480 IMMUNITY 



property disappeared when the haeraolytic serum was heated at 

 55 C., but, as in the case of a bacteriolytic serum, was regained 

 on the subsequent addition of some serum from a fresh (i.e. non- 

 treated) animal. These observations have been fully confirmed 

 and greatly extended. Ehrlich and Morgenroth analysed the 

 phenomena in question, and showed that the specially developed 

 and heat-resisting substance, "immune-body," entered into com- 

 bination with the red corpuscles at a comparatively low 

 temperature, namely at C. ; whereas complement does not 

 combine at this temperature. In this way a method is supplied 

 by which the immune-body can be removed from a hsemolytic 

 serum while the complement is left. They came to the con- 

 clusion that immune - body combined with the complement 

 though the combination was less firm and only occurred 

 at a higher temperature best about 37 C. They therefore 

 consider that 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. Bordet, 

 on the other hand, holds that the immune-body acts merely as 

 a sensitising agent hence the term substance sensibilisatrice 

 and allows the ferment-like complement to act. 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 complement. 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 haemolytic 

 dose of complement might thus be used up. It is a matter of 

 considerable importance that the union of immune-body and red 

 corpuscles can be shown to be a reversible action. If, as was 

 found by Morgenroth and Muir independently, corpuscles treated 



