STUDY OF ANTISTREPTOCOCCUS SERUM. 105 



The infection caused by this streptococcus, although not varying 

 in general appearance, differs somewhat in details according to the 

 animal species employed. 



Much larger doses are necessary to kill a guinea-pig than are 

 fatal for a rabbit. The minimal intraperitoneal dose for a medium- 

 sized guinea-pig sufficient to cause a generalized infection and 

 death of the animal is generally 0.2 of a cubic centimeter. The results 

 following such an intraperitoneal dose in a normal guinea-pig are 

 as follows: By puncturing the abdominal wall of the animal and 

 withdrawing a little exudate at intervals with a small pointed tube 

 it is easy to follow the course of the infection. 



A fatal dose. — Following the inoculation of the culture the perito- 

 neal fluid is more or less limpid and contains only a small number of 

 cells. This is the period of phagolysis which, as Metchnikoff has 

 shown, regularly follows the introduction of cultures into the 

 peritoneal cavity.* The leucocytes in this exudate, consisting 

 generally of the mononuclear type, with admixtures of a few true 

 eosinophiles and infrequent amphophiles, do not long remain 

 scattered either because they are destroyed, as Metchnikoff is in- 

 clined to believe, or because they adhere to the peritoneal walls, as 

 Durham thinks. 



This period of phagolysis is usually short, particularly when the 

 amount of fluid introduced is inconsiderable, and is followed by the 

 appearance of mononuclear and polynuclear phagocytes. These 

 latter cells appear particularly during the first hours of the phe- 

 nomenon and increase rapidly in number, so as to constitute the 

 majority of cells present. 



The first polynuclears arriving on the scene (say an hour after 

 injection) take up a few streptococci; and a considerable number 

 of the organisms introduced are soon found to be phagocyted. 

 The mononuclears also frequently take up a good many of them. 

 There are, however, among the micro-organisms injected, certain 

 ones which are not engulfed. These latter, to be sure, are very few if 

 the minimal lethal dose is employed and they remain scattered in 

 the fluid in the midst of an increasing number of cells. 



* This phenomenon of phagolysis is very slight if as small an amount as 0.2 of 

 a cubic centimeter of culture is injected; but it becomes more marked if the 

 amount of fluid injected reaches 0.5 to 1 c.c. 



