PRODUCED BY ALCOHOLIC FERMENTS. 221 



from which disease yeasts become introduced into the brewery ; 

 the deposits in the lager casks form another source of infection. 

 This will almost always contain more or less wild yeast, even 

 in breweries which are kept in good order ; and when the beer 

 has been attacked by disease yeast such deposits become espe- 

 cially dangerous. Formerly this point was generally much 

 neglected in breweries. The cask deposit was thrown into 

 the yard, and a portion was then carried on the boots of the 

 workmen into the fermenting room ; a large portion would 

 dry up to dust, and be carried by the wind on to the coolers 

 and into the fermenting room. Some years ago I drew the 

 urgent attention of brewers to this source of danger. At the 

 present time greater attention is certainly paid to this point 

 than was formerly the case, but it may not be superfluous to 

 again draw attention to it. 



Most frequently, however, a brewer introduces wild yeast 

 into the brewery when he obtains his pitching yeast from another 

 brewery ; there is always more or less danger in this. On 

 this account the more important breweries have now adopted 

 the system of pure yeast culture. 



Mixtures of Different Species of Brewery Yeasts. 



Each of the two bottom yeasts which I introduced into 

 the Old Carlsberg brewery in 1883 and 1884 gives a good 

 and satisfactory product, yet, as pointed out on p. 86, they 

 differ widely from each other. When regarded from a purely 

 practical point of view, we find in the first place that the beer 

 produced with the help of Carlsberg bottom yeast No. 2 is 

 fuller and contains more carbonic acid gas than that obtained 

 with Carlsberg bottom yeast No. I ; the latter beer, on the 

 other hand, is much more stable. These results naturally 

 led to the idea of experimenting with mixtures of the two 

 species. 



Captain Kiihle, the director of the brewery, kindly con- 



