His attention was first directed to the disease affecting the silkworm, and known as the _Pebrine_, which at one time seemed likely to destroy the silk cultivation both in France and Italy. It had been ascertained that the bodies of the silkworm, in all its stages of chrysalis, moth, and worm, were in this disease infested by minute corpuscles which even obtained entrance into the undeveloped eggs. After a prolonged and difficult inquiry, Pasteur found that these minute corpuscles were really independent, self-propagating organisms, introduced from without, and were not merely a sign of the disease, but its real cause. As a result of the application of these discoveries, the silkworm disease has been extinguished, or so controlled as to have saved a most important and valuable culture. Between the years 1867 and 1870 above 56,000 deaths from a disease variously designated as "anthrax," or "carbuncular disease," and "splenic fever," and in France known by the terms "charbon," or "pustule maligne," are stated to have occurred among horses, cattle, and sheep in one district of Russia, Novgorod, occasioning also the deaths of 528 among the human population. It occurs in two forms, one more malignant and rapid in its action than the other. In France the disease appears to be scarcely ever absent, and is estimated to entail on the breeders of cattle an annual loss of many millions of francs. As a milder epidemic it has prevailed in this country, and the disease which has lately broken out in Bradford and some other towns in the north among wool-sorters, has now been shown to be a modification of the same disease communicated by the wool of sheep that have been infected.