SYSTEMATICALLY SELECTED YEASTS. 49 



Fig. 12 shows the arrangement of the whole apparatus 

 in the form in which it is at the present time generally 

 fitted up. 



With regard to the tinning of the cylinder, it must be 

 pointed out that the tin should not contain an appreciable 

 amount of lead. If this is the case, the yeast grown in the 

 apparatus will, according to Prior, be unsatisfactory. 



A careful study of our apparatus will show that it is 

 constructed on the principle of the flasks employed in the 

 laboratory in experimenting with micro-organisms, and that 

 especially Pasteur's two-necked flasks have served as the 

 model. The principles involved and the apparatus neces- 

 sary for effecting sterilisation were discovered by Pasteur's 

 predecessors, and the discoveries of Schwann (1837) m P ar ' 

 ticular were of fundamental importance in this connection. 

 They are discoveries which were made before I was born, 

 and I can therefore lay no claim to priority with regard to 

 them, and I have, indeed, never thought of doing so. The 

 attacks in the ' Berliner Wochenschrift,' which have been 

 directed against me in connection with this are therefore 

 perfectly groundless. (See further the historical account, 



P- 157). 



In putting up the apparatus, it ought above all to be 

 borne in mind that it should remain in its position undis- 

 turbed. When possible, it will generally be best to place it in 

 the fermenting cellar. There is then, as a rule, no trouble 

 with regard to regulating the temperature, and in drawing off 

 the beer and the yeast there will also be less work involved, 

 for those occupied can, in the interval, do other work close at 

 hand. If the temperature of the fermenting cellar is below 

 6 C. it is advisable to have the fermenting cylinder jacketed. 

 In putting up the apparatus it is, of course, necessary to at 

 once consider whether one or two fermenting cylinders are to 

 be employed ; in any case a single wort cylinder will suffice. 



The apparatus having been fixed, it is necessary in the 



E 



