CULTIVATION WITHOUT OXYGEN 



175 



Fig. 34. 



gelatin. The growth that occurred along the track of 

 the needle was supposed to be anaerobic in nature. 



Methods of Liborius. Liborius has suggested two 

 useftil methods for this purpose. The one is to fill a 

 test-tube about three-quarters 

 full of gelatin or agar-agar, 

 which, after having been ster- 

 ilized, is to be kept in a vessel 

 of boiling water for ten min- 

 utes to expel all air from it. 

 It is then rapidly cooled in 

 ice-water, and when between 

 30° and 40° C, still fluid, is 

 to be inoculated and very rap- 

 idly solidified. It is then 

 sealed up in the flame. An- 

 aerobic bacteria develop only 

 in the lower layers of the 

 medium. Another method is 

 that in which he employs a 

 special tube, known as "the 

 Liborius tube." Its construc- 

 tion is shown in Fig. 34. 



Through the side tube hydrogen is passed until all air 

 is expelled ; the contracted parts,' both of the neck of 

 the tube and the side arm, are then sealed in the flame.' 

 This tube can be used for either solid or liquid media, 

 but, owing to its usual small capacity, gives better re- 

 sults with fluid media. (For precautions in using the hy- 

 drogen method see note to Frankel's method, page 178.) 



Liborius's tube for anaerobic 

 cultures. 



' As the tubes come from the maker the contracted parts marked x in the 

 cut are usually so thick as to render the sealing in the flame during the pas- 

 sage of hydrogen somewhat troublesome ; it is better to draw them out in the 

 flame quite thin before passing the hydrogen into the tube. This makes the 

 final sealing a matter of no difficulty. 



