If we consider first the respective agents or causes of pleasure and pain, we must acknowledge that they are very generally of a nature to accord with the view now stated. How many of the sources of pleasure are obviously sources of increased energy of some vital organs. The case of food is too obvious to need any comment. Warmth within limits both confers pleasure and stimulates the skin, the digestion, and other func tions. Fresh air exhilarates the mind, while quickening the respiratory function. Light is believed to stimulate the vital actions no less than the mental tone. And if there be some pleasures of sense, such as mere sweetness of taste, fragrant odors, music, etc., that do not obviously involve greater energy of vital function, they might be seen to do so, if we knew more than we do respecting the operation of the various organs, and we are certain that they do not have the opposite effect. Medical authorities are so much impressed with the general tendency of pleasures, that they include them in the list of stimulants in cases of low vitality. If we pass from the senses to the special emotions, such as wonder, power, tender affection, taste, we find that when those are pleasing, they also increase the animal forces at some point or other. A stroke of victory sends a thrill through the whole system; and if the pulse were examined at that moment, we should find that it beats stronger. The illustration for pains is exactly parallel, but still more striking. It is notorious that hurts, 'wounds, fatigue, ill-health, hunger, chillness, nauseous tastes and odors, the silence of a prison, the gloom of utter darkness, failure, humiliation, contumely, deprivation of one's usual comforts and pleasures—while caus ing pain, cause in a corresponding degree a depression of the powers of the system. There are some apparent exceptions, as in the stimulus of the whip, the bracing agency of cold, and the effect of misery generally in rousing men from lethargy to action, but these could all be shown to be quite compatible with the main principle.
If we turn from the agents to the expression, or modes of manifestation, of the opposing mental conditions, we shall find that the facts are of the same general tenor, although with some seeming exceptions. Joy makes a man spontaneously active, erect, animated, and energetic. It is as if a flush of power were diffused through his members; and the efforts he is then prompted to, lead to no painful exhaustion. The opening up of the features, by the elevation Of the eyebrows and the retraction of the mouth, indicates that the stream of energy has coursed over the face. In a still greater shock, the convulsiveness of laughter, by which respiration is quickened, attests the superabundance of the animal spirits. The body stands more erect, and every act done is done with more emphasis. Grief and depression are the opposite in every par ticular. The frame is languid and stooping, the features lifeless, the voice is a feeble wail; and although there is a species of convulsion attending on this condition of mind, it is a marked contrast to the other. The sob is caused by the partial paralysis of the diaphraglim, which necessitates great voluntary efforts in order that the breathing may proceed. The choking sensation at the throat is also a species of paralysis from loss of vital power. The convulsions arising under such circumstances are productive of an exhausting reaction, which is the case with the energetic movements stimulated by extreme action.
Such is undoubtedly the general fact. But why should pain stimulate, or give strength to, some special muscles, such as the corrugator of the eyebrow, and the depressor of the angle of the mouth? This has appeared a great difficulty to the ablest physiologists. It would look as if pleasure coincided with an energetic wave sent to
some muscles, and pain with an energetic wave sent to others; so that the opposite con ditions of mind are equally accompanied by an accession of power. to some bodily mem ber. But if we examine the matter more narrowly, it will probably turn out that the muscles that seem to be stimulated under pain, are not so in reality, but obtain the upper hand through the general relaxation of the system. Thus, take the mouth. We know the state of the mouth in languor, inaction, and sleep. We know that when we are roused in any way, the muscles of the face operate and draw the mouth asunder in a variety of forms. Pleasure corresponds with our energetic moods, pain causes a col lapse towards the sleepy and exhausted condition which represents a state of departed energy. So the collapse of the body might seem an exertion of the flexor muscles, or those that bend the frame forward; but we are well aware that such collapse takes place when the system is totally lifeless. A renewed energy, as a matter of course, makes us stand erect.
This is a part of the case in reply to the objections arising from a specific expression of pain, but not the whole; and the answer to the difficulties still remaining is furnished by a fact that, if well authenticated, will probably dispose of nearly al: the exceptions to the general principle now contended for. It is the organic functions, more than the muscular systetn, whose increased vitality coincides with pleasurable feeling, and their diminished action with pain. Muscular exercise is often highly agreeable, but the pleasure of resting after exercise is still more so. Now, there can be little doubt that what happens in the state of healthy repose is this: the amount of vital force stimulated by exercise—the increased energy derived from plying the lungs and heart—is now allowed to leave the active members, and to pass to the other organs—the digestion, skin, and various secreting glands—and it is their aggandizement that is associated with the com fortable sensations of repose and sinking into sleep. Thus, the abating of muscular energy may be a cause of Pleasure, provided the organic functions are raised in conse quence; but it may be maintained as a highly probable supposition, that a certain health and energy of some or all of these functions (it is difficult to draw a specific line) is essential to pleasurable feeling. We may doubt whether even mental causes can mate rially raise the tone of enjoyment, if they do not also raise the activity of some of these organs. Not only may a person be very happy and comfortable in the prostration of the muscular energy, even in a sick bed, but one way of procuring comfort is to induce a total inaction of the moving members, to allow all the available nervous power to pass to the viscera and secretions. Hence a forced relaxation of the muscles generally, by the employment of some of them, is a means of soothing the mind under pain. Thus, the active intervention of certain small muscles—such as the corrugator of the eyebrows, the orbicular muscle of the mouth, and the depressor of the angle of the mouth—by relaxing a much greater body of muscle, is the means of setting free vital energy for behoof of the other parts of the system. This would explain the mental relief furnished by an assumed sadness of feature, and a voluntary collapse of the body generally.