STRUCTURES RESEMBLING ORGANIC GROWTHS. 183 



circuits should be equally possible in such cases, and these may 

 be associated under certain conditions with chemical change. 

 The action of strong electrolytes upon poorly conducting material 

 (e. g., wood, rubber, leather, etc.) is probably accompanied by 

 electrolytic action of this or similar kind. The distinction be- 

 tween ordinary chemical action and chemical action due to 

 electrolysis is in fact rendered arbitrary by the facts of chemical 

 action at a distance. Wherever electrical transfer is possible 

 under conditions not resulting in the development of a counter 

 E.M.F. or other polarizing effect which arrests the current, the 

 chemical influence may be transmitted to a distance. This 

 explains why circuits are necessary to this process. Of course 

 the rate of any reaction thus conditioned varies inversely with 

 the electrical resistance of the circuit which determines it; and 

 it is only when the resistance is relatively low as in circuits 

 consisting of a metallic conductor combined with an electrolyte- 

 solution, or in circuits of two electrolyte-solutions separated by 

 a polarizable semi-permeable partition that such transmission 

 can take place through considerable distances. 



A difficulty may be felt in accounting for the conduction of 

 electricity across the membrane in living cells. This is normally 

 semi-permeable, i. e., impermeable to ions and other diffusing 

 substances; the continued existence of the cell depends in fact 

 upon this condition. The assumption of a selective permeability 

 to cations (or reversibility to cations) may remove the difficulty 

 of explaining how the current can be conducted across the resting 

 regions of the cell-surface. At the active regions conduction 

 may take place by chemical reaction accompanied by electron- 

 transfer, as already suggested. It seems possible, however, that 

 at times the positive stream may pass from the cell-interior to 

 the external medium without such chemical change; thus the 

 addition of cations to the membrane from within, following 

 stimulation at some other region, might disturb the polarization- 

 equilibrium and detach corresponding cations from the outer 

 surface; at such regions the current would flow from within 

 outward without change in the membrane, as observed at the 

 resting regions of the cell. In such a case the membrane w r ould 

 behave like a non-polarizable electrode. To what degree and 



