. When Pasteur made his discoveries with regard to fermentation the Empress of the French asked to be shown just what his investigations had demonstrated. Pasteur went to Court for the purpose, and after the Emperor and Empress had been shown the ferment cells, and expressed their interest, Eugenie said: "Now, you will develop this discovery industrially, will you not?" Pasteur replied. "Ah, no, that will be left for others. It does not seem to me that it would be worthy of a French scientist to allow himself to be diverted to the industrial applications of his discoveries, even though it might prove eminently lucrative for him." As a matter of fact, had Pasteur allowed himself to be allured into the foundation of an immense manufactory constructed and directed on the great principles which he had discovered, there seems no doubt that this would have been a wonderful money-making scheme. Certain it is that the capital for such an adventure would have been readily available. Had Pasteur yielded to the solicitations made him he might have died worth many millions, instead of the very modest competency which came to him in the ordinary course of his scientific labors. The money might have seemed a temptation for the sake of his children, but the world would have lost all the great discoveries with regard to human diseases. It is not unlikely that these would have been made even without Pasteur, There is no doubt, however, that their discovery [{320}] would have been very much delayed and that as a consequence almost untold human suffering that has been prevented would have occurred. It must never be forgotten that such men as Lister and Koch derived their most fertile suggestions from the discoveries made by Pasteur. Pasteur's life may very well be held up, then, as a model to the present and future generations of what the highest ideals of a scientific career can be. Dr. Christian Herter, in the discourse already quoted from, has stated this so well and at the same time has joined with it so felicitously a quotation from Pasteur's advice to young men, that we can find no better way in which to close this consideration of Pasteur's career than by quoting him once more: "To have fought the long battle of life with unwavering constancy to the loftiest ideals of conduct, toiling incessantly without a thought of selfish gain; to have remained unspoiled by success and unembittered by opposition and adversity; to have won from nature some of her most precious and covert secrets, turning them to use for the mitigation of human suffering;--these are proofs of rare qualities of heart and mind. Such full success in life did Louis Pasteur attain, and from the consciousness of good achieved his noble nature found full reward for all his labors. "'Young men, young men, devote yourselves to those sure [{321}] and powerful methods, of which we as yet know only the first secrets. And I say to all of you, whatever may be your career, never permit yourselves to be overcome by degrading and unfruitful skepticism. Neither permit the hours of sadness which come upon a nation to discourage you. Live in the serene peace of your laboratories and your libraries. First, ask yourselves, What have I done for my education? Then, as you advance in life, What have I done for my country? So that some day that supreme happiness may come to you, the consciousness of having contributed in some manner to the progress and welfare of humanity. But, whether our efforts in life meet with success or failure, let us be able to say, when we near the great goal, 'I have done what I could.'"
"Of the children whom nature has endowed with splendid gifts there are few whose lives have affected so profoundly and so beneficently the fate of their fellows, few who have earned in equal degree the gratitude and reverence of all civilized men. Although not many can hope to enrich science with new principles, all of us may gain from Pasteur's life the inspiration to cultivate the best that is in us. Let us keep living in our memories the inspiring words which the master spoke on the seventieth anniversary of his birthday: