338 



Scientific Proceedings (123). 



lating antibodies in animals treated respectively by the four above- 

 mentioned methods. A series of normal rabbits were divided 

 into four groups of two animals each and immunized by the re- 

 peated introduction of a suspension of Type I pneumococcus 

 (heated for 30 minutes at 6o° C.) by the four above-mentioned 

 routes. In all the animals received 9 injections each, over a 

 period from October 1 to November 17. Special care was taken 

 to maintain the uniformity of the amount of bacterial protein 

 injected in respective series. Ten days after the last injection the 

 blood of all the animals was tested for its bactericidal power, for 

 its opsonic power and for its power to protect mice against infec- 

 tion with virulent culture. 



Bactericidal power was tested by the technique of Heist and 

 Solis-Cohen. 1 Bacterial suspension containing 1,600,000 pneumo- 

 cocci per cubic centimeter was diluted as indicated on the chart 

 below. 



Rabbit No. 



Route of Immunization. 



Dilutions of Bacterial Suspension. 



2:25 



1:125 



1:625 



328 



Intravenous 



+ + 



+ + 



+ + 



329 



Intravenous 



+ 



+ 



+ 



330 



Intratracheal 









33i 



Intratracheal 



+ 







332 



Subcutaneous 



+ + + 



+ + 



+ + 



333 



Subcutaneous 





+ 



+ 



334 



Intrapleural 



+ + 



+ 





335 



Intrapleural 



+ + 





+ 



336 



Normal controls 



+ + + 



+ + + 



+ + + 



337 





+ + 



+ + 



+ + + 



The bactericidal power of the blood is of course inversely pro- 

 portional to the extent of growth. 



Opsonizing power of the respective sera was determined by using 

 mouse leucocytes and was expressed in terms of percentage rela- 

 tion of the number of leucocytes in the state of active phagocytosis 

 to the total number of leucocytes counted. 



1 Heist, George D. and Cohen-Sol is, Solomon, Journal of Immunology, 19 19, 

 iv. No. 4. 



+ + + Very good growth. 

 + + Medium growth. 

 + Poor growth. 

 — No growth. 



