216 A MANUAL OF BACTERIOLOGY 



that bacteriolyses or is taken up or fixed by a bacterial 

 amboceptor. 1 Thus, after haemolysis ot corpuscles with 

 haemolytic serum and complement, the mixture will not 

 induce bacteriolysis with a bacterium and bacteriolytic 

 serum and vice versa (provided, of course, excess of com- 

 plement be avoided). This fact, known as the "Bordet- 

 Gengou phenomenon," is of great importance, for upon 

 it are based the various complement fixation reactions, 

 such as the Wassermann reaction in syphilis. 



Within certain limits, haemolysis is a quantitative 

 reaction. For a given quantity of corpuscles a certain 

 amount of haemolytic amboceptor and of complement is 

 necessary for complete haemolysis of all the corpuscles, 

 but the amounts of the constituents may be varied to 

 some extent. Thus, if with certain quantities of cor- 

 puscles haemolytic amboceptor and complement haemo- 

 lysis is only partial, complete haemolysis can probably be 

 induced by increasing the amount either of amboceptor 

 or of complement, provided the original amount of ambo- 

 ceptor is not below a certain minimum. If excessive 

 amounts of haemolytic amboceptor be used, blocking of 

 complement may occur (as with a bacteriolytic serum), 

 and no haemolysis ensues. 



It is of interest that haemoglobin itself is not antigenic, 

 so that haemolysin dissolves the envelope and stroma of 

 the red corpuscles, setting free the contained haemo- 

 globin. 



Haemolysin formed by the injection of corpuscles of 

 another species is termed " heterolysin." If corpuscles 



1 As previously stated (p. 208), numerous complements undoubtedly 

 exist, yet bacteria will absorb both bacteriolytic and hsemolytic comple- 

 ments. Bordet and Gengou suppose that while a particular amboceptor 

 has a maximum avidity for its homologous complement (which may be 

 termed dominant), it is also able to take up other " non -dominant " comple- 

 ments, and thus bacteriolytic amboceptor is able to absorb both bacteriolytic 

 (dominant) and haemolytic (non-dominant) complements. 



