THE COMPOUND H^MOLYSINS 223 



stance that the corpuscle has no affinity for the immune- 

 body until it is bound to the alexin. Evidently this is only 

 a very artificial circumscription, and no real explanation. 

 Bordet, however, later on proved that even in this case 

 the immune-body is absorbed ; to his investigation on this 

 subject we shall return later (cf. p. 260). 



The first theoretical view of these phenomena was given 

 by Bordet, 1 who regarded the immune-body as a kind of 

 catalytic agent, which " sensibilised " the erythrocytes to 

 the attack of the alexin. The objection that alexin alone 

 does not attack the erythrocytes is evidently untenable. 

 Bordet advanced his experiment on the effect of a fraction- 

 ated addition of haemolytic serum (cf. p. 34) to a given 

 portion of erythrocytes as pleading in favour of his idea. 

 This experiment indicated that the binding to the cells 

 does not take place in constant proportion, as Ehrlich 

 tacitly supposed. But Ehrlich replied that the cells might 

 bind more haemolysin than just the quantity necessary for 

 laking. Since we know now that the immune-body is 

 absorbed by the erythrocytes, this controversy has only 

 an historical interest. In a certain sense we must allow 

 Bordet to have been in the right, the entrance of the 

 immune-body into the erythrocytes is the necessary con- 

 dition for the attack of the alexin, which, as we shall see 

 later, is really bound to equivalent quantities of the im- 

 mune-body dissolved in the erythrocytes. Against Bordet 

 the experiment of Ehrlich and Sachs has been cited, but 

 this is easily explained by the view that the immune-body 

 is absorbed. 



1 Bordet: Annales de rinst. Pasteur, 12. 688 (1898), and 14. 257 (1900). 



