Pupil (eye)

“ If you travel in darkness, you expand the pupil of your eye, which, in forming a perfect circle, describes a larger surface, and collects the greater part of the luminous rays which are scattered in the atmosphere. When you appear in daylight, your pupil takes an elliptic form, diminishes, and receives only a portion of these rays, an excess of which would injure your retina. My dear Cat, you are a perfect optician!
When you wish to descend a precipice, you calculate the distance of the solid points with astonishing accuracy. ”

“ The contraction of the pupil is readily seen when a person passes from a darkened [178] room into a bright sunlight, or when a light is first brought into a room in the twilight of evening. Any person may notice this contraction in his own eye by beholding himself in a glass immediately after passing from a dark to a well-lighted room. So, also, when a person looks at an object near the eye, the pupil contracts, but when he looks at an object more remote, it dilates. The muscles of the iris are somewhat under the control of the will ”

“ The eye also varies much in colour, being blue, yellow, or green. The pupil, or small black aperture in the centre of the coloured portion, is extremely sensitive, dilating greatly in the dark, and contracting to a mere line when the light is strong. ”

“ The eye will accommodate itself to light of different degrees of intensity within a limited range, but both eyes should be exposed to an equal degree of light. The sympathy between the eyes is so great, that if the pupil of one eye is dilated by being kept in the shade, as must, of course, be the case where the light is on one side, the eye which is exposed can not contract itself sufficiently for protection, and is almost inevitably injured. ”

“ Let the eye be kept steadily in one place, and take a distinct view of the object. We know, from the principles of optics, that the rays from any one point of this object, whether they pass through the centre of the eye, or at any distance from the centre which the breadth of the pupil will permit, do all unite again in one point of the retina. ”

“ Some principles may be alleged,—for instance, where there is strong understanding, the look is pleasing, whilst the eye moves calmly, passing in curves, the pupil is contracted, the brows are bent downward, and the ball is prominent; whereas, when the feelings predominate, the eye performs its motions more actively, and is fluctuating and flickering, indicating the emotions of the mind, the pupil is dilated, the iris appears soft, and oft riding in a charmed sea of crystal drops. ”

“ The pupil of your eye is only a gimlet-hole, not so very much bigger than the eye of a sail-needle, and a camel has to go through it before you can see him. You look into a stereoscope and think you see a miniature of a building or a mountain; you don't, you 're made a fool of by your lying intelligence, as you call it; you see the building and the mountain just as large as with your naked eye looking straight at the real objects. ”

“ The pupil of the eye opens into a little, round room where the nerve of sight is. This is a safe place for this delicate nerve, which can not bear too much light. It carries to the brain an account of every thing we see. ”

“ The lines b are pencils of light, as they find entrance through the pupil into the interior of the eye-ball, where each of them is by refraction made to converge to a point, called the focus, which, falling exactly on the retina, forms a distinct image thereon of the point a of the external object from which the pencil of light emanated. ”

“ 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 stronger the external light, the smaller the pupil, and the reverse; so that the eye is capable of functioning at a stronger and also at a fainter illumination than it could function if the width of the pupil were of a medium, unchangeable diameter. ”

“ The nerve of the eye at the back of its chamber can not see without light, and its light comes through the little round window called the pupil, or black of the eye—which is simply a hole in the iris, or colored part. ”

“ Accordingly, the eye is divided horizontally by a dark strip into two distinct and unlike portions, the upper one of which has a pupil adapted to vision in the air alone, while the lower is adapted to seeing in the water only. ”

“ In the presence of a dull light the pupil enlarges, allowing a great amount of the light, such as that falling upon a book, to enter the eye and to stimulate the retina. The iris is a wonderful device, but can not in diverse illuminations perfectly equalize the amount of light entering the eye. ”

“ This difference of effect is produced by the great brightness of the air, which contracts considerably the pupil of the eye, and by so doing diminishes its power. But in dark places the pupil is enlarged, and acquires as much in strength, as it increases in size. ”

“ In some Felidæ, such as the Domestic Cats, the pupil, or small aperture in front of the eye which lets in light to the sensitive retina beyond, has the round shape it possesses in man, only in the dark, when it is dilated to receive every ray of light available. ”

“ He is to be seen with projecting rolling eyes, with oblique lids, or deep sunken small eyes, under a perpendicular, hard, long forehead.
Eyes which show the whole of the pupil, and white below and above it, are either constrained or unnatural, and only observable in restless, passionate, and half-simple, persons, and never in such as have a correct, mature, sound, unwavering understanding. ”