164 PASTEUR : THE HISTORY OF A MIND 



a great number of circumstances, and precedes the ap- 

 pearance of the corpuscles." We recognize there the 

 influence already noted by us of that preliminary ob- 

 servation on a culture which behaved badly although 

 the worms did not contain corpuscles. We know to-day 

 that Pasteur had fallen by chance upon a culture at- 

 tacked by another disease than pebrine, the disease of 

 morts-flats. 1 Pasteur, who, at this moment, spoke only 

 of the disease of silkworms, had confounded everything 

 and could believe in a disease of corpuscles without 

 corpuscles; 



2. "Because the feeding of corpuscular substances 

 often kills the worms without giving them corpuscles." 

 Here again, there was an error of interpretation, due to 

 the same reasons as the above. Pasteur had very clearly 

 perceived that the criterion of the corpuscle as cause, 

 and of the corpuscle as effect and evidence of the disease, 

 was an inoculation experiment. If it had been possible 

 to give the corpuscular disease to healthy worms by 

 causing them to feed upon corpuscles derived from a 

 preceding silkworm culture, one would have singularly 

 enlightened not only the etiology of the disease, but also 

 the causes of its vitality and of its propagation, of its 

 endemic and epidemic character. With Pasteur the ex- 

 ecution followed close upon the idea, and the experiment 

 was made. He had taken, in 1866, as infectious matter, 

 very corpuscular dirt scraped up in a culture chamber, 

 and the mashed substance of a very corpuscular moth 

 or worm. The worms to which he had fed the leaves 

 of the mulberry, thus infected, had showed at the end 

 of some days a considerable mortality which Pasteur 

 had the right to attribute to the infected food and to 

 the prevailing disease: in reality it again resulted from 

 the intervention of the disease of the morts-flats. But 



1 Flacherie. Trs. 



