164 METHOD OF COMPLEMENT FIXATION 



a substance specific for syphilis which could with most probability be considered a 

 luetic antigen, and secondly that infected apes possess antibodies against this 

 antigen. 



The next step was to try the reaction in man. The first experiments of 

 Wassermann, Neisser, Brack and Schucht did not give the hoped-for 

 returns. Although the reaction was obtained with human serum, the 

 percentage of positive results was so small (see next chart) that its practical 

 value as a means of diagnosis offered no great help. Only in general 

 paralysis did the expectation seem promising. In about 80 per cent, of all 

 cases Wassermann and Plaut were able to demonstrate the luetic anti- 

 bodies in the cerebrospinal fluid. 



Schiitze's experiments in tabes led him to the same findings. Citron has obtained 

 a much smaller percentage of positive reacting cerebrospinal fluids in tabes. 



As it seemed that the means of diagnosis was not to be established by 

 the demonstration of the syphilitic antibody, Neisser and Bruck believed 

 that better results may possibly be achieved by the discovery of the luetic 

 antigen in the serum through complement fixation. 



This attempt too was unsuccessful. No antigen could be found, but the extracts 

 of red blood cells from syphilitic individuals when mixed with the serum of highly 

 immunized monkeys gave a positive complement fixation. Neisser and his co-workers 

 concluded therefrom that the erythrocyte extract contained the luetic antigen. 

 Citron soon demonstrated that the extracts of normal individuals gave a similar reac- 

 tion and what was more important, that this so-called blood antigen existed in the 

 blood entirely uninfluenced by mercurial treatment. Since these experiments, not 

 much importance has been attached to this reaction. 



Meanwhile the author working at the Kraus clinic proved by a large 

 series of experiments that luetic antibodies were present in almost all cases 

 of lues. The reaction is dependent upon two rules. 



The First. The longer the syphilis virus has acted upon the organism 

 and the more numerous its recurrent manifestations have been, the more 

 frequently will a positive reaction be obtained and the stronger will the 

 antibody content of the serum be. 



The Second. The sooner a proper mercury therapy is instituted, the 

 more often it is repeated, and the shorter the interval since the last treat- 

 ment, the smaller will the antibody content of the serum be and the greater 

 the possibility of a negative reaction. 



These points were soon corroborated by numerous other workers in the 

 field, so that at the present day they can be taken as absolute facts. The 

 following chart will explain some of the statements aforementioned. 



