IT is one of the prerogatives of mam to have eyes. Many living creatures have none. The eyes which others-forexample, the star-fishes-have, are meresensitive points, dimly conscious of light and darkness, but not perceiving colours or distinguishing forms. The eyes of flies are hard horny lanterns, which cannot be moved about like our restless eyes, but look always in theA FLY"S EYE(MAGNIFIED)same direction; whilst spiders, havingmany more things to look after than one pair of such lanterns will suffice for, have eyes stuck all over their heads, and can watch a trapped gnat with one eye, and peer through a hole in their webs with another.
We are much better provided for than any of these creatures, although we have but two small orbs to see with. Think, first, how beautiful the human eye is, excelling in beauty the eye of every creature. The eyes of many of the lower animals are doubtless very beautiful. You must have admired the bold, fierce, bright eye of the eagle; the large, gentle, brown eye of the ox; the treacherous green eye of the cat, waxing and waning like the moon, as the sun shines upon it or deserts it; the pert eye of the sparrow; the sly eye of thefox; the peering little bead of black enamel in the mouse"shead; the gem-like eye which redeems the toad from ugliness;and the intelligent, affectionate expression which looks out from the humanlike eye of the horse and the dog.
There are these and the eyes of many other animals full of beauty; there are none, indeed, which are not beautiful; but there is a glory which excelleth in the eye of man. We realize this fully only when we gaze into the faces of those we love. It is their eyes we look at when we are near them, and recall when we are far away. The face is a blank without the eye; and the eye seems to concentrate every feature in itself. It is the eye that smiles, not the lips; it is the eye that listens, not the ear; it that frowns, not the brow; it that mourns, not the voice. Every sense and every faculty seems to flow towards it, and find expression through it-nay, to be lost in it: for allmust at times have felt as if the eye of another were not his,but he; as if it had not merely a life, but also a personality of its own; as if it were not only a living thing, but also a thinking being.
But apart from this source of beauty, in which man"s eye must excel that of all other creatures as much as his spirit excels in endowments theirs; it is in itself, even when life has departed from it, and the soul no longer looks through its window, a beautiful and a very wonderful thing. Its beauty is, perhaps, most apparent in the eye of an infant, which, if you please, we shall suppose not dead, but only asleep with its eyes wide open. How large and round they are; how pure and pearly the white is, with but one blue vein or two marbling itssurface; how beautiful the rainbow ring, opening its mottled circle wide to the light!
How sharply defined the pupil, so black and yet so clear,that you look into it as into some deep, dark well, and see a little face look back at you, which you forget is your own, whilst you rejoice that the days are not yet come for those infant eyes when "they that look out of the windows shall be darkened"! And then, the soft pink curtains which we call eyelids, with their long silken fringes of eyelashes, and the unshed tears bathing and brightening all! How exquisite the whole! How precious in the sight of God must those little orbs be, when he has bestowed upon them so much beauty!
But apart altogether from that beauty which delights the painter, the human eye is a wondrous construction. Let us glance for a moment at its wonderfulness.
It is essentially a hollow globe, or
small spherical chamber. There is no
THE HUMAN EYE
a.Cornea.
b.Aqueous humour.
c.Iris.
d.Pupil.
e.Crystalline lens.
f.Vitreous humour.
g.Retina.
h.Choroid.
i.Sclerotic coat.
j.Optic nerve.
human chamber like it in form, unless we include among human dwelling-places the great hollow balls which surmount the Cathedral or Basilica Domes of St. Peter"s and St. Paul"s.
The eye is such a ball. The larger part
of it, which we do not see when we look in each other"s faces, forms the white of the eye, and consists of a strong, thick, tough membrane, something like parchment, but more pliable. This forms the outer wall, as it were, of the chamber of the eye. It may be compared to the cup of an acorn; or to a still more familiar thing, an egg-cup; or to a round wine-glass with a narrow stem. It is strong, so that it cannot easily be injured;thick, so that light cannot pass through it; and round, so that it can be moved about in every direction, and let us see much better on all sides with a single pair of eyes than the spider can with its host of them.
