328 ELECTRO-PHYSIOLOGY CHAP. 



touching its cross-section with a fluid is a tolerably sure indication 

 as to whether such a fluid is a good or bad conductor. Upon 

 this assumption we may explain other easily verified experiments, 

 which to some degree are mere modifications of the fundamental 

 experiment quoted. If a drop of salt solution is allowed to fall 

 upon a cut at right angles to the direction of the fibres in a 

 muscle, the cut ends usually twitch, and the wound gapes open. 

 Again a twitch can be provoked from the transversely cut sartorius 

 if the lonoitudinal and transverse sections are connected bv a moist 



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conductor (e.g. strip of liver, dead muscle, etc.) The preparation 

 can also be laid upon unpolarisable zinc trough electrodes with 

 mercury closure, leading off from the fresh transverse section 

 and a point of the longitudinal section adjacent to it. Again, if 

 the cross-section of a freely dependent sartorius is brought into 

 contact with the longitudinal surface by bending the end with a 

 glass rod, the muscle will twitch from the sudden closure of its own 

 current. Finally, Hering succeeded in producing a twitch in an 

 uninjured, by current from an injured, muscle. To this end the un- 

 injured sartorius was fixed by the bones so as to hang down in a slack 

 curve. The second vertical muscle was then brought into contact 

 with it, the cross-section being applied to the surface of the first 

 muscle. " When both muscles are very excitable they may both 

 twitch ; for as, on contact with the cross-section, it is very likely 

 that part of the longitudinal surface also will be in contact with 

 the uninjured muscle, closure of current in the injured muscle 

 is effected by the uninjured, and both are simultaneously excited." 

 This always occurs, indeed, if the cut end is bent over. In all 

 these experiments short-circuiting of the muscle current is effected 

 by moist conductors. Metals indeed are of very little use on 

 account of their extraordinarily rapid polarisation, though at first 

 sight the contrary might be expected. Hering, like Ku'hne (5), 

 found little or no twitch, when contact was formed at the fresh 

 cross-section of a curarised sartorius by a platinum plate, while 

 a wire of the same metal, connected with a mercury key, effected 

 contact at different points of the conducting surface. 



The fact that current from the longitudinal muscle section 

 may under certain conditions excite not only the nerve of a 

 rheoscopic leg, but also the injured muscle itself, or even one 

 that is uninjured, gives a iiriori reason to suppose that the 

 same factor plays a part in all electrical excitation of injured, 



