BACTERICIDAL PROPERTIES OF BLOOD SERUM 159 



know to exist in many cases. Thus the blood serum of goats may 

 normally often contain hemolysins against rabbit corpuscles. Is it 

 not reasonable to suppose that possibly these may furnish the point 

 of attachment and the source of further antibody production when 

 rabbit cells are injected into goats? In criticism of Ehrlich's as- 

 sumption of the mode of action of heat-stable lytic antibody, Bordet 

 very justly maintains that no proof whatever exists of the "ambo- 

 ceptor" nature of this substance. All that is certain is that the 

 stable substance must unite with the antigen before the alexin or 

 complement can exert its action upon it or be fixed by it. There is 

 no entirely valid proof of 

 the existence in this anti- 

 body of a "complemento- 

 phile" and a "cytophile" 

 group, and no satisfactory 

 instance has been observed 

 in which alexin has united 

 w i t h a heat-stable anti- 

 body which has not previ- 

 ously been united with an 

 antigen. 55 All that has 

 been shown is that the an- SCHEMATIC BEPRESENTATION OF BORDET 's VIEW 

 .-i .,1 . , CONCERNING THE INABILITY OF COMPLEMENT 



tigen, together witn its T0 UNITE WITH EITHER ANTIGEN OR SEN- 



specific antibody, forms a SITIZER ALONE AND ITS ABILITY TO BE 



pom-nW whiph haq an FIXED BY THE COMPLEX FORMED WHEN 



,ompiex w n i en THE ANTIGEN IS SENSITIZED< 



avidity for alexin, a com- Compare this figure with that representing 

 plex which IS endowed Ehrlich 's conception of the same process, 



with properties of absorp- 

 tion for complement which neither of its constituents alone possesses. " 

 Bordet speaks of the "amboceptors," therefore, as "sensitizers," 

 meaning by this that the antigen, by union with its antibody, is sensi- 

 tized to the action of the alexin. The term "sensitizers" in no way, 

 therefore, implies a preconceived notion, experimentally unproved, 

 of the mode of action or structure of the sensitizer. Since we have 

 graphically explained Ehrlich's opinions, a similar diagrammatic 

 representation may be permitted of Borders opinion of the same 

 process of union of antigen and heat-stable antibody with the conse- 

 quent development of alexin-nxing property. 



In this diagram the ability to absorb or unite with complement 

 becomes evident only after a complex has been formed by the union 

 of the two elements, antigen and antibody. The diagram must not 

 be assumed to mean that the notch into which the complement fits 

 symbolized necessarily an "atom group," but merely expresses the 

 idea of "ability to absorb alexin," not assuming that this ability is 



55 Refer also to the discussion of the conglutinins at the end of this 

 chapter. 



