COLON-AEROGENES GROUP OF BACTERIA 279 



diacetyl is colorless as such, but when brought into contact with 

 a small amount of peptone or other protein material produces 

 the characteristic eosin-like red coloration. 



Walpole (1910) further observed that by passing a current of 

 air through the B. aerogenes culture five to six times as much 

 acetyl-methyl-carbinol is produced as when the culture fluid is 

 left undisturbed. Thompson (1911) found that the chemical 

 action of B. cloacae of Jordan on glucose is practically the same 

 as that of B. aerogenes, in so far as the production of carbinol is 

 concerned. 



The actual correlation of the Voges and Proskauer reaction 

 with the source of the organism and with its other characteristics 

 was the work of Levine (1916). Soon after Rogers and his co- 

 workers announced the definite relationship between the gas 

 ratio, gas volume and the hydrogen ion concentration of the coli 

 and aerogenes types of bacteria, Levine showed that an added 

 correlation could be established with the Voges and Proskauer 

 reaction. He found that bacteria of the aerogenes type con- 

 sistently gave a positive V and P reaction, whereas those which 

 were positive to the methyl red test were regularly V and P 

 negative. 



In the present study an attempt was made to determine : first, 

 the relative value of the three media previously described in 

 this paper, namely the Clark and Lubs' Witte peptone-glucose- 

 phosphate, the synthetic phthalate-glucose-phosphate, and the 

 Difco peptone-glucose-phosphate medium, for the study of the 

 Voges and Proskauer reaction; second, the most favorable period 

 of incubation; and third, a rapid and practical method for carry- 

 ing out the test. 



In the original method of applying the Voges and Proskauer 

 test the alkaline fluid was exposed to the atmosphere for twenty- 

 four hours or longer at room temperature. Walpole tried to 

 hasten the oxidation process by passing a current of air through 

 the medium, while West, following "Test No. 1" of Revas, boiled 

 his cultures. More recently Levine introduced various oxidizing 

 agents, and Bunker, Tucker and Green (1918) advocated the use 

 of Syracuse watch glasses. These methods, and particularly 

 the last two, appear to us too uncertain and too laborious. 



THE JOURNAL OP BACTERIOLOGY, VOL. T, NO. 3 



