STREPTOCOCCUS HEMOLYTICUS 



197 



per cent glucose broth, lies between Ph 7.5 and 8.1. If the mean 

 of these two exponents be taken, the value, Pn 7.8, represents the 

 optimum hydrogen-ion concentration for growth and acid pro- 

 duction. This corresponds to the optimum found by Fennel 

 and Fisher (1919) for Streptococcus hemolyticus. It is interesting 

 to note that this point corresponds exactly to the optimum estab- 

 hshed for the pneumococcus (see chart) and other pathogenic 

 cocci, and that it is only slightly different from the Ph of human 

 blood. 



TABLE 10 

 Experiment XI 



— No growth; 

 excellent growth. 



;rowth doubtful; + fair growth; ++ good growth; + + + 



Wolf and Harris (1917a) working with Clostridium welchii and C. 

 sporogenes have found that the final hydrogen-ion concentration 

 produced by these organisms in media adjusted to different 

 levels is by no means a constant. By constructing curves to 

 show what they term ''reaction resultants" an orderly relation- 

 ship between the point of initial and final Ph was noted. More- 

 over, in media adjusted within the acid range the character of 

 the "reaction resultant" curve was dependent upon the type of 



