242 INNERVATION. [CHAP. XI. 



Prevost and Dumas, who are advocates of the electrical theory, as 

 well as in those of Person, of Miiller, and of Matteucci ; and on 

 several trials we have been unable to observe the slightest move- 

 ment of the needle. Person connected the wires of a galvanometer 

 with the surfaces of the spinal cord in kittens and rabbits, in which 

 spasmodic action of the muscles had been excited by the influence 

 of nux vomica, and could not discover any evidence of electrical 

 action. It has also been affirmed that needles introduced into the 

 nerves of a living animal become magnetic, so as to attract iron 

 filings. No such result, however, could be obtained by Miiller, or 

 by Matteucci, from their repetition of these experiments. The latter 

 philosopher took the precaution of employing astatic needles for the 

 purpose, but could discover no trace of magnetization. He also 

 introduced the prepared limbs of a frog into the interior of a spiral 

 covered on its inside with varnish : the extremities of this spiral 

 were united to those of another smaller spiral, into which he intro- 

 duced a wire of soft iron. The nerves of the frog were irritated to 

 excite muscular action, and at the same time Matteucci sought to 

 ascertain if an induced current would traverse the spirals, and mag- 

 netize the wire. But, he adds, all his endeavours were useless. 



No one has tried to obtain a spark from a nerve during its action, 

 as a test of the electrical nature of the nervous power. Nor have 

 any experiments been devised with a view to ascertain whether 

 decompositions similar to those which occur in electrolysis may be 

 effected by it. The separation of certain elements from the blood, 

 in the various secretions, has, indeed, been attributed to a kind of 

 electrolytic influence of the nerves upon the secerning organs. But 

 it has been proved that the secretions may go on to a considerable 

 extent independently of nervous influence, and it seems highly pro- 

 bable that the nervous system can affect the act of secretion only 

 through its influence upon the blood-vessels of the secreting organ. 



But even were it certain, that an electrical current passes along 

 the nerve-fibres during nervous action, it does not seem likely that 

 the required evidence of such a current could be obtained from any 

 of the experiments above detailed. For if the nerve-tubes are to be 

 regarded as insulated conductors, of which the central axis is the 

 active portion, and the white substance of Schwann merely the insu- 

 lator, sinking a needle between these fibres will not obtain that con- 

 tact with the true conducting material which is necessary to affect 

 the galvanometer. Let it be remembered, that these nerve-fibres 

 are of microscopic size; and that, when a needle is sunk into a bundle 

 of them, it does not pierce the nerve-tubes, but passes in between 



