222 STUDIES ON FERMENTATION. 



On December 15th, 1872, we bought nine samples of beer in 

 different large cafes in Paris, which had all come from the 

 best breweries of Strasburg, Nancy, Vienna, and Burton. After 

 leaving them for twenty-four hours, we decanted all our 

 samples, and then sowed a drop of the deposit of each in flasks 

 of pure wort. On January 2nd, 1873, we examined the ferments 

 formed in these worts, which had been kept in an oven at a 

 temperature of 20° C. (68° F.), and also tasted the beers pro- 

 duced ; they all had an abominable taste, and each contained 

 diseased ferments. 



At the same time, by way of comparison, we impregnated 

 other flasks of wort with pure ferments. None of the beers of 

 this series acquired a bad taste or produced foreign ferments ; 

 they only became flat. 



When we review the operations of the brewer^s art, we are 

 surprised by the comparative perfection to which that art has 

 been brought by the laborious experience of years, and the 

 more so when we consider that, as regards the question of the 

 diseases of beer, the brewer has never been guided by any such 

 rigorous principles as those which we have explained in this 

 work. We have already given proofs of this in our first 

 chapter. 



The beer is racked and separated from its yeast before 

 fermentation has entirely ceased. The principal reason for 

 this is that it is necessary that the beer, after being run into 

 cask, should work again and undergo a secondary fermentation, 

 in order that it may not be invaded by the parasites, of which 

 we have already spoken, as would not fail to be the case if the 

 beer were suffered to remain in a state of perfect quiescence. 

 Not only is the beer racked before it has attained its limit of 

 attenuation, but in addition to this, and also with the view 

 of checking the development of parasites, it is placed in cellars 

 sensibly cooler than the temperature of fermentation, low as 

 that is in the case of " low " beers : the temperature of the 

 cellars being not higher than 2° or 3° C. (36° F.). 



Unfortunately, the requirements of trade prevent our com- 



