may be intensified and prolonged within vastly wider limits, with a proportionate increase of external excitement. No doubt painful feelings, even when intense, may prompt brief spasmodic movements, as we see in the sudden and fitful actions prompted by anger and bitter vexation. But here one may probably recognise, in addition to the influence of past associations just spoken of, the effects of simple emotional stimulation. All pungent sensations of pain, if not unduly prolonged, are, as lively pulsations of feeling, highly stimulative; and this fact explains the characteristic virtue of the whip. In these cases the pungency of the sensation seems to effect more in raising activity than the volume of its attendant pain in depressing it. Now in all angry moods there are constantly presenting themselves to the mind new impressions and ideas of a poignant and irritating character, each of which has an appreciable effect in stimulating momentary action. Hence, perhaps, the series of brief abortive movements which attend these fits of emotion. But when once the current of painful consciousness has swollen to a certain height the stimulative effect of these cumulative shocks disappears, and the waste of energy that ever attends painful conflict distinctly betrays itself. Again, the quiet pleasures referred to by Mr. Darwin, as for example the satisfaction of maternal love, may be regarded as producing their healthy effect on the nervous energy in other directions than that of motor stimulation. Mr. Darwin is, perhaps, scarcely exact in regarding maternal affection as customarily a quiet emotion. It would rather seem that the outbursts of maternal love include some of the most vigorous of emotional movements. It is probable that the more energetic outgoings of maternal delight have gradually been brought under voluntary restraint, as the discovery was made that sudden movements and sounds, not to speak of eager embraces, are likely to injure the tender sensibilities of the infant organism. Lastly, it may be said that this law of pleasurable and painful expression is always limited by the supply of nervous and muscular energy stored up at the time. A stimulus of given intensity, say a sudden sound or a sharp blow, will produce unequal amounts of movement in two animals, one of which is much more lively than the other. There is probably a varying quantity of energy always latent in the nervous system,

applied to all feelings alike, irrespectively of their qualitative differences-would not infer that the writer recognised any radical distinction between pleasures and pains, in respect to their accompanying physical expression.

which implies a readiness for movements of all kinds. As these outbursts of wanton force are usually attended with an exhilarating feeling, an enjoyment of life, as we call it, it would be possible of course to regard them as cases of the concomitance of pleasure with an increase of energy. But it seems best to look on this mode of energy, existing independently of the processes of external sensation and emotion proper, as a distinct force which co-operates in all the effects of stimulation, whether peripheral or central. When this latent central force is abundant a very slight stimulation of pleasure will produce a long series of lively movements and, conversely, all moderate pains will be apt to exhibit the stimulative effect of emotional shock rather than the depressing effect of nervous waste. These phenomena are best studied in the actions of the young, whom it is always a far easier task to cheer and stimulate than to check and master. In feebler states of the nervous energies even intense pleasures may fail to call forth energetic movements, whereas the baneful effects of pain are rendered very conspicuous.

How far this characteristic difference in the outward effects of pleasure and pain is due to some qualitative peculiarities of the nervous processes, cannot, perhaps, as yet be ascertained. It is easily conceivable that all pain, which does not arise from over stimulation and nervous exhaustion, involves a wasting conflict between adverse currents of nervous force. At the same time, the investigations of Helmholtz into the phenomena of musical discord -which will be spoken of in a future chapter-suggest the possibility, that even pains of conflict may be due to excessive stimulation of the nervous fibres. In any case, it seems pretty certain that pain involves a harmful drain of nervous energy, which betrays itself in a decrease of muscular and other activity.

There are other points of interest in these new theories of expression which ought not to be overlooked. Thus, for example, both Mr. Spencer and Mr. Darwin call attention to the action of the will in modifying expression, as it may be observed in the trembling of the lips which attends half suppressed grief, and in the fumbling movements of the hands which accompany an effort to conceal a feeling of uneasiness before others. Mr. Spencer works out rather fully the explanation of these partially transformed expressions. Yet possibly much more might be said on the same subject, and the fact illustrated that emotion is not only acquiring a "secondary language" from incomplete volitional control, but is gradually assuming

new forms of expression, from the growing necessity, in polite life, of habitually simulating certain orders of feeling, such as the complacency of the hostess and the sympathetic interest of the courteous listener.

