76 



METHODS OF CULTIVATION OF BACTERIA. 



Fig. 39. — Chamberland's 

 candle and flask arranged for 

 filtration. 



is arranged as in Fig. 39. The fluid to be filtered is placed in 

 the cyhndrical vessel a. . Into this a " candle " or " bougie " of 

 — - porcelain dips. From the upper end of 

 ^T S the bougie a glass tube with thick rubber 



^"^"^^ * connections, as in Fig. 39, proceeds to 



flask b and passes through one of the two 

 perforations with which the rubber stop- 

 per of the flask is furnished. Through 

 the other opening a similar tube proceeds 

 to the exhaust-pump. When the latter is 

 put into action the fluid is sucked through 

 the porcelain and passes over into flask b. 

 This apparatus is very good, but not suitable for small quantities 

 of fluid. 



{b) A very good apparatus can be 

 arranged with a lamp funnel and the 

 porcelain bougie. These may be fitted 

 up in two ways, (i) An india-rubber 

 washer is placed round the bougie c at 

 its glazed end {vide Fig. 40). On this 

 the narrow end of the funnel d, which 

 must, of course, be of an appropriate 

 size, rests. A broad band of sheet 

 rubber is then wrapped 

 round the lower end of 

 the funnel and the pro- 

 jecting part of the bougie. It is firmly wired to 

 the funnel above and to the bougie below. The 

 extreme point of the latter is left exposed, and 

 the whole apparatus, being supported on a stand, 

 is connected by a glass tube with the lateral tube 

 of the flask b ; the tube a is connected with the 

 exhaust-pump. The fluid to be filtered is placed 

 between the funnel and the bougie in the 

 • Pi°-4i--Boug>e space e, and is sucked through into the flask b. 



inserted through ^ ^ 



rubber stopper for (2) This modification is shown in Fig. 41. Into 



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. 



Fig. 40. — Chamberland's bou- 

 gie arranged with lamp funnel for 

 filtering a small quantity of fluid. 



same purpose as in ^^^ narrow part 

 Fig. 39. ^ 



