9 o 



TEXT-BOOK OF PHYSIOLOGY. 



When the natural longitudinal and artificial transverse surfaces are 

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

 provided with non-polarizable electrodes, an electric current is at once 

 developed. In all instances the current, as shown by the deflection 

 of the needle, originates at the transverse surface, passes through 

 the muscle to the longitudinal surface, thence through the galvan- 

 ometer to the transverse surface. The longitudinal surface is, there- 

 fore, electropositive, the transverse surface electronegative. The 

 two points exhibiting the greatest difference of potential, and 



hence the most powerful current, lie 

 in the equator and in the center of the 

 transverse surface. Currents of grad- 

 ually diminishing intensity are ob- 

 tained 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 

 corresponding or opposite sides of the 

 equator, are connected; in either case 

 the current flows from the point lying 

 nearest the equator to the point farth- 

 est from it. Similar currents are ob- 

 tained when two points on the cross- 

 section situated at unequal distances 

 from the central axis are connected, in 

 which case the direction of the current 

 will be from the point lying nearest 

 the periphery toward the center. On 

 the contrary, no current is developed 

 when two points on the longitudinal 

 surface equally distant from the equa- 

 tor, or two points on the transverse 

 surface equally distant from the cen- 

 tral axis, are connected. Such points 

 are said to be isoelectric. These facts 



are shown in Fig. 34. 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 longitu- 

 dinal surface with the axis of the transverse surface have an electromo- 

 tive force in the frog muscle of from 0.037 to -75 f a Daniell cell. 

 The electric currents in the muscle are intimately associated with 



FIG. 34. DIAGRAM TO ILLUSTRATE 

 THE CURRENT IN MUSCLE. 

 The arrowheads indicate the 

 direction; the thickness of the 

 lines indicates the strength of 

 the currents. 



