GENERAL PHYSIOLOGY OF MUSCLE-TISSUE. 



77 



conducted to the galvanometer an electric current the intensity and direction 

 of which are indicated by the deflection of the galvanometer needle. The 

 existence of this current is most conveniently demonstrated with single 

 muscles the fibers of which are parallel e.g., the sartorius, or the semimem- 

 branosus of the frog. If the tendinous ends of either of these muscles be 

 removed by a section made at right angles to the long axis, a muscle prism is 

 obtained which presents a natural longitudinal surface and two artificial 

 transverse surfaces. A line drawn around the surface of such a muscle 

 prism at a point midway between the two transverse sections constitutes the 

 equator. 



When the natural longitudinal and artificial transverse surfaces are 

 connected with the wires of a galvanometer the terminals of which are pro- 

 vided with non-polarizable electrodes, an elec- 

 tric current is at once developed. In all in- 

 stances the current, as shown by the deflec- 

 tion of the needle, originates at the transverse 



face, passes through the muscle to the 

 longitudinal surface, thence through the gal- 

 vanometer to the transverse surface. The 

 longitudinal surface is, therefore, electroposi- 

 tive, the transverse surface electronegative. 

 The two points exhibiting the greatest differ- 

 ence of potential, and hence the most power- 

 ful current, lie in the equator and in the cen- 

 ter of the transverse surface. Currents of 

 gradually diminishing intensity are obtained 

 when the electrode placed on the longitudinal 

 surface is removed toward either end. Feeble 

 currents are developed when two points situ- 

 ated at unequal distances, either on correspond- 

 ing or opposite sides of the equator, are con- 

 nected; in either case the current flows from 

 the point lying nearest the equator to the point 

 farthest from it. Similar currents are obtained 

 when two points on the cross-section situated 

 at unequal distances from the central axis 

 are connected, in which case the direction of 

 the currents will be from the point lying near- 

 est the periphery toward the center. On the 

 contrary, no current is developed when two points on the longitudinal surface 

 equally distant from the equator, or two points on the transverse surface 

 equally distant from the central axis, are connected. Such points are said to 

 be isoelectric. These facts are shown in Fig. 35. The natural ends of the 

 muscle, enclosed by sarcolemma and tendon, do not exhibit, if carefully 

 preserved from injury, the negativity characteristic of the artificial transverse 

 ends. 



Similar electric conditions are exhibited by the muscles of man and other 

 mammals, by the muscles of birds, reptiles, amphibia, etc. The currents 

 developed by connecting the equator on the longitudinal surface with the 



FIG. 35. DIAGRAM TO ILLUS- 

 TRATE THE CURRENT IN MUSCLE. 

 The arrowheads indicate the direc- 

 tion; the thickness of the lines in- 

 dicates the strength of the currents. 

 (Landois and Stirling.') 



