THE CULTIVATION OF BACTERIA. 



93 



FIG. 27. 



Cultivation of Anaerobic Bacieria under Hydrogen: 

 Method of Frank el: A test-tube containing a large amount 

 of the liquefied culture-medium is closed with a sterilized 

 rubber stopper, through which pass two sterilized glass 

 tubes, bent above the stopper at a right angle. One of 

 these tubes is cut off just underneath 

 the stopper, and the other is long 

 enough to project nearly to the bottom 

 of the culture-tube. The horizontal 

 projecting parts are drawn to a small 

 caliber at some point, although not 

 quite closed, to facilitate sealing later 

 on. Through the longer of these 

 tubes hydrogen gas is passed until the 

 atmosphere inside of the culture-tube 

 is pure hydrogen, entirely free from 

 mixture with air. The horizontal 

 parts of the small glass tubes project- 

 ing from the stopper are then sealed 

 in the flame at the places where they 

 were previously drawn out to a small 

 caliber, and the tubes are thus closed. 

 (Fig. 27.) 



The stopper should be surrounded 

 with melted paraffin, 

 according to this plan may, if desired, be 

 converted into an Esmarch roll-tube. The hydrogen is gen- 

 erated according to the common method with pure zinc and 

 pure sulphuric acid, 25 to 30 per cent. The precautions 

 advised by chemists for the generation of hydrogen must 

 be carefully followed, because when hydrogen mixed with 

 oxygen or air is ignited a violent and disastrous explosion 

 may occur. 



The well-known Kipp's generator may be used. First 



A tube prepared Cultivation of Anaerobes 



by Frankel's Method. 



