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cover about one-third of the total area, and nearly one-third is pasture or rangeland; much of the rest is arable. Agriculture is the main industry; peanuts are the most impor¬ tant cash and export crop. Other important industries are fishing, mining, manufacturing, and tourism. Senegal has large reserves of phosphates and iron ore. It is a republic with one leg¬ islative house; its head of state and government is the president, assisted by the prime minister. Links between the peoples of Senegal and North Africa were established in the early centuries ad. Islam was introduced in the 11th century, although animism retained a hold on the country into the 19th century. The Portuguese explored the coast about 1444, and in 1638 the French established a trading post at the mouth of the Senegal River. Throughout the 17th and 18th centuries, Europeans exported slaves, ivory, and gold from Senegal. The French gained control over the coast in the early 19th century and moved inland, checking the expansion of the Tukulor empire; in 1895 Senegal became part of French West Africa. Its inhabitants were made French citizens in 1946, and it became an over¬ seas territory of France. It voted for a degree of autonomy in 1958, was federated with Mali in 1959-60, and became an independent state in 1960. In 1982 it entered a confederation with Gambia, called Senegambia, which was dissolved in 1989. Separatists fighting in the southern part of the country since the early 1980s signed a peace accord with the government in 2003.
Senegal River River, western Africa. It rises in Guinea and flows northwest across Mali, then west to the Atlantic Ocean, forming the bor¬ der between Mauritania and Senegal. It is 1,020 mi (1,641 km) long. Its two major headstreams, the Bating and Bakoye, meet in Mali to form the Senegal proper. Dams control floodwaters and prevent the encroachment of saltwater during the dry season.
Senegambia Confederation of Senegal and Gambia, 1982-89. The two countries agreed to integrate their military and security forces, form an economic and monetary union, coordinate their foreign policies and communications, and establish confederal institutions controlled by Sene¬ gal. Each country maintained its independence. The confederation was dissolved in 1989. The name Senegambia also refers to the region around the Senegal and Gambia rivers.
Senghor \seq-'g6r\, Leopold (Sedar) (b. Oct. 9, 1906, Joal, Sene¬ gal, French West Africa—d. Dec. 20, 2001, Verson, Fr.) Poet, president of Senegal (1960-80), and cofounder of the Negritude movement in Afri¬ can art and literature. He completed his studies in Paris and became a teacher there. Drafted in 1939, he was captured and spent two years in Nazi concentration camps, where he wrote some of his finest poems. He was elected to the French National Assembly in 1945. In 1948 he edited
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senna ► seppuku I 1721
Hosties noires, an anthology of French-language African poetry that became a seminal Negritude text. That same year he founded the Sene¬ galese Progressive Union, which, as the Socialist Party (since 1976), remains Senegal’s governing party. When Senegal gained independence in 1960, he was unanimously elected president. Advocating a moderate “African socialism,” free of atheism and excessive materialism, he became an internationally respected spokesman for Africa and the Third World. In 1984 he became the first black inducted into the French Acad¬ emy.
senna Any of several plants, especially of the genus Cassia, in the pea family (see legume), mostly of sub¬ tropical and tropical regions. Many are used medicinally; some yield tanbark used in preparing leather.
Some sennas are among the showi¬ est flowering trees. In the eastern U.S., wild sennas (C. hebecarpa and C. marilandica ) grow up to 4 ft (1.25 m) high and have showy spikes of yellow flowers. Some species are Old World shrubs or small trees.
Sennacherib Vso-'na-ko-robX (d.
January 681 bc) King of Assyria (r.
705/704-681 bc), son and successor of Sargon II. Between 703 and 689 he undertook six campaigns against Elam (southwestern Iran), which was stirring up Chaldean and Aramaean tribes in Babylonia; Babylon was sacked during the last campaign. He dealt firmly with an Egyptian-backed rebellion in Palestine in 701, sparing Jerusalem after receiving payment of a heavy indemnity. He rebuilt the city of Nineveh, around which he planted fruit trees and exotic plants, including cotton, building extensive canals to bring water to the plantations. He devised less laborious methods of bronze casting and improved methods of raising water from wells. He was assassinated by a son during a rebellion.
Sennett, Mack orig. Michael Sinnott (b. Jan. 17, 1880, Richmond, Que., Can.—d. Nov. 5, 1960, Holly¬ wood, Calif., U.S.) Canadian-born U.S. film director. He performed in burlesque and vaudeville before joining the Biograph studio in 1908, and he soon was directing comedies under D.W. Griffith’s tutelage. He left to form his own Keystone Co. in 1912. Considered the father of slap¬ stick comedy in motion pictures, he produced the first U.S. feature-length comedy, Tillie’s Punctured Romance (1914), and made over 1,000 com¬ edy shorts, often featuring the wild antics of the Keystone Kops. He hired stars such as Mabel Normand,
Fatty Arbuckle, and Charlie Chaplin.
Important directors such as Frank Capra and George Stevens also received experience under Sennett.
Sennett excelled in comic timing, improvisation, and effective editing, and he used trick camera work and high-speed and slow-motion photography to produce his famous comic chase scenes. In 1937 he received a special Academy Award.
sensation Mental process (such as seeing, hearing, or smelling) due to immediate bodily stimulation, usually as distinguished from perception. When a stimulus impinges on a sense organ and the organism responds, it is said that the stimulus has been sensed. See also psychophysics, sense- data.
sense or sensory reception or sense perception Mechanism by which information is received about one’s external or internal envi¬ ronment. Stimuli received by nerves, in some cases through specialized organs with receptor cells sensitive to one type of stimulus, are converted into impulses that travel to specialized areas of the brain, where they are
analyzed. In addition to the “five senses”—sight, hearing, smell, taste, and touch—humans have senses of motion (kinesthetic sense), heat, cold, pressure, pain, and balance. Temperature, pressure, and pain are cutane¬ ous (skin) senses; different points on the skin are particularly sensitive to each. See also chemoreception, ear, eye, inner ear, mechanoreception, nose,
PHOTORECEPTION, PROPRIOCEPTION, TASTE, THERMORECEPTION, TONGUE.
sense-data Entities that are the direct objects of sensation. Examples of sense-data are the circular image one sees when viewing the face of a penny and the oblong image one sees when viewing the penny from an angle. Other examples are the image one sees with one’s eyes closed after staring at a bright light (an afterimage) and the dagger Macbeth sees floating before him (a hallucination). In each case, according to sense- data theorists, there is something of which one is directly aware, and that something is the sense-datum.
sensitive plant Either of two plants in the pea family (see legume) that close up their leaves and droop when touched. This unusually quick response is due to rapid water release from specialized cells at the bases of leaftsalks. The more common plant is Mimosa pudica (see mimosa). Spiny and shrubby, with fernlike leaves and small, globular, mauve flower puffs, it grows about 1 ft (30 cm) high as a widespread tropical weed and a greenhouse curiosity. Wild sensitive plant ( Cassia nictitans) is less sen¬ sitive to touch; a larger plant, 20 in. (50 cm) high, it is native to the east¬ ern U.S. and the West Indies.