COMPLEMENT FIXATION TESTS. 



141 



homologous, as the complement is left free, and given a chance to unite with 

 the added erythrocytes and hemolytic amboceptor. In the case where the 

 bacteria are known, e.g., typhoid bacilli, the occurrence of hemolysis indicates 

 that the examined serum contains no typhoid amboceptors. If the serum 

 is known (e.g., meningococcus serum) the occurrence of hemolysis proves 

 that the bacteria under examination are not meningococci. The absence of 

 hemolysis, will in the first case point out that the unknown serum contains 

 typhoid amboceptors, i.e., is a typhoid serum; while in the second case the 



Typhoid bacilli (antigen) 



Inactive typhoid serum (typhoid 

 amboceptor) 



Complement 



Hemolysin (hemolytic ambo- 

 ceptor) 



Sheep's red blood cells (2nd antigen) 

 Result: Due to the union of complement 

 with the complex typhoid bacillus + the 

 typhoid amboceptor. Hemolysis did not 

 take place. 



FIG. 15. 



Typhoid bacilli (antigen) 

 Inactive cholera serum (cholera ambo- 

 ceptor) 



Complement 

 Hemolysin 



Sheep's red blood cells 

 Result: The complement unites with the 

 hemolysin and the sheep's red blood 

 cells thus producing hemolysis. 



Typhoid 

 bacilli 



Cholera 

 amboceptor 



FIG. 16. 



\ / Red blood cell 



VI 



Hemolytic 

 amboceptor 



Complement 



absence of hemolysis would bear definite evidence in favor of meningococci. 

 The accompanying figures, 15 and 1 6, represent schematically, the positive 

 and negative complement fixation test. 



Gengou further showed that not only cellular antigens can stimulate the 

 formation of amboceptors, but that during the course of immunization with 

 proteids in solution (milk, serum, etc.), complement binding amboceptors are 

 also formed in addition to the precipitins. Citron has therefore proposed the 

 term "antigenophile," to designate the " cytophile" group of the amboceptor. 



Widal and Lesourd, were the first to make practical application of the 

 complement fixation property. They found that the Bordet-Gengou reaction 

 could be obtained far more frequently and earlier with the serum of typhoid 



