28o PROTOPLASMIC ACTION AND NERVOUS ACTION 



into account the processes at the two opposite surfaces 

 of each element, since if these surfaces are close enough 

 together, there is mutual interference of the two processes, 

 and more complex conditions have to be assumed. Yet 

 the fundamental condition assumed by Nernst's theory 

 — a membrane partitioning an electrolyte solution — 

 exists in the living tissue, hence polarization effects must 

 result when a current is passed; and it has been found 

 that the foregoing law relating the current-intensity to 

 the duration required for a constant polarizing effect holds 

 true also for the stimulating effect of the current within 

 a considerable range of intensities and durations, and 

 especially for higher intensities. This general result, 

 that polarizing effect and stimulation run closely parallel, 

 indicates that stimulation is a consequence of the 

 polarizing action of the current. 



Hermann^ and others had previously referred the 

 stimulating action of the current to its polarizing action, 

 since in any tissue the presence of a reverse current 

 (polarization current) can always be demonstrated 

 immediately after the passage of a brief constant current. 

 A high degree of polarizability is characteristic of living 

 tissues, and this peculiarity is undoubtedly dependent 

 on the semi-permeable properties of the cell membranes, 

 since the polarization current is greatly diminished at 

 death, at which time the membranes lose semi- 

 permeability, as already pointed out. Both polariza- 

 bility and semi-permeability are thus manifestations of 

 the same condition, hindrance to diffusion of ions. 

 Lapicque has shown that the polarization currents 

 obtained from dead partitions (parchment or bladder 



^ L. Hermann, FawJJwc/f der Physiologie,Leipzig, II (1879), Part 1, 193. 



