488 



Dr. A. D. "Waller. 



through the galvanometer, whatever had been the direction of the 

 exciting current — i.e., with A previously anodic or previously kathodic. 

 On repealing the experiment, with lead-off through B and C there is 

 little or no effect. The results are independent of the position of C, 

 which may be transferred to the lower surface without altering them. 

 The inefficacious combination B C is at once rendered efficacious by 

 transferring B to the upper surface. (It is of course understood that 

 any accidental current between A and C and B and C is compensated 

 before each excitation.) 



The experiment may be further varied in several ways, of which the 

 most obvious is that in which all three electrodes are external or 

 internal. 



With external exciting electrodes A and B and subsequent effects 

 led off from A C and B C, the direction of deflections indicates current 

 in the skin from C to A and from C to B, i.e., outgoing in A and B 

 respectively, for both directions of excitation A to B or B to A. With 

 internal exciting electrodes and the same (moderately strong) excita- 

 tion there is little or no effect between C and A, or C and B, or even 

 A and B. 



3 



£jcC, 





G 





A 







f f===r-======= — £>xin ^ ^ — ^ 



Conclusion. — The two facts that I consider to be of principal im- 

 portance as regards the further study of skin-phenomena are — 



1. That the normal current of the unexcited skin is ingoing. 



2. That the normal response of the excited skin is outgoing. 



The hypothesis or figment in accordance with which these facts may 

 be understood, or at least remembered, can be expressed as follows :- — 

 In a passive mass of living (animal) matter acted upon by its environ- 

 ment, there must be greater chemical change at any external point of 

 its surface than at any internal point of its mass, and therefore an 

 ingoing current. In an active mass of living (animal) matter giving 

 out energy to the environment, chemical change must be greater 

 within the mass than at the surface, and therefore an outgoing 

 current. In the passive state any point of the surface is electro-posi- 

 tive to any point of the interior ; in the active state internal points 

 become less electronegative or actually electropositive in relation to 

 the external surface. 



Bibliographical Note. 



Normal Current, or Current of Best. — Du Bois-Keymond,* in connection 

 with his investigation of muscle currents, was the first to definitely 

 * ' Thierisclie Elektricitat,' 1854-57, passim. 



