220 MICRO-ORGANISMS AND FERMENTATION. 



highly favourable results which were obtained in the brewery 

 with pure yeast; and, finally, also the fact that in 1887 

 Professor Hansen, in conjunction with Captain Kuhle, suc- 

 ceeded in devising a pure yeast apparatus which enabled 

 them to produce large quantities of the pure yeast which had 

 been prepared on a comparatively small scale in the laboratory. 

 At the present time hundreds of breweries obtain a pure 

 cultivated standard yeast from institutions in which pure 

 cultivations of beer-yeast are prepared, and thousands of 

 breweries do the same indirectly in that they obtain their 

 pitching-yeast from the above breweries. The universal 

 employment of pure yeast in the brewing industry is 

 therefore now only a question of time. 



" If we now weigh with the most complete objectiveness 

 the significance of these facts as applied to the conditions 

 obtaining in European bottom-fermentation breweries, we are 

 compelled to acknowledge that the reform introduced by 

 Professor Hansen is still more far-reaching than is generally 

 assumed. A result of this reform is already being discussed 

 in brewing circles, namely, the abandonment of open coolers 

 in all breweries where pure yeast is employed, as these freely 

 permit of the contamination of the wort with micro-organisms 

 and especially with bacteria and the so-called " wild " yeasts. 

 It is therefore proposed to filter the hopped wort, or to 

 separate the suspended matter (cooler-deposits) by another 

 method, to saturate the wort with filtered air, and to cool it 

 by artificial means. But these are by no means all the 

 precautions which must be adopted in order to guard against 

 further infection of the wort in the fermenting-rooms and in 

 the lager-cellar. Only when these questions have been 

 solved perhaps by means of closed fermenting-vessels of a 

 suitable material, by the sterilisation of the fermenting and 

 storage vessels, by a more rational arrangement of the fer- 

 menting-rooms and lager-cellars, and by the ventilation of 

 these by means of filtered air, &c. only then will it be 

 possible amongst beer producers and consumers to enjoy to 



