12 



INTRODUCTION 



an hour to a temperature of 56 C. (about 133 Fahr.) ; but the lytic 

 power may be restored by adding fresh serum of the normal Guinea 

 pig. These experimental facts are thought to show that there are two 

 substances in lytic blood, which act together : one of these substances is 

 stable or active at 56 C., and the other, which exists in normal serum, 

 becomes inert at 56 C. The stable substance active at 56 C. is the 

 so-called immune body (amboceptor). The unstable substance, inert at 

 56 C., is the alexin. The immune body may be obtained free from 

 alexin by the application of heat. The alexin may be obtained, by cer- 

 tain processes, free from the immune body. In cytolysis, however, the 



Alexm 

 ^(Complement; 



inticomplement 



Amboceptor 

 immune body) 

 Receptor 



Alexm 



I (Com element) 

 v Amboceptor 



'immune body) 



^^ ~~ 

 Anti-immune body 



Receptor 



Fig. ii. Anticomplement protecting the re- 

 ceptor by uniting with the complement (alexin) . 



Fig. 12. Anti-immune body protecting the re- 

 ceptor by uniting with the immune body. 



two bodies alexin (complement) and the immune body must act 

 together. It is assumed that the alexin cannot combine directly with 

 receptors, but that it can combine with the immune body and through it 

 with the receptors. 



Immune Bodies (Amboceptors). The immune body has two affini- 

 ties, one for the complement and one for the receptor ; and it is on 

 account of this property that it is called the amboceptor. Figure 10 is 

 a rough illustration of this theory. The alexin is often called the com- 

 plement, and the immune body (amboceptor), the interbody. 



Antibodies. Experiments have shown that in the body of an 

 animal in which serum containing alexins and amboceptors has been 



