THE TECHNIQUE OF SERUM REACTIONS 263 



mixture was shaken in a shaking apparatus for twenty-four hours, and 

 after this the coarser particles were removed by centrifugalization. 

 The reddish supernatant fluid was used as the antigen and could be 

 preserved for a long time in dark bottles in the ice chest. 



MichaeHs ^ obtained the antigen in the following way: The liver of 

 a syphilitic fetus was preserved in a frozen state and from time to time 

 small quantities of extract were prepared for the purpose of obtaining 

 antigen. This was obtained by thoroughly grinding up a small piece 

 of the liver in a mortar and adding five parts of salt solution and about 

 0.5 per cent of carbolic acid. This mixture was shaken in a shaking 

 apparatus for several hours and was then allowed to stand at a tem- 

 perature slightly above 0° C. for several days. Finally it was cleared 

 by filtration or centrifugalization. 



Alcoholic extracts of syphilitic organs have been used by a number 

 of authors. Forges and Meier ^ extract the chopped-up syphilitic liver 

 for twenty-four hours with five times the volume of absolute alcohol. 

 This is then filtered through paper and the alcohol evaporated in vacuo 

 at a temperature not above 40° C. The greenish sticky residue should 

 have an alkaline or neutral reaction. About 1 gram of this material 

 is then emulsified in 100 c.c. of salt solution to which 0.5 per cent 

 of carbolic acid has been added. The fine emulsion which results is 

 filtered through thin paper and the filtrate used as the antigen. 



Forges and Meier, as well as a number of others, have discovered that 

 in actual practice it is not necessary to make use of syphUitic organs in 

 order to obtain an antigen which wiU combine with syphilitic immune 

 body. This fact, of course, has thrown much suspicion upon the 

 specificity of the phenomenon. In practice, however, it appears as a 

 purely empirical fact that many of the non-specific antigens, neverthe- 

 less, give reasonably reUable results. The authors mentioned above 

 have found that a 1 per cent emulsion of commercial lecithin (Kahlbaum) 

 in carbolized salt solution furnishes a suitable antigen. This has not 

 been universally confirmed. The same authors have obtained good 

 results by extracting a normal fetal liver by alcohol in the same way as 

 they extracted the syphilitic organ. Landsteiner, Miiller, and Poetzl ^ 

 have successfully employed an alcoholic extract of the heart substance 

 of a guinea-pig. 



> Michaelis, Berl. klin. Woch., 1907. 



' Porges und Meier, Berl. klin. Woch. , xv, 1908. 



' L/undsteiner, Miiller und Poetzl, Wien. klin. Woch., .50, 1907. 



