Sense Organs: Eyes, Ears, Nose, Mouth, Skin

It  is through the sense organs chiefly eyes, ears, nose, mouth (tongue), and skin that the brain comes in contact with the reality of the external environment which human beings and other living creatures inhabit. Without senses vision, hearing, touch, smell, taste and others a human being as such can hardly be said to exist.

Perception of reality finally takes place in the brain, but the impressions which make this possible come via the nerve pathways of the sensory organs. The brain "dwells in utter darkness" in the cavity of the skull; but it is the brain that sees, hears, feels, and makes interpretations of all the sensory impressions brought to it.

Here we will place emphasis on the princi­pal sense organs. There are several practical reasons for this. Eyes, ears, and skin particu­larly are complex and specialized organ sys­tems, each of which demands its own special­ized kind of care and attention. Furthermore, all the sensory organs (with the exception of the eye) have functions beyond reporting sense impressions to the brain. For a com­plete understanding of the human organism, these specialized systems deserve to be studied   in   their   own   right.   They   are   often abused.

Eyes and ears are two of the greatest assets a human being possesses. Yet many people fail to make the most of them. Eye special­ists (ophthalmologists) constantly encounter people with faulty vision who have accepted the blurred, imperfect images of the world they half-see as perfectly normal. "Oh, I see fine," they say until they surprisingly dis­cover how much better they can see when their visual defects have been properly cor­rected. Ear specialists (otologists) similarly report that patients have usually lost a full third of their hearing before they take any steps to overcome their partial deafness.

End Organs of the Peripheral

Nervous System

To provide a more exact picture of the op­eration of sensory organs, we must briefly describe the operation of the peripheral ner­vous system. As its name implies, it is located at the periphery or outside ends of the ner­vous systems. It consists primarily of nerve trunks, attaching to the central and auto­nomic nervous systems, and end-plates, or end-organs. These end-organs pick up specific types of stimuli (light, sound, heat, cold, pain,

Pressure,etc. They also deliver back message or orders to the organs to which they are attached. End plates that pick up sensations are called receptors. Those that deliver orders are effectors. The end plates are specific for their particular sensations. Thus, the eye reacts to light, the ear to sound, the nose and tongue to chemicals in solution.

The specificity of the end plates explains some peculiar reactions. Why do you sometime see stars when you get a punch in the eye? Because the receptors server only one function. The end plates on the retina of the eye connect directly with the visual center in the brain. Stimulating the end plates of the retina with a powerful blow can be translated by the brain only in visual images that is, the flashes of light we describe as seeing stars. Similarly a blow on the ear may come as an explosive sound.

Man has far more than the traditional five senses. There are end organs for hot and cold sensations, for pressure, for pain and combinations of impacts on end organs that give a sense of vibration, a feeling of fullness or tension, a sense of balance, even the most basic feelings of hunger, thirst, and sexual desire. The end organ for hot and cold are irregulary distributed on the skin and in the mouth and esophagus, there are many of them of the feet and very few on the chest. The designers of women‘s fashions, though not deliberately, abide by these hot and cold spots.

THE HAIR AND NAILS

Like the skin, the hair and nails are part of the tegumentary system of the body. We shall therefore discuss them briefly here. They are not sense organs, although the hair, as noted, is highly sensitive even to a light touch.

The distribution and growth of hair on the head and on the body are definitely linked to

the endocrine tides of life. Hair growth is overt evidence of secondary sex characteris­tics, and its relationship to sexual attractive­ness is commonly recognized. The Biblical story of Samson and Delilah demonstrates how ancient is the concept that hair means strength and cutting it, loss of essential man­hood or womanhood.

The emotions involved with human hair have given rise in our time to a number of commercially inspired superstitions which are costly nonsense. The brand of soap or oil used on the hair is usually irrelevant to sim­ple proper hair care. Too frequent washing may remove essential oils. The hair is cleaned by combing and brushing with a stiff brush. It is hygienically immaterial whether the hair is waved and set with a "home permanent" or by a beauty-shop treatment.

No "Cure" for Baldness or Gray Hair

There is no scientifically demonstrated "cure" for baldness (alopecia). The receding hairline is apparently a hereditary charac­teristic transmitted through mother to son. No hair tonic or "treatments" will restore hair to the head that is bald by reason of he­reditary tendency. The loss of hair that occa­sionally follows acute diseases will, however, usually be made up. Hair cells are not "starved" through lack of circulation in the scalp, though stimulation of the scalp may possibly help to prevent premature baldness.

No "cure" for gray hair has yet been dis­covered either. The color of the hair is deter­mined by the pigment in the cells of the cen­tral shaft of the hair, which is no longer living tissue when it emerges from the hair follicle. Gray hair, which lacks pigment, can be dyed to change its color, but there is no known and practicable way of stimulating the production of hair pigment.

One type of cosmetic preparation that must be used with special caution is the depilatory for removing unwanted hair. Those which claim to "dissolve" the surface hairs may also same kind of protein substance. The saf­est and surest way to remove unwanted hair is with the electric needle in the hands of a competent technician under medical supervi­sion. The needle actually destroys the hair root. Other methods, such as shaving, rubbing with pumice stone, or yanking out with wax, do not.

The Skin-Tactile Sensation

Like the nose and tongue, the skin is a sense organ with many other functions. Covering approximately 17 square feet of tangible surface in adults and weighing together about five pounds the skin is the largest single organ of the human body. It is a vital organ. Destruction of a little more than one-third of the skin area, as by burning or scalding, is usually fatal.

