Popular Science Monthly/Volume 79/July 1911/Pasteur: A Study in Greatness

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THE

POPULAR SCIENCE

MONTHLY

 

JULY, 1911




PASTEUR: A STUDY IN GREATNESS
By Professor FERNANDO WOOD MARTIN

RANDOLPH MACON WOMAN'S COLLEGE

GREATNESS is a matter of judgment. The degree of worth accorded anything whatsoever is determined solely by the intellectual and moral content of the individual, or the age, that plays the rôle of judge. We speak of great architects, musicians, orators, painters, poets, sculptors, soldiers, statesmen; and cite as examples such men as Wrenn, Beethoven, Demosthenes, Raphael, Homer, Angelo, Cæsar, Bismarck. These men, I say, were great. Why do I say so? Well, the world has pronounced them great. But you ask me, "Have you no grounds for formulating an opinion of your own?" Oh, yes, I have heard rendered the music of many composers; seen the masterpieces of many artists, and so on. And the achievements of none appear to me to surpass those of the men whose names I have mentioned. Perhaps you would name another in each line whom you hold to be more illustrious. You ask me then—"Is there no objective absolute standard by which the achievements of men may be definitely measured?" I answer "None."

You stand before Michel Angelo's "Moses" in the church of St. Peter in vinculo at Rome. "This" (you say) "is the finest statue in the world!" Please enlighten me as to the manner by which you have reached your decision. I grant at once that the judgment of the critics coincides with yours; but, of course, you are uninfluenced by that fact. "Is it" (I ask you) "because the statue is a true representation of a real person and event?" You answer—"No, oh no! But it seems to me that a man who dared the wrath of the most powerful potentate in the world; who wrestled with desert, and famine, and pestilence to shape the beginnings of a nation; who talked face to face with God—would have looked like that!" Ah, now you have found the standard of greatness; and you perceive that it is an ideal thing.

This being true, is it not remarkable that such unanimity of agreement should have resulted from its application? It appears to predicate the existence of a racial concept of greatness. Undoubtedly this racial idea exists. Philosophers of esthetics have troubled themselves not a little to account for its origination. While considering this elusory problem, the following solution has occurred to me. I offer it as an hypothesis.

An investigation of the specific works accomplished by men ranked great reveals a curious fundamental similarity: They all relate to the heroic. That is to say they are either actual deeds which relieved an individual, a community or a nation from danger, or they commemorate such deeds in a masterly way. The favorite theme of poets has always been "arms, and the man." And painters and sculptors have immortalized men whose acts furnish the implied answer to the query of brave Horatius, the keeper of the gate:

How can a man die better than by facing fearful odds,
For the ashes of his fathers and the altars of his gods?

By this analysis, the statesman is but the warrior who, with intellect as weapon, defends his nation.

If we consider the evolution of human society, it is not difficult to understand how this conception of greatness has grown up and established itself in the subconscious racial mind.

Back yonder in the gray and murky dawn of time, man was not that we see him to-day. Then, indeed, the conditions were exactly reversed; and man—puny, naked, defenceless—cowered in caves, or wandered miserably about seeking the sustenance which his nature demanded, but for the winning of which he was more illy equipped than the beetle that he crushed beneath his heel. Behind every rock, in every bunch of herbage, in every stream and pool, in the air he breathed, in the clouds that rolled above his head, in the glare of the sun, and in the gloom of night lurked death and a thousand dismal terrors.

That the human species escaped extermination at its very beginning is a marvel, and due solely to the one point wherein man is superior to other animals, namely, greater development of the frontal brain wherein lie the centers of memory and language. In that primitive society were some who remembered what things were good for food and where to be found; and so provided against death by poison and famine. Some devised protection against carnivorous animals or enemies of their own kind. These became head men. And, on account of their superior knowledge or prowess, they were esteemed while living and revered when dead. The memory of their deeds lived after them in song and story. And so they were gradually transformed from men into heroes and, later, into gods.

