REACTIONS DEPENDING UPON COMPLEMENT FIXATION 271 



the various components takes place according to units, it is clear 

 that if ten units of antigen, for example, were to combine with ten 

 units of the corresponding antibody, and if ten units of complement 

 were absorbed, then upon the subsequent addition of ten units of 

 corpuscles and ten units of hemolytic amboceptor, no hemolysis 

 whatever could take place. 



If no antibody corresponding to the antigen were present, the 

 ten units of complement would remain free, and could then combine 

 with the ten units of the hemolytic amboceptor, in which case 

 complete hemolysis of the ten units of red cells would take place. 

 Between these two extremes, various grades of hemolysis are, of 

 course, possible, according to the quantity of antibody that is present. 



This reaction, like the agglutination reaction and the Pfeiffer reac- 

 tion, can be used both for the purpose of identifying a given organism, 

 as also for demonstrating the presence or absence of certain ambocep- 

 tors in the blood serum. The recognition of this fact led to the dis- 

 covery that in syphilis, antibodies appear in the serum which are dif- 

 ferent from the common bacteriolytic amboceptors, in so far as they 

 will combine with substances that are normal constituents of the body, 

 i. e., certain lipoids. Between the latter and the corresponding syphi- 

 litic antibody, however, an analogous reaction takes place, as between 

 bacteria and their amboceptors, in consequence of which complement 

 is absorbed, so that the same principle can be utilized in the diagnosis 

 of syphilitic infections as well. Applied to this end, the reaction 

 is spoken of as the Wassermann reaction, as Wassermann was the 

 first to purposely employ the principle as originally understood, to 

 the diagnosis of the infection in question. The discovery of this 

 reaction must rank as one of the most important in the history of 

 medicine, and in its absence the triumphs of Ehrlich's salvarsan 

 could never have been achieved. Its employment, as a matter of 

 fact, forms the basis of the modern treatment of syphilis, and serves 

 as the most delicate indicator of the resultant changes which lead 

 to the recovery of the patient, besides being the most delicate method 

 that we possess for the diagnosis of latent syphilitic lesions. 



The Wassermann Reaction. When Wassermann first applied the 

 principle of complement fixation to the study of syphilitic patients 

 his idea was that antibodies of amboceptor character might be 

 present in the blood serum of such individuals, in which case it should 

 be possible to demonstrate these by bringing them together with 



