76 ME THODS OF CUL TIVA TION OF BA CTERIA. 



pump. The fluid to be filtered is placed between the funnel 

 and the bougie in the space , and is sucked through into 

 the flask b. (2) This modification is shown in Fig. 30. 

 Into the narrow part of the funnel an india-rubber stopper 

 is fitted, which has a perforation in it sufficiently large 

 to receive the candle, which it should grasp tightly. 



(c] Muencke's modification of the Chamberland principle 

 is seen in Fig. 31. It consists of a thick- walled flask, a, 



the lower part conical, 

 the upper cylindrical, 

 with a strong flange on 

 the lip. There are two 

 lateral tubes, one hori- 

 zontal to connect with 

 exhaust-pump, and one 

 sloping, by which the 

 contents may be poured 

 out. Passing into the 

 upper cylindrical part 

 of the flask is a hollow 

 porcelain cylinder b, 

 of less diameter than 

 the cylindrical part of 

 flask a. It is closed 

 below, open above, and rests by a projecting rim on the 

 flange of the flask, an asbestos washer, c, being interposed. 

 The fluid to be filtered is placed in the porcelain cylinder, 

 and the whole top covered, as shown at / with an india- 

 rubber cap with a central perforation ; the tube d is 

 connected with the exhaust-pump and the tube e plugged 

 with a rubber stopper. 



Before any one of the above apparatus is used, it ought 

 to be connected up as far as possible and sterilised in 

 the Koch's steriliser. The ends of any important un- 

 connected parts ought to have pieces of cotton wool 

 tied over them. After use the bougie is to be sterilised 

 in the autoclave, and after being dried is to be passed 

 carefully through a Bunsen flame, to burn off all organic 



FIG. 31. Muencke's modification of 

 Chamber-land's filter. 



