82 



BACTERIOLOGY. 



In order to test the production of gas, a culture 

 medium composed of glucose-agar, containing about 

 1 per cent, grape sugar, may be used. At the end of 

 eight to twelve hours in the incubator (or twenty-four 

 hours 7 room-temperature) the agar will be seen to be 

 full of gas-bubbles or broken up into holes and fissures. 



For the determination of the quantity and kind of 

 gas produced by a given micro-organism the fermenta- 

 tion tube recommended by Theobald Smith is the best. 

 This is a bent tube, constricted greatly at its lowest 

 portion (Eichorn's), supported upon a glass base, as 

 shown in Fig. 14. The graduation shown in the 



FIG. 14. 



Fermentation tube left side, ordinary tube on right side. 



upright arm is not essential for ordinary laboratory 

 work. The tube is filled with a culture media consist- 

 ing of 1 per cent, glucose, peptone bouillon (without 

 air-bubbles), and sterilized in the steam sterilizer. It 

 is then inoculated with a loopful of a culture of the 

 organism in question, and observations taken: 



1. If there is a turbidity produced in the open bulb 

 it indicates the presence of an aerobic species; if this 



