THE NERVOUS FLUID 317 



since we can only appreciate it by its effects, yet since the discovery of 

 galvanism, it has become increasingly probable that it is closely 

 analogous to the electric fluid. I am convinced even that it is electric 

 fluid, which has been modified in the animal economy and to some 

 extent animalised by its residence in the blood, and which has there 

 undergone suflicient change to have become containable and to remain 

 entirely within the medullary substance of the nerves and brain, to 

 which it is incessantly provided by the blood. 



I base this statement, viz. that the nervous fluid is only electricity 

 modified by its residence in the animal economy, on the fact that 

 this nervous fluid, although its effects closely resemble some of those 

 produced by the electric fluid, is yet distinguished from it by some 

 peculiar properties, among which that of being retained within an 

 organ and moving about there, sometimes in one direction and some- 

 times in another, appears to be characteristic. 



The nervous fluid is therefore quite distinct from the ordinary 

 electric fluid, since the latter passes through every part of our body at 

 its usual velocity and without any pause, when we complete a circuit 

 in the discharge of a Leyden jar or electric conductor. 



It is different even from the galvanic fluid obtained from Volta's 

 pile : the latter indeed, which is still only electric fluid acting in a 

 smaller quantity, density and activity than the electric fluid of a Leyden 

 jar or charged conductor, derives from its special circumstances 

 certain properties or faculties which distinguish it from the electric 

 fluid collected and condensed by our ordinary methods. This galvanic 

 fluid therefore has more action on our nerves and muscles than the 

 ordinary electric fluid : yet since it is not animaUsed, that is to say, 

 has not undergone the influence imparted by a residence in the blood 

 (especially of warm-blooded animals), it does not possess all the qualities 

 of the nervous fluid. 



The nervous fluid of cold-blooded animals, being less animalised, 

 is more allied to the ordinary electric fluid and especially the galvanic 

 fluid. This is the reason why our galvanic experiments produce very 

 energetic effects on the tissues of cold-blooded animals like frogs ; 

 and also why in certain fishes such as the torpedo, the electric eel, and 

 the trembhng catfish, a large electrical organ generates electricity 

 which is completely adapted to the animal's needs. (See the interest- 

 ing Memoir of M. Geoffroy on these fishes in the Annales du Muséum 

 d'Histoire naturelle, vol. i., p. 392.) 



In spite of the modifications by which the electric fluid is converted 

 into nervous fluid, it still preserves to a great extent its extreme 

 subtlety and rapidity of movement ; qualities which render it suitable 

 for performing its functions in the animal. 



