FIXATION OF COMPLEMENT 



299 



hand, and to identify, on the other hand, antigens whose 

 true nature may only be suspected. 



The important points brought out in their fundamental 

 experiment are: that complement is not specific in its 

 affinities and that when once fixed by an antibody to an 

 antigen the union is not dissociable. The experimental pro- 

 cedures necessary to this demonstration consisted in two series 

 of mixtures one in which antibody, its antigen and comple- 



FIG. 59 

 SERIES I. 



Plague antigen. 



Plague amboceptor. 



= Complement. 



The three factors 

 united after a 

 time. 



FIG. 60 

 SERIES II. 



Plague antigen. 



Non-specific amboceptor 

 of normal serum. 



= Complement. 



Only two necessary fac- 

 tors present; no union 

 possible. 



Washed corpuscles and inactivated hemolytic immune serum now added to 

 each series. 



ment were together, the other identical in its ingredients save 

 for the absence of antibodies specific for the antigen used. 

 Figs. 59 and 60. It is obvious that in the first mixture all 

 factors necessary to the saturation of the haptophores of 

 the amboceptor were present therefore, complement, being 

 one of these factors was bound by the amboceptor to the 

 antigen. In the other mixture this was not possible as there 

 were no amboceptors specific for the antigen in it. But to 