Clendening speaks lyrically of the skin as "one of the most interesting and mystic of structures." He calls it "that outer rampart which separates us from the rest of the uni­verse, the sack which contains that juice or essence which is me or which is you, a moat defensive against insects, poisons, germs. The very storms of the soul are recorded upon it."

The variety of sensations recorded and re­ported to the brain by the skin is undoubtedly one of the factors that make it so "interest­ing." Tactile sensation touch is only one of five types of sensation to which the specific end-organs of the skin respond. They can also be stimulated by pain, pressure, heat and cold, and combinations of sensations. Pain, apparently, is registered by bare nerve endings; but for each of the other sensations there are specific types of end-organs, called corpuscles and discs. Meissner's corpuscles, located mainly in the hairless parts of the skin, are the chief end-organs of the sense of touch. They react individually to touch and collectively to pressure. Another type of tac­tile sense organ surrounds the individual hairs on the skin. These end-organs are highly responsive to the slightest movements of the hairs, such as those caused by a light touch or a draft of air.

The end organs for touch are distributed unevenly on the total skin surface of the body. Most sensitive areas are the lips and the tip of the tongue. Fingertips are quite sensitive; back, arms, and legs much less so.

The eyes

 The eye is an extremely complex organ, and we need not enter into all the technical details of its structure and function. Seeing however, depends on the relationship of the eye with that even more complicated structure, the brain. Mechanically speaking, the eye functions as a camera whose images are relayed to the visual centers of the brain

Protected by eyelids and eyelashes, the eye itself, set in the sockets of the skull, is a globe or sphere filled with fluid. Three coats or membranes enclose the fluid. The fluid in the rear of the eyeball is called the vitreous fluid; it has a jellylike consistency. That in the front bulge of the eye is known as the aque­ous fluid.

The outer membrane of the eyeball is known as the sclera a tough, fibrous mem­brane, it covers the entire eyeball and ap­pears as "the white" of the eye. However, at the front of the eye, this coat is crystal clear and is called the cornea.

The middle layer of membrane, called the choroid, also encloses the whole eyeball ex­cept altogether at the front of the eye, where the pupillary opening is found. The middle layer is pigmented and makes up the iris or colored part of the eye. The iris has tiny radiating and circular muscle fibers which enable it to expand when light is dim and to contract when light is bright so that light can enter its central opening, the pupil, in the right amount.

The inner layer of the eyeball is the retina; it lines the entire inner (posterior) chamber of the eye except in the region of the iris. This layer is composed of nerve tissue and millions of light sensitive receptors, known as rods and cones. These are connected with the optic nerve, which attaches to the back of the eye­ball. Where the optic nerve connects with the retina, there is a small "blind spot." The optic nerve conveys images to the brain, where they are "interpreted."

One more crucial part of the human camera must be mentioned, namely the crystalline lens of the eye. It is situated immediately be­hind the iris, which lies between the two chambers of the eye. It is held in place by suspensory ligaments and can be flattened or thickened by the operation of ciliary muscles. The lens is transparent and refracts light. The changes in its shape (degrees of convex­ity) serve to focus light rays on the retina.

THE EARS

Next to the eyes, the ears are the most important sense organs and avenues of commu­nication with the world about us. Like the eyes, they are complicated anatomical structures whose receptor end-organs communicate with the brain. The sensation of sight is carried by light waves capable of traveling in a vacuum. The sensation of sound is transmitted to the ears through vibrations in the air. You cannot hear in a perfect vacuum.

The value of good hearing can hardly be overestimated.  Cover your ears with your hands tightly for two minutes and you will begin to understand what a lonesome world apart the deaf and partially deaf inhabit. It is no wonder that they often become seclusive and suspicious. In human experience danger is usually heard before it is seen.

All ears are divided into three parts: an outer, a middle, and an inner ear. The middle ear is a small, irregular chamber, lined with mucous membrane. It is connected with the throat through the narrow, short (IV2 inches long) mucus-lined opening called the auditory or Eustachian tube. The purpose of this tube is to permit equalization of air pressure in the middle ear, so that the pressure on the ear­drum will be the same on both sides. Air is forced into the Eustachian tube whenever you swallow, as you do automatically every few moments. You can "open" your Eustachian tubes by yawning. The inner ear is a very small, delicate, and complicated structure set deep in the temporal bone of the skull. It con­sists of two parts:

(1) a series of three semi­circular canals, which are essential to the maintenance of equilibrium, and

(2) the cochlea, a snail-shaped bony structure about the size of a pea, which carries the end-organ receptors of the hearing process.

Over stimulation of the receptors of the semi­circular canals confusion of them, one might say can produce dizziness, vertigo, and concomitant nausea and vomiting. This is what happens in motion sickness, when rid­ing in a tossing ship, a bumpy airplane, a fast automobile, or an ordinary merry-go-round. Many changes in the direction of motion over stimulate the receptors in the semicircu­lar canals. It is unaccustomed motion that produces motion sickness. Seasick individuals recover when they become used to the mo­tions of the boat. With experience in riding, people outgrow carsickness and trainsickness.

The middle ear is the most vulnerable to serious infections. These often travel up the Eustachian tube from the nose and throat. Swimming and diving can encourage such infections.

