SYSTEMATICALLY SELECTED YEASTS. 53 



manufactured by Mr. W. E. Jensen have this modification, 

 whilst others are without it. 



If it is thought desirable that the wort should deposit its 

 sediment, an hour can be allowed for this to settle. To guard 

 against impure air being drawn in, the filter must not be 

 completely closed, the current of air being merely checked. 

 There is, however, no objection to the sediment remaining in 

 the wort, which may therefore be transferred to the ferment- 

 ing cylinder as soon as it is cooled. By this time a very 

 considerable sediment will have formed, and as the mouth of 

 the pipe k is at a moderate height above the bottom of the 

 wort cylinder, only a small portion of the sediment is carried 

 through. 



The wort at first introduced should not reach above the 

 small tube j, through which the yeast is introduced. The 

 yeast is previously collected in large two-necked glass flasks, 

 and in the transferring operation a spirit lamp may be made 

 use of if a gas flame is not at hand. Particulars regarding 

 the preparation of the yeast and its introduction into the 

 cylinder will be given later on. 



The stirring apparatus is now set in motion and the yeast 

 well mixed with the wort. As soon as this is done the 

 remainder of the wort is added until its level rises to the 

 upper mark on the glass tube /, the volume then measuring 

 about 170 liters. The column of liquid in this tube is forced 

 by the pressure of the air passing through the filter into the 

 cylinder, the cock on the upper horizontal tube e being closed, 

 and the cock on the lower tube h opened. When it is not 

 desired to continue the aeration during the fermentation, the 

 latter cock is of course also closed, but only after the cock 

 above the filter has been closed. 



After about ten days the desired portion of the newly 

 formed yeast can be drawn off. It is here assumed that the 

 cylinder has been exposed to the ordinary temperature of 

 the fermenting cellar ; if the temperature has been higher, the 



