HEMOLYTIC AND OTHER SERA 575 



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. 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 

 disputed point whether there are several distinct complements in 

 a normal serum with different relations to different immune- 

 bodies, for which Ehrlich and his co-workers have brought 

 forward a certain amount of evidence, or whether, as Bordet 

 holds, there is a single complement which may, however, show 

 slight variations in behaviour towards different immune-bodies. 

 There is at least no doubt that all the complement molecules in 

 a serum are not the same. For example, Muir and Browning 

 have shown that the treatment of a normal serum with a small 

 amount of emulsion of a bacterium will remove the bactericidal 

 action for another bacterium, whereas the amount of complement 

 as tested by hemolysis is practically unchanged. They accord- 

 ingly consider that there is a moiety of complement, " bacterio- 

 philic complement," which is specially concerned in bactericidal 

 action. On the other hand, many of the arguments adduced 



