THE CORPUSCULAR DISEASE [pEBRINE] 153 



scientific man, these corpuscles existed normally in all 

 the moths. 



A real progress had, however, been realized the day 

 that Osimo had discovered the corpuscles in the eggs 

 of silkworms, and the day Vittadini, after having rec- 

 ognized that their number increased in a laying of 

 eggs in proportion as they approached the period of 

 hatching, had based a method of distinguishing the 

 good from the bad upon a microscopic examination of the 

 eggs. The corpuscle is, indeed, actually, as we shall 

 see, the cause of the disease, and an egg which contains 

 it can never give cocoons; but these two facts not being 

 demonstrated, uncertainty existed as to the theoretic 

 value of the procedure. As to the practice, it often 

 gave out detestable eggs for good ones, and when it 

 condemned the eggs it was in the name of principles so 

 uncertain that the silk grower could not be held culpable 

 for having no confidence in the advice of science. 



The same Osimo, in 1859, had endeavored to push 

 science and practice in another direction. He had ad- 

 vised examination not only of the eggs but also of the 

 chrysalids, and rejection of the layings of those stocks 

 which were found too corpuscular. This time it would 

 have been to approximate correct procedure, as we shall 

 see immediately, but this advice, given offhand, and 

 without experimental support, had been followed and 

 tested, offhand also, by Cantoni, who, after having 

 cultivated the eggs coming from non-corpuscular moths, 

 had seen the worms become corpuscular during the 

 culture, which proved, he had concluded, that "the 

 microscopic examination of moths was also unfortunately 

 as worthless" as the other remedies. 



By good fortune, of all this past history, of all this 

 mixture of truth and falsehood, Pasteur knew nothing 

 at the beginning of his studies. To his complaint of 



