Popular Science Monthly/Volume 20/April 1882/Sketch of M. Louis Pasteur

PSM V20 D742 Louis Pasteur.jpg



Louis Pasteur, the distinguished French chemist and author of researches in fermentation and the germs of disease which have been fruitful in valuable discoveries, was born at Dôle, in the Jura, December 27, 1822. He entered the university in 1840, became a supernumerary Master of Studies at the College of Besançon, was received as a pupil in the École Normale in 1843, took the degree of Doctor in 1847, and was appointed Professor of Physics in the Faculty of Sciences at Dijon in 1848, and of Chemistry at Strasburg, in 1849. In 1854 he was appointed Dean of the newly created Faculty of Sciences at Lille, and was intrusted with the duty of organizing it. In 1857 he returned to Paris, and became Scientific Director of the École Normale. In December, 1863, he was appointed Professor of Geology, Physics, and Chemistry at the École des Beaux-Arts, and was elected a member of the Institute. He has written numerous works relating to chemistry, and has contributed much to the "Recueil des Savants Étrangers" and the "Annales de Chimie et de Physique"; and for his researches relative to the polarization of light he received, in 1856, the Rumford medal from the Royal Society of London. His work in pure chemistry, however meritorious, and brilliant enough though it was, has been eclipsed by his vastly more important and more fruitful researches in fermentation; into the causes of certain diseases of plants, animals, and man; and into the modes of reproduction of the lower organisms (or the theory of spontaneous generation), and the parts which those lower organisms play in the production of chemical changes, and in the origination and spread of disease—in which field he may almost be said to have constituted a new science, and has certainly performed a work of incalculable benefit to mankind. These investigations have been pursued under the light of the theory, to which their results in turn have given additional force, that all fermentations are processes connected with life, and that this life—and any life—is not of spontaneous production, but proceeds from some previously existing life or parent. Hence, he has held, and has aimed to show, that fermentation can never take place if all access of germs to a fermentable substance is prevented. From fermentation he has extended his theory of the agency of microscopic organisms in working changes, to the explanation of the origin and multiplication of various infectious diseases, each of which, as well as each kind of fermentation and putrefaction, is caused by its own specific organism.

M. Pasteur took a prominent and most active part in the controversy respecting spontaneous generation, which raged quite bitterly a few years ago. He performed the most decisive experiments that were made, and has contributed more than any other person to turn the current of scientific thought against that theory, and to bring the weight of opinion in favor of his own theory of panspermy. The controversy on this subject, which had been resting for many years after the researches of Siebold, Leuckart, and others, into the mode of development of sexless parasites, was reopened as to the infusoria in 1858 by Pouchet, who affirmed that previous experiments in regard to boiled infusions were inexact, and that boiling did not prevent the appearance of infusorial life, as it would necessarily do if such appearance was dependent on the existence of living organisms or germs in the liquids previous to boiling. M. Pasteur, having become interested in this subject through his studies in fermentation, came forward with his test experiments. The question seemed a very difficult one, and incapable of a definite solution, so that Pasteur's friends, Biot and Dumas, were impelled to counsel him against wasting too much time upon it. They had, however, good reason afterward to revise their opinions. M. Pasteur boiled a suitable organic infusion in glass flasks, which he sealed hermetically while the boiling was going on, so as to exclude the air that might bring in new germs to take the place of those which the boiling had killed. The flasks were then taken to different localities, where, after a time, the necks were broken and air was admitted to the boiled infusion. Pasteur reasoned that if the organisms, which were produced in the liquid on exposure to the atmosphere, were spontaneous growths excited to life by the action of the atmosphere alone, the products would be the same wherever the bottles were broken; but if the manifestation of life depended upon the introduction of new organisms or their germs from the air—since the air of different places would probably contain different organisms and be charged in different proportions with them—there would be different results in different places. The experiments showed manifest differences, in accordance with Pasteur's anticipations, and were considered to demonstrate the existence in the atmosphere of extraneous particles, the introduction of which into an infusion was the necessary condition of life appearing there. Professor Tyndall says of them that they, "carried out with a severity perfectly obvious to the instructed scientific reader, and accompanied by a logic equally severe, restored the conviction that, even in these lower reaches of the scale of being, life does not appear without the operation of antecedent life. The main position of Pasteur, though often assailed, has never yet been shaken. It has, on the contrary, been strengthened by practical researches of the most momentous kind. He has applied the knowledge won from his inquiries to the preservation of wine and beer, to the manufacture of vinegar, to the staying of the plague which threatened utter destruction to the silk-husbandry of France, and to the examination of other formidable diseases which assail the higher animals, including man. His relation to the improvements which Professor Lister has introduced into surgery is shown by a letter quoted in his 'Études sur la Bière.' Professor Lister there expressly thanks Pasteur for having given him the only principle which could have conducted the antiseptic system to a successful issue."

