308 : THE OUTGO OF ENERGY 



Thus the apparent continuous contraction of 

 muscle B is in reality a series of simple contrac- 

 tions, as stated, corresponding in number to 

 the make and break currents of the inductorium. 

 For each contraction there is one action current 

 in each muscle. 1 



When a muscle and its nerve are removed 

 without injury to the muscle, electrodes placed 

 on the latter will show no difference of potential, 

 as already stated (page 289). Stimulation of such 

 a muscle through its nerve causes a current of 

 action to start at the point at which the nerve 

 enters the muscle fibres. The contraction wave 

 begins also at this point, as may be shown very 

 beautifully by "fixing" the contraction in the 

 muscles of certain insects by plunging the con- 

 tracting muscle into a solution which arrests and 

 " sets " the fibre instantly. In such cases fibres 

 will be found in which the contraction wave is 

 caught at its beginning in the neighborhood of 

 the nerve end-plate. 



The action current, beginning at the entrance 

 i of the nerve into the muscle fibre, passes in both 

 directions along the fibre. As may be shown 

 with the differential rheotome, or by photograph- 

 ing the meniscus of the capillary electrometer, 



1 The experiment .also demonstrates that the meniscus has no 

 after vibrations, but follows unerringly the changes of potential. 



