THE PHENOMENA OF ADSORPTION. 441 



We recognize that these facts were indicative simply and were 

 not an aosolute demonstration. As concerns the phenomenon of 

 agglutination, Bordet noted that it takes place in two distinct 

 phases: during the first a complex is formed by the union of the 

 agglutinin with the bacteria; in the second the salt precipitates this 

 complex. In the analogous instances of clay flocculation we have 

 to deal, then, with the second phase only and obtain no light on the 

 mode of union of the agglutinin with the receptors of the bacteria. 



The presumptions that we deduced from these preliminary 

 observations led to researches on molecular adhesion which soon 

 brought out serious experimental confirmations. In comparing the 

 fixation of hemolysins on corpuscles with the adsorption of analin 

 dye by filter paper, Bordet mentioned as an analogy that the cor- 

 puscles do not fix the active substances according to the law of defi- 

 nite proportions. Thus we find that a given volume of hemolytic 

 serum destroys a larger amount of corpuscles when they are added 

 to it in a single dose than when they are added in successive divided 

 doses at relatively long intervals. If the second method is used it 

 is evident that the first corpuscles become overladen with active 

 principles and monopolize a larger amount than is necessary to 

 hemolyze thein, thus leaving less for subsequently added corpuscles. 

 In the same way, if a leaf of filter paper is placed in a given amount 

 of methylene-blue solution it takes a uniform color of a given inten- 

 sity. But if a piece of the same size is first cut up into small 

 pieces and these pieces introduced at intervals, we find that the 

 first of them stain deeply and the last ones find no color left. 

 The same experiments were made with the same result by Danysz 

 with ricin and antiricin, by Bordet with alexin and anti-alexin, and 

 by von Dungern with diphtheria toxin and antitoxin : the neutral- 

 izing dose varies depending on whether the toxin is added in a 

 single or in several doses. The same conclusion may be drawn 

 with agglutinins and bacteria, as Craw has shown. We do not 

 wish to insist at this point on the obvious interest brought out by 

 the fact that toxins unite with antitoxins in variable proportions.* 



The analogies between phenomena brought about by sera and 

 those due to substances which certainly do not act chemically, 



* Consult on this subject the former article on the mode of action of antitoxins 

 on toxins, p. 259. 



