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hunger, when it begins, is unable to impel its removal; but gradually this excitement increases in power, so as to overthrow all opposite impulses, and impel the action of eating
The excitement called uneasiness, when unremoved, has a tendency to increase to the more powerful state of impulse called pain; and likewise in the removal of impulses, the action of removing increases the power of the impulse to that state called pleasure. When a hungry person sits down to eat, the consciousness soon changes to a state of pleasurableness: this change is an increase of power to the impulse. The impulse of a thirsty man to drink, when he puts the goblet to his lips and gulps a mouthful of the fluid, is much stronger from it being the state of consciousness called pleasure, than the mere uneasiness was: it will be found much easier to overcome the uneasiness a dog may have for a piece of meat that he sees, and prevent him from taking it, than to overcome the pleasurable impulse that he is actuated by, when he commences devouring the food, and disposses him of it.
There are then three states of an impulse, painfulness, uneasiness, and pleasurableness-the first and third of which
be called the powerful states. An impulse to do a given action often varies by slow, and sometimes by rapid changes, through these different states; thus, the uneasiness of hunger, when unremoved, gradually increases to a painful degree; but this state of the impulse to eat, soon after the commencement of a meal, changes to pleasure: it is the reigning impulse till it gradually becomes weaker, and then the full state of the stomach excites an impulse to desist from eating ; this gradually increases until it becomes the stronger, when à cessation of the meal takes place, if no other impulses be excited besides those mentioned.
The continuance in existence of animate beings would have been impossible without the excitement by which the material states regulate themselves, and equally impossible, without the susceptibility to the excitement of impulses by the power of external substances; for ani.
mals being surrounded by things of a beneficial or destructive nature to their organization, it is essential that those things, which are destructive, should, on contact, excite impulses to move the animal from them and those that are beneficial should be able to excite impulses to the use of the substance. The pleasantness or unpleasantness, or, in other words, the pleasurableness or painfulness excited in the animal by any thing, generally depends on the supporting or destructive influence it has over the animal organization and life. The taste of milk is pleasant to the young mammalia, in consequence of the want in the animal frame for the matter composing milk: the taste of flesh is pleasant to the carnivori, because their system demands such concentrated nutriment. The herbivorous animals are impelled to consume certain herbs suitable to the support of their bodies, by the pleasure of taste, and are impelled to shun others of a poisonous or useless nature by their disagreeableness.
The subtile matter emanating from bodies, which excites sensations of smell, when of a beneficial nature, causes a pleasant smell, when of an injurious, an unpleasant one; the aroma of thyme is pleasant, the putrid effluvia of a stagnant pool offensive; the one is healthy, the other poisonous.
A certain degree of heat is essential to the system, and too great or too small a quantity destroys it; the bodily temperature must therefore be neither too high nor too low, either of which would be destructive. Impulse is the instrument of animal preservation from these extremes; too much heat, or too little, excites disagreeable sensations, impelling their own removal; the proper degree is pleasant, and hence impels its own continuance.
Contact with things of an injurious nature excites pain in the part touched and injured, and thus powerfully impels the removal of the part from that which is injurious to it. When a person unwittingly puts his hand on a sharp point, and is pricked by it, immediately an impulse is excited, causing the removal of the hand from that which excites the pain. Or when a person accidentally puts his finger on a piece of hot iron, the pain remores it immediately.
An intense brightness, such as that of the sun, excites a painful sensation in the eyes, which immediately closes the lids; if it were not so the strong rays of light would
prove destructive to the organs of vision. The rule that the ability of external things to excite pleasure or pain, depends upon their being useful or injurious to the organization; though ultimately always correct, yet, in a few instances, it is not so immediately; arsenic, for instance, though a poison, tastes sweet.
From what has been advanced it will follow that, according to the variations in the material proportions of the system, so the uneasinesses for different kinds of matter, and also the pleasantness or disagreeableness of the smell or taste of such inatter, will vary. In the warmer climates, where continual exhaustion of the fluids takes place, the uneasiness of thirst is common, and acid, juicy fruits, such as the orange or lemon, excite pleasurable tastes. In a very cold climate, thirst is not often an impulse, and the taste of cooling fruits not frequently pleasant.
