LOUIS PASTEUR. 243 



At the close of the Franco-Prussian war, during which, 

 of course, all scientific work ceased, especially as far as 

 Pasteur, who was an ardent patriot, was concerned, he 

 was anxious to recommence his investigations. Again his 

 thoughts reverted to the question of fermentation, especially 

 in so far as it bore on an industry which he thought might 

 be revived in his beloved country. The diseases of beer 

 were, he pointed out, the result of the activity ol lactic, 

 butyric, and other ferments which found their way into 

 the wort during the process of brewing, either accidentally 

 or along with the yeast. In order to get rid of these he 

 tried to obtain pure cultures of yeast. In this he succeeded, 

 and so far improved the character of the ferment. Further, 

 by applying his process of Pasteurisation — heating in 

 bottle at a temperature sufficient to kill most non-spore- 

 bearing organisms — he was able to prevent the develop- 

 ment of most of the organisms accidentally admitted, with 

 the result that he practically revolutionised the method of 

 brewing beer, and from a mere rule of thumb process con- 

 verted it into one strictly accurate and scientific. He ulti- 

 mately found that when the beer is made with pure yeast 

 and under proper precautions, no extraneous organisms find 

 their way into it at any part of the process, and no Pasteur- 

 isation is necessary. 



This study of beer, however, was merely an interlude, 

 and Robert Boyle's prophecy that "he that understands the 

 nature of ferments and fermentation shall probably be much 

 better able than he that ignores them to give a fair account 

 of divers phenomena of certain diseases (as well fevers as 

 others), which will perhaps be never properly understood 

 without an insight into the doctrine of fermentations," was 

 now about to be fulfilled most completely and literally. Pas- 

 teur was not a physician or a surgeon, and it was but natural 

 that the first practical application of his theories of fer- 

 mentation to the study of disease in the human subject 

 should be made by surgeons. In 1863 Traube in Ger- 

 many pointed out that the alkaline fermentation of urine 

 does not take place in the bladder except in those cases in 

 which " vibrios find access to the bladder from without ". 



