DISCRIMINATION OF DEGREES OF EXERTION.

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rises or falls, our difference of sensibility leads to a comparison, and the comparison gives birth to what we call the sense of difference. There is implied in it a certain amount of permanence of a past impression along with the full reality of the present; without some such endurance of impressions comparison would be impossible; we should live in the present moment and in that alone. This sentiment of difference determines our voluntary activity; that is to say, it prompts a continuance of the action that heightens a pleasure or soothes a pain. It goes still further, and is the foundation of all those discriminative impressions of outward things entering into our intellectual comprehension of the world. Sights and sounds, and touches and tastes, have a variety corresponding in some degree to the variety of natural objects, and thereby constitute what we call our 'knowledge' of those objects.

To apply this to the case now before us, we have a certain feeling or emotion when called to exert our muscular energy in setting on movement, or in encountering resistance. We have a certain degree of consciousness for some one degree of exertion; when the exertion increases, so does the consciousness. If a porter has a load on his back of one hundred weight, he has a peculiar and distinct muscular feeling associated with it; if other thirty pounds were added, he would have a sense of the addition in the increased expenditure of force; if thirty pounds were removed, he would have a feeling of diminished expenditure. In short, there is a perfect discrimination of degrees and difference of muscular energy, which serves us as a means of discriminating the resistances that we encounter. By this means we say that one body resists more than another, possesses in greater degree the quality that, according to circumstances, we call momentum, inertia, weight, or power. When we encounter two forces in succession, as in a wrestling match or a dead push, we estimate them according to this sensibility, the one greater, the other less, as it may happen.

24. Among the various cases where the sense of graduated resistance comes into play, we may mention first, the momen

tum or force of moving bodies. Where we have to check or resist something in motion, as in bringing a vehicle to rest, our sensibility to expended exertion leaves with us an impression corresponding to the momentum of the vehicle. If we were immediately after to repeat the act with another vehicle heavier or swifter than the first, we should have a sense of increased effort, which would mark our estimate of the difference of the two forces. If the impressions thus made were gifted with a certain kind of permanence, so that they could be revived at an after time, to be compared with some new case of checking a moving body, we should be able to say which of the three was greatest and which least, and we could thus have a scale of sensibilities corresponding to the three different degrees of moving force.

The effort of traction presents another example of measured estimate of expended force. Every carriage horse knows the difference of draught between one carriage and another, between rough and smooth ground, and between up hill and down hill. This difference the animal comes to associate with the carriage, or with the sight of the road, and in consequence manifests preferences whenever there is an opportunity; choosing a level instead of a rising road, or the smooth side in preference to the rough.

The appreciation of weight comes under the same description of sensibility. This applies to burdens in general, and also to the discrimination of quantity of material through weight. We remark a difference between half an ounce and an ounce, or between five pounds and six pounds, when we try first the one weight and then the other. The generality of people can appreciate far nicer differences than these. A sensitive hand would feel the effect of a very small fraction of an ounce added to a pound. In this respect, there would appear to be wide constitutional differences, and also differences resulting from practice, among different individuals. We are all sensitive to some extent, but there is for each person a degree of minuteness of addition or subtraction that ceases to be felt; this is the limit of sensibility, or the measure of delicacy in the individual case.

APPRECIATION OF WEIGHT.

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There are two modes of appreciating weight, the relative, and the absolute. By relative weights we understand the comparison of two or more weights together, or by taking them in turn, they being all actually present; as when among a heap of stones we pick out what we deem the heaviest. Absolute weight implies a permanent standard, and a permanent impression of that standard. When taking up a lump of lead, and feeling the weight of it, I pronounce it to be seven pounds, I make a comparison between the sense of the lead and the impression acquired by handling the standard weight of seven pounds, or things known to be equivalent thereto. This absolute comparison, therefore, implies that enduring and revivable sensibility to impressions of resistance above alluded to as a possible fact of the human constitution. The fact is not only possible but real, as every one knows. We can acquire a permanent sense of any one given weight or degree of resistance so as to be able at all times to compare it with whatever weight may be presented. A receiver of posted letters acquires an engrained sensibility to half an ounce, and can say of any letter put into his hand whether it produces a sensibility equal to or under the standard. This is a result pre-eminently intellectual in its nature; the process of acquisition that brings it about ranks as a foundation of our intelligence. The sensibilities that can assume this permanent character, so as to be used in comparison, without reference to their original cause, are truly intellectual sensibilities. speaking of the pains and pleasures arising out of the muscular system, I ventured to give as one of their attributes that they were not liable to be revived as mere impressions in the absence of the reality, that therefore they stood low in the intellectual scale. This description points to some other feelings that have a more abiding place in the life of intellect or ideas; and the feelings now specified are of that nature. In other words, I mean to affirm, that the sense of difference or degree in resistance is more endurable, more recoverable, more independent of the actual pressure, the real presence of the objects, than the emotional excitement, the pleasure or pain of intense muscular action. Of two burdens that stimulated