In the front of the eye is a clear, transparent window,exactly like the glass of a watch. If you look at a face sideways, you see it projecting with a bent surface like a bow-window, and may observe its perfect transparency. The eyelids, which I formerly described as curtains, may perhaps be better compared to a pair of outside shutters for this window, which are put up when we go to sleep, and taken down when we awake.
But these shutters are not useless, or merely ornamental, during the day. Every moment they are rising and falling; or, as we say, winking. We do this so unceasingly, that we forget that we do it at all. But the object of this unconscious winking is a very important one. An outside window soon gets soiled and dirty; and a careful shopkeeper cleans his windows every morning. But our eye-windows must never have so much as a speck or spot upon them; and the winking eyelid is the busy apprentice who, not once a day, but all the day, keeps the living glass clean: so that, after all, we are nearly as well off as the fishes, who bathe their eyes and wash their faces every moment.
Behind this ever-clean window, and at some distance from it, hangs that beautiful circular curtain which forms the coloured part of the eye, and in the centre of which is the pupil. It is named the iris, which is only another name for the rainbow; for though we speak of eyes as simply blue, or gray, or black, because they have one prevailing tint, we cannot fail to notice that the ring of the eye is always variously mottled, andflecked or streaked with colours as the rainbow is.
This rainbow curtain, or iris, answers the same purpose which a Venetian blind does. Like it, it can be opened and closed at intervals; and like it, it never is closed altogether. But it is a much more wonderful piece of mechanism than a Venetian blind, and it opens and closes in a different way.
There is nothing this iris so much resembles, both in shape and in mode of action, as that much-loved flower, the daisy. The name signifies literally day"s eye; the flower whichopens its eye to the day, or when the day dawns. Shakespeare, who saw all analogies, referring to the similar action of the marigold, in the morning song in Cymbeline, tells how"Winking Mary-buds begin To ope their golden eyes."The daisy and the iris agree in this, that their opening and closing are determined by their exposure to light or darkness: but they differ in this, that the daisy opens widest when the sun is at its height, and shuts altogether when the sun goes down; whilst the iris opens widest in utter darkness, and closes so as to make the pupil a mere black point when sunshine falls upon it.
If we wish to observe this in our own eyes, we need only close them for a little while before a looking-glass, so that the dropped eyelids may shut out the day, when, like shy night- birds, the living circles will stretch outwards; and the pupil of the eye, like a hole which the sun is melting in the ice, will quickly widen into a deep clear pool. If now we open our eyes,we see the rainbow-rings contractas the light falls uponthem, and the dark pupil rapidly narrow, like the well-head of a spring almost sealed by the frost.
But probably all have seen the movement I am describing in the eyes of a cat, where the change is more conspicuous than in our own eyes; and have noticed the broad iris spread out in twilight, till the look, usually so suspicious, softened into a mild glance; whilst when pussy is basking in the sun, as she dearly loves to do, she shows between her frequent winkings only a narrow slit for a pupil, like the chink of a shutter, or the space between the spars of a lattice-blind.
The endless motions of this living curtain, which, like theunresting sea, is ever changing its aspect, have for their object the regulation of the flow of light into the eye. When the permitted number of rays have passed through the guarded entrance, or pupil, they traverse certain crystal-like structures, which are now to be described.
regulation, control. restless, roving. sensitive, susceptible. spherical, globular. surmount, rise above. suspicious, distrustful. traverse, cross. treacherous, faithless. unceasingly, constantly. unresting, ever-moving.
QUESTIONS
What is peculiar in the eyes of flies and spiders? Mention some of the lower animals that have beautiful eyes. Why does the eye of man excel all these? When is its beauty most apparent? What part of it looks like a deep, dark well? What do you always see in it? What is the shape of the whole organ as it exists in the head? Of what does the larger part of it consist? What is there in front of the eye? What purposes do the eyelids serve? What is the iris? What purpose does it serve? What flower does it much resemble? With what great difference? How may we observe the contracting of the iris? In what animal are its changes most perceptible?
