THE ELECTROMOTIVE PHENOMENA 315 



quicker than the descent. The latent period is 

 probably absent; the process begins as soon as 

 the stimulus reaches the muscle. The electro- 

 motive force of the action current for a single 

 contraction of the frog's gastrocnemius is about 

 0.08 volt 



Direct stimulation of the whole of a normal 

 uninjured muscle produces no action current 

 whatever, because the whole muscle becomes 

 active at the same moment. 



ACTION CURRENT OF NERVE 



1. Negative Variation. Sever the nerve of a 

 nerve-muscle preparation close to the muscle, 

 and lay the nerve in the moist chamber on non- 

 polarizable electrodes placing the equator on one 

 and a cross-section on the other. Lead them 

 through a short-circuiting key to the capillary 

 electrometer. Place a second pair of non-polar- 

 izable electrodes near the other cross-section 

 of the nerve. Connect this second pair to the 

 secondary coil of an inductorium. Connect the 

 primary coil through a key and the wheel inter- 

 rupter with a dry cell. Bring the meniscus into 

 the field. Open the short-circuiting key. The 

 meniscus will be displaced by the demarcation 

 current. Stimulate the nerve with induction 

 shocks at different rates. 



