Mentality and Self-Consciousness 77 



ence of potential there would be no movement of 

 ions through them. 



Since electrically charged ions of the same sign 

 cannot accumulate in considerable numbers, it ap- 

 pears that the end-organs must be permeable to 

 such ions so that the positive and negative ions 

 will be able to migrate through them in opposite 

 directions when an impulse is created. In order 

 to produce such an impulse, nothing more is neces- 

 sary than a change in the relative permeability of 

 the end-organs to positive and negative ions, the 

 necessary energy of motion being already pos- 

 sessed by the ions themselves. Although it may 

 be true that the nerves undergo a certain amount 

 of metabolism during activity, yet it seems more 

 reasonable to regard this metabolism as the re- 

 sult, rather than the cause of nerve-activity. It 

 is inconceivable how any sort of metabolic activity 

 could produce differences of potential in different 

 parts of an organism unless the surrounding phys- 

 ical and chemical structures are properly organ- 

 ized for such a purpose, and if these structures 

 are in themselves adequate to produce such differ- 

 ences of potential then we do not need to invoke 

 metabolism. The metabolism that does occur may 

 be due to wear and tear of the end-organs during 

 activity and to the efforts of the spirazines to re- 

 pair the worn structures. 



