FIFTH PART 

 STUDIES ON THE DISEASES OF SILKWORMS 



I 

 ORIENTATION TOWARDS PATHOLOGY 



I still recall the day when Pasteur, returning to the 

 laboratory, said to me with some emotion in his voice: 

 " Do you know what M. Dumas has just asked me to do? 

 He wants me to go into the South and study the disease 

 of silkworms." I do not recall my reply; probably it 

 was that which he had made himself to his illustrious 

 master: "Is there then a disease of silkworms? and 

 are there countries ruined by it?" This took place so 

 far from Paris! and then, also, we were so far from Paris, 

 in the laboratory! 



However that may be, Pasteur had reached one of the 

 turning points of his life. For a long time he had had a 

 presentiment that all the new ideas he had introduced 

 into science might be of importance for the physiology 

 and pathology of the higher animals. For a long time 

 the two notions of fermentation and disease had been 

 connected, as we have seen during our consideration of 

 spontaneous generations. But this relation had become 

 closer since it had been known that it was living cells 

 which presided over the processes of fermentation. 

 However, let us keep from believing that the logic of 

 the ideas of Pasteur led him, at this time, to the spot 

 where we see him so naturally to-day, namely to the con- 

 clusion that disease could result from the development, 

 in the normal tissues, of a living microscopic organism, 

 10 145 



