150 COMPARATIVE ELECTRO-PHYSIOLOGY 



equator, and the other, is increased as the latter is moved 

 further and further away, say towards the right transverse 



section. The distribution 

 of electrical tension on 

 the left side of the 

 equator is symmetrical 

 with this (fig. 104). On 

 these facts was based the 

 theory of Du Bois- 

 Reymond ; but this has 



FIG. 104. Distribution of Electrical . , r , , . 



Tension in Muscle-cylinder. since been found to be in - 



adequate. I shall later 



return to the explanation of the particular distribution of 

 electrical tension involved. 



According to the theory of Bernstein, known as the 

 Electro-chemical Molecular Theory, the fundamental attribute 

 of the molecule is chemical. Its poles are supposed to attach 

 to themselves electro -negative groups of atoms, while its 

 sides attach oxygen, and stimulation is supposed to be 

 attended by explosive chemical changes. 



According to Hermann's Alteration Theory, finally, all the 

 electro-motive activities of living tissues are supposed to be due 

 to chemical rather than molecular changes of the substance. 

 Jn amplification of this theory, Hering attributes all electro- 

 motive phenomena to the disturbance of equilibrium by 

 up and down chemical changes. 



It is my intention to show in the course of the present 

 chapter that the current of injury is an after-effect of 

 over-stimulation. And since excitation is fundamentally 

 due to molecular upset, we shall best understand the 

 electro-motive changes concomitant with it, if we first study 

 it and its after-effect under the simplest conditions, namely 

 those of inorganic substances. For here the action of such 

 complicating factors as assimilation and dissimilation is 

 clearly out of the question. 



We have found for example that a piece of well-annealed 

 wire was iso-electric throughout its length. In the first 



