68 METHODS OF CULTIVATION OF BACTERIA. 



to employ such in order to obtain the toxic products of the 

 growth of anaerobes. Glucose broth is most convenient. 

 It is placed either (i) in a conical flask with a lateral open- 

 ing and a perforated india-rubber stopper, through which a 

 bent glass tube passes, as in Fig. 23, a, by which hydrogen 

 may be delivered, or (2) in a conical flask with a rubber 

 stopper furnished with two holes, as in Fig. 23, b, through a 

 tube in one of which hydrogen is delivered, while through 

 the tube in the other the gas escapes. The inner end of 

 the gas delivery tube must in either case be below the 



FIG. 23. 



a. Flask for anaerobes in liquid media. Lateral nozzle and stopper fitted for 

 hydrogen supply, b, A stopper arranged for a flask without lateral nozzle. 



surface of the liquid, and the inner end of the lateral nozzle 

 in the one case, and the inner end of the escape tube in the 

 other, must of course be above the surface of the liquid. 

 The single tube in the one case and the two tubes in the 

 other ought to be partially drawn out in a flame to facilitate 

 subsequent complete sealing. The ends of the tubes 

 through which the gas is to pass have pieces of cotton wool 

 tied on them. It is well previously to place in the tube, 

 through which the hydrogen is to be delivered, a little plug 

 of cotton wool. The flask being thus prepared, it is 

 sterilised by methods B (2) or B (3). On cooling it is 

 ready for inoculation. In the case of the flask with the 



