io THE POPULAR SCIENCE MONTHLY 



the silkworm industry. Whence the disease came or how it was con- 

 tracted no one knew. Its onset was recognized only by the presence 

 of the little brown or blackish spot from which it got its name (pe- 

 brine). 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 chem- 

 ist, hitherto interested chiefly in the study of crystallography and fer- 

 mentation, thrown at once into a new and strange field. That his re- 

 sults 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 hav- 

 ing demonstrated this, the remedy lay in using the eggs of non-in- 

 fected 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 common- 

 place 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 infec- 

 tion with a psorosperm, but unmasked also a second disease of the silk- 

 worm (flacherie), 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 heat- 

 ing 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 : 



Nothing is more agreeable to a man who has made science his career than to 

 increase the number of discoveries, but his cup of joy is full when the result of 

 his observations is put to immediate practical test. 



The term, pasteurization, is now most frequently heard in con- 

 nection with milk, but when it is recalled that all commercial and 



