ELECTRO-PHYSIOLOGY. 595 



the longitudinal surface. They are surrounded by a non-electrie 

 conducting surface. When an electrode is placed on the longitu- 

 dinal surface and would touch the positive side of the molecules, the 

 other electrode on the transverse section would be in contact with 

 the negative side. 



ALTERATION HYPOTHESIS. It was shown that muscle not 

 injured exhibited no electrical current. Hermann states that these 

 currents are due to the chemical constitution of the tissue at the 

 cross-section. He believes that the current is the result of injury, 

 causing death of a small part of the muscle fiber at the cross-section, 

 and so producing differences in potential. The difference of poten- 

 tial arises at the demarcation between dying and injured muscle; 

 hence the name "demarcation current." The dying portion of the 

 cross-section of the muscle behaves negatively to the living, and 

 the electromotive force has its seat in the demarcation zone between 

 the living and dying. 



Hering is in accord with DuBois-Reymond, that the normal 

 resting muscle is the seat of electromotor forces which are not 

 exhibited. The electrical currents are due to chemical changes in 

 the tissues. Anabolism causes a positive electrical phenomenon, 

 and katabolism a negative condition of the part. The majority 

 of physiologists have accepted the alteration theory as the one explain- 

 ing the majority of the facts observed. 



Neither theory explains all the facts. 



