SENSATIONS OF MOVEment.

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In the second place, all movements will differ on their conscious side according to other characters which have to do with their range or extent, To begin with, then, the motor experience, like passive sensation, varies according to its duration. This is an important circumstance, for, as we shall see, it is partly by help of this feature of duration that we come to know how much movement we have carried out in any given case.

Again, our motor experience varies according to the velocity of the movement. Thus we have one kind of muscular experience in moving the arm or the eyes slowly, another in moving it rapidly. This sense of velocity is, it is manifest, connected with the rapidity with which the successive phases of the movement on their conscious side succeed one another. We are capable of discriminating fine shades of velocity, and this greatly helps in the development of an intellectual consciousness of movement.

Duration and velocity would in themselves constitute sufficient sense-data for reaching a perception of range or extent of movement. But, as already pointed out, there are other data given us in the scale of sensational differences answering to successive stages of a movement. Thus a flexing movement of the arm carried to the extreme point is accompanied by characteristic cutaneous and other constituents of the muscular sensations which might serve as signs of range or amount of movement. Our perception of range or extent is, as we shall see, built up by help of all these sense-data.

A word in concluding this account of our sensations of movement on the difference between the active and the passive experience. The latter is illustrated when we have our arm flexed by another person. Here the characteristic of the active

1 That is to say, the range of a particular movement. It is evident, however, that, so far as these positional sensations are employed, we cannot so accurately compare the range of different stages of the same movement. It is probable that when a movement takes an extreme range other muscles become involved, which supply a differentiating psychical concomitant. (See Münsterberg, Beiträge, iii. p. 67, and Die Willenshandlung, p. 81.)

The experiences being carried by another, riding, and so forth, sometimes called passive movements, differ from passive movement of a limb through the absence, or at least considerable reduction, of the muscular element. In indolently swinging I know I am swung mainly by the change of visible scene, the current of air, etc.

consciousness is wanting. There is no sense of exertion, such as attends our self-initiated movements, so that the movement is not regarded as our own. At the same time it is clearly a motor experience. The sensations connected with the altering positions of the joints and the skin are similar to those which attend active movement. It is possible that a certain amount of contraction of muscular fibre is also involved. Hence the explanation of the surprising fact that we can estimate the extent of movement almost as well in passive as in active movement.1

(b. 3.) Experience of Impeded Movement: Sense of Resistance. The remaining variety of muscular experience is that which arises when our impulse to move is counteracted by some obstruction; an experience which has been marked off as "dead strain" (Bain) and as consciousness of resistance. This experience may be given either by our own body, as in pressing the arm against the side, the chin against the chest, or by foreign objects. It is these last which are commonly thought of in connexion with obstructed movement. As examples of this experience of resistance we may take pressing against a heavy body, supporting or lifting a weight, pulling or dragging an object.

Here it is evident muscular sensations are complicated by ordinary tactile sensations, viz., sensations of pressure. The experience is, indeed, made up of a muscular and a tactile experience, the latter being dependent on and varying in degree with the muscular exertion or strain. As we shall see by-and-by, it is by means of this complex experience varied in different ways that we come to perceive the fundamental qualities of material things, viz., impenetrability in its various modes, hardness and softness, density and rarity, etc., as well as weight and inertia, i.e., immobility and mo

mentum.

1 This is the conclusion reached by Goldscheider from some recent experimental investigations. (See James, op. cit., ii. p. 192.) The passive movement here referred to must be distinguished from that which arises through an electric stimulation of the motor nerve. Here, too, though muscular contraction is evidently involved, there is a falling off in the muscular discrimination which accompanies normal contraction. Münsterberg considers that this is due to the fact that fewer muscles take part. (Die Willenshandlung, p. 82.)

SENSATIONS OF RESISTANCE.

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The measurement of the discriminative delicacy of this aspect of the muscular sense (sense of resistance) has been carried out by Fechner with respect to the estimation of weight. His experiments consisted in a series of liftings of weights of different magnitudes by one hand, and also by both hands. According to these experiments, when a small weight was taken (300 grammes) a difference of was recognised (in a certain proportion of trials). When a heavier weight was taken the discriminative sensibility showed itself to be finer. As in the case of the passive appreciation of weight by touch, the discrimination by one and the same hand was more delicate than that by the two hands. In these experiments touchdiscrimination is, of course, not eliminated. But a comparison of the results with those which we just now saw to be gained in the case of touch-discrimination alone (apart from muscle-discrimination) shows that we have here to do mainly with muscular sensibility. And this conclusion is borne out by the observations of Leyden and Bernhardt. according to which the sensibility of the skin can be partially or even wholly destroyed without affecting materially the discriminative appreciation of weights.1

The muscular

§ 31. Active Sense: Touching, Seeing, etc. sense, though sharply distinguished from passive sensation in its character and mode of production, is, as already suggested, conjoined in our experience with such passive sensation. As pointed out above, all sensory stimuli tend to excite some amount of muscular action, and it is probable that all passive sensation is complicated by a factor of muscular sensation.2 Not only so, since all our sense-organs are supplied with muscles by the action of which they are moved (wholly or in some of their parts), we may say that each class of special sensation has its own motor concomitant. Thus the movements of the tongue enter into active tasting, those of the nostrils and respiratory organs into active smelling or sniffing, while certain muscles of the ear, and, to a larger extent, those of the head, co-operate in active hearing or listening.

