Leto Vle-to\ In classical mythology, the mother of Apollo and Artemis. She was made pregnant by Zeus, and she wandered in search of a place to give birth until she found the barren island of Delos. The island was a floating rock borne about by the waves, but it was fixed to the bottom of the sea for the birth of Apollo and Artemis. In some versions, Leto’s wan¬ derings are ascribed to the jealousy of Zeus’s wife, Hera.
Letterman, David (b. April 12, 1947, Indianapolis, Ind., U.S.) U.S. television talk-show host. He began his career as a stand-up comedian and was a guest host of Johnny Carson’s Tonight Show from 1979. He hosted NBC’s post-midnight Late Night with David Letterman (1982-93), win¬ ning six Emmy Awards and great popularity with his ironic, abrasive, flip¬ pant style of interviewing, which critics viewed as a parody of talk shows. Since 1993 he hosted The Late Show with David Letterman on CBS.
letterpress printing or relief printing or typographic print¬ ing In commercial printing, process by which many copies are produced by repeated direct impression of an inked, raised surface against sheets or a continuous roll of paper. Letterpress is the oldest traditional printing technique, the only important one from the time of Johannes Gutenberg ( c. 1450) until lithography (late 18th century) and especially offset print¬ ing (early 20th century). The ink-bearing surface for a page of text was originally assembled letter by letter and line by line. The Monotype and Linotype were the first keyboard-activated typesetting machines. Letterpress can produce high-quality work at high speed, but requires much time to prepare and adjust the press. For the sake of speed, newspapers are now printed by the offset process.
Lettish language See Latvian language
lettre de cachet \ , letr 3 -d3-ka- , sha\ (French: “letter with a seal”) Let¬ ter bearing an official seal, signed by the king and countersigned by a secretary of state, used primarily to authorize someone’s imprisonment without trial. An important instrument of administration under the ancien regime in France, lettres de cachet were greatly abused in the 17th—18th century. Their use was abolished in 1790.
lettuce Cultivated annual salad plant ( Lactuca sativa ) that produces clus¬ ters of crisp, water-filled leaves. The best-known varieties are head, or cabbage, lettuce (variety capitata)', leaf, or curled, lettuce (variety crispa)’, cos, or romaine, lettuce (variety longifolia)', and asparagus lettuce (variety asparagina). Head lettuce is further divided into butter heads and crisp heads (e.g., iceberg lettuce). In the U.S, large-scale farms grow mainly crisp-head varieties, shipping them nationwide. Small- scale, local farmers raise leaf and butter-head varieties. Lettuce is an early annual crop that grows best in cool weather and with ample water.
Though usually consumed in salads, it may also be cooked.
leucine Vlu-,sen\ One of the essential amino acids, present in most com¬ mon proteins and particularly abundant in hemoglobin. One of the first amino acids discovered (1819), it is used in biochemical research and as a nutritional supplement.
leucite \'lu-,slt\ One of the most common feldspathoid minerals, potas¬ sium aluminosilicate (KAlSi 2 0 6 ). It occurs only in igneous rocks, particu¬ larly potassium-rich, silica-poor, recent lavas. Some important localities include Rome, Italy; Uganda; and Wyoming’s Leucite Hills. Leucite is used as a fertilizer in Italy (because of its high potassium content) and as a source of commercial alum.
Lesseps
CULVER PICTURES
Lettuce (Lactuca sativa, variety capitata )
DEREK FELL
L_
M
N
© 2006 Encyclopaedia Britannica, Inc.
1102 I Leucothea ► Levi-Strauss
L_
N
Leucothea \lii-'ka-the-3\ In Greek mythology, a sea goddess. She is first mentioned in the Odyssey, in which she rescued Odysseus from drowning.
