The Mechanism of Pneumococcic Immunity. 213 



128 (1060) 



On the mechanism of pneumococcic immunity. (Preliminary 



note.) 



By Kay J. Kitagawa. (By invitation.) 



[From the Department of Bacteriology and Immunity, Leland 

 Stanford Jr. University.] 



Normal rabbits. — First generation pneumococci injected intra- 

 venously into normal rabbits decrease in number in the circulating 

 blood during the first thirty minutes. The pneumococcic count 

 (plate method) at the end of thirty minutes is usually about 25 

 per cent, of the initial count. After thirty minutes the number 

 either slowly increases or slowly decreases depending upon the 

 dosage and virulence of the organism injected. 



Immune rabbits. — First generation pneumococci injected intra- 

 venously into actively immunized rabbits generally disappear 

 with great rapidity from the circulating blood. By the end of ten 

 minutes the blood is usually sterile. 



Little or no decrease in the pneumococcic count is observed 

 in samples of blood isolated from the general circulation between 

 ligatures placed about a blood vessel. Even at the end of an 

 hour the count in the isolated blood sample may be nearly as 

 great as the initial count at the time the ligatures were closed. 



From this it is evident that the rapid disappearance of the 

 pneumococci from the circulating blood of actively immunized 

 rabbits is not due to a destruction of the pneumococci by the 

 plasma or leucocytes, but to their mechanical removal or destruc- 

 tion by the fixed tissues through which the blood circulates. 



