CORRELATION BETWEEN METABOLIC GRADIENTS. 319 



therefore, to insist . . . that these functions were essentially chem- 

 ical, and that the intrinsic chemical nature of the vital processes 

 must not be overlooked in favor of their physical symptoms. . . . 

 Hermann's weighty dictum of the isoelectricity of uninjured ' rest- 

 ing' nerve or muscle signifies to me that such a tissue develops 

 no current that can be led off externally, so long as its metabolism 

 i.e., internal chemical function is equal in all parts. Every dis- 

 turbance of this equilibrium sets up currents that can be led off. 

 Alteration of chemical function in any part of a living continuum 

 may, however, be expressed, not merely in its becoming negative, 

 but equally in its becoming positive to unaltered parts. Hence, if 

 we are to characterize the point differing in chemical function 

 from the rest of the substance, as (relatively) altered, we must, in 

 my opinion, distinguish between a (relatively} positive and a 

 ( relatively} negative alteration. And it is not altered chemical 

 composition, but altered chemical function, which may lead to 

 altered composition, that characterizes this change. ... If all 

 parts of a living continuum are in equilibrium or alter at the same 

 rapidity, ascending or descending, 3 there will be no current to lead 

 off. Every difference in rate or direction of alteration, however, 

 produces a current that can be led off. We may, accordingly, con- 

 ceive of all the different rates of positive and negative alteration 

 as forming a series of such a character that the most rapid ascend- 

 ing alteration forms the upper i.e., positive the most rapid 

 descending alteration tlie lower i.e., negative end of the iseries. 

 If two parts of a living continuum, which differ in chemical func- 

 tion, are joined by an external circuit, there will, cccteris paribus, 

 be a stronger current in proportion as the distance between the 

 two points connected in circuit is greater in the above series, and 

 the positive current will always flow through the external circuit 

 from the point nearest the positive end of the series to that nearest 

 the negative end. This is the universal law of all physiological 

 currents in nerve and muscle." * 



3 By the term " ascending " Hering means assimilatory metabolic change, 

 and by "descending," dissimilatory metabolic change. 



* The quotation is taken from the English translation in Brain with a 

 few changes which follow the translation in Biedermann's " Electro-physiol- 

 ogy." Italics of the original are preserved. 



