234 BACTERIOLOGY. 



the bacteria deep down to near the bottom of the tubes 

 while the media are still semi-solid. An anaerobic 

 growth will take place in the lower part of the tube. 

 In a similar way the closed arm of the fermentation 

 tube will suffice for anaerobic growth, if the opening 

 connecting it with the open bulb is quite small. In 

 the more complicated methods the plates or tubes are 

 placed in jars (Fig. 34), in which the oxygen is dis- 



FIQ. 34. 



Jar for anaerobic cultures. 



placed by a stream of hydrogen developed by the Kipp 

 apparatus through the action of pure granulated zinc 

 and a pure 25 per cent, solution of sulphuric acid. 

 When all the oxygen has been displaced the jars are 

 sealed by rotating the stopper. In another method the 

 oxygen is extracted by a mixture of pyrogallic acid and 

 caustic potash. To each 100 c.c. of air space in the jar 

 1 gramme of pyrogallic acid and 10 c.c. of 6 per cent, 

 solution of potassium hydroxide are added and the jars 

 immediately sealed. When spores are present, a simple 

 method suggested, I believe, by McFarland can be 

 successfully employed. Vessels plugged with stoppers 



