Page:Popular Science Monthly Volume 20.djvu/847

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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