74 



A MANUAL OF BACTERIOLOGY 



joints are tight, and they may be paraffined with advan- 

 tage. The gas should be passed through a strong solution 

 of caustic potash, and may be passed through some 

 alkaline pyrogallic acid if the most rigorous condition of 

 anaerobiosis is desired, but for ordinary purposes this is 

 not essential ; it should also pass 

 through two or three fairly firm plugs 

 of cotton- wool to remove organisms ; 

 these must be dry, for if moist the 

 passage of the gas may be stopped. 



For tube cultures Frankel's method 

 may be adopted (Fig. 12). The broth 

 or gelatin is introduced into a large 

 strong test-tube which is plugged with 

 a rubber cork, through which two 

 pieces of glass tubing pass, one to the 

 bottom of the tube, the other just 

 through the cork. Outside the cork 

 these tubes are bent over at right 

 angles, and each is drawn slightly out 

 so as to contract its lumen at about 

 the middle. The long tube is con- 

 FIG. l2.-^Frankel's tube nected with the hydrogen supply, and 

 for anaerobic cultiva- a current of the gas is passed through 

 and escapes by the shorter tube. After 

 the gas has been passing for twenty minutes to half an hour, 

 and all oxygen has been expelled, the distal, i.e. shorter, tube 

 is sealed off at the contracted portion in the Bunsen or 

 blowpipe flame, and then the proximal or longer one in 

 the same manner. The rubber cork must, of course, fit 

 well, and the joints should be paraffined. If gelatin be 

 the medium, it should be kept fluid in a bath of warm 

 water while the hydrogen is passing. 



For broth or other fluid cultures, which are essential 

 for obtaining toxic products, flasks are used which are 



