152 LOUIS PASTEUR. 



suddenly. In a cultivation of 100 worms, ten, fifteen, 

 twenty dead ones were picked up daily : these turned 

 black, and became putrid with extraordinary rapidity, 

 often within the space of twenty-four hours. Some- 

 times they were soft and flabby, like an empty, 

 crumpled intestine. Consulting the authors who had 

 written upon silkworms, Pasteur could not doubt that 

 he had before his eyes a characteristic specimen of the 

 disease called morts-flats, oiflaclieric. Not only were 

 these worms free from all pebrine spots, but no cor- 

 puscles were to be found in any part of their bodies. 

 A still more significant fact was, that corpuscles were 

 also absent from the chrysalides and the moths of 

 those few worms which were able to spin their cocoons. 

 Although this sample was confined to a single group 

 of eggs derived from parents free from corpuscles, 

 Pasteur continued to entertain doubts as to the exist- 

 ence of only a single disease, and also as to the neces- 

 sary connection of pebrine with flacherie. 



These suspicions were confirmed by his cultiva- 

 tions of April and May. Numerous cases of flaclierie 

 presented themselves. Uncertainty was no longer 

 possible as to the mutual independence of the two 

 maladies pebrine and flaclierie. The cultivations 

 most seriously invaded by the last-mentioned disease 

 came from eggs produced by parents free from cor- 

 puscles, and led on to reproducers also free from this 

 parasite. On visiting a multitude of industrial cultiva- 



