396 PROTOPLASMIC ACTION AND NERVOUS ACTION 



that it depends largely upon the direct physical com- 

 pensation of the bioelectric current of the approaching 

 excitation-wave, which in the region beyond the actual 

 area of excitation traverses the surface in a direction 

 opposed to that of the polarizing current (Fig. 6). 

 An analogous effect is observed in a passive iron wire 

 in nitric acid when a piece of platinum foil is pressed 

 into close contact with it; an activation wave started 



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Fig. 6. — Showing the opposed directions of action current and polarizing current 

 through the resting portion of the nerve in the anelectrotonic region; the excitation 

 wave is nearing the anodal region of a battery current led into the nerve by non-polarizable 

 electrodes. 



at another region of the wire is blocked in the vicinity 

 of the platinum. This effect is dependent on the 

 intersection of the two local circuits, active-passive and 

 platinum-passive, which are opposed in direction. 



The mutual interference of excitation-waves in living 

 tissues is probably to be explained in an essentially 

 similar manner as an instance of mutual compensation 

 of oppositely oriented bioelectric circuits. This phe- 

 nomenon is best demonstrated in rings of medusa 

 tissue^ or rings of heart muscle;^ two contraction-waves 



^ Cf. A. G. Mayor, Carnegie Institute Ptiblications, No. 102 (1908), 

 p. 115; American Journal of Physiology, XXXIX (1916), 375; cf. 



P- 379- 



" W. E. Garrey, American Journal of Physiology, XXXIII (19 14), 

 409. 



