IS THE CORPUSCLE THE CAUSE OF THE DISEASE? 163 



consequences. What signified these healthy individuate 

 in a progeny strongly infected from both parents, and 

 evidently attacked by a hereditary taint? "Can it be 

 that among the eggs of a laying, derived from a male 

 and a female badly diseased, there are some healthy 

 eggs? Or will some eggs slightly diseased give worms 

 which recover health during the culture? I do not 

 know which of these two interpretations is the better, 

 and both are perhaps correct." 1 The phrase is curious, 

 and bears witness that Pasteur began to doubt in 1866 

 concerning the interpretation of the phenomena which 

 he had accepted hitherto. The idea of a constitutional 

 disease of which corpuscles were only the external and 

 later sign did not harmonize very well with this presence 

 of a few healthy eggs in the midst of their diseased 

 neighbors. Excluding parasitism, one does not com- 

 prehend this immunity of some individuals in the midst 

 of others entirely alike in that they are the descend- 

 ants of the same organism. But this idea of 

 parasitism, which was blended with the idea of the cor- 

 puscle as a cause of the disease, was repulsed by Pasteur 

 at this moment with a kind of obstinacy, and with such 

 a singular mixture of true and false arguments that it is 

 useful to pass them in review. To do so will be to study 

 him in a vital point of his career, that in which he aban- 

 dons tradition and launches out into new ways. 



He enumerated these arguments himself the following 

 year, for his scruples were of long duration. "Is the 

 disease parasitical?" 2 he asks himself in the note pre- 

 sented to the Imperial Commission of Silk Culture, in its 

 sitting of January 12, 1867, and he rejects this opinion 

 for the f ollowing reasons : 



1. "Because the disease is certainly constitutional in 



1 Etudes BUT la maladie des vers a sole, t. II, p. 165. 



2 Etudes sur la maladie des vers a soie, t. II, p. 181. 



