(1.) It is necessary to keep the morsel in the mouth as long as possible. Now the habit thus formed of eating very slowly is of the utmost importance, for if farinaceous articles of food are swallowed before the saliva has had time to act on them, they are little better than so much waste material taken into the system; and if meat is not thoroughly masticated, the stomach is overloaded with work which should have been done by the teeth; the result, in either case, is dyspepsia. It has been suggested that Mr. Gladstone owes his remarkable physical vigor to certain rules for chewing food, which he adopted in 1848, and to which he has adhered ever since. "He had always," we are told, "paid great attention to the requirements of Nature, but he then laid down as a rule for his children that thirty-two bites should be given to each mouthful of meat, and a somewhat lesser number to bread, fish, etc."
(2.) Besides this indirect advantage resulting from the effort to get at the fragrant odors of food, there is a still more remarkable direct advantage. It is one of the most curious psychologic facts that odors exert a strong influence on our system, either exhilarating or depressing. While an unpleasant odor may cause a person to faint, the fumes of the smelling bottle will restore him to consciousness. The magic and value of gastronomic odors lies in this, that they stimulate the flow of saliva and other alimentary juices, thus making sure that the food eaten will be thoroughly utilized in renovating the system.—HENRY T. FINCK, in "The Gastronomic Value of Odors." HYGIENE OF THE EAR (p. 236).—Never Box a Child's Ear.—Children and grown persons alike may be entirely deafened by falls or heavy blows upon the head. Boxing the ears produces a similar effect, though more slowly and in less degree, and tends to dull the sensibility of the nerve, even if it does not hurt the membrane. I knew a youth who died from a terrible disease of the ear. There had been a discharge from it since he was a child. Of course his hearing had been dull; and his father had often boxed his ear for inattention! Most likely that boxing on the ear, diseased as it was, had much to do with his death. And this brings me to the second point. Children should never be blamed for being inattentive, until it has been found out whether they are not a little deaf. This is easily done by placing them at a few yards' distance, and trying whether they can understand what is said to them in a rather low tone of voice. Each ear should be tried, while the other is stopped by the finger. Three things should be remembered here: 1. That slight degrees of deafness, often lasting only for a time, are very common among children, especially during or after colds. 2. That a slight deafness, which does not prevent a person from hearing when he is expecting to be spoken to, will make him very dull to what he is not expecting. 3. That there is a kind of deafness in which a person can hear pretty well while listening, but is really very hard of hearing when not listening.
Avoid Direct Draughts in the Ear.—There are some exposures especially to be guarded against. One is sitting or driving with the ear exposed to a side wind. Deafness has also been known to come from letting rain or sleet drive into the ear.
Do not Remove the Earwax.—It ought to be understood that the passage of the ear does not require cleaning by us. Nature undertakes that task, and, in the healthy state, fulfills it perfectly. Her means for cleansing the ear is the wax. Perhaps the reader has never wondered what becomes of the earwax. I will tell him. It dries up into thin fine scales, and these peel off, one by one, from the surface of the passage, and fall out imperceptibly, leaving behind them a perfectly clean, smooth surface. In health the passage of the ear is never dirty; but, if we attempt to clean it, we infallibly make it so. Washing the ear out frequently with soap and water keeps the wax moist when it ought to become dry and scaly, increases its quantity unduly, and makes it absorb the dust with which the air always abounds. But the most hurtful thing is introducing the corner of the towel, screwed up, and twisting it round. This does more harm to ears than all other mistakes together. It drives down the wax upon the membrane, much more than it gets it out. But this plan does much more mischief than merely pressing down the wax. It irritates the passage, and makes it cast off small flakes of skin, which dry up, and become extremely hard, and these also are pressed down upon the membrane. Often it is not only deafness which ensues, but pain and inflammation, and then matter is formed which the hard mass prevents from escaping, and the membrane becomes permanently diseased.
The Eustachian Tube.—The use of this tube is twofold. First, it supplies the drum with air, and keeps the membrane exactly balanced, and free to move, with equal air pressure on each side; and, secondly, it carries off any fluid which may be in the drum, and prevents it from being choked by its own moisture. It is not always open, however, but is opened during the act of swallowing, by a little muscle which is attached to it just as it reaches the throat. Most persons can distinctly feel that this is the case, by gently closing the nose and swallowing, when a distinct sensation is felt in the ears. This sensation is due to a little air being drawn out of the ears through the open tube during swallowing; and it lasts for a few minutes, unless the air is again restored by swallowing with the nose unclosed, which allows for the moment a free communication between the ear and the throat. We thus see a reason for the tube being closed. If it were always open, all the sounds produced in the throat would pass directly into the drum of the ear, and totally confuse us. We should hear every breath, and live in a constant bewilderment of internal sounds. At the same time the closure, being but a light contact of the walls of the tube, easily allows a slight escape of air from the drum, and thus not only facilitates and regulates the oscillations of the air before the vibrating membrane, but provides a safety valve, to a certain extent, against the injurious influence of loud sounds.
