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CHAPTER VIII.

NOTOR NERVOUS CENTRES OR MOTORIUJI COMMUNE, AND

ACTUATION OR EFFECTION.

MHUS far we have been engaged in considering the formation

of the so-called mental faculties by the organization of residua, as this takes place in the production of simple or presentative ideas out of sensory impressions,—that is, in apprehension; in the production of representative ideas or conceptions by alustraction from the simple ideas,-that is, in comprehension; and in the production of volition as the result of the complex interworking of desires and conceptions. But it is not man's function in life merely to think ; his inner life he must express or utter in action of some kind. Consequently there are other residua besides those already dealt with, which enter as constituents into his mental life--the resiilua, namely, that are left behind by movements or actions. The movements that are instigated or actuated by a particular nerve centre de, like the ilea, leave behind them their residua, which, after several repetitions, become so completely organized into the nature of the nerve centre that the movements may henceforth le autoInatic. There is then, intervening between the volitional impulse and the action, a department or repository of motor residua, in which exist the immediate agents of movements--i region, psychologically speaking, of abstract, latent, or potential movements. If recourse be had to physiology, it is found that, conformably with whit psychological analysis teaches, there are numerous special moterial nervous centres, or nuclei of minglionic cells, cerebral and -; inal, from which motor nerves proceed, and by the experine:ital irritation of which movem-uts may

be artificially excited. The term which we have taken leave to use for the purpose of designating psychologically the common centres of movement is the motorium commune.

This region of motor residua, or, if we may venture so to call it, this motorium commune, is related to conception on the reactive side of human life, as sensation is on the receptive side. As the residua of sensorial activity, as already seen, minister and are necessary to a definite representative conception, so the residua of motorial activity in their turn enter into conception, and are indispensable to its realization in action. It may not be amiss, then, to take notice here, again, how the highest mental action comprehends or contains the whole bodily life. The sensory life enters essentially into conception; the organic life, as previously set forth, participates in the emotional quality of it; and the motorial activity of the body is essential to its due effectuation. How mischievously unjust, then, is the absolute barrier set up between mind and body! How misleading the parcelling out of the mind into separate faculties that answer to nothing in nature !

What name may most properly be given to this neglected but important motorial region of our mental life? The motor residua that mingle in our conceptions have been called, in Germany, motor intuitions (Bewegungs-anschauungen); but this description, though adinirably expressing their intervention in conception, is perhaps too psychological to convey an adequate idea of their plıysiological importance as the immediate agents or faculties of all movements. The motor intuition, furthermore, intervenes not alone between conception and respondent action, but also between sensation and the motor reaction thereto, and even between the stimulus and the resultant reflex action; so that the term intuition is not altogether suitable, and may perhaps produce confusion. More appropriately might this region of motor residua be described generically as the departinent of actuation ; a department containing the powers or faculties through which the nervous centres, excited into activity, act upon the muscular system, and, by thus utterin: or expressing their energies, restore the equilibrium. It contains the means by which will, idea, or sensation actuates definite movements, or prevents their occurrence. To describe it as the locomotive faculty would bring us

to the inconsistency of calling locomotive that the aim of which is often inhibitory or preventive of motion, and would scarcely include the organic reflex movements.

However it be named, there can be no doubt that such a region of mental activity exists, and that in it are contained, predetermined and co-ordinated, the faculties of different groups and series of movements. It is easy to perceive, then, why the will can only determine the result-cannot determine the action of a particular muscle, or the combined actions of certain muscles which have not acted together before. All it can do is to will the event, and thereupon the proper nerve-fibres and muscles are put in action through the medium of the motor intuition. If the result wished is a new, unfamiliar one, no residua thereof from previous experiences existing in the motor centres, then the will is unequal to the accomplishment of it; there is not an exact and definite idea of the end to be effected, the necessary motor intuition being wanting. After repeated trials, the desired skill is firmly acquired, and the movement is henceforth automatic, the motor intuition having been gradually organized in the proper nervous centres: the result stored up strictly corresponds with that which in other nervous centres we describe as abstract idea. Here again we are taught that the design manifest in any act of will is due to organic processes similar to those which build up the design in the nerve centres of sensori-motor action and of reflex action; it is only because of its being attended with consciousness that we describe the energy of one of these detinitely organized residua in the highest centre as a conception or notion of the result-speaking posychologically rather than physiologically. But even here consciousness disappears when the organization is complete.

