162 PASTEUE: THE HISTORY OF A MIND 



Finally, another prime fact was that even in the most 

 corpuscular broods, where the mortality of the worms 

 or of the chrysalids had been the greatest, one always 

 found some non-corpuscular moths that would give better 

 eggs than those from which they themselves had come. 

 From a practical standpoint this was of the highest 

 importance. Among the objections made to Pasteur, 

 from the beginning, the following had actually figured: 

 If the disease is indeed characterized by the presence 

 of an abundance of the corpuscles, as you say it is, and 

 as you prove it to be, it is then widespread, universal, 

 and, this being so, how shall we proceed to find the neces- 

 sary eggs, we do not say for the regeneration, but for 

 the simple conservation of the French and Italian races, 

 very superior from the point of view of yield and of the 

 quality of the silk to the Japanese races, which are 

 replacing them little by little in all the silk-growing 

 lands. To this Pasteur could reply: But here are co- 

 coons of a French race which I have just brought from 

 one of the most infected districts ! Look at them, study 

 them under the microscope, and you will see that they 

 promise results still more beautiful for next year. Do, 

 therefore, as I do : let each one procure eggs for himself, 

 as I do for myself. If you tell me that the microscope 

 frightens you, and that its manipulation seems to you 

 not easy, I reply that there is in my laboratory a little 

 girl eight years old who knows how to do it very well. 



V 

 IS THE CORPUSCLE THE CAUSE OF THE DISEASE? 



But this apparent disappearance of corpuscles in some 

 of the moths descended from a corpuscular pair had theo- 

 retical consequences more far-reaching than its practical 



