154 PASTEUR: THE HISTORY OF A MIND 



not being familiar with the subject, Dumas had replied 

 one day: "So much the better! For ideas, you will 

 have only those which shall come to you as a result of 

 your own observations!" Such a reply is not always 

 a paradox, but one must be careful to whom he makes it. 



Ill 

 STUDIES OF 1865 



The first act of Pasteur on reaching the South was to 

 seek this famous corpuscle, which he had never seen. 

 He had no trouble in finding it. In the neighborhood of 

 the little city of Alais, in which he had installed himself, 

 all of the cultures, already near their end, were infected. 

 Sick worms and moths showed the corpuscles by thou- 

 sands. Some rare worms of healthy appearance did not 

 show any. What seemed especially to result from this 

 first rapid examination was the exactitude of the relation 

 pointed out by de Quatrefages between the existence of 

 the corpuscles and the presence on the surface of the skin 

 of the black spots of the pebrine. All the worms hav- 

 ing pe"brine showed corpuscles in enormous numbers. 

 But this fact, even though it might have been more 

 thoroughly settled than it was really, did not signify 

 very much. In continuing his researches, a little at 

 random, Pasteur one day encountered one of those 

 unexpected facts which it is so useful and so dangerous 

 to find on our pathway, when we begin any research 

 whatsoever. They have a sphinx-like physiognomy, and, 

 in fact, they put the riddle clearly: " Guess or be de- 

 voured." Pasteur did not guess and was not devoured. 

 Therein lies the interest of this history. 



Near the silk nursery in which he had installed himself, 



