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stomach

(Encyclopedia)stomach, saclike dilation in the gastrointestinal tract between the esophagus and the intestines, forming an organ of digestion. The stomach is present in virtually all vertebrate animals and in many ...

fluorine

(Encyclopedia)fluorine flo͞oˈərēn, –rĭn [key], gaseous chemical element; symbol F; at. no. 9; at. wt. 18.9984; m.p. −219.6℃; b.p. −188.14℃; density 1.696 grams per liter at STP; valence −1. Fluorin...

Hertwig, Oscar

(Encyclopedia)Hertwig, Oscar ôsˈkär hĕrtˈvĭkh [key], 1849–1922, German embryologist. He studied medicine with Haeckel and Gegenbaur. In 1875 he established the fact that fertilization consists of the union ...

meninges

(Encyclopedia)CE5 Meninges: Section of spine showing meningeal layers meninges mĭnĭnˈjēz [key], three membranous layers of connective tissue that envelop the brain and spinal cord (see nervous system). The ...

switch

(Encyclopedia)switch, electrical device having two states: on, or closed; and off, or open. Ideally a switch offers a zero impedance to a current when it is closed, and it offers infinite impedance when open. Mecha...

New Red Sandstone

(Encyclopedia)New Red Sandstone, name for the thick red layer of the Triassic formation in Great Britain (see Triassic period). It is many thousands of feet thick and is composed chiefly of red sandstones, clays, a...

gasohol

(Encyclopedia)gasohol, a gasoline extender made from a mixture of gasoline (90%) and ethanol (10%; often obtained by fermenting agricultural crops or crop wastes) or gasoline (97%) and methanol, or wood alcohol (3%...

stromatolite

(Encyclopedia)stromatolite, layered structures produced by the binding together of sediments by a thin layer of cyanobacteria. The layers, which are deposited very slowly, gradually produce rounded or hummocklike f...

hail, in meteorology

(Encyclopedia)hail, precipitation in the form of pellets composed of ice or of ice and snow, occurring at any time of the year, usually during the passage of a cold front or during a thunderstorm. Small hailstones ...

bark, in botany

(Encyclopedia)bark, outer covering of the stem of woody plants, composed of waterproof cork cells protecting a layer of food-conducting tissue—the phloem or inner bark (also called bast). As the woody stem increa...