'.J 



EXTERNAL AND INTERNAL 



85 



" Current of rest " from E to I. 

 " Current of action " from I to E. 



acted upon by its environment, any point of its surface E is 

 chemically more active than any point of its mass I ; E becomes 

 electro-positive to I ; there is therefore current from E to I, an 

 ingoing current, the so-called " current of rest." Let the lump 



become active, any point I is 

 chemically more active than any 

 point E ; there is current from 

 I to E, outgoing current, the 

 " normal organ-current of action." 

 Now, the currents that we call 

 " electrical " and actual currents of 

 matter, streaming through a porous 

 substance, generally occur in the 

 same direction, so that there is an association of phenomena 

 (i) in the case of ingoing electrical current and centripetal 

 current of matter (and of energy) from environment to living 

 substance, and (2) in the case of outgoing electrical current 

 and centrifugal current of matter (and of energy) from living 

 substance to environment. A priori, therefore, we should 

 expect the " skin " of living substance to be the channel of a 

 double current, material and electrical (i) of a current of rest 

 or reception, ingoing and centripetal, subserving the synthetic 

 accumulation of energy ; (2) of a current of action or emission, 

 outgoing and centrifugal, subserving the analytic expenditure 

 of energy. If you are accustomed to think in terms of charged 

 ions, you will imagine the kation as travelling from without 

 inwards with a receipt of energy, from within outwards with a 

 discharge of energy. 



And now consider further what kind of modifications we may 

 expect and look for with the differentiations of function and 

 of structure that have occurred in the external surface of plants 

 and animals. 



Consider, in first place, the principal difference of chemical 

 direction in the main drift of vegetable and of animal metabolism. 

 Vegetable protoplasm is in major degree an instrument of syn- 

 thesis and accumulation, in minor degree the seat of analysis 

 and emission. Animal protoplasm is in major degree an instru- 

 ment of analysis and emission, in minor degree the seat of 



