164 RALPH S. LILLIE. 



general and fundamental basis of a reciprocality of this kind is 

 electrical; morphological polarity, a closely related phenomenon, 

 would then have a similar basis, 1 and probably also other cases of 

 reciprocality, like reciprocal inhibition in the nervous system. 

 It is well to recognize, however, that together with this factor 

 others often undoubtedly enter, partly independent, partly 

 dependent upon the electrical factor. 2 



The distances through which these inhibitory and accelerating 

 influences are perceptible in metals vary with the conditions, the 

 chief factors being the nature of the metals in contact and the 

 electrical conductivity of the solution. An iron wire in contact 

 with a metal of higher solution-tension (Al, Mg, Mn, Zn), and 

 immersed in a 2 per cent, albumin-containing solution of KsFeCye, 

 remains free from filaments for a distance of several centimeters 

 from the region of contact. Conversely, a strip of zinc in contact 

 with a nobler metal (Pt, Cu, Fe) or carbon shows an accelerated 

 formation of filaments for a similar distance. Theoretically, the 

 current of the circuit extends through the whole of the metal 

 and the adjoining solution; the intensity of the current between 

 metal and solution at any point is a measure of the rate of 

 electrolysis at that point (Faraday's law) ; this intensity is deter- 

 mined by the E.M.F. of the circuit and by the resistance of the 

 intervening stretch of solution (that of the metal being negligible 

 in comparison). The rate of action is thus greatest near the 

 metallic junction, and grades off from there. A similar rule will 

 hold for the formative or other influence of a circuit arising through 

 local alteration in a living cell, tissue, or organism. Any local 

 alteration of potential, due to injury, increased metabolic activity, 

 or other condition, may thus exert an electrical influence at a 

 distance from the site of alteration. In the case of a single cell, 

 or other continuous element like a nerve, a current typically 

 flows through the extracellular part of the circuit toward the 

 region of alteration or physiological activity; presumably such 

 a current produces at different points along its course the usual 

 physiological effects of electrical currents, varying according to 

 its intensity, local density, time-relations, etc. It is to be pre- 



1 Cf. Mathews, Amer. Journ. Physiol., 1903, Vol. 8, p. 294. 



- E. g., the flow of a hormone-containing solution may depend on an electrical 

 endosmose effect, etc. 