Oliver Wendell Holmes, alluding to the influence of heredity, sa "We are but stage-coaches in which all of our ancestors ride." By listening attentively we can hear at any time "ancestral voices prophesying war." This is why the heroic, in act or representation, moves us so profoundly. And this is my explanation of our racial ideal of greatness.

The man whose life sketch I now lay before you differed apparently from the traditional hero as widely as the dove from the eagle. He was no sower of dragon's teeth. Instead of sending sword and fire on every side, life, health and prosperity attended his career as the beneficent effects of light accompany the sun. And yet the recital of his bloodless wars and peaceful victories touches the same chords and thrills us with the same emotions as do the exploits of an Alexander.

Louis Pasteur was born at the village of Arbois, near Dole, in the province of Jura, France, on the twenty-seventh day of December, 1822. He died at St. Cloud, near Paris, on the twenty-eighth of September, 1895.

Like Napoleon, Pasteur was the first ancestor of his stock. His grandfather was a serf who purchased his own freedom. His father was a tanner who rose to no higher rank than sergeant in the service of the first consul. But he was a man of ability and fine instincts. Believing in the capability of his child to achieve something in the world, he studied diligently in order to assist the lad with his primary studies, and conducted his household with an economy that touched closely upon sacrifice that thereby a collegiate education might be made available for his son.

At fourteen, Pasteur was sent to College of Besançon. He remained there but a half year. Translated suddenly to a wholly strange environment, the shy country boy suffered so much from homesickness that he made little progress in his studies; and his health became so affected that his life was actually endangered. His father was compelled to bring him home. And now for the first time the self denial which had been practised on his account became apparent to the youth. Filled with an agony of shame that he should have so illy requited the love of his family, he resolved that he would spare no resource of his being in an endeavor to retrieve the consequences of his childish folly. The next year he requested his father to enter him at the home college of Arbois, a rural lycée little better than a grammar school.

Here he studied diligently, but received no instruction in the subjects which appealed to his nature. The old master assigned to teach the sciences frankly acknowledged that he knew nothing about them. But he allowed the young student access to the limited equipment; and young Pasteur spent much time in laboriously teaching himself some of the elementary principles of physics and chemistry. His teachers considered him slow. Drawing was the only subject in which he attained "honorable mention."

However, the head-master, Romanet, appears to have possessed more discernment than the rest of the faculty; for he frequently engaged young Pasteur in private talks in which he endeavored to arouse in him the ambition to prepare for teaching as a career.

At graduation, he was offered the position of preparation assistant or coaching tutor to the younger pupils, a post which carried the munificent salary of 300 francs per annum with board and lodging. He accepted the position gladly; and, with charming modesty, expressed the conviction that the salary was much beyond his deserts.

Small as his salary was, still he managed to save out of it something to help educate his sisters. Meanwhile he worked hard on the studies required for his B.S. degree, a prerequisite to his entering the Ecole Normale Supérieure at Paris. On this examination he was graded "mediocre" in chemistry.

Pasteur had thus far been a hard student; but he does not appear to have been an enthusiastic one till he had been for some time at the École Normale under the instruction of Balard, the discoverer of bromine, who was probably the only real teacher he ever had.

But even in this highest school for the training of professors afforded by the France of that day, the scientific equipment was so meager that only a few simple experiments were allowed for repetition by the students of chemistry. An incident in this connection will show the stuff that Pasteur was made of. Not content with being told how phosphorus is prepared, he bought some bones, calcined them, treated the calx with sulphuric acid, distilled the product with charcoal, and placed the distillate in a vial neatly labelled phosphorus. This was his first scientific joy. His comrades dubbed him "the laboratory pillar."

About this time he was shown a sample of a strange new acid of the same composition as tartaric acid, but manifesting strikingly different physical characteristics. His curiosity was intensely aroused.

Tartaric acid had been discovered in the "tartar" of wine casks by Scheele, of Sweden, in 1770. Thann, an Alsatian manufacturer of tartaric acid, discovered some of the anomalous variety in the output of his factory in 1825. He was unable to reproduce it. It was studied by Gay Lussac and Berzelius in 1826. The latter proposed for it the name of paratartaric acid; the former suggested that it be called racemic acid. Mitscherlich, of Berlin, in 1844 reported it as isomorphic with tartaric acid; and discovered that while the latter rotates a beam of polarized light to the right, racemic acid is inactive in this respect.

