COLLOIDAL THEORY OF ANTIBODIES 327 



(b) the salts which gradually diffuse therefrom ; and (c) the 

 colloid or agglutinin. They brought forward strong evidence 

 in favour of this theory by showing that agglutination is less 

 powerful when the corpuscles are suspended in normal saline 

 solution (the salts of which inhibit the exosmosis of the salts 

 in the corpuscles) than when they are in isotonic sugar solu- 

 tion (in which exosmosis is unchecked). Further deductions from 

 their theory (for which the original articles must be consulted) 

 were verified experimentally. 



The analogies between colloid adsorption and the interactions 

 of toxin and antitoxin have been studied by Biltz, Pauli, and 

 others, and very remarkable facts adduced. For instance, there 

 appear to be phenomena indicating that the action of some anti- 

 toxins at least is reversible when a large amount is present. Thus, 

 according to Jacoby, the action of crotin (a phytotoxin of simple 

 nature and closely analogous with the bacterial exotoxins) is 

 increased by the addition of minute amounts of antitoxin, large 

 quantities of which neutralize its activity. Phenomena somewhat 

 similar are seen with the true toxins for example, Danysz (cor- 

 roborated by von Dungern and Sachs) has proved that diphtheria 

 antitoxin will neutralize more toxin when added at once than when 

 added in successive portions. Thus if the amount of toxin which 

 is just neutralized by a certain amount of antitoxin be divided into 

 two parts, and added to the antitoxin at an interval of twenty-four 

 hours, the whole may be toxic, although the amounts of toxin and 

 of antitoxin present are exactly the same in the two cases. Both 

 these effects can be explained on Ehrlich's pluralistic conception. 

 Thus Jacobi's results may be explained on the assumption that 

 small amounts of anticrotin combine with the non-poisonous 

 prototoxoid, and that this renders the mixture more toxic, because 

 this prototoxoid would otherwise seize on the receptors of the 

 sensitive cells, to the exclusion of the active toxin. This, however, 

 is very difficult to believe. Taking the action of crotin in pro- 

 ducing haemolysis as a test, it would appear that the neutralization 

 of some of the toxin, even if inert, would render the substance 

 less haemolytic ; this appears to follow from Bordet's proof that 

 red corpuscles can take up much more than their haemolyzing dose 

 of an antibody. The Danysz effect is also explicable on the 

 theory of the presence of a non-toxic epitoxonoid of no toxicity 

 and of feeble combining affinity. This slowly forms a firm com- 

 bination with the antitoxin, and renders it useless for neutralizing 



