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