260 NERVOUS FORCE. LECT. XIV. XV. 



employed a very delicate galvanometer; the nerve was ex- 

 posed for a considerable extent of its course, and I could 

 traverse it with the platinum extremities of the galvano- 

 meter, by passing from a distance of 2 or 3 centimetres to 

 that of 15 or 20. We never obtained distinct signs of the 

 derived current, and in a constant direction, even when the 

 muscles of the animal were violently contracted. 



Lastly, I may add that, from what we know of the pro- 

 perties of electricity, and of the laws of its propagation, it 

 is impossible to conceive the existence of a current circu- 

 lating in the nerves. In order that an electrical current 

 should pass from one extremity of the nervous system to 

 the other, it would be necessary to compare the nerve to 

 a metallic wire varnished or otherwise insulated, an as- 

 sumption which is not in accordance with fact. An elec- 

 tric current which, subjected to the will, would set out from 

 the brain to reach the muscles, by traversing the nerves, 

 could not be stopped in its course by the ligature of the 

 nerve ; whereas, we well know, that the propagation of the 

 nervous force is prevented by that proceeding. Lastly, its 

 circulation in the nerves requires that the nervous system 

 should form a closed circuit ; but the labours of anatomists 

 are very far from having proved such an arrangement, espe- 

 cially in the ultimate ramifications in the muscles, where it 

 would be especially necessary. 



I have often tried an experiment, which, had it given 

 me a positive result, would have proved, in an indirect 

 manner, that the nervous system forms a complete chain 

 for the electric current. I exposed a nerve in a living ani- 

 mal at two distinct parts of its course, namely, at the top 

 of the thigh, and at the lower extremity of the leg. I in- 

 troduced the latter into a spiral, similar to that which I 

 described a few minutes ago, and which put into commu- 

 nication with a second much smaller spiral, containing within 



