STREPTOCOCCUS HEMOLYTICUS 



185 



the sixth and twelfth hours of incubation, provided the inoc- 

 ulum be taken from an eighteen-hour parent culture. If it be 

 assumed that during this interval the organisms are growing 

 rapidly and that their metabolic activities are at a maximum it 

 would be anticipated that transplantation of organisms during 

 this period to a favorable medium would result in resumption of 

 growth and metabolism with a minimum of lag. The close 

 parallelism in the curves of (1) and (2) bears out this supposition. 

 That the organisms decrease progressively in vitality with the 

 lengthening of their period of contact with the products of their 

 own metabolism is brought out in the curves of (3) and (4). 



TABLE 6 

 Experiment VII 



Here are seen more prolonged lag periods, indicating that the 

 organisms required more time to recover from the injury sus- 

 tained in the previous environment. The injury, however, 

 appears to be only temporary for in all cases acid production is 

 seen to proceed at practically the same rate following the onset 

 of the maximum period. The entire absence of lag in acid 

 production has never been observed with the streptococcus. 



Experiment VIII. The rates of acid formation of Streptococcus 

 hemolyticus in glucose broth and in glucose-serum broth 



Forty cubic centimeter portions of infusion broth (initial Ph 

 7.20) containing (1) 1 per cent glucose, and (2) 1 per cent glucose 

 plus 5 per cent horse serum were inoculated with 1.6 cc. of an 

 eighteen-hour glucose broth culture and incubated at 37°. 

 Determinations of hydrogen-ion concentration were made at 



