370 Dr. Faraday's Experimental Researches in Electricity, xv. 



they were allowed to remain. These, with other considera- 

 tions, lead me to look at these parts with a hope that they 

 may upon close investigation prove to be a species of natural 

 apparatus, by means of which we may apply the principles of 

 action and re-action in the investigation of the nature of the 

 nervous influence. 



1790. The anatomical relation of the nervous system to 

 the electric organ; the evident exhaustion of the nervous 

 energy during the production of electricity in that organ ; 

 the apparently equivalent production of electricity in propor- 

 tion to the quantity of nervous force consumed ; the constant 

 direction of the current produced, with its relation to what 

 we may believe to be an equally constant direction of the 

 nervous energy thrown into action at the same time ; all in- 

 duce me to believe, that it is not impossible but that, on 

 passing electricity per force through the organ, a reaction 

 back upon the nervous system belonging to it might take 

 place, and that a restoration, to a greater or smaller degree, 

 of that which the animal expends in the act of exciting a cur- 

 rent, might perhaps be effected. We have the analogy in 

 relation to heat and magnetism. Seebeck taught us how to 

 commute heat into electricity; and Peltier has more lately 

 given us the strict converse of this, and shown us how to con- 

 vert the electricity into heat, including both its relation of hot 

 and cold. Oersted showed how we were to convert electric 

 into magnetic forces, and I had the delight of adding the 

 other member of the full relation, by reacting back again and 

 converting magnetic into electric forces. So perhaps in these 

 organs, where nature has provided the apparatus by means 

 of which the animal can exert and convert nervous into elec- 

 tric force, we may be able, possessing in that point of view a 

 power far beyond that of the fish itself, to re-convert the 

 electric into the nervous force. 



1791. This may seem to some a very wild notion, as as- 

 suming that the nervous power is in some degree analogous 

 to such powers as heat, electricity, and magnetism. 1 am 

 only assuming it, however, as a reason for making certain 

 experiments, which, according as they give positive or nega- 

 tive results, will regulate further expectation. And with re- 

 spect to the nature of nervous power, that exertion of it which 

 is conveyed along the nerves to the various organs which 

 they excite into action, is not the direct principle of Zz/<?; and 

 therefore I see no natural reason why we should not be al- 

 lowed in certain cases to determine as well as observe its 

 course. Many philosophers think the power is electricity. 

 Priestley put forth this view in 1774 in a very striking and 

 distinct form, both as regards ordinary animals and those 