These were the facts brought to Pasteur's attention at the time when he was shown a specimen of the acid. Although immensely interested in the mystery presented by racemic acid, he put it aside, resolving to take it up when through with the final examination of his course of study, an ordeal for which he was just then preparing.

His usual examination fortune attended him upon this occasion. His classmates, who were wise in their generation, merely cramming for the test, came through with flying colors while his name appeared near the bottom of the list. And in the state examination which followed, his name was put next to the last. Apparently his not being rejected was due solely to the excellence which he displayed in the practical phase of the examination wherein the candidates went through the form of actually teaching a class. The lessons in physics and chemistry given by Pasteur caused the jury to declare "he will become an excellent teacher."

He was appointed laboratory assistant to Laurent, the first to formulate an hypothesis of the substitution of hydrogen in hydrocarbons. This theory was elaborated, and enunciated in its final form, by Dumas in 183-1. At this time, Laurent was working on sodium tungstate. One day he showed his assistant, under the microscope, some crystals of this salt supposedly pure but which manifested three distinct forms of crystallization. Pasteur began at once to learn how to use the goniometer. In order to master its technique, he made elaborate measurements on all easily crystallizable tartrates, thus revealing the fact that his curiosity concerning the two known tartaric acids had remained lively throughout the preceding two years.

In the meantime he was working toward the doctorate, which he achieved August 23, 1847, on the strength of two small papers, the one entitled "Researches on the Saturation Capacities of Arsenious Acid: A Study of the Arsenites of Soda, Potassa and Ammonia," and the other "A Study of the Phenomena Relative to the Polarization of Liquids."

He himself said of these papers, "They are elementary, and little more than programs for future work." Again he attained but poor ranking.

He now desired to study in Germany; but poverty frustrated his plans. On March 20, 1848, he read before the Académie des Sciences a part of a paper on dimorphism which was little more than a catalogue of all known substances crystallizing in two forms. Of itself, one might say that it was almost valueless. But to the student of Pasteur's life it was a proof that his work on the tartrates was still being prosecuted; and it afforded an index pointing out the tenacious purpose and the resolute will of the man.

After a flash of republican ardor in 1848, in which he not only volunteered service but also contributed to the cause all his savings, 150 francs, he returned to his crystals, and soon had the fortune to discover hemihedrism in the tartrates, a fact that had escaped the scrutiny of Mitscherlich and of Provostaye.

So far as his investigations showed, all crystals of tartaric acid had hemihedral faces; but he had found none on the racemates. Conceiving that this aspect of crystals might be an index of their molecular structure, he reasoned that the diverse optical behaviors of solutions of tartaric and racemic acids might be explained by a structural law. On fire with this new idea, he carefully examined a lot of tartrate crystals, and found, as he had anticipated, that each had hemi-hedral facets. He turned now to racemate crystals, expecting to find them destitute of hemihedrism. Imagine his disappointment, therefore, upon finding that here also each crystal distinctly displayed hemihedrism. But upon laboriously going over his work again he discovered a fact that had previously escaped his notice, namely, that the half-form facets of tartaric acid were all turned toward the right while those of the racemates were half right-handed and half left-handed. A new idea flashed into his mind. Carefully picking apart the two kinds of racemate crystals, he made a solution of each and, with anxious mind and throbbing heart, applied the polariscope. The solution of right-handed crystals deflected the beam to the right. They were pure tartaric acid. The solution of left-handed crystals deflected the beam to the left. They were a new acid—lævo tartaric acid. He mixed his solutions in equal proportions. The mixture did not affect the beam. It was racemic acid.

His excitement was so great that he could not look through the instrument again. Like Archimedes, he exclaimed "I have found it," and rushed into the corridor, where he met an assistant whom he embraced in a transport of joy.

