394 BIOLOGY OF PNEUMOCOCCUS 



terfering with the capacity of the animal to dispose of organisms 

 introduced into the blood, taken in connection with the specific ac- 

 tion of serum on the cocci, Wright laid particular stress on the 

 importance of humoral immune elements in bringing about the 

 destruction of invading pneumococci. 



That circulating antibodies and not leucocytes play the domi- 

 nant part in recovery from pneumococcal infection was also the 

 contention of Robertson, Woo, Cheer, and King (1928). 1152 The 

 blood of cats and rabbits surviving experimental pneumococcal in- 

 fection possessed the ability to promote the destruction of highly 

 virulent pneumococci in rabbit serum-leucocyte mixtures, which 

 mixtures in themselves had no growth-inhibitory action. The bac- 

 tericidal action of the serum was associated with a marked in- 

 crease in acquired resistance to infection. In cats, which were 

 studied in greater detail, the pneumococcidal promoting power of 

 the serum as well as the opsonic, agglutinative, and mouse-pro- 

 tective properties, which were found to be type-specific, became 

 demonstrable at the time of recovery, and their appearance in the 

 serum always marked the termination of blood invasion. The ani- 

 mals succumbing to infection failed to develop detectable immune 

 properties in the serum and showed persistent bacteriemia. Ac- 

 cording to the authors, the degree of leucocytosis had no constant 

 relation to the outcome of the disease. 



In two communications, Terrell ( 1930 ) 1385 " 6 presented the results 

 of experiments carried out to determine the changes in humoral 

 immunity occurring during the early stages of experimental pneu- 

 mococcal infection. Using the technique of Robertson and Sia 1144 " 8 

 to determine circulating antibodies, the author, after infecting 

 normal cats and dogs with virulent cultures of Type I and II 

 pneumococci, found that in a generalized and overwhelming infec- 

 tion accompanied by early blood invasion, there was a prompt and 

 rapid decrease in the concentration of native humoral immune 

 bodies, which frequently disappeared entirely by the time of death. 

 Animals surviving a moderately severe, generalized infection 



