We are forced then by the results of the re markable experiments above detailed to adopt the conclusion at which AIatteucci has himself arrived—that there is no current of electricity in the act of muscular contraction. What then is the evolved force ? It is either an electric discharget or a force very analogous to electri city, aflecti lig nerves in a similar way, travelling apparently with great rapidity, traversing bodies which the galvanic current cannot traverse, and yet restrained by substances which freely con duct it.
I confess myself at a loss to understand how Matteucci comes to regard this as a phenomenon of the nervous force. In truth, it is a pheno menon svhich accompanies muscular contrac tion, and has no relation to the nervous force, excepting so far as that is the excitant of the muscular action. The essential point of the phenomenon is, that during the contraction of a muscle a nerve which is laid on it is stimulated just as it would be by electricity, and causes the muscles to which it is distributed to contract. The electric discharge from a muscle which is excited to contract through the exercise of ner vous power is in close analogy with the electric discharge from the electrical organ of the Gymnotus or Torpedo, which is excited through the same agency.
Now the proved existence of a muscular force, the developement of which is accompa nied with heat, and tnost probably electricity, and in some instances, if the statements of Quatrefages be correct, with light, justifies us in adopting the opinion, as regards the nervous force, that this is of an analogous kind, yet exhi biting still less resemblance to electricity than the muscular force; and it strikingly illustrates the remark of Faraday, that if there he reasons for supposing that magnetism is a higher rela tion of force than electricity, so it may well be imagined that the nervous power may be of a still more exalted character and yet within the reach of experiment.
We are thus led to these conclusions respect ing, the muscular and nervous forces.
1. That both are polar forces and in close analogy with light, heat, electricity—magnetism.
2. That either may be excited by or trans. formed into the other—the nervous may excite the muscular, or the muscular the nervous. It seems not improbable that it is by this reaction of the muscular upon the nervous force that the muscular sense is developed, and as Alatteucci has ingeniously suggested, many movements independent on the will, yet following others which may be voluntary or otherwise, may result from the same cause.
3. That the same analog,y which exists be tween electricity and tnagnetism is found be tween these organic polar forces ; the muscular being more nearly allied to the former, the ner vous to the latter.
4. Both these forces are dependent on the healthy nutrition of their respective tissues, muscle and nerve, and the slightest disturbance in that process in either tissue will readily affect the intensity of the force.
5. Nevertheless there is a certain mutual de pendence between these two tissues and their forces; for the exercise of each is, within certain limits, impossible without the other; and as this exercise is necessary to maintain healthy nutrition, so these forces are to a certain extent dependent on each other for their normal dere lopement. The practitioner in medicine will duly appreciate the great importance of this conclusion.
The mutual reactions of the nervous and muscular forces constitute a new and highly important field of inquiry, which, if duly culti vated, may clear up many obscurities in the physiology and pathology of the nervous system..
Having thus far considered certain generali ties in the physiology of the nervous system, we may now proceed to inquire into the share which each part of this great system takes in the production of nervous phenomena. This nquiry naturally divides itself into two branches, namely, first, the functions of nerves; secondly, those of nervous centres.
Of thelitnctions of nerves.—Nerves are in ternuncial ; they possess in themselves (sepa rate from the nervous centre) only a very limited power of developing the nervous force, and that only in response to a physical stimulus, for connection with a centre is necessary for the exercise of a mental stimulus.
In inquiring into the function of any parti cular nerve, the problem is to determine whether it propagates the nervous force centrad or periphe rad, and whether it be connected with the centre If sensation or with the centre qf volition; whe ther, in short, it be sensitive or motor. It must be always borne in mind that most nerves con tain nerve-fibres of different endowments, and that the office of any given nerve will be deter mined by the endowment of the greatest por tion of its fibres. When we say, therefore, that a nerve is motor or sensitive, it is not to be un derstood that all its fibres are exclusively of that function, and that it contains no others of a dif ferent endowment.