tinuing during sleep when volition is in abeyance, and occasioning no fatigue. It appears to be excited through the medium of the nerves, though independently of the will, for when the nerves are cut it ceases, and then the muscles nearly become flaccid : the stimulus which acts on the nerves is not known.'

PROOFS OF SPONTANEOUS ACTIVITY.

6. We have now to consider the evidence that there is for the existence of a class of movements and actions, anterior to, and independent of, the sensations of the senses. This question, brought on here to settle a point of precedence or arrangement, has a far wider import, and will re-appear on various occasions in the course of the subsequent exposition.

The proofs principally relied on are the following :

(1.) The already mentioned fact of the Tonicity of muscles. This fact I regard as proving the existence of a central stimulus in the nervous system. The tonicity does not, indeed, amount to actual movement; still, it is only a lower degree of the same thing: and what one centre does in a low degree, another may do in a higher; the peculiar mode of operation is established as a fact of the nervous mechanism.* (2.) The permanent closure of certain of the musclesthose named sphincters-is an effect of the same nature as the tonicity, but displaying a more energetic stimulus still,

Some physiologists would ascribe the tonicity, not to the exclusive influence of the centres, but to the existence of a constant stimulation proceeding from the extremities by the incarrying nerves. They allege in support of this view, that when all the sensory roots of the spine are cut, the tonicity disappears. This, however, would not affect the general doctrine in question. Granting that the muscular stimulus is in one sense reflex, and arises from a perennial irritation of the incarrying fibres, this constant irritation is not what we usually understand by stimulation from without. It is a current arising out of some constant condition of the sensitive tissues, and not out of visible and remitted applications to the parts. A constant stimulus is no stimulus at all. The real point is given a certain intensity of outward stimulation, the resulting movements will vary according to the condition of the nerves and nerve centres; the same stimulus finding at one a feeble, and at another time an energetic, response.

PROOFS OF SPONTANEOUS ACTIVITY.

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such as we can refer only to central influence. It cannot be referred to any impression from without. Neither can it be wholly ascribed to the muscle's own contractility, seeing that the destruction, or paralysis, of certain of the centres leads to the total relaxation of those muscles.

The singular rotatory movements, arising from uni-lateral section of the pons varolii and other ganglia, suggest, in a particularly marked manner, the existence of a high permanent charge of nervous power, ordinarily disguised by being in a state of equilibrium.

(3.) It is not altogether irrelevant, to cite the activity maintained by involuntary muscles, as showing the existence of a mode of power originating with the nerve centres. Nervous influence is required for maintaining the circulation of the blood, the movement of the food along the alimentary canal, &c., all which points to an inward evolution of force, although modified by stimulation in the several organs. It may be said that, when the movements are once commenced, the completion of one may be a stimulus to the succeeding; still the question would recur-by what force does the heart begin to beat?

Thus the notion of an initiative existing in the nerve centres is borne out by the tonicity, by the action of the sphincters, by the still more energetic movements of rotation, and by the analogy of the involuntary muscles. Seeing that the spinal cord and the other inferior ganglia are found capable of originating muscular contractions, we are entitled to suppose that the larger masses of the brain may be the sources of a much more abundant and conspicuous activity than these examples afford. The proofs that follow are intended to put in evidence the existence of such movements.

(4.) In wakening from sleep, movement precedes sensation. If light were essential to the movements concerned in vision, it would be impossible to open the eyes. The act of wakening from sleep can hardly be considered in any other view, than as the reviving of the activity by a rush of nervous power to the muscles, followed by the exposure

of the senses to the influences of the outer world. The first symptom of awakening that presents itself is a general commotion of the frame, a number of spontaneous movements— the stretching of the limbs, the opening of the eyes, the expansion of the features-to all which succeeds the revival of the sensibility to outward things. Mysterious as the nature of sleep is in the present state of our knowledge, we are not precluded from remarking so notable a circumstance, as the priority of action to sensibility, at the moment of wakening.*

But if this be a fact, we seem to prove, beyond a doubt, that the renewed action must originate with the nerve centres themselves. The first gestures must be stimulated from within; afterwards, they are linked with the gestures and movements suggested by sense and revived by intelligence and will. The higher degree of permanent tension in the muscles when we are awake, is partly owing to the increased central force of the waking states, and partly to the stimulus of sensation. But in all cases, the share due to the centres must be considerable, although rendered difficult to estimate when mixed up with sensational stimulus. Thus the force that keeps the eye open throughout the day, is in a certain measure due to the spontaneous energy that opened it at the waking moment, for that force does not necessarily cease when the other force, the stimulus of light, commences.

