174 PASTEUR: THE HISTORY OF A MIND 



master more and more anxious. He kept us so remote 

 from his thought that we could not explain his uneasiness 

 till that day when he appeared before us almost in tears, 

 and, dropping discouraged into a chair said: "Nothing 

 is accomplished; there are two diseases!" 



He had in mind this disease of the marts-flats, con- 

 cerning which I have already made brief mention. 

 He had known it for a long time, indeed since his 

 first sojourn in the South in 1865, where one of the two 

 cultures of silkworms which served for the beginning 

 of his deductions was attacked by this disease at the 

 same time as by that of the corpuscles. But the cases 

 of association were so frequent, precisely because the 

 disease of the corpuscles was widespread, that Pasteur 

 had considered the two affections as intimately con- 

 nected and likely to disappear together. 



During the silkworm cultures of 1866, the two diseases 

 were somewhat separated both in fact and in his mind. 

 He had sometimes seen the second appear in cultures 

 hereditarily exempt from the first, and he had asked 

 himself whether they were not independent. His pub- 

 lications at this time bear the trace of these preoccupa- 

 tions, which had not yet become a source of uneasiness. 

 The cases of morts-flats had been rare, and had besides 

 appeared here and there, without visible preference, 

 like cultural accidents attributable to the growers. 



It was in 1867, in the preliminary trials, and especially 

 in the large cultures, that the gravity of the danger first 

 appeared. Almost entire lots of eggs free from cor- 

 puscles and bred by various growers had perished 

 everywhere of the disease known as morts-flats, what- 

 ever might be the circumstances of place, time, climate 

 and culture. It could not be any longer a question of 

 accidents: it was the manifestation of an inherited dis- 

 position, and on seeing these mishaps renewed, on finding 