This was one of the most illuminating discoveries known to the history of chemistry up to that time. Measured by its ultimate results, it is doubtless the most far-reaching discovery ever made. Developing in one direction, it was the germ of a new science—stereo-chemistry; in another it transformed medicine and agriculture from empirical practises into true sciences; and incidentally it enriched the world by a number of other discoveries of unparalleled practical value. Done at the age of twenty-five, this first great work of Pasteur's was a prophecy of that brilliant career throughout which he continued to manifest the same marvelous capacity for seeing the unseeable. It led to his appointment at once as professor of chemistry in the college of Dijon.

Finding that the duties of this position consumed all his time in teaching, he asked the government for a transfer to some place which would admit of his going on with research. Quite unexpectedly to himself, he was sent at the beginning of 1849 to the University of Strasburg to relieve Bersoz, professor of chemistry there, who desired to go to Paris.

Eealizing fully the value of the vein he had discovered in tartaric acids, he directed his energies along that line. He had found out what para-tartaric, or racemic, acid is; but neither he nor any one else knew its origin. He now undertook the discovery of this. In 1852 he visited all the factories of tartaric acid in Germany and Austria, endeavoring to trace the production of racemic acid to its source. He ascertained that the manufacturers generally had an idea that racemic acid was either potassium or magnesium sulphate, and consequently rejected it in the process of refining tartaric acid. This accounted for the limited quantity which had accidentally found its way to the market. As most of the tartars came from the south of Europe, and had been subjected to a preliminary rectification before shipment, it was further evident that but a moiety of racemic acid ever reached the factories. He pushed on his enquiries, visiting factories and vineyards until he positively located it in the crude tartar, where he found, as he had anticipated, that it was produced abundantly simultaneously with tartaric acid in the fermentation of wines. He wrote of this quest "Never was treasure sought, never adored beauty pursued, with greater ardor."

Having located the natural source of racemic acid, Pasteur next undertook to synthesize it from tartaric acid. This appears an easy problem in light of what every student now knows of the methods for effecting hydration, for constitutionally racemic acid differs from tartaric merely in possessing water of crystallization. In June, 1853, he was able to announce the completion of this great work, which had been accomplished by maintaining cinchona tartrate at a high temperature for several hours. This synthetic product was also optically inactive. It is known as meso-tartaric acid, and is the fourth form of the series. This research brought its author the grand prize of the Académie Française, and the ribbon of the Legion of Honor from the government.

Looking now at the tartaric acids, Pasteur's mind took a wider sweep. He saw that they were typical of all living things, which present asymmetry everywhere, and that they themselves were products of a form of life.

While engaged upon the racemates, he had found that the dextrocrystals alone were altered by fermentation, the lævo-forms remaining unchanged in the liquor. "The reason for this," said he, "can only be because this special ferment feeds, so to speak, more easily on the dextro-forms."

He pondered this problem long before he saw his way clear to its solution. At the same time he sought to unravel the indicated physiological significance of chemical affinities.

In September, 1854, Pasteur was appointed professor of chemistry and dean of the new faculty of sciences at Lille. Upon taking up his duties, he was greatly hampered at first by lack of facilities. The conditions which he encountered would have disheartened any other man. The scientific equipment consisted of a coke-heated stove with which his room was warmed and one student's microscope. This institution had recently been established by the municipality for the promotion of its industries, which were largely associated with alcohol.

Pasteur at once began the study of fermentation. This was a field which lay enshrouded in darkness with the exception of one tiny ray of light. In 1836, Cagniard de Latour had remarked that yeast, the ferment of beer, was composed of cells which were capable of reproduction by a sort of budding. He expressed the opinion that this microscopic plant probably acted on sugar by some sort of vegetative effect. A similar observation was made about the same time by Schwann, of Germany.

Pasteur set himself the problem of solving the mystery of fermentation. His notes show that he commenced by projecting an hypothesis associating fermentation with the dimorphism he had discovered in tartaric acid, which must have been caused in some way, he thought, by the action of a ferment on the grape juice.

