Pasteur’s researches on micro-organisms further had a profound influence on operative surgery. To the presence of bacteria is due many of the dangers which used to follow on operations. If precautions are taken to exclude the harmful germs much suffering and danger are avoided. It was about this date—namely, in the spring of 1865—that Dr. (now Lord) Lister, who nobly acknowledged the debt he owed to Pasteur, performed his first operations under antiseptic treatment at the Glasgow Infirmary. This date marks an epoch in the history of human suffering.
The chemist Dumas was about this time a member of the French Senate, and in 1865 was charged with the duty of reporting on the petition of some 3,500 ‘propriétaires des Départements séricicoles’ on an epidemic which had for some years been destroying the silkworms of Southern France. Dumas was a native of Alais, a town of the Département Gard, situated in the centre of the silkworm industry, where also the distinguished zoologist Quatrefages was born. Anything that affected Alais affected Dumas; and the epidemic was destroying the prosperity of his native town. The disease was indeed becoming serious. Already in 1849 the silkworms were sickening. The stage at which the symptoms appeared varied—sometimes the eggs were sterile; at other times the silkworms hatched out but to die. If they survived they became shiny; black spots showed themselves; the worms moved with difficulty, refused to eat, and perished; or, if they lived long enough to pupate, the pupa either perished or the moth emerged in an enfeebled state and promptly died.
Efforts had been made to improve the stock by importing eggs from Spain and Portugal, but the Peninsula was soon affected. Eggs were then fetched from Turkey, Greece, and the adjacent islands. These countries too becoming infected, the French cultivators sent further afield and brought eggs from Syria and the Caucasus. Even this resource failed them, and in 1864 every silk-producing country in the world was infected, with the solitary exception of Japan. The loss to commerce was prodigious. In a normal year the value of the cocoons produced in Southern France is, roughly speaking, about £4,000,000; in the years 1863 and 1864 it had fallen below £1,000,000.
When Dumas first asked Pasteur to investigate the disease which was ruining large tracts of the South of France, the latter not unnaturally hesitated. ‘Considérez, je vous prie, que je n’ai jamais touché un ver à soie. Si j’avais une partie de vos connaissances sur le sujet, je n’hésiterais pas,’ he wrote to his friend; but in spite of his hesitation, he left for Alais, and at once commenced a campaign which lasted during the summers of the next five years. Almost immediately on his arrival he detected in the sick silkworms the corpuscles of Cornalia and Filippi, which we now call the Micrococcus ovatus. These micrococci are comparatively large and very bright; they occur in the tissues and blood of the silkworm, and are found even in the eggs of the moth. They cause the disease known as Pébrine. The occurrence of the micrococci in the eggs was one of the most important new facts observed by Pasteur. It was the first recorded instance of a parasitic organism being conveyed from one generation to another by the egg; and, although recently the germ of the Texas fever (allied to the malarial organism) has been shown to pass from one brood to another through the egg of the tick which conveys it, it is satisfactory to record that the cases in which this occurs are restricted in number and comparatively rare. The ease with which Micrococcus ovatus could be detected suggested a remedy. A child, when trained, can readily identify the organism. Healthy moths produce sound eggs and healthy larvæ; diseased moths produce diseased progeny. At the present day, throughout the silkworm districts of the South of France, as soon as the moth has deposited her eggs on the piece of linen provided for that purpose, she is pinned up with the cloth; and during the ensuing autumn and winter the women and children are occupied in microscopically examining the body of the moth, crushed in a little water, for traces of the micrococcus. Should any be found, the eggs on the corresponding piece of linen are at once destroyed. Pasteur also showed that the infected stock spread the disease by distributing the micrococci on the mulberry-leaves, whence they enter the silkworm by the mouth; and that the sick inoculate the healthy by crawling over them and piercing the skin with their pointed claws. He therefore emphasized the importance of segregating the sound caterpillars.
