190 



LAURENCE F. FOSTER 



sequently this procedure was abandoned. Curves of acid 

 formation are shown in figure 6. At each point on the curves 

 the number of organisms, expressed as milHons per cubic miUi- 

 meter, is shown. Examination of figure 6 shows that the two 

 curves are analogous to those of experiment VIII (fig. 5), though 

 the lag registered by the glucose-serum culture is of less duration. 

 The numbers of viable organisms as shown by plate counts bear 

 out the assumption that the earlier rise in acidity in a glucose- 

 serum broth is associated with a corresponding period of multi- 

 plication at a rapid rate. 



Experiment X. The relation of the initial Pn of glucose-broth to 

 the rate of acid formation by Streptococcus hemolyticus 



Beef infusion broth was adjusted to various Ph levels, divided 

 into six portions, and sterilized in the usual manner. After 

 adding the proper amount of glucose, the tubes, containing 20 



TABLE 8 

 Experiment X 



cc. of medium each, were incubated to insure sterility. The 

 inoculum consisted of 1.33 cc. of an eighteen-hour second-genera- 

 tion culture in 1 per cent glucose broth. A massive inoculum 

 was employed to complete the experiment within the fourteen 

 hours. The results are found in table 8. 



Reference to figure 7 reveals an interesting point, namely, 

 that the cultures of initial Ph 7.0, 7.5, 8.1 reached practically 

 the same level of hydrogen-ion concentration after eight hours 



