SENSATION AND PERCEPTION.

Common Sense Applied to Religion; Or, The Bible and the People by Catharine Esther Beecher, is part of the HackerNoon Books Series. You can jump to any chapter in this book here. SENSATION AND PERCEPTION.

CHAPTER IX. SENSATION AND PERCEPTION.

As there is no distinction between sensation and perception except in the fact that one is attended with the belief of a cause and the other is not, they will be treated of together.

The mind of man is an immaterial existence, confined in its operations by the body it inhabits, and depending upon the construction and modifications of this envelope for much of its happiness or suffering.

The exercise of the imagination, when the eyes are closed and the body at rest, will probably give us the best idea of what is the nature of spiritual existence when disconnected with matter. It is one of the offices of our bodily system to retain the spirit in its operations in one particular place, so that ordinarily it can have direct communion with no other mind which is not in the same place. Whether this is the case with mere spiritual existence is a question for conjecture, and not for any rational decision.

While the spirit of man is resident in its material frame, it is furnished with facilities of communication with other minds, and with organs which fit it to receive suffering or enjoyment from the material objects by which it is surrounded. These organs of communication are the several senses. They consist of expansions of the substance of which the brain is formed, which, descending to the body through the spinal bone of the back, are thence sent out in thousands of ramifications over the whole system. Those branches which enter the eyes, and are spread over the interior back part of this organ, are called the optic nerve. Whenever the particles of light enter the eye, they strike the optic nerve, and produce the sensation which is called sight. Those branches which are spread over the tongue are the organ of taste. Those that are extended through the cavities of the nostrils are called the olfactory nerves. When the small particles of matter that escape from odoriferous bodies come in contact with these nerves, they produce the sensation of smell.

The nerves that constitute the organ of hearing are extended over the cavity of the ear behind the tympanum, or ear-drum. This cavity is filled with a liquid, and when the drum of the ear is caused to vibrate by the air which is set in motion by sonorous bodies, it produces undulations of this liquid upon these nerves, and thus the sensation of sound is produced. By the expansion of other nerves, the sense of feeling is extended all over the body, excepting the nails and the hair. It is by the action of matter, in its different forms, on these several senses, that the mind obtains ideas, and that ideas are imparted from one mind to another.

Perception never takes place unless some material object makes an impression upon one of the senses. In the case of the eye, the ear, and the nostrils, the object which is regarded as the cause of the sensation does not come immediately in contact with the organs of sense. When we see a body, we consider it as the cause of that perception; but it is not the body that comes in contact with the organ of sight, but merely the particles of light reflected from that body. In the case of smell, the fragrant body is regarded as the cause of the sensation; but that which acts on the sense is the material particles of perfume which flow from that body.

Thus, also, with hearing. We consider the sonorous body as the cause; but the sensation is produced through the medium of the air, which affects the drum of the ear. But in the case of taste and touch, the body which is regarded by the mind as the cause must come in contact with the nerves of the tongue or the body to produce the sensation.

Smell.

The sense of smell is one which greatly conduces to the preservation, the comfort, and the happiness of man. It is a continual aid to him in detecting polluted atmosphere or unhealthy food. The direct enjoyment it affords is probably less in amount than that derived from any of the other senses; yet, were we deprived of all the enjoyment gained through this source, we should probably find the privation much greater than we at first might imagine. When we walk forth among the beauties of nature, the fresh perfumes that send forth their incense are sources both of immediate and succeeding gratification. The beautiful images of nature which rise to the mind in our imaginative hours, would lose many of their obscure but charming associations were the fields stripped of the fragrance of their greens and the flowers of their sweet perfumes. Nature would appear to have lost that moving spirit of life which now ever rides upon the evening zephyrs and the summer breeze. As it is, as we walk abroad, all nature seems to send forth its welcome, while to its Maker's praise

"Each odorous leaf,

Each opening blossom, freely breathes abroad

Its gratitude, and thanks Him with its sweets."

Taste.

When a sapid body is applied to the organ of taste, two sensations are produced, one of touch and one of taste. We are conscious of the difference of these sensations when we apply a body to the tongue which has taste, and then immediately one which has not. It is probable, however, that the same set of nerves serve both purposes.

