COMPLEMENTS 



355 



(Fig. 97). If these amboceptors were not present, then the complement 

 would remain unfixed and be free to hemolyze the sensitized corpuscles, 

 a negative reaction being indicated, therefore, by hemolysis, whereas 

 the absence or inhibition of hemolysis indicates a positive reaction. 



C.A.C. 



FIG. 97. MECHANISM OP COMPLEMENT FIXATION. 



Tube 1 shows the hemolytic system; C, a red blood-corpuscle; A, a hemolytic 

 amboceptor; Cp, complement; C.A.C., complement united to a corpuscle by means 

 of the specific amboceptor. Hemolysis results. 



Tube 2 shows complement fixation by bacterial antigen and amboceptor; Ai 

 antigen; C, complement united to the antigen A\ by the amboceptor A. When 

 hemolytic amboceptors are added hemolysis does not occur because the complement 

 has been previously fixed by the bacterial antigen and amboceptor. 



Tube 3 shows absence of complement fixation because the bacterial amboceptor 

 Ai is not specific for the bacterial antigen A 2 and hence complement is not fixed; 

 when hemolytic amboceptor and the corresponding corpuscles are added comple- 

 ment unites with these, C.A.C. and hemolysis occurs. 



Wassermann, Neisser, and Bruch have applied this test to the serum 

 diagnosis of syphilis, the technic of the test being considered in a subse- 

 quent chapter. 



Deviation or Deflection of Complement. While large doses of anti- 

 toxin are indicated in the treatment of diphtheria and tetanus, theoretic- 

 ally the administration of too large an amount of a bacteriolytic serum 



