THE MUSCULAR CURRENT. 



139 



rents cannot be thus ascertained ; but their relative electrical activity in par- 

 ticular tissues, under various conditions, may be determined. 



The muscles of the Mammalia, including man, give very strong currents ; but 

 those of the frog are usually employed in experiments, as the currents in them 

 are more persistent. An oblong piece of muscle is so prepared, that its longi- 

 tudinal surfaces correspond with the sides of the muscular fibres, and its trans- 

 verse sections with their ends. It is then placed, in various positions, Diagram 

 B, 1, 2, 3, on the cushions of the apparatus just described, and the results on 

 the galvanometer needle, #, are watched. When so placed, it is also made to 

 contract, by any appropriate stimulus, and the effect on the galvanometer 

 needle is recorded. 



In a piece of living quiescent muscle, Diagram B, 1, 2, currents are 

 found constantly passing from the longitudinal surface or section, 



Diagram B. 

 I 



Diagram C. 



Diagram B (Vierordt). Views of pieces of muscle, m, placed on the cushions, b, of the preceding appa- 

 ratus, in three different positions. In 1, the piece of muscle has its cut end in contact with one cushion, 

 and its surface with the other; in 2, the piece of muscle has points at different distances from its centre or 

 equator, touching the two cushions; in 3, the piece of muscle has points at equal distances from its equator 

 in contact with the cushions, when no current passes. 



Diagram C (Author) shows the direction of the normal muscular current, both within and without the 

 piece of muscle. 1, 2, 3, three cylindrical pieces of muscular tissue ; d, the axis or pole, and e, the equator 

 of each piece. The black curved lines, with the arrows, in 1 and 2, show the direction of the muscular 

 current outside the muscle, that is, as it would pass through the galvanometer circuit. The dotted curved 

 lines show the path of the currents within the pieces of muscle. In 3, the dotted curved lines show lines of 

 equilibrium, no current passing. In each piece, the signs + and , show the electrical states of the equa- 

 tor and poles, or of the surface and ends. 



through the galvanometer, g, to either transverse section, i. e., from 

 the sides to the two ends of its component fibres ; so that the longitu- 

 dinal surface or section of a muscle, or the sides of its fibres, are posi- 

 tive, -f , and the transverse sections, or cut ends of the fibres, are neg- 

 ative, . Within the substance of the muscle, however, the current 

 passes from the cut ends to the lateral surfaces or sides. 



A series of larger diagrams, Diagram C, will better serve to illus- 

 trate the course and character of these currents. The strongest cur- 

 rents are found to pass from the middle of the piece of muscle, which 



