Eye
2 of the 7 encyclopedias on this shelf carry an entry for Eye. Both are reproduced below, so you can see where they agree and where they differ.
Collier's New Encyclopedia (1921)
the organ of sight. The principle on which the human eye is constructed is that of the camera obscura, a dark chamber with a small opening for the admission of light, a quantity of black matter for the absorption of superabundant rays, and a nervous expansion on that wall which receives the rays of light. For protection it is deeply sunk M N P E L B J G F K H C L E D P 0 EYE-CROSS-SECTION OF HUMAN EYE A. Optic nerve K. Arteria centrali B. Retina retinæ C. Choroid L. Orbital fat D. Sclera M. Levator palpebræ E. Vitreous humor superioris muscle F. Lens N. Rectus superior G. Aqueous humor muscle H. Cornea O. Rectus inferior I. Iris P. Eyelids J. Fovea centralis Q. Eyelashes in a fatty cushion within a bone cavity. The human eye is nearly globular, but the anterior part formed by the cornea is part of a smaller sphere, and slightly protuberant, in the proportion of 20 to 19. In the globe itself the chief constituents are: (1) The retina, the expansion of the optic nerve; (2) the transparent refracting media (the vitreous body or humor, the crystalline lens, the aqueous humor, the iris, and the pupil); (3) the tunica sclerotica, forming a dense tunic inclosing the first two. It is opaque except in front, where it becomes (4) the cornea, perfectly transparent, to allow the light to enter (5) the choroid membrane, lying between the retina and sclerotica, and containing a layer of dark pigment. The vitreous humor is immediately within the cup formed by the retina, and gives the support inside which the sclerotica does outside; it forms four-fifths of the whole globe, and its perfect fluidity allows for the expansion and contraction of the pupil and of the lens itself to or from the cornea. The crystalline lens is divided into three equal parts by three lines, which radiate from the center to one-third of the surface; each one of these layers consists of hundreds of concentric layers, connected by finely serrated edges. This beautiful dove-tailing of fibers is not peculiar to man; the best example is the lens of the common codfish. The eyes of the vertebrata are essentially like those of man. The eyes of insects are of two kinds: compound eyes and simple eyes or stemmata. The compound eyes are immovable. They consist of vastly numerous lenses; thus in the dragon-fly there are 12,000. Spiders have compound eyes; the higher members of the class have ocelli; many of the lower parasitic species are blind. The eyes of crustacea vary greatly, from a sessile median eye-speck to two distinct eyes placed on movable peduncles. The centipedes have many simple eyes; in -A Iulus these are so near as almost to make two compound eyes. Of mollusks, the cephalopoda have large eyes, the gasteropoda possess them, as do the pectens among the conchifera, though in most other genera of the class, and in brachiopoda, they seem wanting. The animals of lower organization are destitute of eyes. In Architecture. (1) The circular aperture in the top of a dome or cupola. (2) The circle in the center of a volute scroll. (3) A circular or oval window. In Nautical Parlance. (1) A circular loop in a shroud or rope. A worked circle or grommet in a hank, rope, or sail. (2) The loop of a block-strap. (3) The hole in the shank of an anchor to receive the A B B C D EYE-CROSS-SECTION OF HUMAN EYE A. Lachrymal gland C. Nasal sac B. Lachrymal canal D. Nasal duct ring. The foremost part of the bows of a vessel, on which formerly eyes used to be painted. The term is also applied to the hawse-holes. The strands of a rope's end opened and divided into two parts and laid over each other, marled, parceled, and sewed together, and so forming an eye, is called a Flemish eye.
Aiton's Encyclopedia (1910)
the organ of vision. In its simplest and essential form an eye is the end of a nerve sensitive to light. In many lower forms of animals it is merely a sensitive spot from which nerves run to the nervous center. Many insects have what is known as a compound eye. The bundle of optic nerves, on reaching the surface, spreads out like a treetop, each fiber terminating in a simple eye or facet. The eye of the ant is composed of about fifty of these fiber ends. There are 4,000 in the eye of the house fly. The prominent, handsome eye of the dragon fly or devil's darning-needle is made up of 20,000 facets. The structure of the human eye may be compared to a two-lens microscope. At the front, there is a body shaped like a watch glass, called the cornea, and a double-convex body, called the crystalline lens. These two are transparent and form an image. The wall of the rear or retina is composed of the fibers of the optic nerve. The image formed by the lenses falls on the retina. The impression is conveyed to the brain. The eyeball is merely a chamber designed to hold the lenses at the necessary distance from the retina. The various muscles and liquids, the iris, the eyelid, the eyelash, and eyebrow are mere accessories that adjust and protect the essential parts. The retina of the white man's eye is scarlet or vermilion; that of the Nubian negro is of a chocolate brown. Man sees more accurately than other animals; at least he is a better judge of shape and distance. See Blindness 2026 Editor's Note: This page uses language about race that was commonplace when the book was published and is offensive by today's standards. The text has been left exactly as it was printed, rather than cut or softened, so that the historical record — including how ordinary such language once was — is preserved. (Ed: BR 2026-07-22)