STUDY OF ANTISTREPTOCOCCIC SERUM. 123 



the vaccinated animal, a peritoneal infection in such an animal 

 may last much longer than in a control, without leading to a 

 septicemia. This is the point of importance to us for the moment. 



A. Young cultures. — What happens to virulent streptococci 

 in a young, 24-hour culture when injected into the peritoneum of 

 a rabbit containing many leucocytes owing to a previous injection 

 of 10 c.c. of serum subcutaneously and 6 c.c. of bouillon intraperi- 

 toneally? There are two distinct conditions to be considered. 



First: — The number of bacteria injected may be very few, less 

 than 0.5 of a cubic centimeter of culture; let us take, for example, 

 0.1 of a cubic centimeter. Under these conditions the number of 

 bacteria in the peritoneal cavity is relatively small in proportion 

 to the number of cells, so that they are frequently difficult to find 

 in stained preparations. Under these conditions the culture is 

 rapidly and, as far as may be estimated, completely engulfed. For 

 example, after an hour or two no free cocci are found ; when stained 

 with boracic carmin followed by Gram they are seen to have be- 

 come the prey of cells. As a result, no extracellular development 

 of bacteria takes place under these conditions and the animal gets well. 

 In a control animal that has received an intraperitoneal injection 

 of bouillon but no protective serum a very distinct phagocytosis is 

 generally found if small doses of bacteria are injected; free bacteria 

 are only exceptionally found in such preparations. A multiplica- 

 tion, nevertheless, takes place, and within three or four hours 

 numerous cocci with an intense negative chemiotactic influence 

 are found. Such an animal usually dies within twelve hours 

 with the ordinary symptoms occurring in normal animals as 

 already described. 



Second : — The results are quite different if instead of a very small 

 amount of culture, that is 0.1 of a cubic centimeter, a dose of 0.5 of a 

 cubic centimeter or slightly more is given. Under these conditions* 



* We may mention that when 0.5 of a cubic centimeter of a culture is injected 

 into a peritoneum prepared by bouillon the number of streptococci at first in the 

 exudate is very small in proportion to the number of cells. Notwithstanding this 

 fact reproduction occurs and as we shall see presently the animal is saved only by 

 a delayed phagocytosis. 



Denys and Leclef (La Cellule, 1895) made a mixture of normal rabbit leucocytes 

 and preventive serum in vitro. When they injected this mixture with the strep- 

 tococcus they found there was a distinct inhibition in the growth of their culture 

 owing to an abundant initial phagocytosis, although the organism grows rapidly 



