8 



Mr. J. Thompson. Action of 



[Aug. 27, 



In three further experiments, the carbon dioxide and acetic acid only were 

 determined, the following results being obtained : — 



c. d. e. 



Carbon dioxide 2-86 2-36 2-39 grms. 



Acetic acid 1-21 070 0'82 „ 



The molecular ratios CO2/C2H4O2 calculated by the formula x ^ 



44 C2H4U2 



are : — 





a. 



I. 



c. 



d. 



e. 



C 2 H 4 2 



4-25 



4-06 



3-21 



4-62 



3-99 



The action of B. cloacce on malic acid in the presence of oxygen probably 

 goes on in two ways : the one, an oxidation of the acid to carbon dioxide and 

 acetic acid by atmospheric oxygen, and the other, an oxidation accompanied 

 by reduction of a portion of the malic acid to succinic acid. The degree of 

 access of the oxygen during fermentation will thus account for the difference 

 in the proportions of succinic acid formed. 



Assuming that growth in a sufficient supply of oxygen leads to complete 

 oxidation of the malic acid to carbon dioxide and acetic acid, the following 

 equation may be put forward as representing the changes which take place : — 



3C 4 H 6 5 + 50 2 = 2C2H 4 2 + 8C02+5H 2 0. 



This gives a ratio CO2/C2H4O2 of 4 and a respiratory coefficient of 8/5 = T6, 

 the latter being in good agreement with the results of the experiments 

 previously described. In these experiments it is to be noted that a small 

 quantity (10 c.c.) of medium is in contact throughout with a good supply 

 of air, so that oxidation may be considered to be almost complete. If any 

 oxidation were due to the oxygen derived from a second molecule of malic 

 acid, the respiratory coefficient would be increased. On the other hand, 

 oxidation of the acetic acid would decrease the coefficient. The numbers 

 actually found were T67, 1*67, 1-7, 1"7, 1-64 and 1'4. 



V. Contrary to the statement of Eitter (2), it was found that B. cloacce 

 would not grow on ammonium malate in the absence of oxygen. 



VI. Chemical Action of B. cloacae on Citric Acid in the Presence of Oxygen. 



The substances produced from citric acid by B. cloacae in the presence of 

 oxygen were found to be the same as from malic acid. The amount of acetic 

 acid produced is markedly greater in the former case, and the molecular 



