FIXATION OF COMPLEMENT 97 



cians. A great deal of work is being done upon the 

 antigen question, and it is hoped that in the near fu- 

 ture some definite standard will be adopted and uni- 

 versally employed. We believe, in the light of pres- 

 ent knowledge, that in the Wassermann reaction there 

 is probably a specific factor as well as a non-specific, 

 certainly that the organisms of syphilis cause an over- 

 production of the special lipoid antigenic substance in 

 the tissues, and that the most reliable results will be 

 obtained by using an alcoholic extract of syphilitic 

 tissue, in which this substance is found in greatest 

 abundance. We adhere to this view as the result of 

 the use of syphilitic liver-extract in several thousand 

 tests, in which our results have differed in no material 

 way from those of reliable workers. 



We recently reported (J. A. M. A,, Jan. 31, 

 1914) the results of a trial of some cholesterinized ex- 

 tracts of guinea-pig heart and human heart. These 

 extracts are made by adding cholesterin to the ordi- 

 nary alcoholic extract of normal heart in the propor- 

 tion of 0.4 per cent. The cholesterinized guinea-pig 

 heart-extract was used by us along with our antigen of 

 alcoholic extract of syphilitic liver in the routine ex- 

 amination of 100 cases, the cholesterinized human 

 heai-t-extract being employed in thirty-three cases. 



Careful preliminary titration of the antigens was 

 carried out before doing the tests, and at no time was 



7 



