234 BACTERIOLOGY. 
the bacteria deep down to near the bottom of the tubes _ 
while the media are still semi-solid. An anaérobic 
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 anaérobic 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- 
Well 
Jar for anaérobic 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 