Two self-inflicted complications must be mentioned: indiscriminate use of nasal drops or sprays and improper blowing of the nose Infectious material from the running nose or sore throat is often forced up the Eustachian tube by noseblowing. When you blow your nose, especially if you have a cold, blow it gently. Do not close both nostrils at the same time.

Wax in the Ear

The accumulation of wax in the external auditory canal on occasion forms a plug which temporarily impedes hearing. This can be a frightening sensation, but it is not a serious condition. The important thing here is not to try to get the wax out by digging into the ear with a hairpin, matchstick, nail file, or paper clip. Such effort may force the plug in tighter, and may even result in scratching or perfo­rating the eardrum.

Wax plugs are best removed by a competent physician or an ear specialist, who will usu­ally float them out by irrigating the ear with a syringe. This is the best way to remove a foreign body, even an insect, from the ear There is much merit in the old axiom, "The only thing to put in your ear is your elbow."

Sun Tan

The protective mechanism of the skin is expressed in still another way, namely, the release of skin pigment (melanin) to protect against injury to the skin from strong doses of sunlight. In the white races, which have comparatively little skin pigmentation, exposure to sunlight increases the amount of pigment produced by the specialized Malpighian cells. The result is a coat of sun tan. The tan­ning is caused by the invisible ultraviolet rays from the sun. The coat of tan disappears as the more highly pigmented cells die and move toward the surface of the skin.

The development of additional skin pig­ment under the influence of sunlight is not an instantaneous process. The attempt to get a coat of tan too quickly, therefore, usually re burn like any other and should be treated accordingly. It can be serious.

The right way to get a sun tan is to limit your exposure at first and gradually increase the amount of time spent in the direct sun­light. If you know that you do not tan, because your skin is light-sensitive, avoid exposure.

Freckles are produced by the same mecha­nism as skin tanning. In this case, however, the areas of increased pigmentation are spotty instead of consistent.

Cosmetics

Cosmetics are beauty aids. Since the search for beauty is a universal and perennial pas­time, the history of cosmetics stretches back into remotest antiquity and may be expected to be reformulated in all future generations. Today in the United States cosmetics are big business. Well over a billion dollars a year is now spent annually on all varieties of cos­metic preparations, including soaps, sham­poos, hand lotions, and the like.

From the standpoint of mental health, the increasing use of cosmetics is probably justi­fied. The pursuit of beauty is a legitimate aim of civilized life. The woman who does not use cosmetics today stands starkly apart from her "sisters under the skin." It is not uncommon to hear a woman say, "I feel positively un­dressed without my lipstick."

The people in the cosmetics business know all this and they say, "We don't sell merchan­dise, we sell illusion." The danger in this is that many cosmetic preparations are over-enthusiastically promoted and overpriced. Women are repeatedly cozened to expect mir­acles from cosmetics, and those miracles never happen.

Cosmetics are not and can never be a sub­stitute for good health. There is no way to "nourish" the skin by creams or lotions or falsely labeled "skin foods" applied from the outside. The skin is nourished, like all body tissues, through its own blood supply. False and misleading names are applied to many cosmetic products. You ought to know that there is no known substance or combination of substances that can live up to the promises suggested in any of the following names: contour cream, crow's-foot cream, deep pore cleaner, enlarged pore preparation, eye wrin­kle cream, miracle oil, nourishing cream, pore paste, rejuvenating cream, scalp food, skin conditioner, skin firm, skin food, skin tonic, eyelash grower, wrinkle eradicator, spot re­ducer, bust developer, bust reducer.

No better cleansing agent than ordinary soap and water has yet been developed. Fre­quent bathing rather than the use of any spe­cial kind of soap is the best way to prevent body odor. On the other hand, too frequent bathing can be harmful to the skin and may occur as compensation for guilt feelings. Skin deodorants and antiperspirants are not objec­tionable, but they are by no means as impor­tant to social success as the advertisements make them out to be.

Structure of the Skin

 Perspiration

There are from 2 to 3 million sweat glands in the human body. They are most plentiful in the armpits, on the hands and feet, and on the forehead. These tiny coils extract water and some other substances such as salt and urea from the blood flowing through the capil­lary vessels in the true skin. The extracted water (i.e. sweat or perspiration! is then re­leased to the surface of the skin through the minute tubules or openings which we call body pores.

The quantity of perspiration released daily varies greatly and depends on many factors. The sweat glands are never entirely idle. The body, even though it does not feel wet, is con­stantly releasing some water through the skin. This so-called insensible perspiration may amount to a quart a day.

Loss of body heat through perspiration, both visible and invisible, involves not the blood vessels but the sweat glands. The per­spiration that exudes from the pores is re­moved from the surface of the skin by evapo­ration. A stream of warm, dry air speeds evaporation. That is why the warm breeze from an electric fan on a hot day still pro­duces the sensation of cooling.

Underneath the true skin is a layer of sub­cutaneous tissue which is usually largely in­filtrated with fatty tissue. This layer gives the body its more delicate curves and con­tours. It serves as a cushion between the tegumentary covering of the body and the underlying muscles and permits the free rip­pling of the skin during muscular activity.

The Functions of the Skin

The skin serves many vital functions for the body. It is, first of all, a protective covering, a barrier against the invasion of pathogenic bacteria. Second, it is the impor­tant regulator of body temperature and is provided with the mechanism with which to perform this task. Third it is an organ of sensation that provides warning against some of the threats to life or health, found in the im­mediate external environment.

