CHANGES PRODUCED BY A SAPROPHYTIC ANAEROBE 



399 



In our work the irregularities in the total amounts of the various 

 gases were due to the fact that the amounts of gas were deter- 

 mined from the bottles which remained in the incubator for the 

 longest time, and only part of these were analyzed at each period. 

 An examination of the gas volumes as mentioned on page 398 

 will explain this ^'ariation. 



In all cases there was considerable residual gas which could 

 not be accounted for by the amount of air remaining in the bot- 

 tles, since these were exhausted to nearly the theoretical vacuum. 

 No doubt this was nitrogen gas which had been hberated from the 

 medium. In no case was there more than a trace of CO2 formed 

 by combustion with oxygen. For tliis reason we may say that 

 no methane or ethane were formed by these organisms. 



It will be noticed from table 4, that gas is produced slowly in 

 all cases except in presence of glucose and glj^cerol. These sub- 

 stances are easily fermented and all cultures produce gas in large 

 amounts. In the presence of lactose, there is about the same 

 action as upon peptone solution except that slightlj^ more hydro- 

 gen is produced in some cases, and the growth is slightly more 

 vigorous. A sUght action upon the lactose may have occurred 

 in the latter case. 



Ammonia. The ammonia production is not always in inverse 

 ratio to the production of gas and acid by these organisms. The 

 cultures showing larger amounts of gas show smaller amounts of 

 ammonia in some cases but not in all. Glucose reduced the 

 ammonia production for this organism. In the presence of lac- 

 tose, mannitol and sucrose there was practically no reduction in 

 the ammonia formation. In the presence of saUcin there was a 

 decrease, and the organism is to be considered a salicin fermenting 

 type. Peptone solution plus glycerol shows much less ammonia 



