RESULTS OF SCIENTIFIC RESEARCH IN PRACTICE. 209 



breweries. The analysis will, however, always indicate infec- 

 tion long before it has become dangerous, so that a new, pure 

 cultivation of the same yeast can be introduced in good time. 

 A still greater certainty is attained by the continuous working 

 of the yeast-propagating apparatus described below. The 

 main result achieved is that we now no longer proceed 

 flap-hazard, and are not compelled to leave ike fermentations 

 to take their chance, as was formerly the case. 



Since the various species of yeast differ in their power 

 of resisting competing disease-germs, it is in many cases of 

 great importance to be able, at short intervals, to introduce 

 into, the brewery a considerable quantity of a suitable and 

 absolutely pure species of yeast, which has been previously 

 selected by systematic experiments. This object is attained 

 by means of the yeast-propagating apparatus devised by 

 Hansen and Kiihle, and which, when once charged with an 

 absolutely pure cultivation, will work continuously for years. 

 The apparatus (Fig. 55) is described in detail with directions 

 for use in Hanserts " Untersuchungen aus der Praxis der 

 Gfarungsindustrie " x ; it consists of three principal parts with 

 the connecting tubes, namely: 1, the arrangement for 

 aerating the wort, consisting of the air-pump (A) and air- 

 vessel (B) ; "2, the fermenting-cylinder ((7), and 3, 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 hopped wort is run boiling 

 hot into it ; it is then aerated in the closed cylinder and cooled 

 bv water from p. The wort is then forced into tine fermenting- 

 cylinder, which, like the wort cylinder, is constructed on the 



1 Published by R. Oldenbourg, Munich: 1st part, 2nd edition, 1890; 

 2nd part, 1892. In this work will also be found a description of Hansen 's 

 complete system. 



