Is the nervous force electricity?—There is so much resemblance, as regards their mode of developement and propagation, between the nervous force and electricity, that many physiologists have been led to regard these forces as identical. The nervous force, how ever, presents striking points of difference from electricity, which render it highly impro bable that it is identical with that force, and which show that if it be so it must be an electricity of extremely low tension.
1. The ordinary tests for electricity fail to detect the existence of a galvanic current in the nerves, whether during their quiescent or their active state. The most delicate galvanometers have been employed for this purpose, in vain, by Prevost and Dumas, who were themselves advocates of the electrical theory of nervous action, by Person, by Miiller, by Matteucci, and by myself. 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 was unable to discover any evidence of electrical action. It had been affirmed that needles introduced into the nerves or muscles of living animals became magnetic during nervous and muscular action, so as to attract iron filings, but neither Muller nor Matteucci has succeeded in obtaining such a result from their experiments. Matteucci took the precaution of employing astatic needles for the purpose, but could detect no signs of ma9,-netization. He also introduced the pre pared 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 magnetize the wire, but to no purpose.
2. Were it to be admitted that the nervous force and electricity were identical, it cannot be doubted that the provision made for propa gating the latter force in the nerves is very inadequate. The nerves are very imperfect conductors of electricity; Matteucci assigns to them a conducting power four times less than that of muscle; Weber states that they are very inferior to the metals as conductors. And from experiments made on this subject in 1895 by Dr. Miller, Mr. Bowman, arid myself, we were led to conclude that nerve was infinitely a worse .conductor than copper. The provision for insulation, however perfect for the nervous force, seems most insufficient for electricity, unless, perhaps, for a current of very feeble intensity. Yet we know that the nerve fibres convey the mandates of the will Nvith the nicest precision to the muscles, and propag-ate the effects of physical stimuli applied to the peri phery with the greatest exactness to the centre. This could scarcely be if the force so propagated %vere an impel fectly insulated electric current, for it is evident that in such a bundle of fibres as a nervous trunk disturbances would conti nually be taking place, from the secondary currents induced in neighbouring fibres by the electricity passing through those in action.
3. The Man applicatiou of a ligature to a nerve stops the propagation of the nervous power along that nerve below the point of application ; the passage of electricity, how ever, is not interrupted by these means. The nervous trunk, indeed, is as good a conductor of electricity after the application of the ligature as before it, provided it do nut become dry at the point of ligature.
4. If a small piece be cut out of the trunk of a nerve, and its place supplied by an electric conductor, electricity will still pass along the nerve and along the conductor ; but the nervous force, excited by a stimulus applied above the section, vvill not be propagated through the conductor to the parts below.
5. The existence of an org-an in certain ani mals capable of generating electricity is un favourable to the electric nature of the nervous force. The best examples of this organ are found in the Torpedo and the Gymnotus ; and experiment has placed it beyond doubt that the organ generates electricity, which is capable of giving a shock similar to that from a .Leyden jar ; which developes a spark during the dis charge, and can effect electrolysis ; by which, likewise, the galvanometer may be disturbed, and needles rendered magnetic" The electrical org-ans have no resemblance, in point of structure, to nerves; they, however, present a remarkable analog,y in that respect, as well as in their physiological action, to the striped variety of muscles. They are composed of a number of prisms, each of vvhich consists of a membrane closed at both extremities, and containing a soft albuminous substance, but subdivided by transverse very delicate septa into a multitude of small compartments. The bloodvessels and nerves are distributed upon the enclosing membrane and upon the septa, but do not penetrate the albuminous material. On these septa, according to Savi, the nerves form a network, in which the disposition of their terminal fibres differs from that in muscle in there being a true anastomosis or fusion of the primitive tubules. The analogy of the struc ture of the electrical prisms with that of mus cular fibres is sufficiently obvious, the latter being prismatic columns of fibrine, enclosed by a membrane, the sarcolemma, and separable into discs, the nerves and vessels being distri buted upon the sarcolemma, and not penetmting the contained sarcous elements. In both these textures the anatomical disposition has evident resemblance to the artificial arrangements for generating electricity, and accordingly in one (the electric organ) true electricity is generated; in the other, as Nve shall see further on, either electricity, or a force in close relation to elec tricity, is developed. In both cases the genera tion of the force is independent of the nervous system ; its exercise and application, however, are under the influence of that system.