ON ILEMOLYTIC RECEPTORS 119 



combination of immune-body would not be obtained. 

 On the other hand, we have demonstrated that the com- 

 bination of complement with the receptors of the red cor- 

 puscles through the medium of immune-body is a very 

 firm one, and thus a test for the presence of receptors is 

 afforded. To put the matter briefly, we may say that if 

 the receptors are present in a solution or in a suspension, 

 and if complement be added along with immune-body, 

 a certain amount of complement will be taken up in firm 

 combination, so that fresh red corpuscles treated with 

 immune-body do not undergo lysis when they are added 

 to the mixture. 1 The test, then, for the presence of the 

 receptors in question consists in adding complement and 

 immune-body and observing whether or not the former 

 is diminished in amount. As hsemolytic agents we have 

 chiefly used sterile water and a hsemolytic serum, though 

 some experiments have been also performed with ether. 

 With regard to haemolytic sera it may be again noted that in 

 many instances red corpuscles can take up several heemolytic 

 doses of immune-body, or, in other words, there are many 

 more receptors than are necessary for complete haemolysis. 

 Therefore, if we add multiple doses of immune-body and 

 produce lysis with a single dose of complement, there remain 

 many receptors combined with immune-body whose affinity 

 for complement is still unsatisfied. We can test whether 

 these molecules are in the stromata or free in the fluid. In 

 all the experiments we have used ox corpuscles, the corre- 

 sponding immune-body being obtained from rabbits treated 

 with injections of ox's corpuscles (washed in salt solution), 

 while the complement is normal guinea-pig's serum from 

 which the natural immune-body for ox's corpuscles has been 

 removed by contact with these corpuscles for an hour at C. 



1 This is merely an example of the deviation of complement by an 

 antigen plus its anti-substance, a reaction which has come into general 

 application since the above was written. See also Part II (p. 133). 



