118 THE THEORY OF IONS 



In the case of toxins, there must be a connexion 

 between their chemical constitution and action, just 

 as there is in well-known poisons. In cocaine the 

 anaesthetic effect is due to the benzoyl-radical, which 

 in consequence Ehrlich calls the ancesthesiophore ; 

 the soporific effect of sulphonal and other disulphons 

 is due entirely to the ethyl-radical ; and so on. 

 Similarly there is in the toxin a group which causes 

 the peculiar effect of the toxin, and this is called by 

 Ehrlich the toxophore group. 



But the toxophore group is not of itself sufficient 

 to bring about the poisonous action. There must 

 be some peculiarity of the toxin which causes its 

 distribution, and this action he attributes to a 

 haptophore group. Similarly there must be a corre- 

 sponding chemical group in the cellular protoplasm 

 which reacts with them, and this is called the 

 receptor. The toxin action can only occur when 

 there are present such receptors fitted to anchor 

 the toxins. " We can prove the existence of 

 receptors,"* and the binding action or anchoring 

 of toxins by such receptors plays a great part in 

 immunity. 



In order that the poisonous action of the toxin 

 may take place, we must presume not only the 

 presence of fitting receptors, but that they are 

 present in a position favourable for the toxic action 

 to be brought about. When the receptor and the 

 organs sensitive to the action of the toxin are present, 

 the conditions for infection are most favourable ; 

 distribution takes place at once, and the poison 



* Ehrlich: "The Harben Lectures," Jour. Boy. Inst. Pub. 

 Health, p. 326. 



