396 NATHAN BERMAN AND LEO F. RETTGER 



both glucose and lactose media being inoculated with the colon 

 bacillus, while the experiments with Proteus vulgarus were carried 

 out in lactose broth alone, aside from the plain peptone broth 

 cultures. Only the results showing the behavior of Proteus 

 vulgaris in the glucose media are presented here in tabulated 

 form (table 2), as they are thoroughly representative and well 

 illustrate the influence of buffer action of the phosphate on the 

 decomposition of the peptone in the presence of a fermentable 

 sugar. With one exception, the results differ little from those 

 obtained with Bacillus coli in both the glucose and lactose media, 

 aside from the limited ''peptone" utilization by Bacillus coli 

 under even the most favorable conditions for protein metabolism. 



The striking influence of the buffer reagent, dipotassium phos- 

 phate, on protein metabolism is most marked. The acidity of 

 all of the sugar media increased during the first twenty-four 

 hours. Subsequently the titratable acidity rapidly diminished 

 in the solutions containing the phosphate, while in the other 

 tubes it remained fairly constant. The biuret figures were in 

 harmony with the Sorensen data. The reduction in the amounts 

 of biuret-giving substances in the sugar media containing the 

 phosphate was essentially the same as has been observed in 

 plain peptone broth, the protein completely disappearing in 

 two to three weeks. On the other hand, no reduction was 

 noted in the sugar media to which no di-basic phosphate had 

 been added. The Sorensen value of the phosphate tubes was 

 increased two to three fold, while in the glucose broth, and in 

 the case of Bacillus coli in lactose broth, containing no added 

 phosphate, it remained practically constant. 



The indol tests also indicated that protein metabolism occurred 

 only in the solutions containing the buffer. In no instance was 

 a positive indol test obtained in the glucose peptone broth to 

 which no phosphate had been added. In both of the 0.2 per 

 cent glucose media (with and without the buffer) Bacillus coli 

 completely fermented the sugar, within twenty-four hours, while 

 0.4 per cent glucose was used up entirely only in the medium 

 which contained the phosphate, from which it disappeared 

 within the first twenty-four hours. 