The most highly appreciated of Pasteur's earlier researches—because they most closely touched the economical interests of his country, and had a direct bearing on the prosperity of one of its great industries—were those which he made upon the disease of the silk-worm. A plague had raged among the silk-worms of France for fifteen years. The revenue from silk-culture had doubled itself during the twenty years before 1853, and appeared at that time likely to continue to increase. Then disaster suddenly fell on the business, and the production of cocoons fell from twenty-six million kilogrammes in 1853, in the course of twelve years, to four million kilogrammes, the fall entailing, in the single year last mentioned, a loss of one hundred million francs, or twenty million dollars. Dumas, the chemist, whose home lay in the district that was most afflicted by the scourge, asked Pasteur, with almost a personal interest in the matter, to undertake the investigation of the malady. Pasteur, says Professor Tyndall, at this time had never seen a silk-worm, and he urged his inexperience in reply to his friend. But Dumas knew too well the qualities needed for such an inquiry to accept Pasteur's reason for declining it. "I put," he said, "an extreme value on seeing your attention fixed on the question that interests my poor country; the misery surpasses all that you can imagine." The disease had been called pébrine by M. de Quatrefages, a name which Pasteur adopted; it was outwardly manifested by black spots on the bodies of the caterpillars, and also declared itself in their stunted and unequal growth, the languor of their movements, their fastidiousness toward food, and their premature death. It had already been discovered that the unhealthy worms were afflicted with peculiar corpuscles in enormous numbers, which were also sometimes found in the eggs, and which were connected with the disease. Pasteur directed his attention to these corpuscles, and proved that they might be incipient in the egg, and escape detection, and that they might also be germinal in the worm, and still baffle the microscope; but that, as the worm grew, they grew also, and appeared, if they existed, large enough to be detected without difficulty in the moth.

Pasteur's first communication on the facts he had discovered, made to the French Academy of Sciences, in September, 1865, called out some rather sharp criticism on the presumption of the chemist who had ventured to instruct physicians and biologists on a subject that belonged to them. "They found it strange," he says, "that I was so little in the current on the question. They set against me works which had been appearing for a considerable time in Italy, the conclusions of which demonstrated the inutility of my efforts, and the impossibility of arriving at a practical result in the direction in which I was engaged; and that my ignorance was great on a subject on which studies without number had appeared during the last fifteen years." If the scientific men were thus disposed to reject his new truths, it was hardly to be expected that the cultivators would accept his guidance in a direction contrary to that in which they were going. To strike their imagination, and, if possible, determine their practice, he hit upon the expedient of prophecy. Having inspected fourteen parcels of eggs, and examined the condition of the moths which produced them, in 1866, he wrote out predictions of what would be the fate of the lot in 1867, and placed it as a sealed letter in the hands of the Mayor of St. Hippolyte. When the reports of the cultivators were compared with the forecasts in the letter, in the next year, his prediction was found to have been exactly fulfilled in twelve out of the fourteen cases. Two additional parcels of eggs, pronounced by him healthy, produced an excellent crop.

M. Pasteur's researches in fermentation have been practically applied by him in his process for preserving wines by the application of heat, and his process for manufacturing beer by fermentation sheltered from all contact with air.

