THE THEORY OF TOXIC ACTION 199 



different sources may be related to one another. For example, 

 Ehrlich has pointed out that ricin produces in a susceptible 

 animal body an antitoxin which corresponds almost completely 

 with that produced by another vegetable poison, robin (vide 

 supra), though ricin and robin are certainly different. This may 

 be explained on the supposition that robin is a toxoid of 

 ricin, i.e. their haptophorous groups correspond, while their 

 toxophorous differ. The evidence on which Ehrlich's deductions 

 are based is of a very weighty character, but another view of 

 toxic action is that the relation between a toxin and the cell 

 on which it acts is an example of the physical phenomenon of 

 adsorption. The whole subject will be again referred to in the 

 chapter on Immunity. 



With regard to the intracellular toxins we shall see it is 

 difficult to determine whether or not they share with the extra- 

 cellular poisons the property of stimulating antitoxin formation, 

 if they do not, then they may belong to an entirely different 

 class of substances. It is certain that a tolerance against such 

 poisons is difficult to establish and is not of a lasting character. 

 We thus cannot say what the mechanism is by which these 

 poisons act. It may be said that Macfadyen, by grinding up 

 typhoid bacilli frozen by liquid air, claimed that on thawing he 

 obtained the intracellular toxins in liquid form, and he further 

 stated that by using this fluid he could immunise animals not 

 only against the toxins but also against the living bacteria. 



\\V have already pointed out that those who claim for the 

 aggressins a special character hold that the activity of these 

 bodies has as its effect the interference with the phagocytic 

 functions of the leucocytes. They also hold that a special type 

 of immunity can be developed against the aggressins. 



