CORRELATION BETWEEN METABOLIC GRADIENTS. 315 



tion are generally responsible for the origin of potential differences 

 in organisms, this need not necessarily be the case. Other chemi- 

 cal reactions could also give rise to potential differences, and in 

 such cases the direction of the resulting current might be different. 

 That is to say, where an oxidative reaction is the cause of the 

 current, the region of higher rate becomes electropositive (int.), 

 since oxidation consists in the assumption of positive charges (or 

 the loss of negative charges). On the other hand, if some other 

 chemical reaction were concerned, the direction in which the cur- 

 rent would pass naturally would depend on the nature of the re- 

 action, and could not be predicted until the reaction involved were 

 known. It is very likely that in some organismic activities a bio- 

 electric current would be produced in which the region of highest 

 rate of activity or region of stimulation would be electropositive 

 (galv.) to less active or unstimulated regions. It is also, of course, 

 possible that differences, not only in the rate, but also in the kind 

 of chemical reaction at different regions, may give rise to potential 

 differences, in which case again the direction of the current will 

 depend upon the reactions involved. 



Our general point of view, then, is that potential differences in 

 living things usually originate in metabolic processes, probably 

 chiefly the oxidative processes, since oxidation-reduction reactions 

 give rise to currents identical as to direction with those occurring 

 in organisms. Such currents could arise either through the pres- 

 ence of an oxidation process at one point accompanied by a reduc- 

 tion process elsewhere or through a difference in the rate of the 

 oxidation-reduction process at different regions, giving rise to a 

 concentration chain. Although we are unable in the present state 

 of our knowledge to decide between these two possibilities, it seems 

 more probable that the potential differences are due to the second 

 of the two suggestions, since in the organism the oxidation process 

 is not, as far as we know, separated from the reduction process. 

 Differences in the concentrations of ions at different regions would 

 therefore seem to be the usual sources of the potential differences ; 

 such concentration differences arise through differences in the rate 

 of reaction. 



The point of view presented here that the bioelectric currents 

 are chemical in origin has been held by a number of physiologists. 



