258 MICRO-ORGANISMS AND FERMENTATION. 



the yeast-propagating apparatus devised by HANSEN and 

 KUEHLE, which, when once charged with an absolutely pure 

 cultivation, will work continuously for years. The apparatus 

 (Fig. 80) is described in detail with directions for use in 

 HANSEN'S " Practical Studies in Fermentation " ; it consists of 

 three principal parts with the connecting tubes, viz. : (i.) the 

 arrangement for aerating the wort, consisting of the air-pump 

 (A) and air-vessel () ; (ii.) the fermenting-cylinder ((?), and 

 (iii.) the wort-cylinder (D). 



The air, which is partially purified by previous filtration, is 

 pumped into the air-vessel, from which it can be passed to the 

 wort-cylinder or to the fermenting-cylinder. In both cases it 

 has to pass through sterilised cotton-wool filters (g, m). The 

 wort-cylinder is connected by piping directly with the copper, 

 from which the boiling hot hopped wort is run into it ; it is 

 then aerated in the closed cylinder and cooled by water from p. 

 The wort is then forced into the fermenting-cylinder, which, 

 like the wort-cylinder, is constructed on the same principle as 

 the ordinary two-necked flask. It is fitted with a doubly-bent 

 tube (c, d), which dips into a vessel containing water ; a vertical 

 glass tube (/, i, f) for measuring the height of the liquid in the 

 cylinder ; an appliance (b, V) for stirring up the settled yeast, 

 and a cock (I) for drawing off the beer and the yeast. At 

 about the middle of the cylinder there is a small side tube (/), 

 fitted with india-rubber connection, pinch-cock, and glass- 

 stopper. When a portion of the wort has been forced into the 

 fermenting- vessel, the pure yeast which is forwarded to the 

 brewery in a flask specially constructed for this purpose is 

 introduced through the rubber tube at j ; this is again closed, 

 and the remainder of the wort may then be added either at 

 once or after the lapse of a few days, according to the quantity 

 of yeast which has been introduced. 



Where it is necessary to regulate the temperature during 

 fermentation, the fermenting-vessel is surrounded by a water- 

 jacket. 



By means of this simple apparatus it is possible to obtain, 

 at short intervals, absolutely pure pitching-yeast sufficient for 

 about eight hectolitres of wort. As already stated, the 

 apparatus, when once started, works continuously. For further 



