THE VOGES-PROSKAUER REACTION 



161 



With all other test substances Wittes peptone was used. In- 

 cubation was at 37°C. for seventy-two hours. 



Of the 26 supposedly Voges-Proskauer positive organisms, 

 4 failed to give the reaction in this experiment. Whether this 

 phenomenon is due to the difference in peptone, variation in 

 period of incubation, or loss of physiological function needs to be 

 further investigated. With one of these organisms, it was observed, 

 about eight months ago, that the test for acetyl-methyl-carbinol 

 was negative until the seventh day of incubation. 



In the table below are summarized the results. The cultures 

 are arranged in three groups. One group comprises those 

 strains which, repeated tests have shown, do not form acetyl- 

 methyl-carbinol from glucose, even on long incubation (7 days). 

 Another group contains 22 strains which do form this carbinol 

 from glucose. The third group includes the 4 cultures whose 

 Voges-Proskauer reaction is questionable. 



Correlation between the formation of acetyl-methyl-carbinol in glucose peptone 

 solution and in peptone solution containing other carbohydrates and alcohols 



Practically all strains gave a trace of acetyl-methyl-carbinol 

 with maltose. A very striking fact indicated in the table is 

 that coli-like organisms which do not form acetyl-methyl- 

 carbinol from glucose are characterized by an inability to pro- 

 duce this compound from the other substances tested. In only 



