574 IMMUNITY 



the immune-body acts as a sort of connecting-link between the 

 red corpuscle and the complement, hence the term "amboceptor" 

 which Ehrlich afterwards applied. It may be stated, however, 

 that the direct union of complement and immune-body has not 

 been conclusively demonstrated. Muir and Browning, for 

 example, found that when a fresh serum is passed through a 

 Berkefeld filter, complement is largely retained in the pores 

 of the filter, whereas immune-body passes through practically 

 unchanged ; and that if a mixture of complement and immune- 

 body be made and filtered at a temperature of 37 C., the 

 amount of immune-body which passes through is not diminished, 

 whereas it would be if it had united with the retained comple- 

 ment. Accordingly by this method there was obtained no. 

 evidence of the direct union of immune-body and complement. 

 Bordet holds that the immune-body acts merely as a sensitising 

 agent hence the term substance sensibilisatrice and allows the 

 ferment-like complement to unite. It is quite evident from his 

 writings, however, that he does not mean, as is often assumed, 

 that the immune-body causes some lesion in the corpuscle which 

 allows the complement to act, but simply that it -produces in the 

 molecules (receptors) of the red corpuscles an avidity for comple- 

 ment. All that we can say definitely at present is that the 

 combination of receptor + immune-body takes up complement 

 in firm union while neither does so alone ; whether the immune- 

 body acts as a link between the two or not must be left an open 

 question. Even after the corpuscles are laked with water the 

 receptors are not destroyed. Muir and Ferguson have shown 

 that they can still take up immune-body and, through its 

 medium, complement, just as the intact corpuscles do. Ehrlich 

 and Morgenroth showed that in some cases the red corpuscles 

 can take up much more immune-body than is necessary for their 

 lysis, and Muir found in one case studied, that each further 

 dose of immune-body led to the fixation of more complement, so 

 that as many as ten times the hsemolytic dose of complement 

 might thus be used up. It is a matter of considerable import- 

 ance that the union of immune-body and red corpuscles can be 

 shown to be a reversible action. If, as was found by Morgen- 

 roth and Muir independently, corpuscles treated with several 

 doses of immune-body and then repeatedly washed in salt 

 solution be mixed with untreated corpuscles and allowed to 

 remain for an hour, then sufficient immune-body will pass from 

 the former to the latter, so that all become lysed on the addition 

 of sufficient complement. The combination of complement, on 

 the other hand, is usually of very firm nature. It has been a 



