COMPLEMENTS 271 



to its antigen, then like an enzyme it can destroy this antigen 

 (or act Hke toxin to kill it, if it is a living cell). Complement 

 is not an antibody. 



An illustration which may be used in the attempt to make 

 clear to students the relation between amboceptor and 

 complement is the following: 



Agglutinin is a one molecule antibody having at least two 

 atom complexes, a uniting group and an agglutinating group. 

 Imagine that this molecule might be split into two separate 

 molecules, one containing the uniting group for antigen and 

 the other the agglutinating group. This latter cannot agglu- 

 tinate by itself because it cannot unite with antigen. But if 

 it is again united to the agglutinating group then this combi- 

 nation can agglutinate. If they can reunite then the 

 molecule containing the uniting group for antigen must also 

 have a combining group for the agglutinating molecule. This 

 is exactly the situation with respect to amboceptor and 

 complement, they are two separate molecules. The com- 

 plement is the active molecule but cannot unite with antigen 

 directly. The amboceptor has a uniting group for antigen 

 and one for complement. When complement is united to 

 amboceptor and amboceptor to antigen then complement 

 can act on antigen. The amboceptor only is an antibody, 

 complement is not a part of this molecure but a separate 

 molecule and is therefore not an antibody. 



As to whether complements are numerous, as Ehrlich 

 claims, or there is only one complement, according to Buch- 

 ner and others, need not be discussed here. In the practical 

 applications given later as means of diagnosis it is appar- 

 ent that all the complement or complements are capable of 

 uniting with at least two kinds of amboceptors. 



If complement be injected into an animal it may act as 

 an antigen and give rise to the formation of anticoniylement, 

 which may combine with it and prevent its action and is 

 consequently analogous to antitoxin. If amboceptors as 

 antigen are injected into an animal there will be formed by 

 the animal's cells antiamboceptors. As one would expect, 

 there are two kinds of antiamboceptors, one for each of its 

 combining groups, since it has been stated that it is always 



