420 



RESEARCH IN PROTOZOOLOGY 



once satisfactorily performed, will suffice for any particular batch 

 of antigen.) 



Having completed the preliminary titrations, the actual comple- 

 ment fixation test may be performed according to the protocol given 

 in Table 4. In the example given, since no hemolysis occurs in 

 Tubes I through 4, the complement v^as previously fixed by the 

 experimental immune serum and test antigen (positive result), 

 v^hereas had hemolysis occurred in all tubes, it could have been 

 concluded that either immune serum or its specific antigen was 

 absent (negative result). 



As has been indicated previously, the Wassermann test for 

 syphilis is carried out in the same manner as the specific comple- 



TABLE 3 

 PROTOCOL FOR THE ANTICOMPLEMENTARY TITRATION OF ANTIGEN 



ment fixation test, but it employs a non-specific test antigen which 

 is generally derived from normal tissues by extracting with lipoidal 

 solvents. Since normal organ extracts are used, it might be ex- 

 pected that positive Wassermann tests would frequently be found 

 in other diseases. With modern methods of technique, however, 

 such positives are not characteristic of other diseases, and a posi- 

 tive Wassermann test is quite presumptive of syphilis or the closely 

 related yaws. Although protozoan diseases probably do not give 

 positive Wassermann tests, it must be remembered that test anti- 

 gens made from protozoa are extracts of cells and frequently 

 adherent tissues, so that they often serve as efficient Wassermann 

 antigens and give positive reactions with serums from cases of 

 syphilis and yaws. 



