92 PROTOPLASMIC ACTION AND NERVOUS ACTION 



that a relatively great adsorption of polyvalent ions is a 

 general rule. The relative effectiveness of polyvalent 

 cations in certain characteristic physiological effects, 

 e.g., ion-antagonism, is of a corresponding order, indicat- 

 ing that in such cases the ions act by adsorption at the 

 structural surfaces of the living system. Thus Al and 

 Cr ions greatly prolong the activity of cilia in isotonic 

 NaCl solution when present in concentrations of less 

 than M/ 100,000.^ 



It should be pointed out that even if the adsorption 

 constants of mono-, di-, and trivalent ions were equal, 

 the trivalent ions should be effective in less than a third 

 of the concentration of the monovalent ions, because, 

 on account of the characteristic form of the adsorption 

 curve, the ratio between the quantity adsorbed and the 

 quantity remaining in solution is much higher in dilute 

 than in concentrated solution; hence sufficient trivalent 

 ions to neutralize the surface charge may be adsorbed 

 from extremely dilute solution. This is Freundlich's 

 explanation of Schulze's rule.'' Whetham's explanation, 

 based on chances,^ is probably insufficient, although 

 purely mathematical considerations would indicate 

 that the statistical conditions to which he calls atten- 

 tion must play a part in the total effect. The ratio 

 between the effective concentrations of Al and Na in the 

 above-cited experiments seems, however, too great to 

 be accounted for on this ground alone, and a high degree 

 of adsorption of polyvalent cations must apparently be 

 assumed. 



^ R. S. Lillie, American Journal of Physiology, X (1904), 430. 



2 Freundlich, Z. physik. Chem., LXXIII (1910), 385. 



3 Whetham, Theory of Solution, p. 396. 



