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different from those dictated by the figure of a tree. The property belonging to the mental system of causing to cohere movements that have been described in succession, fixes the series for each different view, and gives a permanent hold of all the distinct forms presented to the eye. This adhesive process belongs to the intellect, and will be fully treated of in the proper place.

CHAPTER III.

OF THE APPETITES.

1. IN taking up, at this stage, the consideration of the Appetites, I do not mean to assert that these entirely belong to our primitive impulses, or that in them the operation of intellect and experience is excluded. On the contrary, I am of opinion that Appetite, being a species or form of Volition, is like all our other effective forms of volition, a combination of instinct and education. But the process of acquisition is in this case simple and short; while, on the other hand, the stimulus to action, or the source of the craving, is usually one of the sensations or feelings discussed in the two previous chapters. Indeed, if we look at the craving alone, without reference to the action for appeasing it, that craving is merely what we have all along styled the volitional property of the sensation.

If a spur to action were to constitute Appetite, all our pains and pleasures would come under this designation. But the Appetites commonly considered are a select class of feelings; and are circumscribed by the following propertynamely, that they are the cravings produced by the recurring wants and necessities of our bodily, or organic life. The avoiding of a scald, a cut, or a fall, is an energetic impulse of volition, and yet not a case of appetite; there being no periodic or recurring want of the system in these cases. Sleep, Exercise, Repose, Thirst, Hunger, Sex, are the appetites most universally present throughout the Animal tribes.

The state termed Desire so far agrees with Appetite, in being a volitional impulse growing out of some uneasy and unsatisfied condition. But in Desire, there is a prior experience of pleasure, the memory of which is the spur to seek a

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renewal; we desire to return to a tasted delight. This is not necessary to a mere Appetite; although obviously, after experience of gratification, all our appetites have also the character of Desires.

2. The fact of periodic recurrence is in no case more strikingly exemplified than in Sleep. After a certain period of waking activity, there supervenes a powerful sensation of repose. If we give way to it at once, the state of sleep creeps over us, and we pass through a few moments of agreeable repose into unconsciousness. If we are prevented from yielding to the sleepy orgasm, its character as an appetite is brought out into strong relief. The voluminous uneasiness. that possesses all the muscles and organs of sense, stimulates a strong resistance to the power that keeps us awake; the uneasiness and the resistance increasing with the continued refusal of the permission to sleep, until the condition becomes intolerable, or until a reaction ensues, which drives off the drowsiness for some time longer. The overpowering influence of drowsiness is well seen in infants.

3. The necessity of alternating Exercise with Repose, through the entire range of our active organs, brings on the like periodic cravings and deep-seated uneasiness. The fresh condition of the muscles is of itself a sufficient stimulus to action; without any conscious end, in other words, without our willing it, action commences when the body is refreshed and invigorated. If this spontaneous outburst is checked, an intense uneasiness is felt, being one of the conscious states incident to the muscular system. This state is of the nature of all the other appetites, and increases with privation, unless, by some organic change, the fit passes over for the time. The dog chained up to his couch, the exuberancy of childhood restrained from bursting out, the bird in its cage, the prisoner in his cell-experience all the pains and desire of the active organs for exercise. On the other hand, after exercise, comes an equally powerful craving and impulse to rest, which, if resisted, produces the same intense uneasiness.

Under this head of Exercise and Repose I might include

the more active of our senses, that is, Touch, Hearing, and Sight. These senses all embody muscular activity along with the sensation peculiar to each; and the muscular activity, together with the tactile, auditory, and visual sensations, lead to weariness of the parts, with a craving for rest; while, after due repose, they resume the fresh condition, and crave for the renewal of their excitement. The alternate exercise and rest of the senses is in a great measure involved in the rotation of sleeping and waking; indeed, the involuntary torpor of the nervous system, is almost the only means of giving repose to such constantly solicited senses as Sight, Touch, and Hearing.

A similar train of remarks might be extended to the activity of the thinking organs. But in these, the periodic cravings are less distinctly marked, and more frequently erroneous, than in the case of muscular exercise. There is often a reluctance to engage in thought, when the brain is perfectly vigorous and able to sustain it; and, on the other hand, there is, in nervous temperaments, a tendency to excess of mental action, uncorrected by any regular promptings to take repose.

The sense of fatigue, arising soon after beginning a laborious operation, and then disappearing, is connected with inaction of the brain. A little time is requisite to determine the flow of blood to the parts exerted.

4. Thirst and Hunger I have already touched upon. 'What is called thirst is sometimes rather a call for the cooling influence of cold drinks, as for instance, in the dry, hot state of the air-passages, mouth, and skin, produced in fevers by the increased temperature and diminished turgescence of the parts. Exhalation is in such cases often rather diminished, and the dryness of the surface arises from the circumstance that although blood still flows through the capillary vessels, the reciprocal action between the blood and the living tissues, which is denominated turgescence, or turgor vitalis, is depressed.'-(Müller, by Baly, p. 530.)

Hunger, unlike Thirst, is a state of the stomach, as yet

not exactly understood; while the feeling of inanition, which also grows out of long fasting, must be considered as a general feeling of the system. The urgency of hunger ought to be in accordance with the actual deficiency of nutritive material, but very frequently the case is otherwise. 'It is heightened by cold baths, by friction of the skin, by friction of the abdomen, and by the agitation to which the abdomen is subjected in horse exercise, as well as by muscular exertion.' It is diminished by all nauseating influences, which probably at the same time weaken the digestion. "The local sensations of hunger,' says Müller, 'which are limited to the digestive organs, and appear to have their seat in the nervus vagus, are feelings of pressure, of motion, contraction, qualmishness, with borborygmi (gripings), and finally pain.'

In the case of Hunger, as in most of the appetites, there is a double spur to the taking of food; first, the stimulus of uneasiness, and next the impulse arising out of the pleasure of eating. It is well understood that these two things are quite different, and on their difference hangs the whole art of refined cookery. Very plain food would satisfy the craving for nutrition, but there is a superadded pleasure that we have to cater for. The one is the appetite in its strictest signification, and as found in the lower animals; the other we may call a desire, because it supposes the remembrance and anticipation of a positive pleasure, like the desire for music, or for knowledge.

It is in the process of taking food and drink, that we best see exemplified the activity springing out of the sensations of hunger and thirst. The actual assuaging of the uneasiness produces an intense pleasurable sensation that sets on the most vigorous movements for being continued and increased; while the moving organs themselves, beginning to be invigorated, display a spontaneous and lively energy in the cause. To bring together, and make to unite, the sensation of the appeasing of hunger with the acts of sucking, prehension, masticating, and swallowing, is perhaps the earliest link of