18551859 79 



The sentence in his Lille speech, " in the fields of observa- 

 tion, chance only favours the mind which is prepared," was 

 particularly applicable to him. In the summer of 1856 a 

 Lille manufacturer, M. Bigb, had, like many others that same 

 year, met with great disappointments in the manufacture of 

 beetroot alcohol. He came *to the young Dean for advice. 

 The prospect of doing a kindness , of communicating the results 

 of his observations to the numerous hearers who crowded the 

 small theatre of the Faculty, and of closely studying the pheno- 

 mena of fermentation which preoccupied him to such a degree, 

 caused Pasteur to consent to make some experiments. He 

 spent some time almost daily at the factory. On his return 

 to his laboratory where he only had a student's microscope 

 and a most primitive coke-fed stove he examined the globules 

 in the fermentation juice, he compared filtered with non- 

 filtered beetroot juice, and conceived stimulating hypotheses 

 often to be abandoned in face of a fact in contradiction with 

 them. Above some note made a few days previously, where 

 a suggested hypothesis had not been verified by fact, he would 

 write: "error," "erroneous," for he was implacable in his 

 criticism of himself. 



M. Bigo's son, who studied in Pasteur's laboratory, has 

 summed up in a letter how these accidents of manufacture 

 became a starting point to Pasteur's investigations on fer- 

 mentation, particularly alcoholic fermentation. "Pasteur 

 had noticed through the microscope that the globules were 

 round when fermentation was healthy, that they lengthened 

 when alteration began, and were quite long when fermen- 

 tation became lactic. This very simple method allowed us 

 to watch the process and to avoid the failures in fermentation 

 which we used so often to meet with. ... I had the good 

 fortune to be many times the confidant of the enthusiasms 

 and disappointments of a great man of science." Young 

 Bigo indeed remembered the series of experiments, the 

 numerous observations noted, and how Pasteur, whilst study- 

 ing the causes of those failures in the distillery, had wondered 

 whether he was not confronted with a general fact, common 

 to all fermentations. Pasteur was on the road to a discovery 

 the consequences of which were to revolutionize chemistry. 

 During months and months he worked to assure himself that 

 he was not a prey to error. 



In order to appreciate the importance of the ideas which 