It is worth noting, too, that Mr. Darwin and Mr. Spencer account in a somewhat different manner for the intelligibility of emotional signs. Mr. Darwin appears to think that the cries of pleasure and pain common to all the higher animals were at first voluntary actions, performed with the object of receiving assistance or of sharing some benefit; and, according to this supposition, the meaning of such cries would be learnt, like any fact in nature, by the laws of association. Mr. Spencer offers an ingenious hypothesis in explanation of emotional comprehension. Animals, he tells us, as they became, gregarious, were subjected simultaneously to the same conditions of hunger and satisfaction, of danger and relief; and as similar emotional experiences would thus occur simultaneously in various members of the flock, so also would the vocal sounds, in which these feelings uniformly and instinctively discharge themselves, be uttered simultaneously. Hence a definite association would be established in the mind of each member between a particular sound uttered by its companions and the consciousness of fear or of delight which had so frequently been experienced along with it. In this manner the language of the emotions might become intelligible without any help from the link of similarity which would serve to connect in the mind of each member its own cries with those of its companions in similar states of feeling, though one may presume that Mr. Spencer would admit the co-operation of this mental influence. This appears to be a great advance on Mr. Darwin's views, which leave out of consideration the tendency of all feeling to vent itself in muscular action, quite independently of any good to be obtained. At the same time it is probable, as has been hinted before, that volition, as well as natural selection, has from the first served to render the various expressions precise and easily distinguishable; and accordingly, it must always be a matter for doubt, what part of a given emotional movement is due, not to the direct effects of nervous diffusion, but to gradual modifications consciously aimed at, as well as to actions once performed for other ends but now associated with this particular variety of feeling.

RECENT GERMAN EXPERIMENTS

WITH SENSATION.

THE phenomena of sensation constitute in a peculiar manner the borderland of physiology and psychology. For while all mental operations undoubtedly imply physiological conditions, the direct observation of them is in most cases rendered impracticable through their great subtlety and complexity. In respect to the organs of sense, however, physiological observation is specially favoured.The cause to be observed being some external stimulus, as a pencil of luminous rays or an adjusted series of weights, which is wholly in the experimenter's hand and may be varied and circumscribed at his pleasure, there are presented the most favourable conditions of physical experimentation. Further, the isolation and accessibility of these organs and their nervous connections, as compared with the deep-lying and intricate structures of the centres, very much facilitate the study of the precise changes to which they are liable. For these reasons, the physiology of the senses has attained a very high degree of precision and certainty, and is fast becoming the most elaborate department of the science of organism.

With this increased attention of physiologists to the facts of sensation psychologists have every reason to be content. It is perfectly true that much of this experimentation might just as readily have been undertaken by the latter in the interests of their particular science. Yet they will hardly regret, it may be presumed, that their omissions have been made good by the labours of others. Of course, the aim of the two classes of explorers would not be exactly the same. To the physiologist the mental element is of secondary importance, being simply a co-effect, easily ascertainable, by means of which his inferences respecting the real physiological effect may be corrected. To the psychologist, on the other

hand, the mental factor is the essential part of the phenomenon. Yet while there is this apparent difference in the aims of the two classes of inquirers, the method to be pursued is very much the same for both. The introduction to the several organs of sense of a large variety of well-ascertained stimuli, and the observation of their effects, while necessary for studying the precise physiological functions of the organs, are just the best means of learning the exact nature of sensation itself.

Purely internal observation, it should be remembered, as applied to our sensations, is necessarily very limited. By means of it we learn, it is true, to compare, discriminate, and classify them according to their qualitative peculiarities. But they have other aspects, about which this subjective method tells us scarcely anything. If we wish, for example, to ascertain the exact duration of a given sensation, we find it necessary to resort to some objective measure of time. The mere internal sense of duration, of a pain, for instance, is a very vague instrument of measurement. We all know how commonly in daily life our individual and subjective impression has to be corrected by a reference to an objective standard, as supplied, for example, by a clock or a thermometer. Now it is just this want of precision in our subjective estimate of sensation which renders its systematic study, in connection with its nicely-definable objective causes a matter of such psychological moment.

While these experiments directly contribute to the scientific study of sensation, they serve also to illustrate mental processes and laws previously arrived at by subjective observation. In order to understand how this happens, it should be remembered that the mature sensations which the physiologist deals with are the product, not only of the present external stimulation, but also of the individual's past experiences. It is impossible to produce, and at the same time to obtain an account of, what may be called a virgin sensation, such as may be conceived to be the impression of an infant mind, if indeed even this may be supposed to exist pure from all accretions of transmitted association. Subtly interwoven with all our familiar sensations are ideas of past experiences; so that it is a matter of extreme difficulty to separate the net amount of sensation from the rest of the momentary impression. The physiologist must, it is clear, seek to make this separation, if he is to define accurately the effect of the stimulation; and thus he unintentionally aids the psychologist in understanding how widely the influence of intellectual activity extends in the more rudimentary stages of our mental life.