The Fermentation Tube 221 



I have been inclined to ascribe this to the absorption of COj 

 by the bouillon but Grimbert"'' as well as Frankland'^ finds by 

 exact quantitative determinations of the gases the same in- 

 crease of CO2 as the fermentation progresses. The former ex- 

 plains it by assuming a greater production of alcohol in the 

 later course of the process in accordance with the formulae 

 given above. According to this explanation the type of fer- 

 mentation of B. cloaccB ma}^ differ from that of B. <r^/z simply by 

 an increased production of some alcohol at the expense of an 

 acid. If we go a step farther and bring within the range of 

 comparison another tj^pe of gas production, that of ordinary 

 yeast by which only COj and ethyl alcohol are produced (if 

 we neglect traces of succinic acid) we have eliminated both 

 the hydrogen and the acid element which seem to go to- 

 gether. 



A farther point of interest is the constant presence in all 

 cultures examined of an inflammable, explosive gas which I 

 have assumed to be hydrogen. Most observers, including Ar- 

 loing*, Eschericlv, Frankland'', Pere', Scruel", Grimbert", 

 and others report only CO2 and H. Baginsky'" on the other 

 hand claims the presence of CH^ as well. It would be interest- 

 ing to determine whether bacterial fermentation ever goes on 

 without the evolution of both CO.^ and H at the same time. 



In examining the action of bacteria on the three sugars 

 used, we note that the gas production in glucose bouillon is 

 always rapid though it may be slow or absent in lactose and 

 saccharose bouillon. Glucose is thus the sugar most easily 

 acted upon. A curious preference is shown by certain species 

 for certain sugars. Thus B. colt produces gas rapidly in lac- 

 tose and slowly or not at all in saccharose bouillon. Fried- 

 lander's bacillus on the other hand, acts vigorously upon 

 saccharose and very slightly upon lactose. The latter is not 

 touched by Proteus vulgaris at all. By pushing such com- 

 parative inquiries still farther and including other carbo-hy- 

 drates, as has been done by most of the authorities cited above 

 from a slightly different point of view, still finer lines of dis- 

 tinction might be drawn. Owing to lack of time I have not 



