40 PROPERTIES OF H^MOLYTIC SERA 



to anti-complement. The action of various anti-comple- 

 ments obtained in this way was found to be comparatively 

 specific they had always the greatest effect on the comple- 

 ment of the animal whose serum had been injected, though 

 sometimes also a slight action could be demonstrated on 

 the sera of allied species. The work of Moreschi and others, 

 however, subsequently showed that the anti-complement 

 action referred to was capable of explanation in another 

 way. The whole question is fully discussed below (p. 133), 

 but we give here the fundamental facts. The serum injected 

 in addition to containing complement also contains certain 

 molecules or receptors which act as antigens and give rise 

 to anti-substances. These serum receptors, when com- 

 bined with their anti-substances, absorb or fix complement 

 just as the receptors of red corpuscles or bacteria in combina- 

 tion with their immune-bodies do. If we indicate the serum 

 receptors by S, then the absorption of complement is indi- 

 cated by S + anti-S + C. Accordingly, when the serum is 

 mixed with the anti-serum, complement becomes fixed 

 according to the scheme given and thus an apparent anti- 

 complement action results. All the facts known with regard 

 to anti-complements seem capable of explanation in this 

 way, and the existence of true anti-complements, that is, 

 of simple anti-substances which combine directly with com- 

 plement, has not yet been established. The important 

 work of Bordet * on anti-complements, with his application 

 of the results to the toxin-antitoxin question, and various 

 other researches, must be considered according to the new 

 interpretation. 



In our own investigations on the haptophore or com- 

 bining group of complement we had before us the following 

 facts difficult of explanation. Guinea-pig's and rabbit's 

 complement combine equally well with sensitized ox cor- 

 puscles, and produce lysis therefore their haptophore 

 1 Bordet, Annal. de VInst. Pasteur, vol. xvii, 1903, p. 161. 