The chief use of the Eustachian tube is to allow a free interchange of air between the ear and the throat, and it is very important that its use in this respect should be understood. Persons who go down in diving bells soon begin to feel a great pressure in the ears, and, if the depth is great, the feeling becomes extremely painful. This arises from the fact that in the diving bell the pressure of the air is very much increased, in order to balance the weight of the water above; and thus it presses with great force upon the membrane of the drum, which, if the Eustachian tube has been kept closed, has only the ordinary uncompressed air on the inner side to sustain it. It is therefore forced inward and put upon the stretch, and might be even broken. Many cases, indeed, have occurred of injury to the ear, producing permanent deafness, from descents in diving bells, undertaken by persons ignorant of the way in which the ear is made; though the simple precaution of frequent swallowing suffices to ward off all mischief. For, if the Eustachian tube is thus opened, again and again, as the pressure of the outside air increases, the same compressed air that exists outside passes also into the inside of the drum, and the membrane is equally pressed upon from both sides by the air, and so is free from strain. The same precaution is necessary in ascending lofty mountains.— DR. JAMES HINTON.
THE COLORED CURTAIN IN THE EYE (p. 238).—This ring-like curtain in the eye, of gray, green, bluish-green, brown, and other colors, is one among the very many remarkable contrivances of the organic world. The eye can not bear the entrance of too much light, and the colored curtain so regulates its own movements as to serve this requirement. The dark circular aperture in the center, known as the pupil, is consequently forever altering in size; on a bright, sunshiny day, out in the open, it may be only the size of a pin's head, but at night, when there is no light stronger than starlight, it is even bigger than a pea. The eye curtain is fixed at its outer edge, leaving the inner edge to contract or expand, which it does automatically and quite independent of the will, ever preserving its circular outline. Its movements may be watched in a variety of ways, some of which we shall describe.
The common way of watching the movements of the iris is to regard it closely in a looking-glass while the amount of light entering the eyes is varied. Place yourself before a looking-glass and with your face to the window. Probably the iris will be expanded, and there will only be a very small opening or pupil in the center. Now shut one eye suddenly, while narrowly watching the other in the glass all the time. At the moment the light is cut off from one eye, the iris of the other contracts or is drawn up so as to enlarge the pupil. This shows that there is a remarkable interdependence between the curtains of the two eyes, as well as that they are affected by variations in the quantity of light falling on them.
Perhaps one of the most interesting ways of watching the movements of these sympathetic eye curtains is one which may be followed while you are out walking on the street some dark winter night. A gas lamp seen at a distance is, comparatively speaking, a point of light, with bars of light emanating from it in many directions. These bars, which give the peculiar spoked appearance to a star, are probably formed by optical defects of the lens within the eye, or by the tear fluid on the exterior surface of the eye, or by a combination of all these causes. Be that as it may, the lengths of the spokes of light are limited by the inner margin of the eye curtain; if the curtain be drawn up, then the spokes are long; if the curtain be let down, or, in other words, if the pupil be very small and contracted, then one can not see any spokes at all. Hence, as I look at a distant gaslight, with its radiating golden spokes, I am looking at something which will give me a sure indication of any movements of the eye curtains. I strike a match and allow its light to fall into the eyes; the spokes of the distant gas lamp have retreated into the point of flame as if by magic; as I take the burning match away from before my eyes, the spokes of the gas-lamp venture forth again. The experiment may be utilized to see how much light is required to move the window curtains of the eyes. Suppose you are walking toward two gas lamps, A and B; B about fifty yards behind A. If you steadfastly look at B and at the golden spokes apparently issuing from it, you may make these spokes a test of how soon the light of A will move your iris. As you gradually approach A, you come at last to a position where its light is strong enough to make the spokes of B begin to shorten; a little nearer still and they vanish altogether. I have found that about a third of the light which is competent to contract the pupil very markedly will serve to commence its movement.—WILLIAM ACKROYD.
PURKINJE'S FIGURES (p. 222).—Stand in a dark room with a lighted candle in hand. Shutting the left, hold the candle very near the right eye, within three or four inches, obliquely outward and forward, so that the light shall strongly illuminate the retina. Now move the light about gently, upward, downward, back and forth, while you gaze intently on the wall opposite. Presently the field of view becomes dark from the intense impression of the light, and then, as you move the light about, there appears projected on the wall and covering its whole surface, a shadowy, ghost-like image, like a branching, leafless tree, or like a great bodiless spider with many branching legs. What is it? It is an exact but enlarged image of the blood vessels of the retina. These come in at the entrance of the optic nerve, ramify in the middle layer, and therefore in the strong light cast their shadows on the bacillary layer of the retina. The impression of these shadows is projected outward into the field of view, and seen there as an enlarged shadowy image. These have been called Purkinje's Figures, from the discoverer.—PROF. JOSEPH LE CONTE, in Sight.