Berzelius, whose ideas then reigned supreme in chemistry, was of the opinion that fermentation is a catalytic process. He gave it as his opinion that what de Latour believed that he had seen was organic matter precipitated by the process of fermentation, presenting forms analogous to vegetable life. Liebig's explanation was equally mystic. He defined fermentation as "action due to influence." He held the opinion that a ferment is a mass of organized matter set free from }east cells by their death and consequent rupture. Such matter he supposed to consist of unstable molecules which in the act of changing into new molecular arrangements liberated energy which in turn converted molecules of sugar into molecules of alcohol.

Uninfluenced by the metaphysical speculations of these great scientists, Pasteur held to the sure road of experimentation. In August, 1857, he discovered the fermentative organism which sours milk and produces lactic acid. The same year he was transferred to the École Normale Supérieure at Paris. The next year he discovered that glycerine and succinic acid are both produced simultaneously with ethel alcohol when sugar is fermented.

That Pasteur lost no implication of any phase of his researches is shown by a letter to his friend Chappuis written in January, 1860. He says: "I am hoping to mark a decisive step very soon in the celebrated question of the spontaneous generation of life. Already I could speak; but I shall require the accuracy of an arithmetical problem. I intend to attain even that." In a letter to his father, of about the same date, he says: "These results open new vistas to physiology. God grant that by my persevering labors I may bring a little stone to the frail and ill-assured edifice of our knowledge of those deep mysteries, life and death, where all our intellects have so lamentably failed."

The belief that living creatures of both usual and unusual types are continuously being spontaneously generated about us is very ancient in origin. It originated in the superficial observations and non-scientific explanations of our ancestors, and was perpetuated by the authority of great leaders, such as Aristotle and Augustine. Aristotle, whose ideas dominated the world for two thousand years, states explicitly that living beings are generated spontaneously from decomposing carcases. St. Augustine fulminates against the atheism of any who dare deny the doctrine, and cites what he considers irrefutable proofs of it. The alchemists gave recipes for the creation of various animals. Thus, Van Helmont gravely tells us, "You need only close up a dirty shirt with a measure of wheat in order to see mice engendered in it—the strange offspring of the smell of the wheat and the animal ferment attached to the shirt."

However, the more careful observation of a later period had cast discredit upon the traditional view. Thus, it had been shown irrefutably that the stock-proof of the spontaneous generationists—the appearance of maggots in decaying organic matter—was due to the hatching of flies' eggs. But the invention of the microscope, with its revelation of millions of minute forms hitherto unsuspected, revived the doctrine.

The lapse of a year after the letters cited above enabled Pasteur to announce, "Of gases, fluids, electricity, magnetism, ozone, things known or things occult—there is nothing, in the air, conditional to life except the germs it carries."

This dictum was at once fiercely attacked by the generationists who included in their party savants of European fame, the most notable being Bastian, of London. The discussion held the almost breathless attention of the newspaper-reading world, and ended some years later in Pasteur's triumphant demonstration of his thesis.

You can readily imagine that this research was not prosecuted by Pasteur because of its mere academic interest. He appended to his first paper, quoted above, this query—"What could be more desirable than to push these studies far enough to prepare the road for a series of researches into the origin of various diseases?"

In 1861 Pasteur discovered the ferment of butyric acid. In the following year he discovered the ferment of acetic acid, and showed that microbes could be distinguished into two grand classes—aerobes and anaerobes. The Academy of Sciences, which had rejected his name when offered for membership upon several previous occasions, could not longer refuse to honor a man whose fame was now world-wide. He was elected a member at the end of 1862.

The manufacturers and dealers in fermented liquors had always been subjected to annoyance and loss by their inability to make wines and beers of uniform standard and to keep them in the condition which they were put upon the market. Alterations were constantly taking place in these articles, due, it was supposed, to certain "diseases." Inasmuch as these wares represented a large share of the wealth of France, Pasteur was urged to investigate this matter. He commenced this research in 1864.

The ensuing year, an outbreak of cholera called his attention to that disease, and he studied it with a view to finding a bacterial cause for it, but without result. In the meantime, he was investigating a pestilence of silk worms which was proving so destructive as to threaten the silk industries of southern Europe with extinction. He was quite successful with this, and was quickly able to devise a method of combating it.

