EXCITATION AND TRANSMISSION 77 



regions of less rapid oxidation like a region of excitation 

 with respect to less excited or unexcited regions, i.e., it 

 becomes electronegative and a current similar to the 

 excitation current is set up between it and other less 

 rapidly oxidizing regions. If this current constitutes 

 the exciting factor for adjoining regions and so the 

 primary factor in transmission, then a region of rapid 

 oxidation, however determined, may initiate a process 

 of transmission which induces excitation, involving 

 increase in the rate of oxidation at points within the 

 range of effectiveness of the current, and so may give 

 rise to an oxidation gradient. Doubtless even in such 

 a case membrane changes are involved, but my point is 

 merely that they need not necessarily be regarded as 

 the most significant changes in the complex process. 

 In some of his later papers Lillie calls attention to the 

 probable significance of oxidation-reduction in the more 

 primitive excitation-transmission relations. 



In such a process as this the velocity of transmission 

 may be very low as compared with nerve, so low indeed 

 that it might in many cases scarcely be termed trans- 

 mission in the ordinary sense. Moreover, in such a 

 process a decrement is to be expected, since a relation 

 unquestionably exists between the electrical condition 

 and the rate of oxidation, and this being the case a 

 gradient must result. In fact, in the extreme case such 

 a gradient may arise without any wavelike transmission 

 of excitation, such as occurs in the nerve, electrical 

 transmission only being involved and determining a 

 gradation in rate of oxidation and associated condi- 

 tions from the original region of high rate to a certain 

 limit of distance. 



