20 MICROORGANISMS AND FERMENTATION. 



wool filter (a), and the flask has a small side-tube closed 

 with an asbestos stopper (d). This flask is used partly for 

 the preservation of pure cultures, partly for sending small 

 cultures or samples from the propagating apparatus. 1 

 For the first-named purpose the flask is half filled with a 

 10 per cent, solution of cane-sugar, to which a trace of 

 the yeast-culture is then added. The asbestos stopper and 

 lower edge of the cap is coated with sealing-wax (c). For 

 the last-named purpose the lower part of the flask is 

 filled with cotton-wool (e\ and some cotton-wool (6) is 

 also put into the cap, below the filter. For the mode of 

 employment, see Chapter VI. 



FIG. 5. 

 Hansen Flask. 



For the development of very large cultures the Carlsberg 

 vessels (Fig. 6) are employed. They have a capacity of 

 10 liters, are made of tinned copper, are cylindrical in 

 shape and conical at the top; at the apex of the cone a 

 twice-bent tube (c d) with an enlargement (e) is either 

 soldered or screwed. At one side of the cooe is the 

 inoculating tube and glass stopper (a), and at the bottom 

 of the vessel is another tube (6) for drawing off the 

 fermented liquid and the yeast. This tube is provided 

 with a pinch-cock. When the liquid is sterilised, the 



1 For the description of this apparatus, see Chapter VI. 