Doubtless the strain incident to the many and great investigations being simultaneously pushed by him during the three years, 1865 to 3868, was responsible for a series of paralytic shocks, the first of which struck him October 10, 1868. "While thought to be hopelessly ill and incapable of rational thinking, he insisted upon dictating a method of dealing with flacherie, a second silkworm disease which had been discovered by him in the course of his research on the silkworm pestilence. His treatment for flacherie proved to be a complete success, also. He recovered from this attack, but was physically lamed for the rest of his life. Although crippled in body, the work accomplished by him during his remaining twenty-seven years was not only stupendous in amount, but of transcending importance to mankind. I doubt if the example afforded by the heroic labors of the paralyzed Pasteur can be matched from the annals of all time.

By the close of 1871, he had shown that the "diseases" of wines and beers were caused by certain bacteria, all of which might be killed without injury to the product by heating it for a few minutes at a temperature of 50°-60° C.; and that if hermetically sealed at this temperature the liquors might be preserved perfectly for an indefinite period.

These studies had now thoroughly convinced their author that all diseases are of bacterial origin—a conception, you will recall, which had first come into his mind by a flash of genius ten years before. Indeed, four years prior to this (1867), Pasteur's researches had convinced a British surgeon, Joseph Lister, of Edinburgh, of the microbic origin of those purulent infections which accompany wounds and surgical operations. And although himself unacquainted with bacteriology, he successfully devised the method of asepsis which has made his name a household word.

Before the close of 1873, Pasteur finished the solution of that great problem begun at Lille nineteen years before—the mystery of fermentation. It is this: Certain bacteria, living at the surface of sugary fluids cause no fermentation, because they secure the oxygen which they need from the air. They are aerobic. But if sunk, by accident or otherwise, beneath the surface they must either perish or adapt themselves to their new environment by extracting oxygen from the nearest source of supply. This is the sugar of the solution. They are able to accomplish this but slowly at first, and the bulk of the first submerged bacteria suffocate. But reproducing rapidly by budding, ensuing generations are gradually but, for us, rapidly converted into true anaerobes, which, robbing the sugar molecules of oxygen, cause that chemical change called fermentation.

This problem solved, Pasteur was able to show from it the following results of his work: (1) Precisely what fermentation is, (2) that ferments are living organisms, (3) that every variety of fermentation is caused by a special ferment, (4) that neither bacteria nor any other life forms are spontaneously generated, (5) how to prepare culture media suitable to the growth of various bacteria, (6) how to propagate pure cultures of bacteria, (7) a basis of classification of bacteria, (8) the chemical and microscopical technique of bacteriology, (9) the cause and cure of various "diseases" of fermented liquors, (10) the cause and cure of various silkworm diseases, (11) an explanation of the mystery of the optical behavior of tartaric and racemic acids, (12) two new tartaric acids (13) how to synthesize meso-tartaric and racemic acids, (14) how to make racemic acid available to commerce.

In comparison with this great work of Pasteur's, the classic example of persevering genius—Newton's fourteen-year pondering over falling bodies—sinks into insignificance, no matter how considered, either as to time involved, the difficulties encountered, or the practical value of results obtained. Nor must one fail to note that incidentally Pasteur had beaten out a road into a new world and created two new sciences which were to serve as vehicles for its exploration and exploitation.

Pasteur's health had been so impaired by these arduous researches that he was now compelled to give up his professorship. As he was entirely without private resources, his colleagues exerted themselves upon his behalf, and succeeded in obtaining for him from the government, in 1874, an annual pension of 12,000 francs, the equivalent of the salary he had previously received.

His friends now urged him to abstain from work; but his genius could not endure inaction. He began the study of anthrax and feruncular diseases. While these studies were in progress, the bubonic plague appeared in Russia, and the yellow fever began to work havoc in the French colonies on the west coast of Africa and in the United States. Pasteur prepared a program of preliminary researches upon them. A paper to the Académie des Sciences presented December 30, 1878, closes with these words: "Is it not permissible to believe that a day will come when easily applied preventative means will arrest those scourges which suddenly desolate and terrify populations."

