SERUM DIAGNOSIS 161 



the antigen-antibody compound, the comple- 

 ment is entirely used up and therefore cannot 

 act upon the red cells. The fluid in the tubes 

 remains opaque but, on standing, the cells grav- 

 itate to the bottom of the tubes leaving a clear, 

 colorless supernatant fluid. This phenomenon 

 of disappearance of complement in the mixture 

 of antigen and antibody is now generally called 

 fixation of complement and constitutes a posi- 

 tive reaction. Sometimes it is called deviation 

 of complement on account of the fact that the 

 complement has been deviated by the combina- 

 tion of antigen and antibody and prevented from 

 participating in the hemolytic process. Thus, it 

 will be seen that the hemolytic system acts 

 simply as an indicator to demonstrate an action 

 otherwise without manifestation. 



COMPLEMENT FIXATION IN THE DIAGNOSIS 

 OF GONORRHEA 



The phenomenon of complement fixation was 

 first applied to the study of gonococcus infec- 

 tion by Mueller and Oppenheim in 1906. The 

 technic developed by Schwartz and McNeil has 

 been widely followed and the value of the test 

 in the diagnosis of secondary gonococcus in- 



