CHANGES WROUGHT IN PATHOLOGY. H$ 



those transitional toxin-antitoxin compounds which show 

 great variations in their reactions. This phenomenon 

 has been responsible for the development of a rich 

 nomenclature. All the relations between toxin and 

 antitoxin are much complicated by the fact that diph- 

 theria toxin, as has already been pointed out, may from 

 the start enter into a reaction with antitoxin, with aggre- 

 gates which are by no means all alike. To this is still 

 to be added the following fundamental peculiarity in the 

 reactions of the toxin. The toxicity of diphtheria toxin 

 and its relations to antitoxin are able to vary independ- 

 ently of each other, a behavior which finds expression, for 

 example, in the fact that a toxin requires approximately 

 the^same amount of antitoxin for neutralization no mat- 

 ter whether its toxicity is high or diminished through age. 

 This phenomenon, which represents another of EHRLICH'S 

 discoveries, was explained by assuming that the toxin 

 is composed of a haptophore, or binding group, and a 

 toxophore, or poison- bearing group. We must not fail 

 to consider, however, that we are dealing with a reaction 

 of the colloidal toxin with two different kinds of colloids 

 with the antitoxin and with the constituents of the 

 cell. 



Slight changes in the colloidal properties of a body 

 are, however, able to affect one part of its reactions and 

 leave another part free. An interesting example of this 

 is furnished by the behavior of colloidal gold toward 

 mercury, which I introduce because we are dealing under 

 these circumstances with reactions between elements, 

 reactions which no one will be inclined to attribute to 

 properties of special atomic groups. Colloidal gold 

 shows the properties of the pure metal, except that it 



