304 IMMUNOLOGICAL METHODS OF DIAGNOSIS 



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 ambo- 

 ceptor 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 com- 

 bine 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 

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

 organism as also for demonstrating the presence or absence of certain 

 amboceptors in the blood-serum. The recognition of this fact led 

 to the discovery that in syphilis, antibodies appear in the serum 

 which are different from the common bacteriolytic amboceptors, 

 insofar as they will combine with substances that are normal con- 

 stituents of the body, i. e., certain lipoids. Between the latter and 

 the corresponding syphilitic 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 Wasser- 

 mann reaction, as Wassermann was the first to purposely employ 

 the principle as originally understood, in the diagnosis of the infec- 

 tion 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 amboceptors of the bacteriolytic type might be 

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



