COLLOIDS 101 



the similarity, and even the identity of all the reactions of 

 arsenobenzenes with those of all the other antigens, allows 

 us to assume that the physicochemical constitutions are 

 also identical. This phenomenon of least saturation will 

 explain tHe formation of toxons, toxoids, epitoxons, epi- 

 toxoids in mixtures of toxins and antitoxins (Ehrlich). 



For phenomena of absorption and hydrolysis, the precipi- 

 tant action of neutral salts and the dissolving action of 

 acid or alkaline media which characterize every colloid 

 permit us to consider each colloidal granule as a sort of cell 

 which can be hydrated and inflated, dehydrated and 

 retracted, which can absorb, retain and secrete all sorts of 

 salts by the purely physical phenomenon of osmosis with- 

 out regard to chemical combinations which can affect its 

 amino groups and other molecules by their special affinities. 



The nature of the reactions between colloids or between 

 colloids and salts as well as the quantity of the substances 

 which can be combined or absorbed are determined espe- 

 cially by the physical characteristics of the colloid. These 

 include the form and volume of the granules which compose 

 the colloid as well as the proportion of the different sized 

 granules. So long as "the choice" of substances with which 

 a colloid may combine and the nature of the compounds thus 

 formed, depends eventually on chemical affinities of the 

 molecules which enter into the composition of the granules, 

 it is very possible to imagine, that in a granule composed, 

 for example of one hundred molecules, ten or twenty or sixty 

 of these molecules will form new combinations while the 

 others will remain intact. According to the proportion 

 of different granules the physicochemical properties as well 

 as biologic effects of the colloid will be different. 



Arsenobenzene is the simplest colloid-antigen wh'ch we 

 know; its granules are of different and variable size but all 

 are composed of molecules of the same amine. Biologic 

 antigens in general have a much more complex composition; 

 casein, for example, is composed of a dozen different amino- 

 acids (alanin, leucin, serin, glutamic acid, aspartic acid, 

 arginin, lysin, hystidin, cystin, tyrosin, phenylalanin, 

 tryptophan) and it is certain that between casein and 



