STUDIES ON FERMENTATION 119 



ness of the victors, that he felt constrained to return 

 the diploma of Doctor of Medicine which two years 

 before he had accepted from the University of Bonn. 

 He did so in a letter which contained some expressions 

 of feeling with regard to the head of the invading 

 army. These had better have been omitted, but were 

 perhaps pardonable under the circumstances ; they in 

 no way excuse the terms of reply which Dr. Naumann, 

 Dean of the Faculty of Medicine at Bonn, permitted 

 himself to use — terms which would be discreditable in 

 an ill-bred street gamin. 



From 1 87 1 to 1876, the year in which he published 

 his 'Etudes sur la Biere,' Pasteur was again largely 

 occupied with the study of fermentation. Part of his 

 object was undoubtedly to place the French brewers 

 on an equality with the German; and in this he 

 certainly had a large measure of success. To one 

 who knew Paris under the Second Empire and who 

 revisits it under the Third Republic, one of the first 

 changes observable in the life of the cafe is the enor- 

 mous consumption of ' bocks.' Pasteur's work, how- 

 ever, went far beyond the establishment of a national 

 industry. He started investigations which have 

 changed brewing from an art into a science ; and his 

 most fitting memorial in this respect is the bust which 

 decorates the hall of the Carlsberg Institution at 

 Copenhagen, an institution devoted to the study of 

 all problems of fermentation. In his ' Etudes ' Pasteur 

 laid great stress on the fact that every fermentation is 

 brought about by micro-organisms, and he dwells at 

 length on the marked influence which certain bacteria 

 exercise on the nature of the fermentations, and on the 

 character of the beer produced. He did not, however, 

 see, what Hansen demonstrated in 1883, that many of 

 the commonest diseases of beer are caused by certain 

 species of yeast-cell differing specifically from those 

 which cause its normal fermentation. Indeed, he paid 



