STRUCTURES RESEMBLING ORGANIC GROWTHS. 167 



the conductor be electrolytic or metallic. 1 A local change of 

 potential in a stretch of nerve thus produces instantly an electrical 

 change at all points of the circuit constituted by the nerve and 

 its medium, including therefore inactive regions of the tissue at 

 a distance from the immediate site of alteration; and if the effect 

 at any such region be sufficiently intense, a second state of excita- 

 tion is there aroused, and a similar effect is transmitted from this 

 second region to other resting regions beyond. As a striking 

 concrete illustration of the instantaneous transmission of electro- 

 lytic effects along a conductor to a distance from the region 

 immediately affected, I recommend the following simple experi- 

 ment. A straight piece of copper or platinum wire, e. g., 20 cm. 

 long, is immersed in a vessel containing dilute H-SO4; the wire 

 remains unaltered. If then one end is touched with a piece of 

 zinc, instantly bubbles of hydrogen start out from the surface 

 of the wire along its entire length. The transmission of the 

 effects of a local stimulus in such a tissue as nerve is conditioned 

 by a process of the same type, according to the present theory; 

 hence it is independent of the transfer of material; and the 

 velocity with which the impulse is propagated is limited only by 

 the degree of sensitivity of the tissue to slight electrical disturb- 

 ance and by the rapidity with which the local response takes 

 place. 2 



1 /. e., the speed is that of transmission through the ether equal to the velocity 

 of light, or of electricity through a metallic conductor (apart from retardation 

 due to electrostatic influences or self-induction). An experimental investigation 

 of the velocity of the electric current through solutions is described in the book by 

 Monroe Hopkins, "Experimental Electrochemistry" (London, 1905). The 

 author reaches the conclusion: "An electrolyte solution conducts the electric current 

 as rapidly as a conductor of the first class, regardless of its composition, provided 

 we have an equal ohmic resistance of a non-inductive type" (p. 76). 



2 In a recent article (Amer. Journ. Physiol., 1917, Vol. 42, p. 469) Mayer has ob- 

 jected to this theory of transmission (which I have called the "local action theory") 

 on the ground that it is "too simple." Nothing, however, but the speed of trans- 

 mission of the excitation-wave, and the identity of its effects with electrical effects 

 (stimulation, inhibition, etc.), is directly explained by the theory in question. The 

 entire phenomenon of nerve conduction is indeed exceedingly complex, including 

 metabolic and other factors of a nature as yet imperfectly known; but the detailed 

 nature of these factors need not be regarded by this general theory, which aims 

 merely at accounting for the possibility and rate of nervous and other forms of 

 physiological transmission where direct transfer of material does not enter. This 

 it does by referring the phenomenon to a more general class, regarding which our 



