104 IMMUNE SERA 



inter-bodies, while the rest of the bacterial receptors 

 are occupied by uncomplemented (hence inactive) 

 inter-bodies. As already stated, however, the 

 vitality of such a bacterium is not necessarily 

 destroyed. 



D II represents the last conceivable case. It i^ 

 assumed that the " completion " of the inter-body 

 has resulted in a diminution of the latter 's affinity 

 for the bacterial receptor. In this case primarily 

 only the uncomplemented inter-bodies will com- 

 bine with the bacterial receptors, while the free 

 fluid will contain complemented inter-bodies. 



In cases C II and D II, therefore, the excess of 

 inter-body exerts a deflecting action on ike complement, 

 thus diminishing the end results. 



It is difficult to say to what extent " deflection of 

 complement " really occurs in the experiments 

 referred to above. Studies by Buxton, Gay, and 

 others show that deflection of complement will not 

 always explain the phenomenon, and that in these 

 instances other factors must be responsible for the 

 paradoxical results. 



Practical Value of Injections of Anti-Bacterial 

 Sera. We use the term " antibacterial" advisedly, 

 because, after all, when we immunize an animal 

 against a certain bacterium we do not produce 

 merely a bactericidal serum, but one which con- 

 tains agglutinins, precipitins, opsonins, and per- 

 haps still other antibodies as well. The use of 



