TOXIC ACTION OF COMPLEMENTS 71 



THE COMBINING PROPERTIES OF COMPLEMENTS 

 IN RELATION TO THEIR TOXIC ACTION 



Ehrlich has pointed out the similarity in the constitution 

 of complements and of various toxins, and our own observa- 

 tions, as above detailed, strongly support his views. We 

 may, in the study of haemolysis, consider the complement 

 as a toxin, the red corpuscles treated with the appropriate 

 immune-body as the object on which the toxin is to act, 

 and the haemolysis as the indication of the toxic action, 

 Ehrlich regards the complement as consisting of two chief 

 atom-groups, the haptophore or combining group and the 

 zymotoxic ; but in speaking of the action of sera he does not 

 always carry out this distinction completely. For example, 

 the efficiency of different complements, as tested by their 

 haemolytic or bacteriolytic effects, is often taken as evidence 

 of the degree of chemical affinity between the complements 

 and the immune-body. But it is manifest that theoretically 

 a complement may combine perfectly through the medium 

 of the immune-body, and yet produce little haemolysis, 

 owing to the absence of sensitiveness to the zymotoxic 

 group combination or ' complementing ' may occur and 

 yet haemolysis be deficient or absent. The question which 

 we have investigated is accordingly this Where different 

 complements differ in their action as shown by the dosage, 

 both of complement and of immune-body required, does 

 this depend upon differences in their combining affinities 

 or upon differences in their toxicity ? 



In working out this problem we have made use of three 

 sera, viz. (a) the serum of the rabbit injected with ox's 

 corpuscles, therefore haemolytic towards ox's corpuscles ; 

 (6) the serum of the rabbit injected with guinea-pig's cor- 

 puscles ; (c) the serum of the guinea-pig injected with 

 rabbit's corpuscles. In each case the haemolytic serum 

 is deprived of its complement by heating at 55 C. and, 



