96 APPLIED IMMUNOLOGY 



sues would give the reaction in syphilis with equally 

 good results. Since it is the lipoid material in tissue 

 that is dissolved by alcohol, it followed that this lipoid 

 material must contain the substance that is antigenic 

 for syphilitic serum. 



It was then found by Marie, Levaditi, and Land- 

 steiner that complement-fixation with syphilitic serum 

 occurred when alcoholic extracts of normal tissues, such 

 as liver, human heart, or guinea-pig heart, were used 

 as antigen, and that the results of reactions with these 

 extracts were as reliable as those where extracts of 

 syphilitic tissues were used. These observations 

 showed that the complement-fixation reaction in syph- 

 ilis is not entirely a specific antigen-antibody reaction 

 as in the case of those occurring between bacterial anti- 

 gens and antibodies, but this fact in no way lessened 

 the practical value of the test in the diagnosis of 

 syphilis. 



It has still further been shown that extracts pre- 

 pared from lecithin, cholesterin, etc., can be used as 

 antigens and some workers restrict themselves to these 

 artificial products. The various forms of antigen in 

 use at the present time account to a great extent for 

 the divergence of results in some cases when serum 

 from the same patient is examined by different 

 workers. This has a tendency to throw doubt on the 

 value of the reaction in the minds of skeptical clini- 



