UTILIZATION OF PROTEID AND NON-PROTEID NITROGEN 21 



organisms, but it was soon found that the amount of peptone 

 present should not exceed 0.25 per cent. When the peptone was 

 used in higher concentration sHght reductions in the amount of 

 the proteins could not be detected, or at least could not be 

 determined accurately. In the lower dilutions, however, the 

 various degrees of decomposition were easily observed. 



For the autolysis experiments standard peptone solutions were 

 frequently employed for color comparison, while the work on the 

 relation of the growth of different bacteria to proteoses and pep- 

 tones involved the employment of the standard solution only as 

 a check or control for the inoculated flasks. The results are not 

 given in per cent, but are represented in the tables by 0, X, XX, 

 XXX and XXXX. The first of these symbols, 0, indicates no 

 reduction of the proteoses and peptones, as compared with the 

 controls, X a slight decomposition, XX fair, XXX strong, and 

 XXXX complete reduction of these soluble proteins. Besides 

 the ''peptone" the test media often contained other agents, as 

 will be seen in the tables, namely ammonium sulphate, beef 

 extract and glucose. Furthermore, all of the fluids contained 

 0.5 per cent of sodium chloride. 



The results require but little comment. With few exceptions, 

 no disappearance of albumoses and peptones could be noted in 

 flasks which were inoculated with members of the colon-typhoid 

 group of organisms, even after four weeks of incubation. In 

 the flasks showing a reduction of the biuret reaction the appar- 

 ent loss of the soluble proteins was slight, and may be accounted 

 for by other factors than an actual decomposition by the bacteria 

 with which they were inoculated. In all of these experiments 

 the bacterial growths were fairly luxuriant, particularly when 

 the test medium contained beef extract or ammonium sulphate. 

 Even in those instances in which slight reduction of the soluble 

 proteins was recorded, at least two weeks, and as a rule three weeks 

 or more, were required to show the apparent reduction. 



The above experiments are being repeated. Similar tests are 

 also being made with media containing peptone and the ingredi- 

 ents of the Uschinsky medium, with soluble purified casein, or 

 nutrose and with dialyzed proteoses. Thus far results similar 