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an intense emotion of active expenditure, we can more easily retain the fact of one being greater than the other, or the sensibility that would enable us to compare some new and present burden with them,-than we can realize over again all the vehement sense of exertion, the keen massive emotion, the perspiration, and the heat that constituted the pleasure or the pain of the moment. The mere sense of the difference is evidently a small and limited portion of the entire conscious state; and for that reason alone it would be more revivable. To re-agitate the whole frame with the entire current of that emotion, perhaps at a time when the state of the body and mind is unfavourable to it, cannot be so easy as to revive a portion of the sensibility that is not connected with much excitement. It is not necessary to revive the whole in order to revive the measure or estimate of the whole, and that portion sufficing for the comparative estimate is the portion available for the purpose now under consideration.

The sensitiveness to relative weight, or to things compared together, may not be the same as the sensitiveness to absolute weight, which implies the engrained impression of the standard. Both may be cultivated, but the one is a cultivation of mere sensibility, the other is an intellectual acquisition, and may depend on a distinct quality or region of mind.

Although the use of the balance supersedes to a very great extent the sensibility to weight residing in the muscular system, there are occasions where this sensibility can display its acuteness. In many manual operations, weight is often estimated without the aid of the balance. In throwing weapons, or any description of missile to reach a mark, an estimate of weight must enter into the computation of force expended; and they that have a distinguishing delicacy of the sense of resistance will come much sooner to perfection in the exercise.

In appreciating the cohesiveness of tenacious bodies,—the thickness of a dough, or the toughness of a clay, the same sense of resistance comes into operation. In like manner the elasticity of elastic substances-the strength of a spring, the rebound of a cushion-comes to be discriminated with more or less nicety.

FEELING OF MUSCULAR RANGE.

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25. The second attribute of muscular discrimination relates to the amount of contraction of the muscle, or the degree of shortening, irrespective of the energy put forth. This sensibility qualifies the mind for the perception of a new class of external attributes.

Under this head it may be asserted that when a muscle begins to contract, or a limb to bend, we have a distinct sense of how far the contraction and the bending are carried; that there is something in the special sensibility that makes one mode of feeling for half contraction, another mode for three-fourths, and another for total contraction. Our feeling of moving organs, or of contracting muscles, has been already affirmed to be different from our feeling of dead tension,-something more intense, keen, and exciting; and I am now led to assert, from my best observations and by inference from acknowledged facts, that the extent of range of a movement, the degree of shortening of a muscle, is a matter of discriminative sensibility. I believe it to be much less pronounced, less exact, than the sense of resistance above described, but to be not the less real and demonstrable.

If we suppose a weight raised, by the flexing of the arm, first four inches, and then eight inches; it is obvious that the mere amount of exertion, or expended power, will be greater and the sensibility increased in proportion. In this view, the sense of range would simply be the sense of a greater or less continuance of the same effort, that effort being expended in movement. We can have no difficulty in believing that there should be a discriminating sensibility in this case; it seems very natural that we should be differently affected by an action continued four or five times longer than another. If this be admitted, as true to observation, and as inevitably arising from the existence of any discrimination whatsoever of degrees of expended power, everything is granted that is contended for at present. It is not meant to affirm that at each degree of shortening of a muscle, or each intermediate attitude of a limb, there is an impression made on the centres that can be distinguished from the impression of every other position or degree of shortening; it is enough to require that the range

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