Anatomy, physiology and hygiene for high schools . a small gland, the lachrymal (Latin lachtijma, a tear ) gland,which secretes the tears. This gland is continually secret-ing a small amount of fluid w^hicli washes the front of theeyeball and diains away by small lachrymal ducts to a cis-tern sac, which empties it through the nasal duct to thecavity of the nose. The structure of the eye. The eyeball is a sphere with aprominent bulging portion in front; that is, it consists ofthe segments of two spheres. The front bulging part, THE SPECIAL SENSES 245 through which we see the mottled-colored rin
Anatomy, physiology and hygiene for high schools . a small gland, the lachrymal (Latin lachtijma, a tear ) gland,which secretes the tears. This gland is continually secret-ing a small amount of fluid w^hicli washes the front of theeyeball and diains away by small lachrymal ducts to a cis-tern sac, which empties it through the nasal duct to thecavity of the nose. The structure of the eye. The eyeball is a sphere with aprominent bulging portion in front; that is, it consists ofthe segments of two spheres. The front bulging part, THE SPECIAL SENSES 245 through which we see the mottled-colored ring and the darkcircle in the center, is the cornea. This is attached all aboutto the white coat of the eye, the sclera (Greek sMeros,hard). The cornea and sclera are made up of fibrousmaterial, and together form the outer coat of the eye. Just inside the cornea, and seen through it, is a coloredring, the iris, inclosing a dark circular opening, the pupilBetween the cornea and iris is a clear watery substance,the aqueous (Latin aqua, water ) Plan of eyeball. O, optic nerve; 72, retina; F, vitreous humor; L, lens; O, cornea; (7on, conjunctiva;Sc, sclera; /, iris; A, aqueous humor; Cin, ciliary muscle; Ch, choroid. The iris is differently colored in different people. Thuswe have blue eyes or gray eyes. The iris contains muscle,and can contract and dilate, changing the size of the iris is continuous with a second coat of the eye, whichruns inside the sclera, the choroid. Tliis choroid coat, atits junction with the iris, is thrown into folds, like the 246 PHYSIOLOGY AND HYGIENE tucks of a dress. These folds are called the ciliary (LatmciliiDii, hau) processes. The choroid coat carries bloodvessels to feed the eye. Its inner layer is black, being linedwith pigment granules. The 2^upil is a circular opening bounded by the iris. Atthe back of this opening is the crystalline (Greek Irusfalios,clear ice) lens. This is a double convex, transparentstructure, like the lense
Size: 1724px × 1449px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, booksubje, booksubjectphysiology