It is one of the numberless evidences of the benevolence of our Creator that the process which is necessary for the preservation of life, and which depends upon the voluntary activity of every human being, should be connected with a sense which affords such gratification that the duty is sought as a pleasure. Were mankind led to seek food merely in the exercise of reason for the purpose of preserving life, multitudes, through carelessness and forgetfulness, would be perpetually neglecting that regular supply without which the animal system would become deranged and enfeebled. By the present constitution of the body, the gratification of this sense is an object of desire, and thus we are continually reminded of our duty, and led to it as a source of enjoyment.

Nor is it the gratification of this sense which is the only source of enjoyment connected with it. The regular periods for repast bring around the social board those united to each other by the tenderest ties of kindred and affection. These become seasons of cheerful hilarity and relaxation, seasons of cessation from daily cares, seasons for the interchange of kind feelings and intellectual stores; and while the mere gratification of sense is one source of pleasure, to this is often added the "feast of reason and the flow of soul."

The effect on the best feelings in thus assembling to participate in common blessings is scarcely ever appreciated. Did every individual of our race retire to secrecy and solitude to satisfy the cravings of nature, how much would the sum of human happiness be diminished! But thus has our benevolent Creator contrived that one source of enjoyment should serve as an occasion for introducing many more.

Hearing.

The sense of hearing is one more connected with the intellectual and moral powers of man than either taste or smell, as it is through the medium of this organ that both music and speech operate on the human mind. We can form some imperfect estimate of the amount of happiness derived from this sense by imagining the condition of mankind were they at once and forever deprived of this source of improvement and enjoyment. The voice of sympathy, friendship, and love would be hushed. The eloquence of the forum, the debates of the Legislature, the instructions of the pulpit, would cease. The music of nature—its sighing winds and dashing waters—would be stilled, and the warbling of the groves would charm no more. The sound of pipe, and harp, and solemn harmonies of voice would never again waken the soul to thrilling and nameless emotions. Where now ten thousand sounds of active life, or cheerful hum of business, or music of language and song charm and animate the soul, man would walk forth in silence and solitude.

The operation of mere sound, disconnected with the ideas which are often conveyed by it, is a subject of curious speculation. Sounds differ from each other in quality, pitch, force, and in length. The difference in tone may be illustrated by the sounds of a clarionet compared with the sound of a bell or of the human voice. Every instrument and every human voice has each a peculiar tone by which it is distinguished from all others. The difference in pitch is shown by sounding a low and a high note in succession on an instrument. The difference in force is exhibited by singing or speaking loud or soft.

There are certain sounds that in themselves are either agreeable or disagreeable from their tone alone. Thus the sound of a flute is agreeable, and that of the filing of a saw is disagreeable. Sounds also are agreeable according as they succeed each other.

Melody is a succession of agreeable tones arranged in some regular order as it respects their duration and succession. Some melodies are much more agreeable to the ear than others. Some melodies produce a plaintive state of mind, others exhilarate, and this without regard to any thing except the nature of the sounds and their succession. Thus a very young infant, by a certain succession of musical tones, can be made either to weep in sorrow or smile with joy.

Harmony is a certain combination of sounds which are agreeable to the ear; and it is found that the mind can be much more powerfully affected by a combination of harmonious sounds than by any melody. The effect of music on certain minds is very powerful, often awakening strange and indescribable emotions. It has been, therefore, much employed both to heighten social, patriotic, and devotional feeling.

There is probably nothing which produces stronger and more abiding associations in the mind than musical sounds. As an example of this may be mentioned the national air which is sung by the Swiss in their native valleys. It is said that when they become wanderers in foreign lands, so strongly will this wild music recall the scenes of their childhood and youth, their native skies, their towering mountains and romantic glens, with all the strong local attachments that gather around such objects, that their heart sickens with longing desires to return. And so much was this the case with the Swiss of the French armies, that Bonaparte forbade this air being played among his troops. The Marseilles Hymn, which was chanted in the scenes of the French Revolution, was said to have been perfectly electrifying, and to have produced more effect than all the eloquence of orators or machinations of statesmen.

The mind seems to acquire by experience only the power of determining the place whence sounds originate. It is probable that, at first, sounds seem to originate within the ear of the person who hears; and, even after long experience, cases have been known, when a person suddenly waked from sleep imagined the throbbing of his own heart was a knocking at the door. But observation and experience soon teach us the direction and the distance of sounds. The art of the ventriloquist consists in nothing but the power which a nice and accurate ear gives him of distinguishing the difference between sounds when near or far off, and of imitating them.

Touch.

