IS THE CORPUSCLE THE CAUSE OF THE DISEASE? 167 



question of seeking the relation which existed between 

 the time of the corpuscular feeding and the development 

 of the disease with or without corpuscles. For Gernez, 

 who believed Pasteur converted to the idea of the cor- 

 puscle as cause, the question was simpler: the only 

 question was to know whether the inoculated worms 

 would have corpuscles, and the healthy worms would not 

 have them. From this point of view, his experiment was 

 particularly convincing. Of four lots of 40 worms each: 



The first, fed with ordinary leaves, gave 27 healthy 

 cocoons ; 



The second, fed with leaves moistened with ordinary 

 water, gave 19 cocoons of which not one was corpuscular; 



The third, fed after the third molting with leaves 

 moistened with water containing the debris of corpuscu- 

 lar moths, gave only four cocoons which were very 

 corpuscular. 



The fourth lot, in which the feeding of corpuscular 

 leaves had commenced only after the fourth molt, gave 

 22 cocoons, all or almost all corpuscular. 



Here we behold a spectacle rare in the life of Pasteur: 

 an experiment the full and complete meaning of which 

 he does not immediately comprehend. This experiment 

 was highly pertinent. It realized as in a synthesis the 

 principal aspects of the disease. The third lot was an 

 example of those silkworm cultures which, after having 

 begun w^ell, perish by the way and do not reach the cocoon 

 stage. The fourth lot was an example of those cultures 

 which succeed well but are incapable of furnishing good 

 eggs. The first and the second lot bore witness to the 

 worth, when it is not infected, of a "graine" resulting 

 from egg-selection under the microscope, made upon a 

 diseased culture. All that spoke at the same time in 

 favor of Pasteur's method and of the corpuscle as a 

 cause, but Gernez, who believed his master converted 



