498 



G, C. BUNKER, E. J. TUCKER AND H. W. GREEN 



two hours) than those inoculated into glucose potassium phos- 

 phate and incubated at 30°C. for five days and 37.5°C. for two 

 days, the respective percentages being 89, 73 and 85. The data 

 included in table 3 and other tests not included in this article 

 show that glucose potassium phosphate broth incubated at 30°C. 

 for forty-eight hours is superior to the same medium, and also 

 to Clemesha's medium, when incubated two days at 37.5°C. for 

 yielding positive Voges and Proskauer reactions. 



TABLE 3 



Bacto-peptone furnished by the Digestive Ferments Company 

 has been used entirely in the media mentioned in this article. 

 Due to delay in obtaining other brands of peptone a comparative 

 study could not be made in time to be included in this paper but 

 the results will be presented later in connection with other 

 factors influencing this reaction. 



CONCLUSIONS 



The use of 0.5 cc. of a 45 per cent solution of sodium hydroxide, 

 Syracuse watch glasses, and 1 cc. of the culture results in the 

 development of a greater number of positive Voges and Proskauer 

 reactions in a shorter interval of time than the method given 

 in the latest (1917) edition of "Standard Methods of Water 

 Analysis." 



An incubation period of two days at 30°C. is recommended in 

 place of that of five days in order to obtain the maximum num- 

 ber of positive Voges and Proskauser reactions from glucose 

 potassium phosphate broth. In order to avoid separate cul- 

 tures for this test 1 cc. portions may be withdrawn from those 

 incubated for the methyl red test. 