 Fourth, it concerns itself with those reactions which heighten the body's immunity to disease. And, finally, it is an organ of expression, a mirror if you will, of many disorders, both Infection and psychic, which may affect the body.

Bacterial resistance on the part of the skin is high. This applies also to the mucous mem­branes of the lips, mouth, and other parts of the body. So long as the skin is clean, it very quickly gets rid of unwelcome bacteria that may come to lodge upon it. The mechanism of this repellent action is not altogether clear. Unless the skin is cut, broken, punctured (as by an insect), or abraded, harmful bacteria have a difficult time getting through its horny layer. Of course some bacteria always lie on the surface of the skin, just as some are al­ways to be found in the mouth.

Skin blemishes such as blackheads, pim­ples, sores, and scabs should not be picked at anywhere on the body, but this warning should be doubly observed concerning the area that is called "the danger triangle of the face." This area is bounded by the bridge of the nose and the corners of the mouth. Be­cause of the peculiar arrangement of veins and arteries feeding this area, bacterial in­fections originating here may be carried di­rectly into the brain and set up a possibly fatal inflammation.

Structure of the Skin

The structure of the skin is far more complex than appears on first glance. Most aston­ishing, perhaps, is the fact that the outer skin, the visible surface of the body, is composed of dead rather than living tissue. This same fact is true of the fingernails and toenails and the hair. They grow, obviously from the inside out. The cells thus appearing on the outer surface of the body are no longer alive. They have turned into a highly insoluble form of protein, called keratin, which is also found in the horns and hooves of lower animals.

The outer layer of the skin, composed of dry, dead cells, which are more or less flat­tened out and overlap each other somewhat like shingles on a roof, is sometimes called its "horny layer." These cells are constantly being shed and replaced by new cells, which take their origin in the germinative layer of the skin. This growing layer is made up of what are called Malpighian cells, named after Malpighi, the Italian anatomist, who first identified them.

The pigments which largely, though not altogether, determine the color of the skin are found in the Malpighian layer of cells. The color differences among the races of man­kind,  and  many of the social implications which follow, are thus crucially determined by the amount of skin pigment in the Mal pighian cells.

The outer layers of the skin are called the epidermis. Beneath is the dermis or true skin, also called the corium. This is tough, fibrous living tissue with undulating surfaces that pentrate into the epidermis above and into the subcutaneous tissue below. These undu­lations form series of ridges which are evident on epidermis, especially on the hands and feet. They create the unique pattern of the individual's fingerprints.

The dermis is well supplied with blood ves­sels, small capillaries which can greatly ex­pand and contract under nerve impulses and thus help control body temperature. Blushing is the phenomenon that occurs when the blood vessels expand. In the true skin layer are also to be found lymph vessels, nerve endings, sweat glands, sebaceous glands, and hair follicles.

The sensory nerve endings in the skin are capable of reporting a variety of sensations to the brain as we have already pointed out.

The hair follicles are tiny tubes which harbor the hair roots, one hair to a follicle. As long as the follicle is not atrophied (worn out), injured, or diseased, the hair continues to grow.

The sebaceous glands usually lie close to the hair follicles. Their function is to secrete an oily substance, called sebum, which helps to keep the hair lustrous and the skin soft. An excessive secretion of sebum will produce such appearances as the shiny nose and may be responsible for acne. The glands of the outer ear canal, which secrete ear wax, are

Skin Troubles

Hundreds of skin disorders have been named and classified; many have long and complicated names. Some result from cos­metics. All of them, however, represent the response of the skin to some insult or assault from within or without the body.

The diagnosis and treatment of skin trou­bles requires expert medical judgment. The attempt to treat skin troubles at home often makes them worse. A condition called "over-treatment dermatitis" frequently occurs.

Contact dermatitis, of which poison ivy is a typical example, is the most common skin disorder produced by outside agents. To fight against such agents, the skin pours forth lymph fluid, which forms blisters. Along with the blisters usually come a burning sensation, itching, redness, and swelling. A number of industrial chemicals produce con­tact dermatitis.

Skin inflammations, rashes, and pustules arise also from systemic infections of the body the assault from the inside. Many dis­eases write their signature on the skin, for example, the permanent pock marks of smallpox, the temporary rashes of scarlet fever and other infectious diseases.

Welts, wheals, and bumps sometimes ap­pear on the skin in protest, one might say, against something in the victim or his envi­ronment to which he is peculiarly sensi­tive. In other words, hives (urticaria) is a sign of allergy. So, for example, is "straw­berry rash."

Acne

Acne is often the bane of adolescent years. The skin appears greasy; it is covered with blackheads; pimples are numerous. The blackheads are the result of the clogging of the seborrheic ducts with oily plugs sur­rounding a dirt particle. An increased but sometimes excess secretion of sebum seems to be a normal event in the many body changes that occur with puberty. A clean face may well help prevent the development or aggra­vation of acne. Regular washing with soap and water is the important step. Avoidance of tampering with the facial skin will fur­ther help to ward off the risk of disfiguring secondary infection. However, the treatment of acne is not always quite so simple as this. The persistent case requires medical attention. New methods of treatment are constantly being devised. Some cases of acne respond to psychotherapy, just as others do to nutritional therapy. A lowered intake of fatty foods is sometimes helpful.

There is a gross, vulgar, and completely erroneous superstition that acne is "caused" by autoerotic practice or by "sexual experi­ence" or, conversely, by the lack of it. This is pure nonsense.

