STUDY OF ANTISTREPTOCOCCUS SERUM. 121 



inoculated in such a fluid, no development takes place and the next 

 day the fluid is found to be sterile. 



This serous fluid loses its bactericidal power when heated for a 

 few moments to 60 degrees, and in such heated fluid the strepto- 

 coccus grows in long chains of rather small organisms. As the 

 fluid part of rich leucocytic exudate is bactericidal in vitro, the 

 question arises as to whether it is as much so in the animal body. 

 Experiment gives a negative reply to this question. When strepto- 

 cocci are injected into the rabbit peritoneal cavity containing many 

 leucocytes the organisms are not engulfed, but develop well. If 

 a little of this exudate is removed when the streptococci are not yet 

 very numerous, and placed in the incubator, the growth stops; at 

 times the fluid becomes quite sterile after 2 or 3 days and at 

 other times the organism finally grows out again after a delay of 

 24 hours or so. 



Experiments performed in vitro with leucocytic exudates can- 

 not be accepted offhand without many reservations as necessarily 

 corresponding to the conditions of similar experiments in the 

 animal body. 



2. THE ACTION OF THE SERUM IN THE ANIMAL BODY. 

 INTRAPERITONEAL INJECTION. 



Let us now consider the phenomenon which takes place in rabbits 

 that have received a preventive injection of serum and are sub- 

 sequently inoculated with the steptococcus. We shall consider 

 first an instance in which the serum is injected subcutaneously 

 24 hours before the culture is injected intraperitoneally. 



The study of the struggle between the cells .and the bacterial 

 culture in the peritoneal cavity is extremely instructive as, by 

 extracting at intervals a little peritoneal exudate with a capillary 

 tube, the course of the infection may be followed step by step. 



The exudate is homogeneous, that is to say, throughout the 

 peritoneal cavity it has an identical constitution in so far as the 

 number, quality, and appearance of cells and bacteria is concerned. 

 The subcutaneous exudate, on the contrary, frequently differs even 

 in adjacent regions, either in the amount of fluid or in the number 

 and condition of cells and bacteria. 



It is possible to produce artificial variations in the number of 



