CHAP. XI. §. I. THE GALYANOMBTEE. 139 



iindly, Is the nerve current affected during nerve 

 action ? a question which will be considered 

 further on. 



In other experiments the abdomen was laid open, 

 so as to expose the lumbar plexus of nerves, and 

 the nerves excited by a current from a pair of 

 Grove's cells, so as to produce a more powerful 

 contraction of the muscles ; the effects were negative, 

 so long as the electrodes remained in their first 

 position in the nerve ; but if, from the motion of the 

 limb, or intentionally, the electrodes were moved, 

 so as to be in contact with heterogeneous parts of 

 the nerve, then vibrations of the needle were occa- 

 sionally produced. The spinal cord was irritated in 

 the lower part of the dorsal region, by passing a 

 copper wire between the vertebrae, so as to excite 

 contraction, but the results were still the same. 

 The nerve was excited by touching it with caustic 

 potash, without any effect being produced upon the 

 needle of the galvanometer ; but if the alkali came 

 into contact with one of the electrodes, then an 

 effect occurred upon the needle, evidently due to 

 the chemical action thus set up. 



The animal was poisoned with strychnine, and as 

 soon as tetanic contractions occurred, the experiment 

 was repeated, but with the same negative results. 



The only conclusion to be drawn from these ex- 

 periments is the following : That when the electrodes 

 of a galvanometer are inserted in a nerve during nerve 

 action, there is no manifestation of current force ; but if 



