450 MANUAL OF PHYSIOLOGY. 



piece of muscle from both the transverse sections or extremities 

 of the muscle block to the middle of the longitudinal surface, 

 whether it be a cut surface (longitudinal section) or the natural 

 surface of the muscle. This is called the muscle current, or some- 

 times natural muscle current. 



If the cylinder in the accompanying figure be taken to repre- 

 sent a block of muscle, e would correspond to the equator, and p 

 to the poles, and the arrow heads show the direction of the cur- 



FIG. 182. 



Diagram to illustrate the Currents in Muscle. (e) Equator, corresponds to the centre 

 of the muscle ; (p) Polar regions of cylinder, representing the extremities of the mus- 

 cle. The arrow heads show the direction of the surface currents, and the thickness of 

 lines indicates the strength of the currents. (After Fick.) 



rents passing through the galvanometer, the thickness of the 

 lines indicating their force. The dotted lines o are connected 

 with points where the electro-motive force is equal, and therefore 

 no current exists. 



The electro-motive force of the muscle current in a frog's 

 gracilis has been estimated to be about .05-.08 of a Daniell cell. 

 It gradually diminishes as the muscle loses its vital properties, 

 and is also reduced by fatigue. The electro-motive force rises 