A sweet taste is ordinarily more pleasurable to English children than a salt taste: this however is not the case all over the globe. Mr. Mungo Park, in speaking of the interior of Africa, says—“But in the interior countries the greatest of all luxuries is salt. It would appear strange to a European to see a child suck a piece of rock-salt, as if it were sugar. This however I have frequently seen; although, in the inland parts, the poorer class of the inhabitants are so very rarely indulged with this precious article, that to say a man eats salt to his victuals, is the same as saying he is a rich
I have myself suffered great inconvenience from the scarcity of this article. The long use of vegetable food creates so painful a longing for salt, that no words can sufficiently describe it.” In addition to the cause ascribed by Mr. Park, it is probable that the circumstances of this locality conspire to produce a reduction of saline matter in the animal system, and so excite an uneasiness for salt, and make the taste of it pleasurable.
There are certain morbid states of the animal system by which new cravings are excited; the human being when feverish, delights in cooling acid drinks; the dog, when unwell, eats grass; and the horse, in a similar state, appears to derive much gratification from chewing rock-salt.
The existence, for a period, of animals possessed of the impulsive sensations described, would be possible; but the organization is gradually worn out by living action : hence death is the effect of life, and, without the means of reproduction, the continuance of animal nature would have been impossible, and it must have ceased soon after commencing existence. Some of the links, in the chain of causation, by which this perpetuation of life takes place, are those states of the consciousness, which are the impelling feelings, or sensations which unite the male and female, and the parent and offspring during the helplessness of the latter. The material states constitute a predisposition to the creation of the impulses to preservation and reproduction, and often excite them : but there is another mode by which these and other impulses are excited, when predisposition exists, namely, by the states of knowing in which the consciousness may be at any time. A man, whose state predisposes him to hunger, though he be not possessed of the feeling, directly on smelling a savoury smell, or hearing of a feast, or having the thoughts of food excited in any way, will, by this knowing state of the consciousness, have the impulse for food immediately excited; so it is with the other impulses resulting from the material states; they can either be excited by the material states of the system, or when a predisposition exists by the states of the consciousness: this constitutes one class of impulses, which may be called material, as significant of the agency necessary to their production; another is made up of those excited always by the knowing states, and hence may be termed spiritual.
Both of these classes of impulses have variations of pain, uneasiness, and pleasure; the uneasinesses are called likes and dislikes, or desires and aversions, &c. The knowledge of the characteristics of each other
produces, in some of the animal sexes, the state of spiritual impulse called fondness or love, which unites the individuals together in pairs. The most violent, as well as the most gentle, are subject to this excitement: it is common alike to the lion and hare, to the eagle and dove.
As soon as the young mother is made sensible that her offspring exists, the consciousness excites within her bosom an uneasiness for its welfare. All female animals, belonging to species, the infancy of which demands the attention of a nurse, are susceptible of this impulse, excited thus through the medium of knowledge, and it is, while it continues, one of the most powerful and active motive principles connected with animated being, and so important that the existence of mammalia, or those animals that suckle their young, also that of most birds, together with some fishes, reptiles, insects, &c., would be impossible without it. This desire towards the young seems to be produced in the female, by the consciousness of pregnancy, and continues in intense excitement during the helpless period of their infancy, instigating all those acts of motherly tenderness so essential to the rearing of young
It is beautifully exemplified in the female bird, in which it causes those actions, by which her young brood is to be matured. Her business, during the breeding season, has always been a philosophic theme of admiration to the naturalist; in the first place, she, in anticipation of the wants of her unborn progeny, prepares a nest of the character best qualified to ensure their comfort, in which she deposits and hatches her eggs: and when at length the young are detatched from the shell, the most lively industry is exhibited by her, in procuring food for their sustenance, and the tenderest fondness displayed in sheltering them, with her wings, from the storm, and in covering them at night time from