Athlete's Foot

"Athlete's foot" is the common name given to a type of fungus infection (epidermophyto­sis) on the feet and between the toes. The fungi grow from spores under favorable con­ditions of heat and moisture. That is why the "seed spores" tend to persist in swim­ming pools and gymnasium showers and locker rooms. Perspiring feet also favor their growth.

Most important on the individual's part in avoiding the itching, scaling, and blistering of "athlete's foot" is to make sure that his feet, socks, and shoes are kept thoroughly clean and dry.

Athlete's foot is sometimes a community problem. The use of a strong fungicide or de­tergent on premises where the spores are likely to be seeded should be undertaken at least twice a week. The ordinary footbath is not likely to have much effect on the fungi.

Sense Organs: Eyes, Ears, Nose, Mouth, Skin

It  is through the sense organs chiefly eyes, ears, nose, mouth (tongue), and skin that the brain comes in contact with the reality of the external environment which human beings and other living creatures inhabit. Without senses vision, hearing, touch, smell, taste and others a human being as such can hardly be said to exist.

Perception of reality finally takes place in the brain, but the impressions which make this possible come via the nerve pathways of the sensory organs. The brain "dwells in utter darkness" in the cavity of the skull; but it is the brain that sees, hears, feels, and makes interpretations of all the sensory impressions brought to it.

Here we will place emphasis on the princi­pal sense organs. There are several practical reasons for this. Eyes, ears, and skin particu­larly are complex and specialized organ sys­tems, each of which demands its own special­ized kind of care and attention. Furthermore, all the sensory organs (with the exception of the eye) have functions beyond reporting sense impressions to the brain. For a com­plete understanding of the human organism, these specialized systems deserve to be studied   in   their   own   right.   They   are   often abused.

Eyes and ears are two of the greatest assets a human being possesses. Yet many people fail to make the most of them. Eye special­ists (ophthalmologists) constantly encounter people with faulty vision who have accepted the blurred, imperfect images of the world they half-see as perfectly normal. "Oh, I see fine," they say until they surprisingly dis­cover how much better they can see when their visual defects have been properly cor­rected. Ear specialists (otologists) similarly report that patients have usually lost a full third of their hearing before they take any steps to overcome their partial deafness.

End Organs of the Peripheral

Nervous System

To provide a more exact picture of the op­eration of sensory organs, we must briefly describe the operation of the peripheral ner­vous system. As its name implies, it is located at the periphery or outside ends of the ner­vous systems. It consists primarily of nerve trunks, attaching to the central and auto­nomic nervous systems, and end-plates, or end-organs. These end-organs pick up specific types of stimuli (light, sound, heat, cold, pain,

Pressure,etc. They also deliver back message or orders to the organs to which they are attached. End plates that pick up sensations are called receptors. Those that deliver orders are effectors. The end plates are specific for their particular sensations. Thus, the eye reacts to light, the ear to sound, the nose and tongue to chemicals in solution.

The specificity of the end plates explains some peculiar reactions. Why do you sometime see stars when you get a punch in the eye? Because the receptors server only one function. The end plates on the retina of the eye connect directly with the visual center in the brain. Stimulating the end plates of the retina with a powerful blow can be translated by the brain only in visual images that is, the flashes of light we describe as seeing stars. Similarly a blow on the ear may come as an explosive sound.

Man has far more than the traditional five senses. There are end organs for hot and cold sensations, for pressure, for pain and combinations of impacts on end organs that give a sense of vibration, a feeling of fullness or tension, a sense of balance, even the most basic feelings of hunger, thirst, and sexual desire. The end organ for hot and cold are irregulary distributed on the skin and in the mouth and esophagus, there are many of them of the feet and very few on the chest. The designers of women‘s fashions, though not deliberately, abide by these hot and cold spots.

Nails

The nails require little care except being cut and cleaned as dictated by social custom, which varies greatly. Nails grow out of a bed of skin beneath them and the cuticle in which they are imbedded. Infections at this margin sometimes occur. If serious, they require medical attention. Nail polish should be kept out of the cuticle. "Hangnails" should be snipped, not pulled off. Ingrown toenails can usually be avoided by cutting the nails straight across.

In summary: We have devoted this chapter to the crucial sense organs of the human being eyes, ears, nose, mouth, and skin. We have also pointed out the numerous other bodily functions these sense organs perform and have discussed the special care and at­tention each requires. A satisfactory feeling of personal fitness can hardly be achieved if these special sense organs are abused or neg­lected. The brain, of course, interprets and gives meaning to the responses of the spe­cialized end-plates of the sense organs. To the extent that these end-plates fail to respond to the great variety of external stimuli in the human environment, a man or woman is robbed of sensations that give value to life.

Eye Injuries

First aid for eye injuries, even trivial ones, is another important consideration in sight conservation. The eye is easily infected, and scratches on the cornea can become scarred and cloudy, interfering with vision. Foreign bodies (dust, cinders) in the eye must be man­aged properly.

When you get something in your eye that cannot be immediately dislodged, shut both eyes for a few minutes and don't rub them. The accumulation of tears will often wash out the particle. This failing, you can try instill­ing a few drops of clean water in the eye. Washing out the eye with an eyecup filled with boric acid solution is the next step.

