LYSINS, AGGLUTININS, PRECIPITINS, ETC. 247 



because of the wide discussion it has aroused. In the light of our 

 present knowledge concerning the relations between antigen, ambo- 

 ceptor, and complement, their conception is obviously erroneous. 



Fixation of the Complement. Bordet and Gengou 1 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 Normal 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 amboceptors. The 

 Bordet-Gengou phenomenon has been extensively used by Wassermann 

 and Bruck, 2 Neisser and Sachs, 3 and others to demonstrate 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 sec- 

 tion dealing with the Wassermann reaction. 



1 Bordet et Gengou, Ann. de Tinst. Pasteur, 1901. 



2 Wassermann und Bruck, Med. Klin., 1905. 



8 Neisser und Sachs, Berl. klin. Woch., xliv, 1905. and i, 1906. 



