200 BACTERIOLOGY 



employment of the fermentation-tube. This is a tube bent 

 at an acute angle, closed at one end and enlarged with a bulb 

 at the other. At the bend the tube is constricted. To it 

 a glass foot is attached so that the tube may stand upright. 

 (See Fig. 36.) To fill the tube, the fluid (it is used only with 

 fluid media) is poured into the bulb until this is about half 

 full. The tube is then tilted until the closed arm is nearly 



FIG. 36 



Fermentation-tube. 



horizontal, so that the air may flow out into the bulb and the 

 fluid flow into the closed arm to take its place. When this 

 has been completely filled sufficient fluid should be added 

 to bring its level within the bulb just beyond the bend, and 

 the opening of the bulb plugged with cotton. The tubes thus 

 filled are then to be sterilized. During sterilization they 

 are to be maintained in the upright position. Under the 



