ADSORPTION POTENTIALS AND ELECTROKINETIC PHENOMENA 291 



present on a wall to a measuring instrument we always obtain only 

 the phase boundary potential, and not the adsorption potential, 

 and these two, as was previously shown, are not identical. The only 

 case in which an adsorption potential yields a direct electric mani- 

 festation which is detectable by electric measuring instruments is that 

 of the hydrodynamic potential (or the potential of falling particles). 

 But as we have shown before, the conditions prevailing in the living 

 organism are most unfavorable for the generation of hydrodynamic 

 potentials. 



But, on the other hand, the adsorption potential manifestations 

 that are undetectable by electric measuring instruments are quite 

 clearly present in colloidal solutions. Only adsorption potentials can 

 exercice an influence upon the state of a colloidal solution. For this 

 state is determined by the tensions existing at the boundary surfaces 

 of the phases. It is on these tensions that changes in the form and 

 size of the particles, coagulation and peptization depend. The most 

 important single agent affecting these tensions is the electric charge. 

 But since all changes in the colloidal state depend upon the recip- 

 rocal action of adjacent boundary surfaces, therefore only those 

 double layers can be of significance which are located on the boundary 

 surfaces, on the walls of the dispersed particles and in the adjacent 

 to them la3''ers of the H" rsion medium. This introduces us to 

 another mode of ar '- of adsorption potentials other than their 

 electrokinetic maniieit^tions, which, moreover, prepares us for the 

 theory of colloidal behavior. 



But all of these processes are really of much greater importance 

 for the interpretation of other significant physiological problems 

 than would first appear from the above discussion. If we consider 

 the capillary-electrical phenomena in diaphragms with very narrow 

 pores, such as can be observed in collodion or gelatin membranes, 

 especially the polarization phenomena described by Bethe, then the 

 physiological apphcability of these processes to such problems as 

 currents of rest, action currents, and of the stimulation of muscles 

 and nerves becomes so evidently manifold that we can hardly attempt 

 to discuss them at greater length in this volume. Bethe'^*^ had made 

 an important beginning in this direction in which the exceptional 

 position of the H-ions is again emphasized. There also the question 

 narrows itself down to the alternative as to whether to base the 



«8 A. Bethe, Pflugers Arch. f. d. ges. Physiol. 163, 147 (1916). 



