CULTIVATION WITHOUT OXYGEN. 197 



must all have 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. Both of these 



Fia. 41. 



£) 



Frankel's method for the cultivation of anaerobic bacteria. 



tubes must be provided, before sterilization, with a 

 plug of cotton; this is to prevent the access of foreign 

 organisms to the medium during manipulations. 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 different 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. The 