In 1874 the Copley medal of the Royal Society was awarded to M. Pasteur "for his researches on fermentation and pébrine." Mr. Spottiswoode, in making the presentation, observed that Professor Pasteur's researches on fermentation consisted essentially of two parts, the first part embracing the examination of the products, and the second the causes of fermentation. Previous observers had noticed the production, in solutions of sugar which had been fermented, of substances other than the two commonly recognized, alcohol and carbonic acid; but it remained for M. Pasteur to show which were essential and which were occasional products. In regard to the cause of fermentation, "it had been found that certain solutions, when exposed to the air, soon became full of living organisms; and Pasteur's experiments led him to support the view that these organisms originated from the presence of germs floating in the air. He found that no living organisms were developed if care were taken to destroy all those which might be present in the solution, and if the solutions were then carefully sealed up free from air. Nor was it necessary to exclude the air, provided that pure air, free from germs, were admitted. By passing the air through red-hot tubes or through gun-cotton before reaching the solutions, he found that the development of organisms, in such boiled solutions, did not take place. [A single exception was noticed in the case of milk, which required a higher temperature to destroy the organisms.]

Professor Pasteur also examined the gun-cotton through which the air had been passed, and he found, among other things, certain cells to which he attributed the power of causing the growth of organisms in solutions. By sowing some of these cells in solutions which had previously remained clear, and finding that such solutions speedily became turbid from the growth of living organisms, it was proved that the air which had passed through the gun-cotton had lost its property of causing the development of life in solutions, because the germs which the air contained had been stopped by the gun-cotton." The results on this point might be summed up: "1. No organisms are developed in solutions if care be taken to prevent the possibility of the presence of germs; 2. This negative result does not depend upon the exclusion of oxygen; 3. The matter separated from ordinary air is competent to develop organisms in solutions which previously had remained unchanged. Not less important were the results of Pasteur's experiments respecting the chemical functions of the ferment. . . . He proved that those conditions which are most favorable to the healthy growth and development of the yeast-cell are most conducive to the progress of fermentation, and that fermentation is impeded or arrested by those influences which check the growth or destroy the vitality of the cell. . . . To the biologist, two of Pasteur's researches are of very great importance. He has shown that fungi find all the materials needed for their nutrition and growth in water containing an ammonia salt and certain mineral constituents, and devoid of any nitrogenized organic matter; and he has proved that all the phenomena presented by the destructive silk-worm epidemic, the pébrine (even the singular fact that it is hereditarily transmitted through the female and not through the male), are to be explained by the presence of a parasitic organism in the diseased caterpillars."

M. Pasteur's later researches have been continued in the same direction as those which we have already mentioned, and have resulted in a great expansion of the germ theory and its application to useful purposes. Those which have so far been most fruitful in practical consequences are the investigations which he has made into the cause of the cholera in fowls and of carbuncular diseases in cattle and sheep, and into the means of preventing them by the cultivation of the infectious germs in diluting fluids and inoculation with them—investigations the results of which have already been heralded over the whole earth, and the inestimable value and importance of which have been almost universally recognized. The processes by which he has arrived at his discoveries and the success which has attended his application of them are best told in his own language, and are thus told in his address before the recent International Medical Congress, which is published in the present number of "The Popular Science Monthly." This address, the "Westminster Review" says, "was as fascinating in the unerring sequency of experiments as in the unbounded prospects of preventive medicine foreshadowed, and the masterly unraveling of some of Nature's most occult secrets."

