THE RECEPTOR APPARATUS OF THE RED BLOOD-CELLS 395 



same, namely, the presence of suitable receptors on the blood-discs, i.e., 

 receptors which fit the haptophore groups of the toxin or the corre- 

 sponding groups of the amboceptor. This view, already generally 

 accepted for the toxin poisonings, is supported by considerations of 

 two kinds. First is the positive proof in the case of the manifold 

 blood poisons, that their injurious action is always preceded by the 

 anchoring of the poison to the blood-cell. Only such species of 

 blood-cells are susceptible to a certain haemolysin which are able 

 to anchor the same. This has been confirmed again and again in 

 the case of amboceptor lysins. Conversely, therefore, there is the 

 closest connection between natural immunity and absence of receptors. 

 That the fixation of the poisons is not due to mechanical effects, 

 such as surface attraction, but to a true chemical process, is at once 

 shown by the strict specificity which obtains. This is observed 

 especially in the amboceptor lysins produced artificially. This 

 .specificity is in marked contrast to the many-sided and non-selective 

 action of surface attraction (charcoal, etc.). The second point 

 which supports the above view is the fact that the action of a 

 certain poison, and only of this one, is inhibited by the correspond- 

 ing antitoxin. According to my views, the action of antitoxins is 

 explained by assuming that they occupy the haptophore groups of 

 the toxin molecule and so prevent these from combining with the 

 receptors of the tissues. It is quite incomprehensible to me how 

 the specificity of the antitoxins can more easily be explained on 

 the basis of the mechanical conception. 



This brings us to a very important point, namely, the surprising 

 plurality of receptors. Even in the blood poisons each antiserum 

 protects only against the substance through which it was produced 

 by immunization. This law of specificity, which has so repeatedly 

 been confirmed in the infectious diseases, is thus seen to apply here 

 without any change. Antiricin serum protects the blood-cells only 

 against ricin, antitetanolysin only against tetanolysin, every anti- 

 amboceptor only against a corresponding amboceptor. 



Hence in every species of blood-cell we shall have to assume 

 the existence of as many different kinds of receptors as there are 

 poisons. This is obviously a very large number. Thus if the blood- 

 cells of rabbits are injured by ricin, crotin, abrin, phallin, by the 

 most diverse products of bacterial metabolism, and by a large num- 

 ber of sera of other species, we shall have to assume a certain recep- 

 tor (ricin receptor, etc.) for each case. Almost every day, however, 



