524 STUDIES IN IMMUNITY. 



rapidly as the concentration; the antigen loses its avidity for anti- 

 body in proportion to the amount of it that has been fixed. This, 

 according to general opinions, is the way in which adsorption 

 phenomena act. 



It is evident from an examination of these facts that the presiding 

 force in the union of antigens with their antibodies is the same as 

 the one which produces the reactions that have been grouped under 

 the name of adsorption phenomena. But is this force or affinity 

 of adsorption sufficiently elective to permit one to attribute to it 

 alone serum reactions, the most striking characteristic of which is 

 their remarkable specificity? It has become more and more certain 

 that adsorbing substances manifest toward adsorbable substances 

 which are mixed with them, tendencies of attraction of very unequal 

 intensity and consequently the affinity of adsorption is similar to 

 a true chemical affinity; both, in other words, are elective. In 

 both instances a struggle may take place between two substances 

 for the possession of a third. In the same way fixation of one sub- 

 stance on another may be inhibited by a monopoly of the first by a 

 third substance which thus protects the second. For example, the 

 albuminous substances of blood protect red blood cells from soap 

 (Meyer), or even against the hemolysin of eel serum (Frouin); 

 sodium citrate protects corpuscles from the agglutinating and 

 hemolytic effect of barium sulphate (Gengou), and so on. The 

 lecithin which is present in bovine serum is probably united with 

 another substance, without doubt of an albuminous nature, for if it 

 were not so agglutination would take place in this serum itself.* 

 In all instances a real struggle occurs between adsorption affinities; 

 similar facts have also been found with animal charcoal. Substi- 

 tutions may also be noted. Barium sulphate manifests avidity for 

 mucin and for sodium citrate. When mixed with lecithin it clumps 

 in large masses, and on adding sodium citrate to them they rapidly 

 dissolve and the mucin is liberated (Gengou), in other words, the 

 sulphate prefers citrate to the mucin. 



Certain substances in the category of lipoids which may be ob- 



* As we know, Toyosumi found that bovine serum has the power of agglutinat- 

 ing an aqueous emulsion of lecithin. Sleeswijk,and I have found that this is also 

 true even with an extract (by means of methyl alcohol) of the lecithin from dried 

 bovine serum. 



