| gray substance | The cortex of the brain which contains nerve cell bodies. The gray matter is in contrast to the white matter, the part of the brain that contains myelinated nerve fibres. The gray matter is so named because it in fact appears gray. The white matter is white because that is the colour of myelin, the insulation covering the nerve fibres. In the mysterious affair at styles (1920), agatha christie first quoted the fictional belgian detective hercule poirot in regard to his gray matter: 'this affair must be unravelled from within.' he tapped his forehead. 'these little grey cells. It is up to them as you say over here.' (12 Dec 1998) |
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| gray syndrome | <syndrome> Gray baby syndrome, gray appearance of an infant at birth and during the neonatal period which can be caused by transplacental toxic effects of the drug chloramphenicol taken by the mother during late pregnancy; the syndrome may be fatal. (05 Mar 2000) |
| gray tuber | Layer of gray matter in the hypothalamus that also forms part of the floor of the third ventricle. (12 Dec 1998) |
| gray tubercle | Greater tubercle of humerus, the larger of the two tubercles next to the head of the humerus; it gives attachment to the supraspinatus, infraspinatus, and teres minor muscles. Synonym: tuberculum majus humeri, greater tuberosity of humerus, tuberculum cinereum. (05 Mar 2000) |
| gray wedge | <microscopy> An elongated rectangular pattern whose brightness changes from black through shades of gray to white along its length. In calibration wedges, the brightness may vary linearly or logarithmically in discrete steps. (05 Aug 1998) |
| gray wing | A prominence in the floor of the inferior fovea of the fourth ventricle that overlies the dorsal motor nucleus of the vagus. Synonym: trigonum nervi vagi, ala cinerea, ashen wing, gray wing, trigone of vagus nerve, va'gi eminentia. (05 Mar 2000) |
| gray-scale ultrasonography | The display of the ultrasound echo amplitude or signal intensity as different shades of gray, improving image quality compared to the obsolete black and white presentation. (05 Mar 2000) |
| grayback | <zoology> The California gray whale. The redbreasted sandpiper or knot. The dowitcher. The body louse. Source: Websters Dictionary (01 Mar 1998) |
| grayfly | <zoology> The trumpet fly. Source: Websters Dictionary (01 Mar 1998) |
| grayhound | <zoology> See Greyhound. Source: Websters Dictionary (01 Mar 1998) |
| graylag | <zoology> The common wild gray goose (Anser anser) of Europe, believed to be the wild form of the domestic goose. Source: Websters Dictionary (01 Mar 1998) |
| grayling | 1. <zoology> A European fish (Thymallus vulgaris), allied to the trout, but having a very broad dorsal fin; called also umber. It inhabits cold mountain streams, and is valued as a game fish. "And here and there a lusty trout, And here and there a grayling." (Tennyson) 2. <zoology> An American fish of the genus Thymallus, having similar habits to the above; one species (T. Ontariensis), inhabits several streams in Michigan; another (T. Montanus), is found in the Yellowstone region. Origin: From Gray. Source: Websters Dictionary (01 Mar 1998) |
| graywacke | <geology> A conglomerate or grit rock, consisting of rounded pebbles sand firmly united together. This term, derved from the grauwacke of German miners, was formerly applied in geology to different grits and slates of the Silurian series; but it is now seldom used. Origin: G. Grauwacke; grau gray + wacke wacke. See Gray, and Wacke, and cf. Grauwacke. Source: Websters Dictionary (01 Mar 1998) |