THE DEFENSES OF THE BODY 285 



thereby favoring the immediate destructive activity of its 

 "zymotoxic" group. 



It is of importance to note in connection with this hypothe- 

 sis, that both "receptors" and "complement" are present 

 in normal susceptible, as well as in immune animals, but 

 that during immunization only the "receptors" are multi- 

 plied as a result of the specific stimulation necessary to the 

 establishment of immunity, hence the commonly employed 

 synonymous designations: "immune bodies" and "anti- 

 bodies." As such bodies are generated during immuniza- 

 tion, the substance used for the purpose is designated 

 "antigen" — i. e., generator of antibodies. 



The Origin of Complement. — ^The origin of complement is 

 a question that is still unsolved. Some investigators are 

 inclined to believe that it is derived from the leukocytes. 

 This is the opinion of Metchnikoff and his associates, while 

 others believe that it is derived from other cells and organs 

 as well as from the leukocytes. Again other investigators 

 believe that it is not derived from the leukocytes at all, 

 but from the cells of certain organs, for instance, the spleen 

 pancreas, liver, and the bone marrow. It is impossible with 

 the knowledge at hand to state definitely the origin of the 

 complement. 



On the Specificity of Complement. — According to Ehrlich 

 and his pupils the term " complement" is to be used generi- 

 cally to indicate a group of closely allied bodies differing 

 from one another in that they possess specific relations to 

 particular antigens. By appropriate methods they claim 

 to have demonstrated the multiplicity of complement. They 

 state that by particular treatment one or more complemen- 

 tary bodies may be removed from normal blood while others 

 remain in the blood intact; even by such mechanical pro- 



