118 BACTERIOLOGY. 



stopper. The oxygen is quickly absorbed by the pyro- 

 gallic acid, aud the organisms develop in the remaining 

 constituents of the atmosphere nitrogen, a small amount 

 of CO 2 , and a trace of ammonia. 



Method of C. FranM. Carl Fraukel suggests the 

 following method : The tube is first prepared as if 

 for an ordinary Esmarch tube. The cotton plug is 

 then replaced by a rubber stopper, through which 

 pass two glass tubes. These have all been sterilized 

 in the steam sterilizer before using. On the outer 

 side of the stopper these two tubes are bent at right 

 angles to the long axis of the test-tube into which they 

 are to be placed, and both are slightly drawn out in the 

 gas flame. At the outer extremity of both of these tubes 

 a plug of cotton is placed ; this is to prevent access of 

 foreign organisms during manipulation. At the inner 

 side of the rubber stopper that is, the end which is to 

 be inserted into the test-tube the glass tubes are of dif- 

 ferent lengths : one reaches to within 0.5 cm. of the 

 bottom of the test-tube, the other is cut off flush with the 

 under surface of the stopper. This rubber stopper, with 

 its glass tubes, is to replace the cotton plug of the test- 

 tube; the outer end of the longer glass tube is then 

 connected with a hydrogen generator and hydrogen 

 is allowed to bubble through the gelatin in the tube 

 until all contained air has been expelled and its place 

 taken by the hydrogen. The organisms are to grow, 

 then, in an atmosphere of hydrogen. When all air 

 has been expelled, the two external ends of the glass 

 tubes are to be sealed in the gas-flame at the portions 

 w r here they have been drawn out. In sealing the tubes 

 in the gas-flame one must be sure that all air has been 

 expelled, otherwise an explosion is inevitable. This 



