246 INFECTION AND IMMUNITY 



Fixation of the Complement. — Bordet and Gengou ' in 1901, devised 

 an ingenious method of experimentation by which even very small 

 quantities of any given immune body (amboceptor) can be demon- 

 strated in serum. The term "fixation of complement," by which their 

 method of investigation is now generally known, explains itself, as the 

 steps of experimentation are followed. They prepared the following 

 mixtures: 



(a) (b) 



Bacteriolytic amboceptor Nonnal serum, heated 



{Plague immune serum, heated) 



+ + 



Plague emulsion Plague emulsion 



+ + 



Complement Complement 



{Fresh normal serum) {Fresh normal serum) 



To both of these after five hours was added 

 Hemolytic amboceptor 

 {Heated hemolytic serum) 

 + 

 Red blood cells 

 Results: 



(a) showed no hemolysis. 



(b) showed hemolysis +. 



The conclusion to be drawn from this was that in (a) the presence 

 of immune body had led to absorption of all the complement. In (b) , 

 there being no bacteriolytic immune body to sensitize the bacteria 

 and enable them to absorb complement, the latter substance was 

 left free to activate the subsequently added hemolytic ambocep- 

 tors. The Bordet-Gengou phenomenon has been extensively used 

 by Wassermann and Bruck,^ Neisser and Sachs,^ and others to demon- 

 strate the presence of immune bodies in various sera. (See p. 262.) 



It should be noted that this method, if valid, must presuppose 

 the identity of the hemolytic and bactericidal complement in the 

 activating serum. 



Complement fixation will be more extensively discussed in the 

 section dealing with the Wassermann reaction. 



1 Bordet et Oengou, Ann. de I'inst. Pasteur, 1901. 

 » Wassermann und Brack, Med. Klin., 1905. 



2 Neisser und Sachs, Berl. klin. Woch., xKv, 1905, and i, 1906. 