The above account conveys no impression of the difficulties under which Pasteur worked. His researches were not only new to himself but to the world. Processes which at the present day are carried out by every medical student had to be devised for the first time. He had to combat the criticism of scientific men, and to overcome the almost invincible ignorance of the agriculturist, an ignorance which at one time advocated the desperate remedy of asperging with absinthe the leaves of the mulberry on which the silkworms fed.
Perhaps Pasteur’s greatest difficulty was the fact that the silkworms did not suffer from Pébrine alone; and it was some time before he recognized that he had to deal, not with one disease, but with two. The second disease, known as the ‘Flacherie,’ is a disease of the digestive system caused by overcrowding and insanitary conditions in the silkworm nurseries. Like Pébrine, it is caused by a micrococcus, Micrococcus bombycis. It was whilst investigating this creature that Pasteur discovered that, although the germ itself cannot survive a lengthy period of desiccation, it does in certain circumstances form spores which can survive conditions fatal to the mature organism. This is the first case recorded of a pathogenic organism producing spores, the existence of which has explained so many problems in the spread of disease.
During the period from 1865 to 1870 Pasteur was by no means occupied solely by the silkworm epidemic. In many respects it was a sad epoch in his life. Only nine days after his first arrival at Alais he was summoned to Arbois to see his dying father, but arrived too late. In the autumn of the same year he lost his little daughter Camille, the second who had died. In 1868 he himself was prostrated by a stroke of paralysis, and, although he slowly recovered, it left traces for the remainder of his life.
Few distinguished men of science are left to pursue their investigations undisturbed; and Pasteur was no exception. He had much to do with promoting the publication of the works of Lavoisier, for whose researches he had the profoundest respect. He actively intervened in the elections of the Academy of Science, which appears to consume an infinity of time. He made some preliminary investigations into cholera, an outbreak of which towards the end of the year 1865 carried off 200 victims a day in Paris. He spent a week at Compiègne as the guest of Louis Napoleon, and in a series of séances explained the methods and results of his labours. He wrote on the work of Claude Bernard; he drew up schemes for certain reforms in the University; he gave advice on the higher education of the country, and tried to stem the troubles of the École Normale. In fact, he drew lavishly upon his reserve of health and energy until the breakdown of 1868 was inevitable.
After a tedious recovery he recommenced his work. The success of his methods had been acknowledged by the Austrian Government, who conferred on him in 1868 the prize of 5,000 florins offered to anyone who should succeed in discovering the best means of dealing with Pébrine. The same year the University of Bonn conferred on him the honorary degree of Doctor of Medicine; and in 1869 he was elected a foreign member of the Royal Society. As was to be expected, detractors were not wanting: but these were silenced by the campaign undertaken in 1869 by Pasteur on foreign soil. The Master of the Imperial Household, Marshal Vaillant, who devoted his declining years to scientific experiments, had repeated in his apartments in the Tuileries the observations of Pasteur on the silkworm disease, and had verified the accuracy of his conclusions. He suggested to the Emperor that the Villa Vicentina, a property belonging to the Prince Imperial, should be placed at Pasteur’s disposal for further research. This villa, situated a few miles from Trieste, belonged at one time to the Princess Élise, one of the sisters of Napoleon I., who had lived quietly there after the fall of the First Empire. On her death it passed to her daughter, the Princess Baciocchi, and she in turn bequeathed it to the Prince Imperial. It had been a great centre of the silkworm industry; but for some years no cocoons had been produced, owing to the ravages of the disease.
By short stages, owing to his precarious health, Pasteur made his way to Illyria, taking with him some sound silk-moth eggs, and during the winter not only confirmed his previous researches, but re-established the industry on such a scale that in the following spring the sale of cocoons from this estate alone reached the figure of 26,940 francs. During this winter he dictated to his wife the classic book in which he recorded the results of his last five years’ work. Pasteur returned to Paris through Munich, where he had the pleasure of meeting Liebig, one of the most determined of his adversaries. Although he was unable to induce the German savant to discuss scientific affairs, he always dwelt with pleasure on the courtesy and cordiality with which he was received.