PLAN OF INVEST I Cr AT ION. 



The investigation of this problem has been done almost 

 entirely in vitro because there is no thoroughly dependable 

 method of controlling results when the experiments are under- 

 taken in vivo . Wright's (16) work has established that even 

 slight changes in the phagocytic activity of the animal can 

 be demonstrated by in vitro methods, so that if there is a 

 decline in opsonic power sufficient to account, even in part, 

 for the bacterial invasion occurring in terminal infections, 

 there could be no difficulty in demonstrating that decrease in 

 effectiveness by the methods employed in this investigation. 

 The bacteria used were those most commonly associated with 

 terminal infections — a pyogenic coccus, Staphylococcus , 

 aureus . recently isolated from a case of human f urunculosis, 

 and a gram negative bacillus, B. coli communis . In addition, 

 two other organisms were commonly used, 3, bronchi gepticus 

 was selected because it is readily taken up in large numbers, 

 making possible dependable counts in weakly pliagocytic cells, 

 while 3. typhosu s resisting engulfment to considerable extent, 

 permits reliable enumeration when phagocytosis with other bac- 

 teria is so vigorous that even a depressed phagocytic capacity 

 is quite sufficient to fill the cells beyond counting. 7;hen- 

 ever possible the specific infecting organism was included 

 in each series of experiments. 



(5) 



