170 



LAURENCE F. FOSTER 



Experiment II. The effect of vanjing concentrations of glucose 



upon the final hydrogen-ion co7icentration of Streptococcus 



hemolyticus 



Ten cubic centimeter amounts of beef infusion broth contain- 

 ing concentrations of glucose varying from 0.10 to 1 per cent 

 were inoculated with 0.4 cc. of an eighteen-hour culture of 

 Streptococcus hemolyticus in 1 per cent glucose broth and incu- 

 bated for three days to insure the completion of the fermenta- 

 tion. Ph readings were then made. The results are shown in 

 table 2. 



TABLE 2 

 Experimen' II 



In (1) which was adjusted to an initial Ph of 6.9 the final Ph 

 was attained in a glucose concentration of 0.2 per cent, whereas 

 in (2) which was adjusted to an initial Ph of 7.35 the final value 

 was not shown in the 0.2 per cent glucose but did appear in the 

 0.3 per cent tube. As would be expected the minimum concen- 

 tration of glucose needed to give the characteristic final Ph is 

 dependent upon the initial Ph of the broth. Amounts of glucose 

 over this minimum concentration have no further effect upon 

 the level of the final hydrogen-ion concentration. 



Experiment III. The influence of a buffer salt upon the final 



hydrogen-ion concentration of Streptococcus hemolyticus in 



broth containing varying concentrations of glucose 



Bacto beef broth was adjusted and distributed in twelve 

 lots in flasks. After autoclaving, the requisite amounts of 

 glucose and di-potassium phosphate, K2HPO4, were added in 

 the form of sterile 10 per cent solutions bringing the total volume 

 of material in each flask to 25 cc. Following twenty-four 



