THE HEMOLYTIC REACTION 



297 



corpuscles which have been " sensitized" by their union with 

 the antibodies. Such destruction is not possible until the 

 complement is boiind by means of the intermediary body with 

 the other object — the blood corpuscle; neither is such 

 destruction possible when complement is, as we just §aw, 

 absent or rendered inert by heat or otherwise. In brief, 

 we have here a "system" the integers of which must all 

 be present and in appropriate adjustment before the desired 

 reaction occurs. The several factors and the reaction may be 

 for convenience of visualization graphically represented, thus: 



Fig. 55 



= Complement 



= Immune body 



= Immune body 



= Antigen 



= Immune body 



Factors present in the serum of ths immune 



animal. 

 No reaction, as antigen is absent. 



Fig. 56 



Factor present in heated immune serum. 

 No reaction, as both complement and 

 antigen are lacking. 



Fig. 57 



Factors present in heated immune serum 

 to which antigen has been added. No 

 reaction, as complement has been de- 

 stroyed by the heating. 



