EYLAU
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is filled with vitreous humor (see diagram); in front of that is the crystalline lens; and, still further forward, is a cavity containing aqueous humor. All of these are transparent. The sclerotic coat in front is transparent and bulges out into the cornea. The choroid coat bends down in front, as a sort of curtain, and forms the colored iris of the eye; this is perforated in front by a circular opening—the pupil of the eye. The iris has circular and also radiating muscle fibres, the contractions of which cause the pupil to vary in size according to the intensity of the light. The retina is a delicate, whitish coat of nervous material. It is very complex in structure, being composed of several sets of nervous structures arranged in layers. The outer ones are rods and cones, and the inner ones are large nerve cells. The optic nerve is made of fibers that spring from the retina and pass into the brain; it used to be supposed that the fiber of the optic nerve grew outward from the brain and spread out into the retina; it is now known that they begin their growth from nerve-cells in the retina and grow inward to the brain. The eyeball is a sort of camera with transparent lenses in front of the retina to focus light upon it. It can readily be shown that any lens, thicker in the center, will focus light on a screen in such a manner as to produce an image. If, for example, one stands by a window with a reading-glass and places a paper behind the glass at the proper distance, there will be an inverted picture of the landscape thrown on the paper by the lens. This is practically what occurs in the eye. The crystalline lens and other transparent parts in front of the retina focus light upon it and produce an inverted image; but it is the brain that does the seeing,— the eye is merely a receiving apparatus. The rays of light that strike the retina excite it to activity, and this is transmitted to the brain and brings aboft changes there which give rise to sight. Not all parts of the retina are equally sensitive to light. The yellow spot is the most sensitive; this lies in a line drawn directly through the center of the lens. It is a rounded, shallow depression, in which the retina is much thinner and is composed mostly of rods and cones. The remainder of the retina is sensitive to light, except the blind spot, which is the place where the fibers are gathered into the optic nerve. The rods and cones are the parts affected by the light—the fibers not at all. Therefore, in the optic nerve, which is composed entirely of these fibers, there is no activity set up by light; they are merely conductors of the effect produced on the rods and cones by the Ight. The optic nerve is not connected with the eyeball symmetrically, but on the part nearer the nose, so that the blind spot is not in the center of the field.
of vision. The eyeball is moved by muscles—four straight ones and two oblique ones—so arranged that the eyeball may be turned up or down, to the right or left, and also slightly rotated. Certain defects in the eye are corrected by wearing glasses. When the lens is too rounding or the eyeball too long, the person is short-sighted; rays of light come to a focus before they reach the retina, and vision is hazy. This is corrected by concave glasses that tend to spread the rays of light. When the eyeball is too short, or the lens too fiat, the person is long-sighted, and the rays of light come to a focus behind the retina. This is corrected by convex glasses that bring the rays of light to a focus earlier. The crystalline lens is capable of being changed to a limited degree. It is an elastic body, and is inclosed in a perfectly transparent membrane. Under ordinary conditions it is pressed upon and rendered slightly flatter than it would otherwise be; when the tension or pressure on it is reduced by the contraction of certain muscles within the eyeball, it bulges out more, and when the muscles return to their state of extension it is flattened again. The eye is accommodated in this way to clear vision for objects at different distances.
Eylau (i'lou), 23 miles by rail south of Konigsberg, has 3,546 inhabitants. Napoleon here encountered the allies—Russians and Prussians—under Bennigsen, Feb. 8, 1807. Darkness came on while the contest was still undecided; but, as Napoleon had a considerable force of fresh troops close at hand, the allies retired during the night upon Konigsberg. Their loss was estimated at about 20,000; that of the French is set down at 10,000, but must have been much greater. The place is called Preussisch-Eylau, to distinguish it from Deutsch-Eylau, a town of 4,574 inhabitants, 89 miles northeast of Bromberg.
Eze'kiel (meaning God shall strengthen or Strength of God), one of the Hebrew prophets, was carried captive, when still a young man, along with Jehoiachin, king of Judah, to Mesopotamia by order of Nebuchadrezzar about 599 B. C. He was a member of the Jewish community which settled on the banks of the River Chebar, and first appeared as a prophet about 594, after the remarkable vision described in the opening chapters of Ezekiel. His career as a prophet extended over a period of 22 years. The date of his death is not recorded. Ezekiel was placed by the Jews among the "treasures," not to be read before the age of 30.
Ez'ra (Help), a Jewish scribe, lived about 450 B. C., and was regarded by the Jews of Christ's time as the second founder, with Nehemiah, of the Judean state. Judaism, as a religion, in distinction from the Hebrew religion before the captivity, dates from his day.
