390 NATHAN BERMAN AND LEO F. RETTGER 



duction of ammonia. Kendall, Day and Walker (1915) failed to 

 demonstrate the formation of an active proteolytic enzyme by 

 Proteus vulgaris in either glucose broth or glucose gelatin. The 

 enzyme produced in carbohydrate-free medium, and freed from 

 the bacteria by filtration, liquefied glucose gelatin as readily as 

 plain gelatin, however. According to these workers, the pres- 

 ence of sugar delays the formation of the proteolytic enzyme 

 until the carbohydrate has been used up. Jones (1916) also 

 concluded that the failure of P. vulgaris to decompose the protein 

 in a glucose gelatin medium is due to the absence of enzyme 

 formation. He states that acidity plays no part in influencing 

 the behavior of the organism. Sears (1916) concluded that glu- 

 cose had a sparing action on nitrogen metabolism. Kligler 

 (1916) offers a similar explanation, and states that the pro- 

 teolytic enzyme of Proteus vulgaris is not formed in the early 

 stages of carbohydrate metabolism. 



Other investigators observed the influence of sugar on indol 

 production. Baginski (1889) reported that he was unable to 

 obtain an indol test in the presence of lactose. P6r6 (1892) con- 

 cluded that a positive test for indol indicated a complete dis- 

 appearance of sugar. He affirms that carbohydrates are more 

 available than protein, and are utilized first. Distaso- (1913) 

 showed that indol formation may occur in a carbohydrate 

 medium containing free tryptophan. B. coli was employed as 

 the test organism. According to this writer the more available 

 substances in a medium are used first, and as a consequence 

 indol is not formed in ordinary sugar media. De Graaff (1909) 

 had previously observed the inhibiting effect of glucose on indol 

 production. 



Rougentzoff (1913) claimed that the carbohydrates, glucose, 

 fructose and lactose, and the alcohol mannite, which are fer- 

 mented rapidly by Bacillus coli, inhibit indol production. Indol 

 was formed, however, in media containing maltose, sucrose and 

 dulcite. The titratable acidity was taken as an index of the ra- 

 pidity with which different saccharides were decomposed. Fischer 

 (1915) reported somewhat different results. He observed that 

 glucose alone inhibited indol formation, while lactose, maltose. 



