ANAEROBIC CULTURE 



91 



black causes the combination of the hydrogen with any 

 oxygen that may be present forming water, so that an 

 absolutely anaerobic condition is obtained. The figure 

 (Fig. 15) shows the details of the apparatus. 



The displacement of the atmosphere by means of 

 hydrogen or nitrogen may be adopted ; the former, being 

 the more readily generated, is generally used. Carbon 

 dioxide cannot be used, as it has a very decided inhibitory 

 action. The hydrogen is best 

 generated from zinc and sulphuric 

 acid in a Kipp apparatus, or the 

 compressed gas in cylinders, or 

 even coal-gas, may be used. Care 

 must be taken that all joints are 

 tight, and they may be paraffined 

 with advantage. The gas may be 

 passed through some alkaline pyro- 

 gallic acid, though for ordinary 

 purposes this is not essential, and 

 also through two or three fairly 

 firm plugs of cotton- wool to remove 

 organisms ; the wool must be dry, 

 for if moist the passage of the gas 

 may be stopped. 



For tube cultures Frankel's 

 method may be adopted ; the 

 illustration (Fig. 16) explains the 

 device a stout test-tube which 

 is plugged with a rubber cork, 

 through which the two pieces of glass tubing pass. The 

 long tube is connected with the hydrogen supply, and the 

 gas escapes by the shorter tube. After the gas has been 

 passing for twenty minutes to half an hour and all 

 oxygen has been expelled, the point of the distal, i.e. 

 shorter, tube is first sealed in the Bunsen or blowpipe 



FIG. 16. Frankel's tube 

 for anaerobic cultiva- 

 tion. 



