206 PHYSIOLOGY OF MUSCLES AND NERVES. 



muscle of one arm, the result is an immediate deflec- 

 tion of the multiplier, which indicates the presence of 

 a current ascending in the contracted arm from the 

 hand to the shoulder. If the muscles of the other arm 

 are contracted, a deflection occurs in the opposite direc- 

 tion. We are, therefore, able by the mere power of the 

 will to generate an electric current and to set the mag- 

 netic needle in motion. 



Summing up all that has been said, it appears that, 

 during muscular contraction, the electric forces acting 

 in the muscle undergo a change which is independent 

 of the alteration of form in the muscle, and is con- 

 nected with the fact of activity itself. As, during this 

 alteration, the current which may be exhibited in an 

 applied arch becomes weaker, the term negative-varia- 

 tion of the muscle-current has been applied to it. 



2. The negative variation of the muscle-current on 

 contraction, as described in the last paragraph, is a 

 proof of the fact that in the electric action of muscle 

 we have to do, not with an accidental physical pheno- 

 menon, but with an action very closely connected with 

 the essential physiological activities of muscle. It is 

 therefore worth while to trace an action of this sort 

 more accurately, as it may possibly aid in the explana- 

 tion of the activity of the muscle. 



It may, in the first place, be safely asserted that all 

 muscles of all animals, as far as they have at present 

 been examined, exhibit the same electric action. Even 

 smooth muscles act electrically in the same way ; 

 though in that case the phenomena are less regular, 

 owing to the fact that the fibres are not so regularly 

 arranged as in striated muscle. Moreover, the electric 

 activity of smooth muscles seems to be somewhat 

 weaker. 



