STUDIES OF 1866' 159 



detail has a very great significance. The second process 

 is the only reasonably safe one. 



On the contrary, the first method is liable frequently 

 to overlook the presence of the corpuscles, and we shall 

 see here how things go on in a research. The method 

 then adopted by Pasteur was the result of his false 

 idea. If Pasteur had considered these corpuscles as 

 parasites, he surely would have concluded that they 

 might be in one place and not in another, and that it 

 would be necessary to seek them in various places. But 

 he was convinced that the corpuscle, being a tardy sign 

 of the pre-existing disease, was a product of transforma- 

 tion, or, to employ a medical expression, a product of 

 retrogression of the cells of the tissues. Now, following 

 this hypothesis, it should occur everywhere in the body. 



The method of research, imperfect because it had been 

 born of a false idea, deceived Pasteur and plunged him 

 deeper into his idea. In the eight couples brought 

 from Alais and which he had studied in Paris, he be- 

 lieved he had found one in which the male presented a 

 few corpuscles, and the female not any. As a matter of 

 fact, she also contained them, as shown by the result of 

 the cultures in which a few corpuscles appeared, not in 

 the worms and the chrysalids coming from these eggs 

 but in the moths. This phenomenon, spontaneous in 

 appearance, of corpuscles in a culture which it seemed 

 ought to be exempt, naturally confirmed Pasteur in his 

 belief in the internal origin of the corpuscle. It is thus 

 that a mode of examination inspired by a false idea leads 

 sometimes to the confirmation of this false idea, and it is 

 thus moreover that, during the whole of the campaign 

 of 1866, Pasteur persisted in likening the corpuscle to 

 pus-globules and even to red blood-globules. He came 

 back definitely to the idea of parasitism only after an 

 experiment of Gernez which we shall find in its place. 