In 1879, he isolated the microbe of feruncles, and in 1880 those responsible for anthrax and chicken cholera. His studies had demonstrated the fact that every infectious disease thus far investigated was produced by a specific microbe; and, further, that such microbes cultivated under certain detrimental conditions become attenuated in pathogenic activity, still capable of producing a mild form of disease in an animal inoculated with them, but occasioning immunity to further attack. Such cultures of microbes of attenuated virus are vaccines.

Prophylactic vaccination had, of course, been known in an empirical way prior to this in connection with small-pox. But these researches of Pasteur's afforded the first explanation of that procedure, and in addition cast a flood of light upon the etiology of disease. They firmly established the germ theory, ushered in a scientific practise of medicine and sent to limbo a thousand pious superstitions about demoniacal possessions and the mysterious visitations of an all-wise Providence that doeth all things well. For these researches, the imperial government conferred upon him the cross and cordon of the Legion of Honor.

During the years of 1880, 1881, 1882, Pasteur gave his attention to hog cholera, rabies, pneumonia in cattle, the bubonic plague, yellow fever and typhoid fever. Of these six diseases he was able to carry to complete success his researches on the first three only. In 1881, a ship having come into Bordeaux from Senegal with several cases of yellow fever on board, he went thither, hoping for a favorable opportunity to study it at first hand. He was not permitted to do so. But his observations convinced him that this fever is not contagious.

Before the close of 1885, he had isolated the microbe of rabies, prepared its vaccine and perfected the method of treatment. This was a disease which caused not merely considerable property loss and suffering, it imbued the popular imagination with a dread but little less than the terror occasioned by a pestilence.

As despite the researches of hundreds of bacteriologists one may still hear it asserted that rabies is an imaginary disease, some statistics may not here be out of place. Accurate account of 320 cases of persons bitten by mad dogs prior to Pasteur's work in this field, showed a mortality of 40 per cent. The first 350 cases treated by his method furnished but one death, that of a little girl brought to the hospital in such condition and so late that Pasteur pronounced the case hopeless from the start, and only undertook it for humanity's sake. After the treatment had been given in 1,726 cases there had been but ten deaths.

The conquest of rabies was the last great work accomplished personally by Pasteur. Reattacked by paralysis in 1888, he conld thenceforth prosecute his ideas only by the labor of other hands. But he had a host of disciples in Europe and America, some of whom had studied under his personal guidance, but many more who, without having seen the great master, had nevertheless lighted their torches at his flame. I know of no surer index of a man's greatness than the measure of inspiration imparted by him.

Already Gayon had proved the bacterial cause of the decay of eggs. Koch had isolated the bacilli of tuberculosis and cholera. Traube had shown the like cause of ammoniacal fermentation; and upon the knowledge thus given, Van Tieghem and Gayon had devised their well-known treatment of diseases of the urinary organs. Lister had introduced asepsis, prior to which hospital statistics showed a mortality of 68 per cent, of cases of puerperal fever, gangrene and septicæmia generally incident to surgical operations. Accounts of surgical wards of army hospitals during our own civil war, typical, of course, of all that had preceded, with their perpetual agony, suppuration and horrible odors, read like a nightmare of insanity. A noted surgeon-teacher of that day said to his students, "When an operation seems necessary, think ten times about it; for too often when we decide upon an operation we sign the patient's death warrant." Another said, "He who shall conquer purulent infection will deserve a golden statue."

But to resume our catalogue: Behring and Kitasato, investigating lock-jaw, had discovered the microbe of tetanus, and ascertained the curious fact that although the patient was constitutionally affected the microbe was localized to the wound. They further found that the systemic effect of the disease was due to a toxin produced by the bacterium which was likewise fatally affected by the toxin. So that diluted solutions of the toxin not only constituted a remedy for the disease, but also a prophylaxis when administered in advance of infection. This was the first of the series of remedies known as anti-toxins.