She was traditionally identified with Ino, daughter of Cadmus, who incurred the wrath of Hera by caring for the infant Dionysus, Zeus’s son by Semele. Hera drove Ino and her son Melicertes mad, and they leaped into the sea, where they were changed into marine deities—Ino into Leuco¬ thea, Melicertes into Palaemon. A dolphin carried Melicertes’ body to the Isthmus of Corinth, and the Isth¬ mian Games were instituted in his honour.
leukemia Cancer of blood- forming tissues with high levels of leukocytes. Radiation exposure and hereditary susceptibility are factors in some cases. In acute leukemias, anemia, fever, bleeding, and lymph- node swelling develop rapidly. Acute lymphocytic leukemia, found mostly in children, was once over 90% fatal in six months. Drug therapy can now cure more than half these children. Acute myelogenous (granulocytic) leu¬ kemia, found mostly in adults, has frequent remissions and recurrences, and few patients survive long. Chronic myelogenous leukemia most often begins in the 40s; weight loss, low fever, weakness, and other symptoms may not develop immediately. Chemotherapy helps the symptoms but may not prolong life. Chronic lymphocytic leukemia, mostly in the elderly, may be inactive for years. Survival rates are better than in myelogenous leuke¬ mia; most deaths are caused by infection or hemorrhage.
leukocyte \ l lu-ko- l sIt\ or white blood cell or white corpuscle
Any of several types of blood cells that help defend the body from infec¬ tion. The different mature forms—granulocytes, including neutrophils (heterophils), basophils, and eosinophils; monocytes, including macroph¬ ages; and lymphocytes —have different functions, including ingesting bac¬ teria, protozoans, or infected or dead body cells; producing antibodies; and regulating the action of other leukocytes. They act mostly in the tissues and are in the bloodstream only for transport. Blood normally contains 5,000-10,000 leukocytes per cu mm.
leukoderma See vitiligo
Levant \b-'vant\ Historical name for the countries along the shores of the eastern Mediterranean Sea. It was applied to the coastlands of Anato¬ lia and Syria, sometimes extending from Greece to Egypt. The term was often associated with Venetian trading ventures. It was also used as a syn¬ onym for the Middle or Near East. In the 16th—17th centuries the term High Levant referred to the Far East (East Asia). The name Levant States was given to the French mandate of Syria and Lebanon after World War I (1914-18).
level Device for establishing a horizontal plane. It consists of a small, sealed glass tube containing liquid and an air bubble; the tube is fixed horizontally in a block or frame with a smooth lower surface. When the bubble is in the middle of the glass tube, the device is on a level surface; adjustment to the horizontal is indicated by movement of the bubble. The glass tube is slightly bowed, and the level’s sensitivity is proportional to the radius of curvature.
Leveler Member of a republican faction in England during the English Civil Wars and Commonwealth. The name was coined by the movement’s enemies to suggest that its supporters wished to “level men’s estates.” The movement began in 1645-46 and demanded that sovereignty rest with the House of Commons (to the exclusion of king and lords), believing that manhood suffrage would make Parliament truly representative. The Levelers dominated the New Model Army, but the Putney debates in the army council discussing the Levelers’ new social contract (1647) ended in deadlock. The generals restored army discipline by force, ending the Levelers’ political power.
Leven Vle-vonX, Loch Lake, east-central Scotland. Roughly 3 mi (5 km) in diameter, it is one of the shallowest of the Scottish lochs, having an
average depth of 15 ft (4.5 m). It contains a subspecies of brown trout known as Loch Leven trout. Castle Island, one of the lake’s seven islands, has the ruins of a 14th-century castle where Mary, Queen of Scots, was imprisoned (1567-68).
lever Simple machine used to amplify physical force. All early people used the lever in some form, for moving heavy stones or as digging sticks for land cultivation. Balance beams for weighing were probably used in Egypt c. 5000 bc; they consist of a bar pivoted at its center with weights on one end balancing the object on the other. As early as 1500 bc people were raising water and lifting soldiers over battlements using the swape or shadoof, a long lever pivoted near one end with a platform or container hanging from the short arm and counterweights attached to the long arm.