M. Pasteur in 1880 proposed the application of the method which he used in seeking the cause of the silk-worm disease, to the detection of a parasite destructive to the phylloxera, and its cultivation as an antidote to that pest of the grape-vine. He said in a "programme for researches," which he communicated to the Academy of Sciences, on this subject, suggesting an inversion of the problem studied in the case of the silk-worm: "Let us seek a parasite for the phylloxera species, and, far from combating it, let us cause it to multiply and fasten upon the phylloxera till it destroys it, as the pébrine parasitic corpuscle so easily destroyed the silk-worms. . . . The rapid multiplication of the phylloxera is only a trifle beside the vital and propagative power of certain parasites. . . . The hall of the Academy of Sciences is very large; it has a capacity of hundreds of cubic metres. I am sure I could fill it with a liquid of such a nature that, on planting in it a parasitic microscopic organism of the fowl, the whole immense mass would, in the course of a few hours, be troubled by the presence of the organism in such abundance that all the phylloxeras in the world would be, in number, only as a drop of water to the sea compared with the numbers of the parasite of which I speak."

Notwithstanding this, he is so confident of the efficiency of the methods of treatment which his researches indicate, that he has been able to say, in his work on the silk-worm disease, that "it is in the power of man to make parasitic maladies disappear from the surface of the globe, if, as is my conviction, the doctrine of spontaneous generations is a chimera."

Another field of investigation, in which M. Pasteur has made a few preliminary steps, is that of the transmission of human diseases by microscopic organisms. He has now numerous co-laborers in these fields, in England, France, Germany, and other nations, many of whom have become famous through their researches, and who are extending the range of investigation every day; but he was the first to direct attention to this branch, and is still the leader of the company.

M. H. Bouley, speaking in the name of the Academy of Sciences, before the annual meeting of the "Five Academies," said, in special reference to M. Pasteur's work: "See how, at once, Nature has suffered one of her most impenetrable secrets to be snatched from her—the mystery of contagions is unveiled; and Science, enlightened by the knowledge of their cause, is resolving that marvelous problem of transforming the agent that causes death into an agent preservative against its assaults!. . . Justice," he continued, "is often tardy for inventors; its pace is frequently so halting that their life is not long enough for them to have time to see it come. M. Pasteur, whom I name at last, has had the privilege of seeing it hasten its pace for him. He is also one of those whose virtue does not rest when it has made their opinion good. Master of what he knew to be the truth, he has desired and has known how to give it force by the evident clearness of his experimental demonstrations, and to force the majority of those who were at first refractory to confess it with him." A writer in the "Westminster Review" gives eloquent utterance to a similar sentiment, when he speaks of M. Pasteur as one "whose researches have yielded so much material profit that one thinks of him as of the orange-tree standing in all the glory of blossom and fruit at the same time."

M. Pasteur was received with enthusiastic acclamations by the International Medical Congress when he arose to make the address which we publish; and the address was distributed by the Government through all parts of the United Kingdom. The "Graphic," publishing his portrait, published also a remark of Sir James Paget, that, by his discoveries relative to carbuncular diseases he had done for cattle what Jenner had done for the human race. And Professor Huxley has said that he considered the discoveries so important that they were worth all the five milliards of francs which France paid to Germany after the war of 1870–'71.

In 1868 M. Pasteur was awarded a prize of 10,000 florins by the Agricultural Minister of Austria for the discovery of the best means of contending with the silk-worm disease. A decree was signed by Napoleon III and M. Ollivier in July, 1870, but never promulgated, making him Senator. The French Government granted him, in 1874, a pension of 12,000 francs, "in consideration of his services to science and industry," and in the next year increased the pension by the addition of 6,000 francs. The Société d'Encouragement, in 1873, awarded him a prize of 12,000 francs for his studies relative to the silk-worm, wine, vinegar, and beer, collectively.

M. Pasteur was elected a member of the French Academy of Sciences in 1862, to take the place of Senarmont in the section of Mineralogy. In 1869 he was elected one of the fifty foreign members of the Royal Society of London. His principal works, besides his communications to the "Recueils des Savants Étrangers" and the "Annales de Chimie et de Physique," are: "Nouvel Exemple de Fermentation déterminé par des Animalcules infusoires pouvant vivre sans Oxygène libre" (Paris, 1863); "Études sur le Vin, ses Maladies, etc." (1866); "Étude sur le Vinaigre, etc." (1868); "Études sur les Vers à Soie" (2 vols., 1870); "Quelques Réflexions sur la Science en France" (1871); and "Études sur la Bière."