PHYSICOCHEMICAL PROPERTIES 39 



reaction is exactly known. For the moment it seems to us 

 important to recall the complete identity of the reactions 

 between serum and arsenobenzene on the one hand and 

 between serums and biologic antigens (albumins, microbes 

 and their secretions) on the other. 



In fact it is more than probable that in the two cases the 

 nature and the mechanism of the reactions are the same. It 

 is the reaction of the acid and the alkaline functions of the 

 antibody, favored by the chlorides and phosphates of sodium 

 and calcium as well as certain substances, such as lipoids, 

 lecithin, cholesterin, which cause coagulation or dissolution 

 of the antigen; the action of the acid and alkaline function 

 ought to be fundamental and always the same. Thus should 

 be explained complement or alexine which is found indiffer- 

 ently in every normal serum, which disappears on heating and 

 which can reactivate the action of a specific serum antibody 

 when this is heated. Specific precipitant action should be 

 determined by the salts of calcium and other substances in 

 the plasma which form with arsenobenzenes, more stable, 

 less soluble combinations of which the quantity increases 

 as the result of a series of injections. Thus should be 

 explained the sensitizing substances or amboceptors which do 

 not disappear on heating, which combine with antigen, but 

 whose action must be assisted first by acids and oxidizing 

 agents, finally by alkalies in order to become appreciable. 



Dioxydiaminoarsenobenzene has several affinities. Tri- 

 valent arsenic can fix two molecules of metallic salts; amines 

 can be bound by acids or by formic aldehyde and through 

 this latter can fix a series of other substances. The oxyhy- 

 drate radicals may exchange their hydrogens for a series of 

 inorganic or organic bases. We know for example that when 

 one binds to the amines of arsenobenzene one or two molecules 

 of formaldehyde sulphonate of sodium, the product becomes 

 soluble in neutral medium and passes from the colloidal 

 state to the state of a salt and that by the substitution for 

 the hydrogen of the oxyhydrate radical one may make these 

 combinations soluble with salts of calcium. 



A non-lethal dose of luargol injected into the blood of an 

 animal in the form of a sodium compound ought then to 



