L32 STUDIES IN IMMUNITY. 



tive scrum. Roth these rabbits have received, (hen. ill the same 

 regioo the same amounts of bacteria and of serum, they differ, in 

 that one has received both substances separately and the oilier 

 received them at the same time. 



Rabbit R. that received preventive serum plus bacteria subjected 

 to it. not only survives longer, but shows the most complete and 

 accelerated phagocytosis. Neither rabbit recovers, as the amount 

 of bacteria given was purposely too large for the dose of serum, 

 but both live longer than the control. In correspondence with 

 the greater rapidity of phagocytosis in rabbit B the total develop- 

 ment of streptococci has remained distinctly more restricted : before 

 phagocytosis occurs the peculiarities already noted in the bacteria 

 are shown more clearly. 



This experiment, which we have repeated a number of times, 

 gives the same results uniformly. The same results are also ob- 

 served in experimenting on rabbits that have not been previously 

 prepared by means of bouillon. 



It is to be noted, how T ever, that the differences between the two 

 rabbits in the experiment cited are only relative differences. In 

 both animals phagocytosis is delayed, but it appears more readily in 

 the one than in the other. At the beginning of the experiment, dur- 

 ing the first hours, however, the phenomena are similar and the bac- 

 terial growth goes on actively in both. A previous contact between 

 the bacterium and the serum in vitro may favor a cure, but even pro- 

 longed contact with the serum apparently causes no modification in 

 the micro-organism evident after its injection into the animal. 



IV. Intravenous, Intraocular and Subcutaneous Inocu- 

 lation of the Streptococcus in Rabbits Treated by 

 Serum. 



We have already seen that a dose of 0.1 to 0.25 of a cubic cen- 

 timeter of streptococcus culture injected intravenously in animals 

 vaccinated by serum does not increase to any great extent in the 

 body. It is evident, however, that the injected bacteria live, as the 

 animal dies in 2 to 4 days. At autopsy few bacteria are found in 

 the blood, but more are present in the liver, spleen, bone marrow 

 and particularly the lung. 



If a small number of bacteria are injected in the first place, it is 