It is, however, in the case of the two most highly mobile sense-organs, those of touch and sight, that we see the cooperation of muscular action most plainly manifested. Touching and seeing or looking are pre-eminently active processes involving movements of the organs concerned, as stretching out

1 See Wundt, Physiol. Psychologie, i. cap. viii. p. 370.

2 This universal concomitance of a muscular element in passive sensations has been recently insisted on by Münsterberg, who has made a number of new and striking applications of the fact, as to the phenomena of attention, the measurement of the intensity of sensation, and so forth. (See his Beiträge zur exper. Psychol. iii. 1.) He seems, however, to be going too far in referring all difference of sensational intensity to the muscular factor.

the hand, running the fingers over a surface, directing the eyes to a point. This co-operation of muscular action with passive sensation is known as Active Sense. The service thus rendered by muscular action to the special senses is a complex one. In the first place, it is evident that the movements of a senseorgan greatly increase the number or range of passive sensations. Just as the mobility of an insect's antennæ enables it to have many more impressions of touch than it would have if the organs were fixed, so the mobility of the human arm, hand, and fingers greatly extends the range of our tactile impressions. By such movements we are able to bring the most sensitive part of the organ, e.g., the finger tips, the area of perfect vision on the retina, to bear on the several portions of a wide area of objects.

A second advantage closely connected with this is the introduction of change of impression. The importance of this will appear when we consider the bearing of change or contrast on the distinctness of our sensations. Movement introduces change in more ways than one. Thus when a person moves his eye over the objects constituting his field of vision, the shifting of the several luminous stimuli to new retinal elements serves to strengthen their effect, that is, to render the sensations more vivid and impressive than they would be if the eye were fixed.1 Of still greater importance is the change which is secured by means of rapid movement between successive impressions received by way of the most sensitive part of the organ. It is by transferring the fingers rapidly from one surface to another (e.g., from a rough to a smooth, from a cold to a warm) that the corresponding qualities are nicely distinguished. Similarly, it is by passing the eye quickly from one colour to another that the finer discrimination of colour is carried out.

But this increase in the range and the comparability of our passive impressions is only one part of the gain resulting from the mobility of the sense-organs. A third and no less important service rendered to the special senses by their muscular apparatus is the addition of the muscular experience itself

1 As we shall see by-and-by, this shifting further subserves the differentiation of the several local characters answering to different points of the retina and the skin.

which accompanies the workings of this apparatus. This experience, as we shall see by-and-by, supplies the two senses of touch and sight with a specially complete means of ascertaining the position of objects in space. The local discrimination of the skin and of the retina acquires its later importance because of its intimate association with muscular discrimination.

Finally, as has been pointed out, the muscular sensations of resistance come into the closest connexion with passive touch. In touching objects we commonly exercise our muscles, not only in moving the organ, but also in pressing against the objects. The muscular sense is thus in a very special way associated with touch, and is on this account dealt with by some psychologists under the head of touch.

(B) ELEMENTS OF FEELING.

§ 32. Primitive Affective Phenomena. In this general account of the elements of mind a brief reference must be made to the other two groups of elementary psychical phenomena, viz., feelings and movements regarded as active or conative phenomena.

With respect to affective elements, that is to say, simple modes of agreeable and disagreeable feeling, it is evident that, like presentative elements or sensations, they are given as the immediate psychical concomitants of nervous stimulation, and are predetermined by the very structure of the child's nervous system. Thus we find them, under normal circumstances, experienced within the first weeks of life. They are, moreover, closely connected with presentative elements or sensations. As examples of these affective elements or Sense-feelings we may take the familiar pleasures and pains of the bodily or organic life, such as the recurring cravings and satisfactions. of appetite, the feelings connected with changing temperature of the body, with digestion and indigestion, with obstruction and furtherance of respiration, etc., with the exercise and fatigue of the muscular system, and, lastly, with the activities of the special senses, e.g., the sensations of sweet and bitter in taste, of smooth and rough in touch. A fuller investigation of these sense-feelings and of their precise relation to the presentative elements will have to be made later on, after completing our account of the growth of mind on its intellectual side.