CHANGES WROUGHT IN PATHOLOGY. 121 



in aqueous solution into its strongly charged ions. In 

 this way mixtures- of antagonistic colloids may approx- 

 imate in their properties salts that have arisen from 

 combinations between weak acids and weak bases. 

 Strictly speaking, we are compelled to assume the existence 

 of at least traces of such a similarity in order to account 

 for the traces of the free substances which we find beside 

 the aggregates in toxin-antitoxin mixtures. Some toxin- 

 antitoxin mixtures might, finally, because of their close 

 relationship to the crystalloid salts, contain the free sub- 

 stances beside completely neutralized aggregates. Accord- 

 ing to the investigations of ARRHENIUS and MADSEN, 

 it is not impossible that such a state of affairs exists 

 in the case of their tetanolysin. We are acquainted with 

 an excellent experimental procedure for analyzing col- 

 loidal mixtures which BILLITZER has employed in a study 

 of the relations existing in mixtures of the electropositive 

 red iron hydroxide and the electronegative yellow arsenious 

 sulphide. If an electric current is sent through such 

 a mixture, the completely neutralized aggregates do not 

 move, while the unneutralized aggregates, which carry 

 the electric charge of the colloid that is present in excess, 

 are slowly carried to the oppositely charged pole. The 

 traces of free colloid still present move most rapidly 

 and to opposite poles, where they evidence themselves 

 in this case through differences in color. 



The transition from the complicated conditions exist- 

 ing in the case of the toxins to the more simple ones 

 in the case of the precipitating and agglutinating sub- 

 stances is rendered easy through the fact that in the 

 latter case we are dealing with the reactions of the rela- 

 tively well-understood proteins, or substances closely 