As a last resort, an attempt can be made to remove the particle-if it is visible, and not on the cornea with the corner of a clean handkerchief. The lower lid may have to be pulled down or the upper lid everted by tak­ing hold of the lashes and pulling gently up­ward and outward.

All these procedures should be done with clean hands and in as sterile a manner as possible. If none of these simple measures succeeds, a physician should be consulted. Removal of metal or glass particles may re­quire special procedures.

Common Questions about the Eyes

Will looking at television harm the eyes? No. Commercial television is more likely to pro­duce cultural than ocular blindness. Prolonged viewing of a television screen which flickers and on which images are in poor focus may induce a temporary eyestrain, but this is easily remedied by finding a clearer channel or turning off the set.

Are "drops" in the eyes safe? Yes, when used by a physician for eye examinations. The indiscriminate cosmetic use of belladonna or similar eyedrops, which make the eyes look big by relaxing the muscles of the iris, is to be deplored.

Can eye exercises make it possible to "see without glasses"? Not if glasses are needed. There is a legitimate place for eye exercises (orthoptics), but not as a substitute for glasses.

What about contact lenses? Contact lenses have been in use since about 1910. They are small lenses that fit directly over the cornea and under the eyelids. They must be very carefully fitted to the exact shape of the cor­nea, and they have proved most useful in people with marked abnormalities of the cor­nea. Various improved types are now avail­able, and a suction cup is no longer needed for inserting them and taking them out. Unfor­tunately, contact lenses usually become un­comfortable after a few hours wear; otherwise the vanity or convenience of "not wearing glasses" would prompt far more people to use them, despite the fact that they are rather expensive.

Contact lenses usually cost between $150 and $350 a pair. Since about 8 million Amer­icans now wear them at least part of the time they represent an investment of about $1.5 billion.

Eye Injuries

Diseases of the Eye

Just as the eye can affect the entire bodily system, as in general fatigue from eyestrain, so, conversely, systemic infections can play particular havoc with the eye. Syphilis, gonor­rhea, and tuberculosis are three top offenders in this role: they have localized ocular effects, but they must be attacked systemically. Some of the childhood diseases, especially measles and scarlet fever, may affect the eyes. Some drugs or poisons taken internally have dis­astrous effects on the eyes, especially quinine and methyl (wood) alcohol.

Any part of the eye may be subject to infec­tion. The most serious are those which affect the cornea (keratitis), the iris (iritis), or the retina (retinitis).

Usually less serious but often very annoy­ing infections can afflict the external portions of the ocular system. Most frequently affected is the conjunctiva, the membrane lining the eyelid and covering the front of the eyeball. A mild form of conjunctivitis often accom­panies a common cold. Very severe infec­tions may be encountered, such as gonorrheal ophthalmia.

Pink eye is a form of conjunctivitis that usu­ally occurs in epidemic fashion. The eyes be­come bloodshot and inflamed, feel itchy and irritated, often feel as if something was in them, and may be stuck shut at night. Con­junctivitis is generally a communicable and contagious disease; the hygiene of cleanli­ness must be invoked against it. Any inflammation of the eyes demands serious medical investigation.

A sty is an infection of the lash roots and associated glands lining the margin of the eyelid. In certain respects it resembles a boil along a hair root. Persistent and repeated sties generally reflect a poor state of general health and are often associated with uncor­rected" errors of refraction and eyestrain.

The most serious infection of the eyelids is the condition known as trachoma, a highly communicable infection. It frequently causes blindness and has been the scourge of many oriental countries. Fortunately the modern sulfa drugs have proved effective in its treatment.

Diseases other than infection can afflict the eyes and cause blindness. Two important disabilities of this type are glaucoma and cataract. Both occur most commonly in mid­dle life or later. The basic, underlying causes are not known for either disease.

Glaucoma is a serious disease whose locale is within the eye itself; probably one in every eight or nine cases of blindness is a result of this disease. In glaucoma the pressure of the fluids within the eyeball unaccountably rises. Cataract is a clouding of the crystalline lens of the eye or its capsule. Light fails to reach the retina in sufficient quantity to make seeing possible. Cataracts usually develop in one eye before the other and progress gradu­ally. They can usually be relieved that is, failing sight can be restored—by a delicate operation removing the clouded lens.

Defects in Focus

The eye is said to have a power of accommodation which permits it to focus on objects at varying distances from it. This ability to focus depends on the action of its small ciliary muscles. In near vision, they contract and make the crystalline lens of the eye thicker. For distant vision, the opposite process occurs and the lens become flatter. There is a limit, however, to the power of accommodation. When the ciliary muscles are constantly overworked, the effect is eyestrain or eye fatigue, which may be reflected in other parts of the body.

In order for a clear image to be seen, the rays of light proceeding from the visible ob­ject must pass through the cornea and crys­talline lens and must be focused more or less exactly on the retina. Defects in focusing of­ten occur as a result of weakness or strain on the ciliary muscles, abnormalities in the shape of the cornea and lens, rigidity of the lens and too-great or too-little depth (or length) of the eyeball.

The four common defects in focusing are myopia (nearsightedness), hyperopia (far­sightedness), presbyopia ("oldsightedness") and astigmatism. These conditions account for most cases of poor eyesight. The correc­tion of these defects is made by fitting and wearing the proper kinds of glasses, which compensate for refractive errors of the eye itself.

Professional Eye Care

Here are the "danger signals" from the eyes that should prompt you to see a doctor: seeing double, seeing blurred outlines around objects that you formerly saw sharply, seeing rain­bows or halos around lights, or seeing poorly in the dark.

