does not irritate the muscle in the same degree. Munk also finds the velocity of transmission in a motor nerve increases as it approaches its termination in the muscle.[103] 59. Nothing can be more unlike the conduction of an electric current than this excitation of Neurility; nothing more accordant with the idea of it as a vital property of the tissue. The notion of its being derived from a centre is on a par with the notion first successfully combated by Haller,[104] that the muscle derived its Contractility from the nerves; or the analogous notion that the electric organ in fishes derived its property from the brain. Indeed, it was in support of the hypothesis that the brain was a battery, and nerves the conductors, that the phenomena observed in electrical fishes were frequently cited. The electric organ was seen to be connected with the brain; its discharges were under the control of the animal, and were destroyed on one side when the brain on the corresponding side was destroyed. But Charles Robin long ago suggested, what indeed ought never to have been doubted, that the brain was not the source of the electricity; but that the tissue of the electric organ itself had this special property, which the nerve merely called into activity. The suggestion has been experimentally verified by M. Moreau, who divided all the nerves supplying the electric organ on one side, and, having thus cut off all communication with the brain, produced electrical discharges by irritating the nerves; precisely as the muscles are made to contract when the divided nerves are irritated. Had the experiment ceased here, it might have been interpreted on the old hypothesis: the electric organ might be supposed to have a certain amount of electric force condensed in it, stored up there, as it is said to be in the nerves, and discharged when the organ is irritated. But experiment has decided this point also. Electric fishes notoriously exhaust their power by a few discharges, and recover it after repose. When M. Moreau had exhausted his mutilated fishes, he replaced them in the water, and allowed them repose. On again irritating the divided nerves, the discharges were again produced.[105] 60. On all sides the idea of nerves deriving their power from another source than their own substance is seen to be untenable. _A priori_ this might have been concluded. Neurility is the vital property of nerve-tissue. “Nerve-force” is nerve-action--molecular changes in the nerve itself, not in some remote substance. That nerve and centre are vitally connected is true; and what their physiological relations are will hereafter be examined; but we must dismiss the idea of nerves having the relation to centres that electrodes have to batteries.