909. The EYELIDS are two movable curtains placed in front of the eye. They have a delicate skin on the outside, muscular fibres beneath, and a narrow cartilage on their edges, which tends to preserve the shape of the lid. Internally, they are lined by a smooth membrane, which is reflected over the front of the eye upon the sclerotica. This membrane is called the _con-junc-ti´va_. It secretes the fluid that moistens and lubricates the eye, and which causes the eyelids to open and shut without friction. _Observation._ When the portion of this membrane that is reflected over the globe of the eye, is inflamed, there is frequently a deposition of whitish material, called lymph. This accounts for the films, opacities, and white spots seen upon the eye after the inflammation has subsided. -=-=-=-=-=-=-=-=-=-=-=-= 906. Name the protecting organs of the eye. 907. Describe the orbits. How are the movements of the eye facilitated? 908. Describe the eyebrows. What does this arrangement prevent? 909. Describe the eyelids. What is the use of the conjunctiva? How are the white spots frequently seen upon the eye accounted for? -=-=-=-=-=-=-=-=-=-=-=-= 910. There are found several small glands on the internal surface of the cartilage, which have the appearance of parallel strings of pearls. They open by minute apertures upon the edges of the lids. The secretion from these glands prevents the edges of the eyelids from being united during sleep. 911. The edges of the eyelids are furnished with a triple row of long, thick hairs, called _eyelashes_, which curve upward from the upper lid, and downward from the lower, so that they may not interlace with each other in the closure of the eyelids. These appendages of the eye, by closing, not only protect it from moisture, but from dust, particularly during sleep. They likewise, by their movements in opening and shutting, spread the lubricating fluid equally over the eye. 912. The LACHRYMAL APPARATUS, which secretes the tears, consists of the _Lachrymal Gland_ with its ducts, _Lachrymal Canals_, and the _Nasal Duct_. 913. The LACHRYMAL GLAND is situated at the upper and outer angle of the orbit. It is about three quarters of an inch in length, flattened and oval in shape, and occupies a depression in the orbital plate of the frontal bone. Ten or twelve small ducts pass from this gland, and open upon the upper eyelid, where they pour upon the conjunctiva the lachrymal fluid, or tears. This secretion is maintained while we are asleep, as well as when we are awake. The eye from this cause is kept constantly moist. 914. The LACHRYMAL CANALS commence at minute openings upon the free borders of each eyelid, near the internal angle of the eye, by two small orifices, called _punc´ta lach-ry-ma´li-a_, (tear points.) Each of these points communicate with the sac at the upper part of the nasal duct. -=-=-=-=-=-=-=-=-=-=-=-=