Utilizing these results in the study of diphtheria, the combined labors of Richet and Herico, Boux and Yersin, Klebs and Loeffler, eventuated in 1894 in complete mastery of this disease, whose investigation had been inaugurated by Pasteur a dozen years before. Prior to the antitoxin method of treatment, diphtheria had justly been regarded as one of the worst scourges of our race, claiming a death-toll of 60 per cent, of all cases, and frequently leaving the survivors seriously injured for the remainder of their lives. At present, the mortality is about four per cent. And vaccination with the serum rendering the recipient immune to the disease for a period of about two months, epidemics of diphtheria may be entirely prevented by utilizing this prophylactic measure.

Closely connected with these researches on tetanus and diphtheria was a remarkable research brought out about this time by Metchnikoff, one of Pasteur's Russian pupils, in which he discovered the rôle of leucophytes, or white corpuscles of the blood. It appears that they constitute, so to speak, an army of defense, attacking and "eating up" invading microbes, thus explaining, by the principle of auto-vaccination or auto-toxination, why an individual may at certain times be immune to contagious disease.

And here, permit a parenthetical word upon vivisection. This vast amount of research had entailed much experimentation with living animals; and, as might have been foreseen, certain false humanitarians raised a great outcry about it. In England this went so far as to lead to the enactment of an antivivisection law, since repealed, I believe, although organized societies there, and on the continent, and in America still carry on an agitation. However kind the surgeon or pathologist may be, he can not avoid inflicting some pain in his efforts to prevent more. Nor can it have escaped your observation that, no less than man, the lower animals profited from these discoveries which could not have been made in any other way. It is also worthy of note that no antivivisectionist has ever offered to sacrifice himself for the good of humanity. The colleagues of Pasteur testify that he always used anesthetics in his work on animals and at such times evinced the most acute sympathetic suffering; only the end in view gave him courage to go on with the experiment. He said of himself that he could never have the heart to shoot a bird for sport.

Pasteur's discoveries were epoch-making, and revealed in him the Copernicus of medicine. Prior to his researches, the causes and rational treatment of disease were no better understood than in the stone age. Naturally, his conclusions were not accepted by medical men till every possible opposition had been exhausted. Physicians resented instruction from a man devoid of medical training. "A mere chemist" was the sneer most frequently on the lips of his adversaries. When they could no longer deny the existence of microbes, adherents to the old school still vehemently asserted that they were merely an epiphenomenon. I recall a choleric colleague of my own in the faculty of a medical college where I was teaching twenty years ago, who in the heat of debate was wont to call out loudly—"Bring on your microbes. I'll eat a pint of any variety!" Fortunately for him no one took him at his word. The distinguished Professor Pettenkofer, of Munich, having made the same remark concerning Koch's bacillus of cholera, he was supplied with the beverage—and actually drank it. Heroic efforts of physicians enabled him to keep his soul between his teeth, and after recovery he had the manhood to publish an admission of error.

In 1880 Huxley estimated that the practical results of Pasteur's discoveries had yielded France a return in excess of the war indemnity wrested from her a decade before—one billion francs. It is safe to assert that at present they represent to the world not less than that sum annually. And how shall an estimate be made of the relief of suffering and the preservation of life?

In 1894 Pasteur's former pupil, Yersin, isolated the bacillus of the bubonic plague, and had the pleasure of exhibiting it to his old master. "There is still much to do!" said Pasteur with a sigh. His health continued to fail steadily till September 28, 1895, when a final hemorrhage quenched forever the most brilliant mind ever bestowed upon a member of the human race.

Pasteur died a poor man, although, had he so chosen, he might have aggrandized himself beyond the dreams of avarice. But, considering that his ideas were heaven-sent, he bestowed them freely upon the whole world.

I can not find more suitable words with which to close this paper than those addressed by Pasteur to the students of the University of Edinburgh in 1884 upon the occasion of his visit there for the purpose of receiving the degree of doctor of laws from that ancient foundation. "Young gentlemen, work perseveringly. Work can be made into a pleasure, and alone is profitable to a man, to his country, to the world. Whatever career you may embrace, look up to an exalted goal. Worship great men and great things."