204 niYSIOLOGY OF MUSCLES AND NERVES. 



tated and the muscle contracts, the current becomes 

 weaker ; the current afforded by the compensator thus 

 gains preponderance, and effects a deflection which is, 

 of course, in exactly the opposite direction to that which 

 was originally effected by the muscle. 



There is stronsf reason to believe that this alteration 

 in the strength of the muscle-current really depends on 

 the activity of the muscle and is not occasioned by any 

 accidental circumstances. Any form of irritant may be 

 used indifferently to effect this activity. Chemical, 

 thermical, or other irritants may be used in place of 

 electricity to irritate the nerve ; or the experiment may 

 be made on a muscle which is still in connection with 

 the whole nervous system, and the contraction may 

 be effected by influences acting through the spinal 

 marrow and the brain. But the result is always the 

 same. Even when external circumstances entirely pre- 

 vent contraction, the irritated muscle, without changing 

 its form, exhibits this decrease in its current as soon as 

 it is brought into the condition of activity by irritation. 

 If, for example, care is taken that the muscle retains 

 its form unaltered, by fastening it in a suitable clamp, 

 and if this muscle is then irritated into activity, the 

 current decreases in exactly the same way as when the 

 experiment is carried out as before described. 



It is an especially interesting fact that this same 

 phenomenon may also be observed in the muscles of 

 living and uninjured men. It is very hard to prove 

 that the electric action of muscles of living animals 

 in their natural position is exactly the same as that of 

 muscles when extracted ; but the fact that on contrac- 

 tion exactly the same electric processes occur in muscles 

 whether they are in their natural position or have been 



