Page:Popular Science Monthly Volume 81.djvu/16

10 the silkworm industry. Whence the disease came or how it was contracted no one knew. Its onset was recognized only by the presence of the little brown or blackish spot from which it got its name (pébrine). Pasteur, who undertook the investigation at the request of his old master Dumas, now a senator, knew nothing of the industry and, as he wrote Dumas, "had never touched a silkworm." But under pressure of Dumas's solicitation he finally yielded, and found himself, a chemist, hitherto interested chiefly in the study of crystallography and fermentation, thrown at once into a new and strange field. That his results were due largely to the training and the point of view obtained through the study of fermentation and the use of the microscope, there can be little doubt, and one is inclined to apply to Pasteur at this stage of his work his own statement of ten years before; "in the fields of observation, chance favors only the mind which is prepared."

Once in the silkworm country he applied himself energetically to the study of the "fatal spots." The story of the complete investigation is a long one, but the main points are that within a month he found that although worms, moths and eggs were infected, the critical stage was the infection of the moths, and that, in these, the infection could be readily demonstrated with the aid of the microscope, and, that having demonstrated this, the remedy lay in using the eggs of non-infected moths only. Thus a new breed of worms free from infection could be obtained and the extension of the disease arrested. In the course of this work he reproduced the disease experimentally by feeding healthy moths with infected mulberry leaves, a novel procedure then, but one, which, with its modifications, was soon to become a commonplace principle of bacteriological investigation. The investigation of the silkworm problem lasted for five years, or until Pasteur cleared up not only the difficulties connected with pebrine, a disease due to infection with a psorosperm, but unmasked also a second disease of the silkworm (flâcherie), a bacterial infection of intestinal origin.

In the meantime Pasteur continued his studies of the diseases of wines (sour, bitter and muddy wines) and invented the process known then and now as "pasteurization." This was the simple process of heating the wine in order to free it of all germs of wine disease and make it suitable for storage and exportation. In this connection he expresses the greatest satisfaction that he was thus able to contribute to the national riches through the practical application of his observations. In 1867 he said:

The term, pasteurization, is now most frequently heard in connection with milk, but when it is recalled that all commercial and