STUDY OF ANTISTREPTOCOCCIC SERUM. 109 



any free bacteria in its peritoneal exudate and that has apparently- 

 returned to normal condition becomes sick again and undergoes 

 a new streptococcus infection. Under these conditions the strepto- 

 cocci found in the peritoneal exudate are of a peculiar form. 



They often occur in short chains with beaclings of unequal diame- 

 ter ; chains are also found here and there of extraordinary length and 

 surrounded by a distinct and well-marked areola differing consider- 

 ably from the one that ordinarily encloses the streptococcus. The 

 chromogenic substance in certain of these chains is a line of nearly 

 regular granulations as is usual in the streptococci, but in other larger 

 chains, the chromogenic substance appears to be more indefinite 

 and at intervals shows indefinitely walled off and poorly stained 

 sac-like dilatations. We repeat that these cases of fatal relapse in 

 apparently cured guinea-pigs occur only rarely and at certain definite 

 stages of the infection. It is probable that the culture that brings 

 about these delayed reinfections is possessed of peculiar qualities 

 of resistance not ordinarily present. 



Larger doses (0.5 to 2 c.c.) are necessary when injected subcutan- 

 eously to cause a fatal infection in a guinea-pig. 



B. Streptococcus Infection in the Rabbit. 



As we have just seen, a dose of about 0.2 of a c.c. is the minimal 

 amount of bacteria necessary to produce a fatal peritonitis in the 

 guinea-pig. This is an infinitely larger amount than is necessary 

 to cause death in the peritoneal cavity of a normal rabbit. The 

 streptococcus finds a very favorable culture medium in the clear 

 peritoneal fluid of this animal which contains only few leucocytes. 

 The streptococci injected into the rabbit are usually scattered and 

 within half an hour become surrounded by an areola not ordinarily 

 present. It is evident that the production of this areola is due to 

 the activity of the bacterial secretions, as its color changes as the 

 infection proceeds. 



Shortly after inoculation the areola is seen as a distinctly out- 

 lined zone which does not color with Kiihne's blue and consequently 

 appears whitish against a bluish background. In one and a half 

 to two hours it begins to take a pale violet or pink color that sub- 

 sequently becomes darker. 



The original injected streptococci may take on this areola, but 