In some cases your doctor will further rec­ommend that you see an eye specialist. The ophthalmologist, formerly called oculist, is a physician (M.D.) licensed to treat all diseases and disorders of the eye and, of course, to use all diagnostic methods. In addition to his reg­ular medical training, the eye specialist has taken postgraduate courses of study in his specialty His competency is in many in­stances certified by the American Board of Ophthalmology, first of the specialty examin­ing boards in American medicine.

The optometrist is also a licensed, profes­sional person, who has taken special college and graduate courses in optometry. Optome­trists are licensed in all fifty states to exam­ine the eyes for errors of refraction in the lens system, to prescribe lenses (glasses) to correct these errors, and to prescribe eye exercises and other non-medical measures in eye care. The optometrist, however, is not a physician. Perhaps three-fourths of all prescriptions for glasses in the United States are written by optometrists.

The optician is a technician; he grinds lenses to the prescription of the oculist or op­tometrist and fits them to the eye in a prop­erly adjusted frame. The adjustment of the glasses to the eye must be accurate, and this requires proper fitting of frames.

Color Blindness Night Blindness

The retina of the eye is lined with millions of rods and cones. The cones permit us to distinguish shapes and colors in bright light. Millions of shades, hues, and tints of colors can be differentiated. In some individuals, however, the cones (and other color-perception apparatus, including the brain connections) fail to distinguishcertain colors; most commonly, they fail to sort out reds and greens. This creates the condition of colorblindness. So far as is known, color blindness is a hereditary defect and there is no treatment for the condition.

The ability to see in dim light and to dis­tinguish movement depends on the rods in the retina. Since the rods are less plentiful at the dead center than on the sides of the ret­ina, vision at night is usually improved by looking obliquely rather than directly at the objects to be seen.

To see in dim light, the rods must contain a chemical substance known as visual purple. The elaboration of this pigment, which goes on constantly, requires the presence of vita­min A. In the presence of light, the visual purple disappears rapidly and must be re­formed. If it is not. owing to a deficiency of vitamin A or other cause, ability to see at night and in twilight is seriously and in some instances, such as piloting an automobile or an airplane, dangerously curtailed. Night blindness can usually be prevented and alle­viated by a diet rich in vitamin A, provided no disease process exists.

Prevention of Blindness

Total blindness in both eyes is a human calamity of top magnitude; few people can rise above it, and they are to be honored. But any degree of blindness is a physical handi­cap that can be economically and emotion­ally crippling.

It is estimated that there are something over 260.000 "legally" or "industrially" blind persons in the United States and that perhaps half of these cases were readily preventable. The leading causes of blindness are infectious and degenerative diseases and accidents.

Color Blindness - Night Blindness

The retina of the eye is lined with millions of rods and cones. The cones permit us to distinguish shapes and colors in bright light. Millions of shades, hues, and tints of colors can be differentiated. In some individuals, however  the cones (and other color-perception apparatus, including the brain connections) fail to distinguish certain colors; most commonly, they fail to sort out reds and greens. This creates the condition of color blindness. So far as is known, color blindness is a hereditary defect and there is no treatment for the condition.

The ability to see in dim light and to dis­tinguish movement depends on the rods in the retina. Since the rods are less plentiful at the dead center than on the sides of the ret­ina, vision at night is usually improved by looking obliquely rather than directly at the objects to be seen.

The critical distance for seeing is the distance between the light source and the observed object. Where close work such as read­ing, writing, or sewing is to be done, the light falling on the book or paper or threads should be of an intensity of about 15 or 30 foot-candles, or more.

The major source of light on the printed page or other close work should come from behind. Direct glare of light into the eyes should always be avoided. Lamps should be well shaded, and bulbs should be frosted. It is better to work in a room that is reasonably well lighted throughout than to depend on "pinpoint" lighting on the work itself. In this respect modern, indirect lighting is an advan­tage. Position while reading for example, reading in bed-makes little difference provided that the proper conditions of illumina­tion are maintained. The book should be about 14 inches in front of the eyes.

You are the best judge of the amount of light you need to read or do other work. If there is not enough light, you will start to squint and frown and become uncomfortable. If there is too much light and glare, you will begin blinking and turn away from the light source.

Glare requires eye muscles to make con­stant and extensive readjustments, resulting in eyestrain and in an extreme case, under special conditions, "snow blindness." Use of tinted glasses, optically correct, can be a help in avoiding undue glare. Too many people, however, wear sunglasses solely for costume effect.

When to Wear Sunglasses

You can buy sunglasses for anywhere from 25 cents to $2750 (diamond-studded frames) a pair. For a good acceptable pair of sunglasses you will have to pay anywhere from about $6 to $20. An "acceptable" pair of sunglasses transmits from about 15% to 30% of visible light (i.e. it cuts out from about 70% to 80%) and also offers adequate protection against infrared and ultraviolet rays of the sun. neutral colors gray, green and tan, in that or der are preferable.

Sunglasses should be worn for the purpose for which they are primarily manufactured: to protect your eyes from discomforting expo­sure to the sun's rays. They should not be worn for night driving that is, to protect the driver from the glare of oncoming headlights.

