326 ELECTRO-PHYSIOLOGY CHAP. 



currents are exhibited by the gastrocnemius provided ab initio 

 with an oblique section. A strong current is effectually obtained 

 on leading off from the upper and lower ends of the muscle, 

 flowing in the muscle itself in an ascending direction. But cur- 

 rents of greater or less strength appear with almost any lead-off, 

 since equipotential points are rare upon the surface. 



If . the ascending gastrocnemius current is not too weak it 

 may easily like all longitudinal currents be demonstrated 

 with the " physiological rheoscope " (rheoscopic leg), and this not 

 merely in the experiment of Galvani and Volta as " contraction 

 without metals," in which the sciatic nerve drops upon the convex 

 surface of the muscle, and causes an external short-circuiting of 

 the current through the nerve, but also by including the nerve 

 in a circuit of low resistance led off from longitudinal and trans- 

 verse section. In this way a twitch is obtained from the leg on 

 closing, and subsequently on opening, the circuit. While at the 

 time of the famous dispute between Galvani and Yolta, it was the 

 excitation of a motor nerve through the muscle current, in the 

 form of " contraction without metals," that excited the greatest 

 interest, since the experiment appeared to be a direct proof of the 

 existence of an electricity peculiar to the animal tissues, the interest 

 in this point subsequently disappeared when it was no longer 

 disputed. On the other hand, another attempt to demonstrate 

 the . muscle current by a physiological method, deserves more 

 attention. If the current of the longitudinal section suffices to 

 excite the nerves of a rheoscopic leg, it is conceivable that the 

 muscle itself may be excited by its own current, or current from 

 another muscle (Hering, 4). 



As early as 1859 Kiihne (3) described a characteristic 

 reaction in the transversely divided frog's sartorius, appearing 

 when the cut surface was dipped into various fluids, and ascribed 

 by him to chemical excitation of the exposed fibres. If the 

 vertically dependent, curarised muscle is brought into contact 

 with a watch-glass of 0*6 / NaCl, immediately after making 

 a section, a twitch almost invariably follows at the moment 

 of contact between cut surface and fluid. The muscle is thus 

 jerked out of the fluid, but on relaxing it dips in again, when 

 a second twitch follows, and so on. In this manner a long 

 series of rhythmical contractions (over 100) may be discharged. 

 The experiment comes off with a number of other fluids. Besides 



