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muscle

(Encyclopedia)muscle, the contractile tissue that effects the movement of and within the body. Muscle tissue in the higher animals is classified as striated, smooth, or cardiac, according to its structure and funct...

Tay-Sachs disease

(Encyclopedia)Tay-Sachs disease tāˈ-săksˈ [key], rare hereditary disease caused by a genetic mutation that leaves the body unable to produce an enzyme necessary for fat metabolism in nerve cells, producing cent...

epilepsy

(Encyclopedia)epilepsy, a chronic disorder of cerebral function characterized by periodic convulsive seizures. There are many conditions that have epileptic seizures. Sudden discharge of excess electrical activity,...

animal

(Encyclopedia)animal, any member of the animal kingdom (kingdom Animalia), as distinguished from organisms of the plant kingdom (kingdom Plantae) and the kingdoms Fungi, Protista, and Monera in the five-kingdom sys...

pigmentation

(Encyclopedia)pigmentation, name for the coloring matter found in certain plant and animal cells and for the color produced thereby. Pigmentation occurs in nearly all living organisms. Almost all plants synthesize ...

lupus

(Encyclopedia)lupus lo͞oˈpəs [key], noninfectious chronic disease in which antibodies in an individual's immune system attack the body's own substances. In lupus, known medically as lupus erythematosus, antibodi...

melanin

(Encyclopedia)melanin mĕlˈənĭn [key], water-insoluble polymer of various compounds derived from the amino acid tyrosine. It is one of two pigments found in human skin and hair and adds brown to skin color; the ...

thallium

(Encyclopedia)thallium thălˈēəm [key], metallic chemical element; symbol Tl; at. no. 81; interval in which at. wt. ranges 204.382–204.385; m.p. 303.5℃; b.p. about 1,457℃; sp. gr. 11.85 at 20℃; valence +...

sea slug

(Encyclopedia)sea slug, name for a marine gastropod mollusk that lacks a shell as an adult and is usually brightly colored. Sea slugs, or nudibranchs, are distributed throughout the world, with the greatest numbers...

septicemia

(Encyclopedia)septicemia sĕptĭsēˈmēə [key], invasion of the bloodstream by virulent bacteria that multiply and discharge their toxic products. The disorder, which is serious and sometimes fatal, is commonly k...