76 THE ORIGIN OF THE NERVOUS SYSTEM 



production and consequent increase in hydrogen ion 

 concentration at points of excitation will not account 

 for the electrical changes, since the currents produced 

 in this way are opposed in direction to those which are 

 actually observed. It is very probable, as Lillie sug- 

 gests, that the membrane changes may be the primary 

 factors in highly irritable tissues like nerve, where the 

 processes of excitation and transmission and recovery 

 are extremely rapid, but it is possible that in excitation 

 in general the changes in the membrane may be incidental 

 rather than primary. In an oxidation-reduction cell 

 the electric currents produced show the same relation to 

 the oxidation end of the cell as do the bioelectric cur- 

 rents to the region of excitation. That is, the region 

 where oxidation is going on in the oxidation-reduction 

 cell is externally electronegative to the region where 

 reduction is occurring. I have repeatedly called atten- 

 tion to the apparent impossibility of dissociating the 

 process of excitation in protoplasm in general from an 

 acceleration of the fundamental dynamic activities of 

 protoplasm, particularly those concerned with the 

 liberation of energy. If current conceptions are correct, 

 the chief source of energy in living protoplasm is oxida- 

 tion. Moreover, it is apparently true that a region of 

 rapid oxidation in protoplasm gives rise to electrical 

 conditions similar to those which we observe in relation 

 to the more highly specialized forms of excitation. 

 While it is by no means necessary, nor at present justifi- 

 able, to maintain that oxidation is the primary factor in 

 excitation, it apparently is true, so far as electrical 

 phenomena are concerned, that a region of more rapid 

 oxidation in protoplasm behaves with respect to 