We are at liberty to suppose that the nourished condition of the nerves and nerve centres, consequent on the night's repose, is the cause of that burst of spontaneous exertion at the moment of awakening. The antecedent of the activity is physical rather than mental; and this must be the case with spontaneous energy in general. When coupled with sen

This is maintained by Aristotle (Physica VIII. 2). He says that these wakening movements come, not from sense, but from an internal source. Some writers have taken the opposite view, but they have not, so far as I am aware, adduced any decided facts in support of that view. If we cannot establish an absolute priority of movement in the act of awakening, we may, at least, maintain that movement concurs with, and does not follow, the re-animation of the senses.

EXUBERANT ACTIVITY OF THE YOUNG.

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sation, the character of the activity is modified so as to render the spontaneity much less discernible.

(5.) The next proof is derived from the early movements of Infancy. These I look upon as in great part due to the spontaneous action of the centres. The mobility displayed in the first stage of infant existence is known to be very great; and it continues to be shown in an exuberant degree all through childhood and early youth. This mobility can be attributed only to one of three causes. It may arise from the stimulus of Sensation, that is, from the sights, sounds, contacts, temperature, &c., of outward things. It may, in the second place, be owing to Emotions, as love, fear, anger. Or, lastly, the cause may be Spontaneous energy.

The two first-named influences, external sensation and inward emction, are undoubted causes of active gesticulation and movement. But the question is, Do they explain the whole activity of early infancy and childhood? I think not, and on evidence such as the following. We can easily observe when any one is under the influence of vivid sensation; we can tell whether a child is acted on by sights, or sounds, or tastes. And if the observation is carefully made, I believe it will be found, that although the gesticulations of infants are frequently excited by surrounding objects, there are times when such influence is very little felt, and when, nevertheless, the mobility of the frame is strongly manifested. With regard to inward feelings, or emotions, the proof is not so easy; but here, too, there is a certain character belonging to emotional movements, that serves to discriminate them when they occur. The movements, gestures, and cries of internal pain are well marked; so pleasurable feeling is distinguished by the equally characteristic flow of smiles and ecstatic utterance. If there be times of active gesticulation and exercise that show no connexion with the sights and sounds, or other influence of the outer world, and that have no peculiar emotional character of the pleasurable or painful kind, we can ascribe them to nothing but the mere abundance and exuberance of self-acting muscular and cerebral

energy, which rises and falls with the vigour and nourishment of the general system.

The activity of young animals in general, and of animals remarkable for their active endowments (as the insect tribe), may be cited as strongly favouring the hypothesis of spontaneity. When the kitten plays with a worsted ball, we always attribute the overflowing fulness of moving energy to the creature's own inward stimulus, to which the ball merely serves for a pretext. So an active young hound, refreshed by sleep or kept in confinement, pants for being let loose, not because of anything that attracts his view or kindles up his ear, but because a rush of activity courses through his members, rendering him uneasy till the confined energy has found vent in a chase or a run. We are at no loss to distinguish this kind of activity from that awakened by sensation or emotion; and the distinction is recognized in the modes of interpreting the movements and feelings of animals. When a rider speaks of his horse as 'fresh,' he implies that the natural activity is undischarged, and pressing for vent; the excitement caused by mixing in a chase or in a battle, is a totally different thing from the spontaneous vehemence of a full-fed and underworked animal.

It is customary in like manner to attribute much of the activity of early human life, neither to sensation nor to emotion, but to 'freshness,' or the current of undischarged activity. There are moments when high health, natural vigour, and spontaneous outpouring, are the obvious antecedents of ebullient activity. The very necessity of bodily exercise felt by every one, and most of all by the young, is a proof of the existence of a fund of energy that comes round with the day and presses to be discharged. Doubtless, it may be said that this necessity may proceed from a state of the muscles, and not from the centres; that an uneasy craving rises periodically in the muscular tissue, and is transmitted as a stimulus to the centres, awakening a nervous current of activity in return. Even if this were true, it would not materially alter the

case we are labouring to