CHANGES PRODUCED BY A SAPROPHYTIC ANAEROBE 401 



total amount of volatile acid, and in most instances some change 

 in the fractionation constant from day to day. With peptone 

 alone, there was little change, but with glucose, salicin, glycerol, 

 and soluble starch, there was an increase, while mannitol caused 

 a decrease. These differences were constant and are probably 

 due to a sUght difference in the fermentation reaction which 

 occurred in these cultures at different ages. The increase in the 

 amount of acid obtained in the first fractions would indicate an 

 increase in the higher acids; a decrease in the amount of acid 

 obtained in the first fractions would indicate an increase in the 

 lower acids over those originally present. 



Less acid was produced in the presence of glycerol and soluble 

 starch than was produced from peptone alone. Apparently the 

 gas and acid production are not always related in the fermenta- 

 tion of the various carbohydrates. This is shown to be especially 

 true of glycerol and soluble starch in which there are very large 

 amounts of gas and only small amounts of acid formed. The 

 distillation curves for glucose, glycerol and inulin indicate the 

 presence of an acid of low molecular weight, probablj^ acetic acid; 

 while curves obtained from starch indicate large amounts of acids 

 of high molecular weight, probably butyric. Usually the same 

 tjT^e of curve was obtained throughout the entire incubation 

 period, indicating that the difference in the gas ratio is not closely 

 correlated to the production of different kinds of acid. Ap- 

 parently the CO2 in the later stages of fermentation comes from 

 the amino-acids present and not from the carbohydrates. 



CONCLUSIONS 



1. We have described a method adapted for the quantitative 

 stud J' of the decomposition products formed by anaerobic bacteria. 



2. The method described has been found very satisfactory for 

 the cultivation of anaerobic bacteria. It has also proven very 

 satisfactory as a means of measuring the amount and kind of gas 

 produced. 



3. The objection to the use of such an apparatus is that it does 

 not give the anaerobes an oxygen tension which might be more 

 favorable to their development. Even the "obligate" anaerobes 



