Fearon — Pasteur Centenary Celebration. 51 



This early discovery brought him no money, but brought him friendships, 

 which were of greater worth, and also indirectly led him to wider fields of 

 research and harvests beyond his anticipation. 



These were the studies of fermentations. In them every aspect of 

 Pasteur's genius is displayed, and in them he first definitely out-topped the 

 men of his time and anticipated in himself the future development of humanity. 



II. 



Fermentation is a process older than civilization. Certain materials when 

 left to themselves are found to undergo a spontaneous and often profound 

 chemical change which alters their whole character. 



Since times forgotten, man has availed himself of these natural changes 

 in the preparation of wine and beer, in the manufacture of vinegar, in the 

 making of butter and cheese. 



The causes of these changes or fermentations were quite unknown, and 

 their occurrences were sometimes so capricious as to appeal to a sense of the 

 supernatural, such as the influence of a comet on a vintage or a thunderstorm 

 on a dairy. The current scientific notions of the nature of fermentation had 

 hardly advanced beyond the time when Lemery — some two hundred years 

 previously — had written : 



" Fermentation is an Ebullition raised by the Spirits that endeavour to 

 get out of a Body ; meeting with the gross Earthy Parts that oppose 

 their passage, they swell and rarefy the Liquor until they find a way out." 



In the middle of the nineteenth century, ferments were considered to be 

 dead chemical substances in the process of decay, and fermentation itself was 

 thought to be akin to oxidation. 



Pasteur's interest in fermentation probably went back to the days when 

 he played in his father's tan-yard in Arbois. 



In 1854 he was appointed Dean of the Faculty of Science newly 

 instituted at Lille. He at once realized that the work of his department 

 should be brought into touch with the important industries of the district, 

 notably the manufacture of alcohol from grain and from beet-sugar. 



These fermentation industries were often visited by strange and quite 

 inexplicable diseases. The wrong substances were produced, and the good 

 were rendered useless. Acids appeared, and wines went sour. Beer developed 

 unpleasant flavours. Pasteur approached the problem with the help of the 

 microscope, and soon detected a difference in the shape of the particles of the 

 ferment in the normal fermentations and the abnormal fermentations. 



In good beer the yeast was round ; in beer that had gone sour the particles 



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