In the animals the motor intuitions, like their other faculties, are mostly innate. There are no distinct, clear conceptions accompanying their instinctive actions; but obscure sensations and feelings excite the motor intuitions, which then dermine the action of the proper muscles. In man, on the other hand, although the faculties of certain co-ordinate moveinents «lu exist, preforinel in the nervous centres, the motor intuitions are inostly acquired; in this regard corresponding with the formation of his other ment.il faculties. Our ideas of distance, size,

and solidity furnish striking examples of the manner in which we are indebted to our muscular intuitions, and of the difference in respect of them between us and the animals. The young swallow's intuition of distance appears to be as perfect when it begins to fly as it is after a life-experience; but it is not so with the young child, which cannot for some time tell how far off or how near an object is. In the first instance, the child's body moves with the eyes, when these are fixed upon a light that is moved about. After a few weeks the moving light is followed by a motion of the head only; next the eye-ball itself is turned also; and ultimately objects are followed with the eye without any motion of the head. As this is going on, there is acquired gradually a recognition of the distance of an object, and the convergence of the axes of the eyes is seen to change regularly and quickly with the distance of the object. Now it is well known that the accommodation of the eyes to distance takes place through a convergence of their axes and an accommodation of their lenses, two actions which are from the first very firmly associated; so much so that a congenital defect in the lens is now recognised to be the frequent cause of squinting in children. But these accommodating movements are not determined by any act of will, nor are they within consciousness; they are consensual movements in respondence to the visual sensation, and strictly comparable with the instinctive movements of the animals. It is not the visual sensation directly which gives us the idea or intuition of distance, but the motor intuition of the accommodating movement which, though imcertain and confused at first in man, soon gets precision and distinctness. In this example we have a type of that which happens, with greater or less rapidity, in the case of every movement in the body. The infant at first kicks out its leg-whether from a so-called spontaneous outburst of energy, or luy reason of some organic or external stimulus, matters not—and bringing it in contact with some external object, gets thereby a sensation, in respondence to which, as in the consensual accommodation of the eyes, adaptations of movements take place, and muscular intuitions are more or less quickly and completely organizel. Certain sensitions and certain movements are thus associad, and the residua of the muscular movements, or the muscular

intuitions, are henceforth essential constituents of our mental life, whether we are distinctly conscious of them or not. Consider, if further illustration be needed, the gradual acquisition of the complex movements of speech, and the intimate connexion which they have with the formation of our conceptions. A weak-minded person, or a person of low cultivation, often cannot content himself with the mental representation of a word, or clearly comprehend a question put to him, without bringing the actual movement to his assistance; he must utter the word or repeat the question aloud, in order to get his conception distinctly; the essential importance of the articulating movements to conception is furthermore attested by the frequent deficiency of them in idiots. It is most necessary, however, to guard against the strong disposition which there is to look upon certain movements, those of the eye and the tongue, as having a special connexion with the mental life which other movements of the Lody have not; they have a specially intimate connexion, but not a special kind of connexion. Unwarrantally separating by an al solute barrier the mind froin the holy, and then locating it in a particular corner of the latter, as is commonly done, we are prone to forget that in mental action the whole bodily life is comprehended-that every muscular intuition, therefore, has its due place and influence in our mental life.

Another consideration which it is necessary to bear well in min i is, that there is no fundamental difference in organic nature between those motor intuitions that are original, or primarily automatic, and those which are acquired in the natural order of development, or are secondarily automatic. between the stimulus and the definite reflex action, whether innate or acquired, between the sensation and its assemblage or succession of muscular movements, the definite motor intuitions intervene as necessarily as between the conseious conception and the ansuring movement; though in the liter case only have we the cons rusness of cffort or motive ener." That the former may take place without consciousness, pron that the motor residua havel, en definitely an adequately or nized in the proper motor centr ·; so that so far from design i.plying consciousness, as meta; laysical psychologi-ts have thougl. consciousness alt.gether vania ,,s when the desin is firmly fixed in the nature of the

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