496 



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



0.05 cm. After several trials a combination of 1 cc. of the cul- 

 ture and 0.5 cc. of a 45 per cent solution of sodium hydroxide 

 was found to produce a deep pink color in about one hour's interval 

 after the addition of the latter. The maximum intensity of the 

 color developed between the first and second hour so that the 

 readings were taken at both intervals. After the latter interval 

 the color started to fade. The use of the Syracuse watch glasses 

 was started in April, 1917. 



Table 2 gives a comparison of the Voges and Proskauer re- 

 actions developing from the same cultures in glucose potassium 

 phosphate broth incubated at 30°C. for five days and at 37.5°C. 

 for two days and in Clemesha's medium incubated for two days 



TABLE 2 



Percentages of 262 methyl red negative cultures giving ■positive Voges and Proskauer 



reactions 



Glucose potassium phosphate broth : 



Five days at 30°C 



Two days at 37.5°C 



Clemesha's medium 2 days at 37.5°C. 



Hours after addition of sodium hydroxide 



76 



82 



73 



85 

 89 



31 

 45 

 65 



49 

 62 

 73 



58 

 67 

 83 



20-25 



37 



65 

 74 



at 37.5°C. The lactose fermenters employed in these tests were 

 derived from Tapir feces, grass, and water samples. 

 From this table it is evident that: 



1. Greater percentages of positive Voges and Proskauer re- 

 actions were obtained in the Syracuse watch glasses (columns 

 headed ''Dishes") than in the test tubes. 



2. Some of the Voges and Proskauer reactions, positive in 

 the tubes at the end of five hours, faded on standing an additional 

 fifteen to twenty hours. 



3. In the case of Clemesha's medium the percentages of posi- 

 tive Voges and Proskauer reactions were 89 and 83, respectively, 

 in the Syracuse watch glasses at the end of two hours and in the 

 test tubes at the end of five hours. With the glucose potassium 

 phosphate medium, at both periods of incubation, the percent- 



