STUDY OF ANTISTREPTOCOCCUS SERUM. 125 



of bacteria relatively large in proportion to the amount of serum 

 employed (for example, a rabbit may be given 6 c.c. of bouillon 

 intraperitoneally and the next day 1 c.c. of culture plus 5 c.c. of 

 serum; a delayed and complete phagocytosis occurs about 25 hours 

 later). 



Delayed phagocytosis may also occur in animals that have simply 

 received serum subcutaneously without any preparation of the 

 peritoneum. But under these conditions the dose of bacteria in- 

 jected must be considerably less. In rabbits protected by serum 

 without previous intraperitoneal preparation by bouillon, an intra- 

 peritoneal injection is much more dangerous than a subcutaneous 

 one and more harmful still if the culture used is young and rapidly 

 growing. Even in a vaccinated animal the inoculated strepto- 

 cocci find a very suitable culture medium in the limpid exudate;* 

 when leucocytes finally come up in considerable numbers they 

 meet with a large number of bacteria. 



In rabbits immunized by serum, in whose peritoneal cavity a 

 delayed phagocytosis occurs, the number of phagocytes gradually 

 becomes considerable. In the first hours, however, this influx of 

 leucocytes is no more marked than in normal rabbits. 



Intraperitoneal injection of filtered culture fluid causes an abun- 

 dant influx of leucocytes both in normal and in treated rabbits. 

 When week-old cultures are used or dead or attenuated cocci, 

 similar results occur in a normal rabbit. 



B. Old cultures. Part of the danger from injection of young 

 cultures lies in the extreme rapidity of their increase before the 

 phagocytes arrive. If streptococci that do not show active repro- 

 duction for several hours are used, a delayed phagocytosis occurs 

 much more readily even if the serum is injected after the bacteria. 

 A brief resume of such an experiment follows: Two normal rab- 

 bits received each an intraperitoneal injection of 8 c.c. of a four- 

 day-old culture on ascites bouillon. Six hours later the phagocytes 

 had become very numerous and the bacteria injected were engulfed 

 (old streptococci, as we have already seen, are easily phagocyted). 



* We have never found a disappearance of bacteria, as noted by Denys and 

 Leclef following inoculation of streptococcus into the pleura of vaccinated 

 rabbits, after injecting a small dose of streptococcus intraperitoneally in a treated 

 rabbit. 



