10 



with three loopfuls, after the exudate had stood in a test tube in the 

 incubator for six hours, contained only 480 colonies. Evidently some of 

 the streptococci were killed in this tube, but the smears show that all of 

 the organisms are in the leucocytes, hence they must have been killed 

 in the leucocytes. 



EXPERIMENTS WITH LEUCOCYTIC EXUDATE IN VIVO. 



In order to determine whether a rabbit is more resistant when in- 

 jected in a pleura containing leucocytic exudate than when injected in the 

 normal pleura, the following experiments were carried out : 



Fig. 3. Photomicrograph x ]50 . Multiplication of streptococci after their 

 ingestion (in vivo) by a guinea-pig's leucocyte, in slightly later stage than Fig- 



ure 2. 



Experiment A. A gray rabbit weighing 1,450 grams was injected 

 into the right pleura with 7 c. c. of aleuronat suspension. Fifteen hours 

 later 2, c. c. of a 4<>hour culture of a virulent streptococcus were injected 

 into this pleura and also into the right pleura of a normal rabbit weigh- 

 ing 1,500 grams. The normal rabbit was found dead in 18 hours, and 

 the one which had been previously injected with aleuronat died 45 hours 

 later. 



Experiment B. A gray rabbit weighing 2,100 grams was injected in 

 the right pleura with 6 c. c. of aleuronat suspension. Eighteen hours 

 later i c. c. of a 24-hour culture of a virulent streptococcus was injected 