The sense of touch is not confined to one particular organ, but is extended over the whole system, both externally and internally. It is in the hands, however, especially at the ends of the fingers, that this sense is most acute and most employed. We acquire many more ideas by the aid of this sense than by either hearing, smell, or taste. By these last we become acquainted with only one particular quality in a body, either of taste, smell, or sound; but by means of the touch we learn such qualities as heat and cold, roughness and smoothness, hardness and softness, figure, solidity, and extension.

It is supposed that it is by this sense that we gain the idea of something external, or without ourselves. The sensation of smell would seem to be within, as an act or emotion of the soul itself. Thus also with hearing, which, being produced within the ear by the undulating air, would seem to originate within. Thus also with sensations within the eye. But when the limbs begin to move and to come in contact with outward objects, and also in contact with various parts of the body, the mind gains an idea of the existence of some outward object. This is probably the first sense by which any idea of existence is wakened in the mind. As one sense after another is called into action, the mind continually gains new ideas, and then begins its operations of comparing, abstracting, reasoning, and willing.

It is by the sense of touch that we gain our ideas of resistance and extension. In the class of ideas included under the head of ideas of resistance may be placed those of solidity, liquidity, hardness, softness, viscidity, roughness, and smoothness; these all being different names for different modes of resistance to the muscles of the hands, arms, or fingers, when applied to the bodies which have these qualities. These ideas are not gained by simple contact; their existence depends upon the contraction or expansion of the muscles, which are the organs of motion and resistance in the human body.

We may suppose the infant to gain these ideas by a process somewhat similar to this: He first moves his arms by instinct, without any knowledge of the effects to follow. By this movement he gains certain ideas of the simple contractions and extension of his muscles, and learns also that by his own will he can exercise his muscles in this manner. At length he attempts to move his arm in a manner to which he has become familiar, and some object intervenes, and motion is prevented, while all his wonted muscular efforts are vain. Thus arises in his mind a new idea, of resistance, in addition to the sensations of touch and of motion, which had before been experienced.

The ideas of different degrees of this resistance are gained by repeated experience, and when age furnishes the ability to understand language, the names of hardness, softness, roughness, and the like, are given to these ideas. In the use of his muscles, also, the infant must first acquire its ideas of extension and figure; for it must be where resistance to muscular effort ceases that he must feel that the cause ceases to exist. The little being extends his hand—an object intervenes which interrupts his muscular motions; he grasps this object, and wherever this feeling of resistance exists, there he feels that the cause of it exists, and that after he has passed certain limits it does not exist.

Figure is defined as the limits of extension, and, of course, it can be seen that ideas of figure can only be gained by thus finding the limits of extension. It has formerly been supposed that ideas of extension and figure were gained by the eye, but later experiments and discussions show that the sense of feeling, including muscular motion, is the medium by which these ideas are first gained, and that afterward the eye, by the principle of association, acquires the power of distinguishing figure and distance.

There is much enjoyment resulting from the sense of touch in many ways, a large portion of which is almost unnoticed. Much also included under the term comfort results from this sense. Much of that which is agreeable in clothing and in objects around us is of this nature. Besides this, there are many endearments of friendship and affection that gain expression only through this medium.

Vision.

The organ of vision is the eye, which is one of the most curious and wonderful parts of the human frame, and displays in astonishing variety the wisdom and skill of its Designer.

The eye consists of a round ball, formed externally of various coverings, and within of humors of different degrees of consistency. The front part of the eye, which is exposed to view, has a small opening in it, which admits the rays of light within this ball, while it is by the operation of light on the nerves, which are spread in fine net-work over the interior, that sight is produced.

In examining the mechanism of the eye, a great variety of contrivances appear, all aiding in accomplishing the object of vision. In the first place, we may observe its modes of protection and defense. The lid is a soft, moist wiper, which, with a motion quick as lightning, protects the eye from outward violence, cleanses it from dust, veils it from overpowering radiance, and in hours of repose entirely excludes the light. On its edge is the fringing lash, which intercepts floating matter that might otherwise intrude, while above is spread the eyebrow, which, like a thatch, obstructs the drops that heat or toil accumulate on the brow.

We next observe the organs of motion with which the eye is furnished, and which, with complicated strings and pulleys, can turn it every way at the will of the intelligent agent. The pupil or opening of the eye, also, is so constructed, with its minute and multiplied circular and crossing muscles, that it can contract or expand in size just in proportion as the light varies in intensity.

