68 



EXPERIMENTAL DAIRY BACTERIOLOGY 



procedure allows not only the qualitative determination to 

 be made, but also permits of a rough quantitative analysis 

 and the determination of the relative amounts of the com- 

 ponent gases formed. 



In case the fermentation tubes filled with sugar broth have 

 not been recently sterilized, heat in the sterilizer in order to 



FIG. 13. FROST'S GASOMETER 



The amount of gas is expressed in per cent of the length of the closed arm of 

 the fermentation tube. (After Heiuemann) 



drive off dissolved oxygen. If they contain bubbles of gas on 

 being taken from the sterilizer, remove them by decantation. . 

 When ready to use, the liquid should fill the closed arm and 

 stand at a low level in the open bulb. When cool, inoculate. 

 At frequent intervals during the incubation, which, as a 

 rule, should be made at 37 C., the presence or absence of 



