The Fermentation Tube 



215 



to 



cfq' 



o 



This type of gas production differs from the B. coli type : i, 

 in the much greater accumulation of gas which drives out all 

 of the fluid from the closed branch in two or three days ; 2, in 



the much larger proportion of CO2, the fraction -— varying 



from yi to yi ; 3, the much feebler acid reaction of the fluid 

 in the open bulb. The lactose fermentation goes on at a slow 

 steady pace and after one or two weeks a considerable quan- 

 tity of gas has accumulated in which the relative quantity of 

 CO2 and H varies considerably. 



