1 86 CHEMISTRY OF THE YEAST CELL. 



into small, gravelly lumps, the brewer is in a position to order 

 the beer to be racked into the storage cask, and thus separated 

 from the sedimental yeast. According as the racking is effected 

 at an earlier or later period, so a larger or smaller number of 

 yeast cells will be carried over into the storage cask ; and the 

 beer is said to be racked green or bright respectively. The 

 latter condition is the more desirable, the exact gradation, how- 

 ever, varying according to cu'cumstances. 



The piogress of clarification in lager-beer, that is to say, its 

 self-pui'ification from the yeast cells, is shown in the following 

 figures, which were determined in 1S96 by F. Schcexfeld (I.) 

 in Berlin lagex'-beer, by means of the yeast counter (§ S3). 



One Cubic Millimetre of Yeast Cells. 



Freshly pitched \Yort contained .... 14,600 



Young beer previous to racking contained . . 54,000 



Young beer, racked somewhat green ,, . . 2,000 



Young beer, racked bright ,, . . 500 



Lager-beer, ready for drinking ,, . . o. I to 10 



Thus, at the end of the primary fermentation, the number 

 of yeast cells carried over into the storage cask amounts to 

 5 per cent, when the " break " is fairly good, and to i per 

 cent, when the same is very good. Similar results were obtained 

 for North American lager-beer in 1889 by R. \Yahl (L). In 

 order to facilitate the deposition of these yeast cells in the 

 storage cask, it is the custom to place in the cask a number of 

 shavings or strips, either of hazel wood or sheet aluminium. 

 This has been reported on by H. Will (XVIII.). On this 

 foundation the cells adhere firmly, and the microscopical ex- 

 amination of such strips from the empty storage cask shows that 

 the cells are, as it were, glued on to the strips by the mucinous 

 substances already referred to. Imperfectly clarified beer is 

 said to suffer from yeast turbidity or haze, and should not be 

 offered for sale, since, even when the yeast is in small amount, 

 it is often the cause of gastric catarrh, diarrhoea, and indeed 

 slight toxic symptoms, in the consumer. The actual and 

 proximate causes of this action are still undetermined. The 

 literatxu-e of this matter will be found collected in a useful 

 work by X. P. Simaxowsky (I.) and in a communication by R. 

 ScHWAXHAUESER (I.), a few experiments on the same point 

 having also been undertaken by J. ISTeumayer (I.). "With regard 

 to the clarification of cloudy beer by filtration, reference may 

 be made to § 75 in Vol. i. The proposal made by Otto Reixke 

 (I.) in 1896, to facilitate the clarification of beer by the aid of 

 light, can hardly be recommended, since, as already shown by 

 W. ScHULTZE (I.) in 1888, the agreeable flavour of the beer 

 rapidly disappears under such treatment. 



