ceramics Traditionally, objects created from such naturally occurring raw materials as clay minerals and quartz sand, by shaping the material and then hardening it by firing at high temperatures to make the object
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364 I Ceratium ► cerium
stronger, harder, and less permeable to fluids. The principal ceramic prod¬ ucts are containers, tableware, bricks, and tiles. See also earthenware, por¬ celain, POTTERY, STONEWARE, TERRA-COTTA.
Ceratium \s3-'ra-she-9m\ Genus of one-celled aquatic protists. Mem¬ bers are dinoflagellates with both plant and animal characteristics. The cell is flattened horizontally and contains yellow, brown, or green pigments. Ceratium species are covered by a theca, or armour, composed of many textured plates that form one horn in the front and usually two in the back; these horns slow the sinking of the organism. The body form varies according to the salt content and temperature of the surrounding water: the spines tend to be short and thick in cold, salty water and long and thin in less salty, warmer water. Members form an important part of the plank¬ ton found in northern seas.
Cerberus Vs9r-b3-r3s\ In Greek mythology, the monstrous watchdog of the underworld. He was usually said to have three heads, though Hesiod says he had 50. Heads of snakes grew from his back, and he had a ser¬ pent’s tail. He devoured anyone who tried to escape Hades’s kingdom, and he refused entrance to living humans, though Orpheus gained passage by charming him with music. One of the labours of Heracles was to bring Cerberus up to the land of the living; after succeeding, he returned the creature to Hades.
cereal or grain Any grass yielding starchy seeds suitable for food. The most commonly cultivated cereals are wheat, rice, rye, oats, barley, corn, and sorghum. As human food, cereals are usually marketed in raw grain form or as ingredients of food products. As animal feed, they are con¬ sumed mainly by livestock and poultry, which are eventually rendered as meat, dairy, and poultry products for human consumption. They also are used industrially in the production of a wide range of substances, such as glucose, adhesives, oils, and alcohols. Measured in acres planted, wheat is the world’s most widely grown cereal crop; rice is the second, but more com is harvested than either. Grains are generally rich in carbohydrates and energy value but comparatively low in protein and naturally deficient in calcium and vitamin A. Breads are usually enriched to compensate for any nutritional deficiencies in the cereal used. Though often consumed in the areas where grown, cereal and cereal by-products are also major com¬ modities in international trade.
cereal Prepared foodstuff of cereal grain. Cereals are used for both human and animal food. The first step in making cereal is milling, grind¬ ing the grain so that it can be easily processed. Modem automated sys¬ tems employ steel cylinders, followed by air purification and numerous sievings to separate the endosperm from the outer coverings and the germ; com is milled by wet processes. Cereal products include minimally pro¬ cessed whole, crushed, or rolled grains, flour, cornstarch, meal (coarsely ground and unsifted grain), and pasta. Breakfast cereals include raw cere¬ als such as oatmeal and farina (which must be boiled), shredded cereals (usually whole wheat that is boiled, dried, and cut), flaked cereals (usu¬ ally corn that is broken down into grits and cooked under pressure with flavoring syrup before being pressed and toasted), puffed cereals (grains heated in a pressure chamber and then released to cause expansion), and granular cereals (flour-based cereals made from dough that is cooked and ground into small bits). All cereals are high in starch.
cerebellum V.ser-s-'bel-onrf Part of the brain that integrates sensory input from the inner ear and from proprioceptors (see proprioception) in muscle with nerve impulses from the cerebrum (see cerebral cortex), coor¬ dinating muscle responses to maintain balance and produce smooth, coor¬ dinated movements. Located below the cerebral hemispheres and behind the upper medulla oblongata and pons, each of its two connected hemi¬ spheres has a core of white matter within a cortex of gray matter. Dis¬ orders usually produce neuromuscular disturbances, in particular ataxia.
cerebral cortex \s3-'re-brel, 'ser-o-brsH Layer of gray matter that con¬ stitutes the outer layer of the cerebrum and is responsible for integrating sen¬ sory impulses and for higher intellectual functions. It is divided into four lobes, roughly defined by major surface folds; sometimes the limbic sys¬ tem, or limbic lobe, is considered to be a fifth lobe. The frontal lobe controls motor activity and speech, the parietal controls touch and position, and the temporal lobe handles auditory reception and memory. The occipital lobe at the back of the brain holds the brain’s major visual-reception area. The limbic lobe controls smell, taste, and emotional responses.
cerebral palsy Paralysis resulting from abnormal development or damage to the brain before or soon after birth. Cases are of four main
types: spastic, with spasms contracting the extremities, and often mental retardation and epilepsy; athetoid, with slow, changing spasms in the face, neck, and extremities, grimacing, and inarticulate speech (dysarthria); ataxic, with poor coordination, muscle weakness, an unsteady gait, and difficulty performing rapid or fine movements; and mixed, in which symp¬ toms of two or more types are present.
cerebral seizures See epilepsy
cerebrospinal \s3- l re-bro-'spI-n a l\ fluid (CSF) Clear, colourless liq¬ uid that surrounds the brain and spinal cord and fills the spaces in them. It helps support the brain, acts as a lubricant, maintains pressure in the skull, and cushions shocks. Analysis of CSF obtained by a spinal tap (lumbar puncture) helps diagnose a number of disorders, including meningitis and hemorrhage in the central nervous system.
cerebrum Nso-'re-brom, 'ser-a-bronrf Largest part of the brain. The two cerebral hemispheres consist of an inner core of myelinated nerve fibres, the white matter, and a heavily convoluted outer cortex of gray matter (see cerebral cortex). Nerve fibres in the white matter connect functional areas of the cortex in the same hemispheres, connect functional areas of the cortex in opposite hemispheres, and connect the cerebral cortex to lower centres (e.g., the spinal cord). A front-to-back fissure divides the cerebrum’s two hemispheres. Each hemisphere controls the opposite side of the body. The corpus callosum, a thick band of white matter, connects them, allowing integration of sensory data and responses from both sides of the body. Other important cerebral structures include the hypothalamus and the thalamus.
Ceres Vsir-ez\ In Roman religion, the goddess of the growth of food plants, sometimes worshiped in asso¬ ciation with the earth goddess Tellus.
Her cult was overlaid by that of Demeter, who was worshiped in Greece and Sicily. According to tra¬ dition, her cult was introduced into Rome in 496 bc to check a famine.
Her temple on Aventine Hill was known as a centre of plebeian reli¬ gious and political activities and for its artwork.
Ceres \'sir-,ez\ Largest known asteroid in the solar system and the first discovered, in 1801. Named after the Roman goddess Ceres, it revolves around the Sun in 4.6 Earth years and is about 575 mi (925 km) across.
cereus Any of various large cacti (genus Cereus and related genera) of the western U.S. and tropical New World, including the saguaro and the organ-pipe cactus ( Lemairocereus thurberi, also L. marginatus or C. thurberi). The genus Selenicereus (night-blooming cereus, or moon cactus), containing about 20 species, is known for its large, usually fra¬ grant, night-blooming white flowers, among the largest in the cactus fam¬ ily. The queen-of-the-night ( S . grandiflorus ), the best-known night¬ blooming cereus, is often grown indoors.