192 



BACTERIOLOGY. 



employment of the fermentation-tube. It 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. 39.) To fill 

 the tube the fluid (it is only used with fluid media) 



PIG. 39. 



Fermentation-tube. 



is poured into the bulb until this is about half full. 

 The tube is then tilted until the closed arm is nearly 

 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 enough 

 fluid should be added to cover the .lowest expanding 

 portion of the bulb, and the opening of the bulb plugged 

 with cotton. The. tubes thus filled are then to be ster- 

 ilized. During sterilization they are to be maintained 