The ball of the eye is filled with three substances of different degrees of density. One is a watery humor, near the front of the eye; back of this, and suspended by two muscles, is the solid lens of the eye, or the crystalline humor; and the remainder of the eye, in which this lens is imbedded, consists of the vitreous humor, which is of the consistence of jelly. These all have different degrees of transparency, and are so nicely adjusted that the rays of light, which start from every point in all bodies in diverging lines, are by these humors made to converge and meet in points on the retina, or the nerve of the eye, forming there a small picture, exactly of the same proportions, though not the same size, as the scene which is spread before the eye.

When the outer covering of the back part of the eye is removed, the objects which are in front of the eye may be discerned, delicately portrayed in all their perfect colors and proportions, on the retina which lines the interior. It is this impression of light on the optic nerve which gives our ideas of light and colors.

The eye is also formed in such a way that it can alter its shape and become somewhat oblong, while at the same time its lens is projected forward or drawn back. The object of this contrivance is to obtain an equally perfect picture of distant and of near objects.

Our ideas of shape and size at first are not gained by the eye, but by the sense of touch. After considerable experience we learn to determine shape and size by the eye. Experiments made upon persons born blind and restored to sight furnish many curious facts to support this assertion.

When the eye first admits the light, all objects appear to touch the eye, and are all a confused mass of different colors. But by continual observation, and by the aid of the sense of touch, objects gradually are separated from each other, and are then regarded as separate and distinct existences.

The eye is so formed that the picture of any object on the retina varies in size according to its distance. Two objects of equal size will make a different picture on the back of the eye, according to the distance at which they are held. The ideas of size at first are regulated by the proportions of this picture in the eye, until by experience it is found that this is an incorrect mode, and that it is necessary to judge of the distance of a body before we can determine its size. This accounts for the fact that objects appear to us so different according as we conceive of their distance, and that we are often deceived in the size of bodies because we have no mode of determining their distance.

But it appears also that our ideas of distance are gained, not by the eye alone, but by the eye and the sense of feeling united. A child by the sense of feeling learns the size of his cup or his playthings. He sees them removed, and that their apparent size diminishes. They are returned to him, and he finds them unaltered in size. When attempting to recover them, he finds that when they look very small he is obliged to pass over a much greater distance to gain them than when they appear large, and that the distance is always in exact proportion to their apparent size. In this way, by oft-repeated experiments, the infant reasoner learns to judge both of the size and distance of objects. From this it appears that, in determining the size of an object, we previously form some judgment of its distance, and likewise that, in finding the distance, we first determine the size.

The shape of objects is learned altogether by the sense of feeling. It has before been stated that at the first exercise of vision every thing is a confused mass of different colors, and all appearing to touch the eye. By the aid of the hands the separate existence of different bodies is detected, and the feeling of touch, which once was the sole mode of determining shape, is now associated with a certain form or picture on the eye, so that, in process of time, the eye becomes the principal judge of shape.

But, in determining the shape of a thing, an act of judgment is necessary. This may be illustrated by the example of a hoop, which in one position will make a picture in the eye which is circular, in another position the picture of it will be oval, and in another only a straight line. If a person will observe a hoop in these different positions, and then attempt to draw a picture of it, he will be conscious of this varying picture in the eye. Of course, in order to decide the shape of a thing, we must decide its distance, its relative position, and various circumstances which would alter the form of the picture in the eye. It is only by long experience that the infant child gradually acquires the power of determining the shape, size, and distance of objects.

The painter's art consists in laying on to canvas an enlarged picture of the scene which is painted in the interior of his own eye. In this minute picture of the eye, the more distant an object the smaller its size, the more indistinct its outline, and the fainter its colors. These same are transferred to canvas in an enlarged form; the distant objects are made small in size, faint in colors, and indistinct in outline, just in proportion to their distance.

The organ of vision is the inlet of more enjoyment to the mind than any of the other senses. Through this small loop-hole the spirit looks forth on the rich landscape of nature, and the charms both of the natural and moral world. The fresh colors, the beauty of motion, the grace of figures, the fitness of proportion, and all the charms of taste, are discovered through this medium. By the eye, also, we learn to read the speaking face of man, we greet the smile of friendship and love, and all those varying charms that glance across the human face divine. By the aid of this little organ, too, we climb not only the summits of earth's domains, but wander forth to planets, stars, and suns, traverse the vast ethereal expanse, and gather faint images and flitting visions of the spirit's future home.

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