SYSTEMATICALLY SELECTED YEASTS. 43 



can be fitted to either side of the cylinder where it is most 

 convenient, but care must, of course, be taken that the water 

 cannot splash into the vessel which is placed under the cock 

 / whilst the yeast is being withdrawn in the manner de- 

 scribed later on. A little below the top is a horizontal tube 

 e provided with a cock, and by means of which the inside 

 of the cylinder is connected with the vertical glass tube /. 

 This is connected at its upper end with the filter g and at 

 its lower end with a second cock and similar horizontal tube 

 h to that described above. 



The top mark on the glass tube is 79 cm. from the 

 bottom of the cylinder, the next 20 cm. and the lowest 

 10 cm. from the bottom of the cylinder. When filled to 

 the top mark, the cylinder holds about 170 liters. The 

 glass tube is fixed into the cocks e and h by a packing of 

 hemp or cotton-wool with vaseline ; rubber is not suitable 

 as it is hardened by steam. 



The filter g consists of a metal capsule containing a 

 tightly packed plug of cotton-wool 22 cm. long and 3 cm. 

 in diameter. This plug consists of at least 35 grams of 

 cotton-wool ; the addition of a few more grams is immaterial. 

 If firmly pressed in, the capsule will hold 50 grams and more, 

 but this is not necessary. The filter is closed above by means 

 of a cover which is screwed on and which is connected with 

 the tube from the air-holder. Before the filter is screwed on, 

 it is sterilised by heating it for two hours at a temperature 

 of about 1 50 C. The filtration of the air will be described 

 below. 



At the opposite side of the cylinder there is a small tube 

 j scarcely i 5 cm. long and fitted with rubber tubing, the 

 latter being closed by means of a pinch-cock and a glass 

 stopper. Passing from the bottom of the cylinder is a tube 

 k through which connection can be made with the wort 

 cylinder D ; this tube is made in two pieces to prevent too 

 great rigidity, and in addition to the two large cocks shown, 



