102 DYNAMICS OF LIVING MATTER 



It is of the greatest importance that the stimulation at the making 

 of a current occurs at the cathode, as this indicates that an increase in 

 the concentration of the cations is responsible for this result. On 

 account of the fact that the migration ' velocity of the potassium ions 

 is greater than that of the other cations in the muscle, it might appear 

 as though the latter were responsible for the stimulating effect at the 

 cathode at the making of the current.* If the current is broken, the 

 stimulation occurs at the anode. It has been suggested by Griitzner 

 that the effect of the breaking of a current is in reality due to a current 

 of polarization which, of course, has the opposite direction from the 

 polarizing current. In this case, too, the stimulating effect at the 

 anode at the breaking of a current is due to an increase in the concen- 

 tration of the cations. 



While a constant current is passing through a nerve, a region of 

 increased irritability exists around the cathode. I pointed out four 

 years ago that such a condition can be produced in the nerve by treat- 

 ing it with a salt which precipitates or diminishes the concentration of 

 the calcium ions, e.g. sodium-oxalate, -citrate, -fluoride, -carbonate, 

 etc. It is not impossible that a substitution of K for Ca, or vice versa, in 

 ion-colloids actually occurs at the cathode, while a constant current flows 

 through the nerve. At the anode we must expect, and we find, a de- 

 creased irritability. Until quite recently the phenomena of catelectrotonus 

 and anelectrotonus, and perhaps the effects of the current in general, 

 were explained on the basis of antagonistic physiological processes 

 being aroused by the current, one being called assimilation, the other 

 dissimilation. As it is impossible to connect an adequately definite 

 chemical idea with these terms, it is useless to discuss this view. It 

 is obvious that those who used these terms did so under the impression 

 of the since refuted notion that a metallic conduction occurs in living 

 tissues, and that therefore a current can directly break up chemical 

 compounds in the nerve or muscle ; while we now know that the disso- 

 ciation exists before the current starts. Moreover, the above-mentioned 

 experiments on the effects of induction on the nerve show that even 

 without any charges being withdrawn from the nerve, and without 

 any secondary chemical effects, the stimulation occurs. This shows 

 that the secondary chemical reactions at the poles, due to the trans- 

 formation of the ions into atoms, have nothing to do with the stimu- 

 lating effects of the current. I believe that for these reasons it is 

 advisable to discontinue the assertion that the current causes dissimi- 

 lation at the one and assimilation at the opposite pole of a cell. 



It seems to be a general law that wherever the constant current 



* I expressed this possibility in my lectures five years ago. 



