132 THE PRINCIPLES OF IMMUNOLOGY 



some complements are destroyed and others remain in the same serum. 

 Weak acids and weak alkalis may differentiate complement similarly; 

 it is stated that digestion by papain also serves so to differentiate. By 

 injection of a complementary serum into foreign species, a so-called 

 anti-complement is obtained which is said to act upon one of the 

 complements of a serum and not upon others, irrespective of whether 

 the complement of the antigenic serum or of some other serum be em- 

 ployed in the subsequent test. Practically all these experiments have 

 been performed in such a way that the complement acts with normal 

 amboceptors and the question at once arises as to whether or not the 

 same phenomena would be observed with immune amboceptors. Even 

 in the case of normal amboceptors, there is experimental contradiction 

 of the original supposition of Ehrlich and Morgenroth. Neisser stated 

 that anthrax bacilli deprive fresh rabbit serum of its bactericidal com- 

 plement, but not of its /hemolytic complement. Wilde showed that if 

 a sufficient mass of anthrax bacilli were added to the fresh rabbit serum 

 all the complement is used, so that further bactericidal action does not 

 occur and no hemolytic action can be demonstrated. Similarly Bordet 

 found that unsensitized red blood-corpuscles deprive a serum of only 

 part of its complement^ but that cells strongly sensitized with hemolysin 

 use up all the complement both bactericidal and hemolytic. He believes 

 that the reason normal amboceptors do not utilize all the available 

 complement is due to the fact that such normal amboceptors do not suf- 

 ficiently sensitize the antigenic cells. Therefore, the complete sensitiza- 

 tion of the cells will result in a complete utilization of complement. 

 After the publication of these experiments, Ehrlich, who confirmed the 

 results, explained the phenomenon as being due to a multiplicity of 

 complements in the serum. In order to do so, he was obliged to alter 

 the original conception of the amboceptor, so that instead of having 

 a single cytophilic group it must contain several cytophilic groups. 

 Therefore, the term was altered to polyceptor instead of amboceptor. 

 The polyceptor was supposed to have one group with an especial affinity 

 for a dominant complement and other receptors with affinities for the 

 secondary complements. If the dominant complement is absorbed by 

 the polyceptor, the secondary complements are also involved, but, on 

 the other hand, if, as has been claimed, it is possible to obtain a serum 

 with only secondary complements present, these may be absorbed 

 without action upon the receptor for dominant complement. This expla- 

 nation, however, rests entirely upon the Ehrlich conception of the ambo- 

 ceptor, and, inasmuch as this conception is not conclusively proven, it 

 is not necessary to accept the idea that complements are multiple. This 

 question, however, is not settled at the present time, and reference 

 will be made to it again in connection with the phenomenon of com- 

 plement fixation. 



Complementoids. The similarity in action and nature of comple- 

 ment and toxin was early recognized, and it was therefore attempted to 

 determine whether or not complement could be broken up in the same 

 way as toxin so as to form complementoids. If such were the case, it 



