64 PURE CULTURES OF 



The pure yeast propagating apparatus is now used in 

 more than 160 of the largest and most important breweries, 

 and it has recently been introduced into some distilleries. 

 Just as the reform has spread with enormous rapidity, so 

 the time will soon come when a highly-contaminated brewery 

 yeast will be uncommon. A thorough comprehension of the 

 employment of the propagating apparatus will constitute an 

 active means towards this end. On pp. 234, 240 and 252 

 will be found a list of the breweries, distilleries, &c., where 

 the pure yeast propagating apparatus has been introduced. 



It must not be forgotten, however, that neither this 

 apparatus nor that which as my system becomes more 

 and more widely adopted is now taking the place of the 

 old cooler, plays more than a secondary part in my system ; 

 they do not constitute, and they can never become the 

 essentials of the system, and it is a gross mistake to regard 

 them as such. The absolutely pure culture of the systematically 

 selected species of yeast is, and always remains, the main point, 

 and it is this only which gives importance to these forms of 

 apparatzts. Good results are obtained when pure yeast is 

 used in accordance with my old method, but not when 

 impure or badly selected yeast is cultivated in the apparatus. 



Filters. 



We should attain our object more quickly and simply if 

 it were possible to employ the cooled and aerated wort from 

 the cooler, and by filtration to purify it from the micro- 

 organisms which it always contains. The wort cylinder 

 would then be superfluous, and the whole process would be 

 simplified. Experiments which were made in this direction 

 did not, however, give any satisfactory result. 



The filter to be employed for this purpose must not only 

 satisfy the condition that the filtrate shall be absolutely free 

 from germs, but also the time required for the filtration must 

 not be too great, and finally, the composition of the liquid 