Fashion has made dark glasses a more popular item of feminine beauty accessories than is physiologically warranted. Too many young women, perhaps, have gotten into the habit of concealing the natural beauty of the eyes and distorting the natural and appealing contours of their faces by hiding themselves behind dark glasses when this is not really necessary. One observer has said of light-tint sunglasses (those that transmit more than 30% of visible light) "They are a cosmetic, a decoration a palliative for neurotics."

Causes of Deafness

A few people are born deaf; many more become deaf as a result of accident, infection, or aging. As one grows older, the eardrum tends to become thicker and less flexible in the transmission of sound waves. In some persons, also, irrespective of age, there is an increase in bony tissue so that the stirrup bone becomes firmly fixed in the oval window and is no longer able to function in the transmission of sound. This condition is called otoscle­rosis. In some such cases, carefully selected, deafness can be alleviated by a surgical oper­ation   (fenestration   operation)   in   which a not so important to his existence as they are to most lower animals. Both senses may warn of danger, as in smelling smoke or biting into some foodstuff that just doesn't "taste right."

The sensory end-organs for smell (olfactory chemoreceptors to give them their technical name) are located at the top of the inner sur­face of the nose. These olfactory cells are imbedded in mucous membrane; from them other nerve fibers pass up to the olfactory lobe in the brain, where the smell is "interpreted." The olfactory cells pick up odors from mole­cules or small particles released by various substances. These particles are present in the air we inhale, and when they come in contact with the olfactory cells, they stimulate the appropriate end-organs.

Human beings can distinguish about 60.000 odors; but these are combinations of a rela­tively few specific classes of odors to which the olfactory cells directly respond. According to one classification, these cells respond to only seven odors, described as burnt, acid, putrid, spicy, fragrant, fruity, and resinous.

Taste is the sense by which we perceive the flavor of substances placed in the mouth. The end-organ receptors through which this is accomplished are called "taste buds." The im­pulses from these receptors are, of course, conveyed to the brain, where they register as taste sensations. For practical purposes the taste buds may be considered to be located on the tongue, though there are a few scattered in the pharynx.

Human beings can actually distinguish only four different tastes: sweet and salt in the buds at the tip of the tongue; sour (or acid) along the sides of the tongue; and bitter at the back of the tongue. The taste buds are react­ing to chemicals in solution. The combina­tions of the four basic taste sensations provide a wide variety of flavors. Whether a food tastes "good" or "bad" to an individual is not based on the intrinsic nature of the foodstuff but rather on his past (learned) experiences with the particular food or flavor.

Stimulation of the taste buds brings about an important unconscious reflex reaction. It induces the secretion of salvia in the mouth and gastric juices in the stomach, thus aiding the process of digestion.

While the nose and tongue, as we have noted, are sense organs, they also serve other functions. The nose and paranasal sinuses are important adjuncts to the respiratory system. The tongue, used for mixing foods in the mouth and for swallowing, assists the diges­tive system. Both tongue and nose are in­volved in the process of human speech.

Artificial Light

For comfortable use of the eyes in artificial light, the source of light should be steady (no flicker), uniform, non-glaring, and of adequate intensity. Intensity of illumination is measured in terms of foot-candles by photoelectric instruments called light meters. A foot-candle is the amount of light projected at

 a distance 1 foot from the flame of a standard candle.

The critical distance for seeing is the dis­tance between the light source and the ob­served object. Where close work such as read­ing, writing, or sewing is to be done, the light falling on the book or paper or threads should be of an intensity of about 15 or 30 foot candles, or more.

The major source of light on the printed page or other close work should come from behind. Direct glare of light into the eyes should always be avoided. Lamps should be well shaded, and bulbs should be frosted. It is better to work in a room that is reasonably well lighted throughout than to depend on "pinpoint" lighting on the work itself. In this respect modern, indirect lighting is an advan­tage. Position while reading-for example, reading in bed - makes little difference pro­vided that the proper conditions of illumina­tion are maintained. The book should be about 14 inches in front of the eyes.

You are the best judge of the amount of light you need to read or do other work. If there is not enough light, you will start to squint and frown and become uncomfortable. If there is too much light and glare, you will begin blinking and turn away from the light source.

Glare requires eye muscles to make con­stant and extensive readjustments, resulting in eyestrain and in an extreme case, under special conditions, "snow blindness." Use of tinted. glasses, optically correct, can be a help in avoiding undue glare. Too many people, however, wear sunglasses solely for costume effect.

When to Wear Sunglasses

You can buy sunglasses for anywhere from 25 cents to $2750 (diamond-studded frames) a pair. For a good acceptable pair of sunglasses you will have to pay anywhere from about $6 to $20. An "acceptable" pair of sunglasses transmits from about 15% to 30% of visible light (i.e. it cuts out from about 70% to 80%) and also offers adequate protection against infrared and ultraviolet rays of the sun. Neu­tral colors-gray, green, and tan, in that order - are preferable.

Sunglasses should be worn for the purpose for which they are primarily manufactured: to protect your eyes from discomforting expo­sure to the sun's rays. They should not be worn for night driving - that is, to protect the driver from the glare of oncoming headlights.

Fashion has made dark glasses a more popular item of feminine beauty accessories than is physiologically warranted. Too many young women, perhaps, have gotten into the habit of concealing the natural beauty of the eyes and distorting the natural and appealing contours of their faces by hiding themselves behind dark glasses when this is not really necessary. One observer has said of light-tint sunglasses (those that transmit more than 30% of visible light): They are a cosmetic, a decoration-a palliative for neurotics."