CULTIVATION WITHOUT OXYGEN. 



195 



air from it. It is then rapidly cooled in ice- water, and 

 when between 30 and 40 C., still fluid, is to be inoc- 

 ulated and very rapidly solidified. It is then sealed up 

 in the flame. Anaerobic bacteria develop only in the 

 lower layers of the medium. His other method is that 

 in which he employs a special tube, known as " the 

 Liborius tube." Its construction is shown in Fig. 40. 



FIG. 40. 



Liborius tube for anaerobic cultures. 



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. 1 This tube can be used for either solid or liquid 



1 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. 



