IMMUNITY 25 



antibodies and endotoxins by way of blood removed, 

 and by the addition of fresh complement in the 

 normal serum injected. This fresh complement 

 activated the amboceptors already in animals' tissues 

 to increased bacteriolytic action, at the same time 

 stimulating the leucocytes to increased phagocytosis, 

 with the consequent increased destruction and re- 

 moval of bacteria and the neutralisation of their 

 endotoxins. 



Fixation of the Complement. — Bordet and Gengou 

 devised a method whereby very small quantities of 

 immune body can be demonstrated in a serum ; their 

 method is generally known as fixation of the 

 complement. The following steps of the experiment 

 explain this method : 



A. B. 



Bacteriolytic amboceptor Normal serum heated, 

 (plague-immune serum), 



+ + 



Plague emulsion. Plague emulsion. 



+ + 



Complement Complement 



(fresh normal serum). (fresh normal serum). 



To both of these, after five hours, was added — 



Hemolytic amboceptor 



(heated hemolytic serum). 



+ 



Eed blood cells. 



Kesults : 



(A) Showed no hemolysis. (B) Showed positive hemolysis. 



In (A) the complement introduced in normal fresh 

 serum has combined with the bacteriolytic amboceptor 



