160 PASTEUR: THE HISTORY OF A MIND 



On the whole, at this time, any one who judged super- 

 ficially would have concluded that Pasteur brought for- 

 ward nothing new. He shared the error of Philippi, 

 of Vittadini, and of Cornalia, upon the origin of the cor- 

 puscle: his method of egg-selection, proposed by Osimo, 

 and then by Cornalia, had miscarried in the hands of 

 Cantoni and of Bellotti. It is necessary to look at the 

 subject closely to see that Pasteur brought into this . 

 study another idea than his predecessors. This idea 

 was that of undertaking comparative cultural experi- 

 ments upon healthy eggs and diseased eggs. The 

 method of egg-selection which he recommended, how- 

 ever mediocre it might be from the theoretical point of 

 view, however bad it might be from the industrial 

 point of view, judging from the results of Cantoni, was, 

 however, sufficient to maintain those original differences 

 between the eggs, the influence of which it was important 

 to examine. "The process of selection to which my 

 first researches had led me seemed to me," says Pasteur, 1 

 "to have an importance more scientific than industrial." 

 It turned out that this process contained the industrial 

 solution of the problem, but if it had not contained it, 

 it would have led to it, for Pasteur introduced experi- 

 ment into a question where there had been hitherto 

 only empiricism. 



His plan of campaign for the cultures of 1866 was, 

 therefore, already outlined. After having obtained the 

 eggs from his different pairs of moths which were more 

 or less corpuscular, he would first try these out ahead 

 of the main brood, which is done in March and April in 

 small lots upon leaves of the mulberry cultivated in 

 hothouses, then in the big cultures of May and June. 

 Made with the same precautions and under the same 

 conditions, the culture of these eggs of different origin 



1 Etudes sur la maladie des vers a sole, t. I, p. 55. 



