| Haidinger's brushes | The perception of two dark yellowish brushes or sheaves radiating about 5 degrees from the point of fixation when an evenly illuminated surface, such as the blue sky, is viewed through a polarising lens. (05 Mar 2000) |
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| Haidinger, Wilhelm von | <person> Austrian mineralogist, 1795-1871. See: Haidinger's brushes. (05 Mar 2000) |
| haidingerite | <chemical> A mineral consisting of the arseniate of lime; so named in honor of W. Haidinger, of Vienna. Source: Websters Dictionary (01 Mar 1998) |
| haikal | The central chapel of the three forming the sanctuary of a Coptic church. It contains the high altar, and is usually closed by an embroidered curtain. Source: Websters Dictionary (01 Mar 1998) |
| hail | An exclamation of respectful or reverent salutation, or, occasionally, of familiar greeting. "Hail, brave friend." All hail. Hail Mary, a form of prayer made use of in the Roman Catholic Church in invocation of the Virgin. See Ave Maria. See: Hail. Source: Websters Dictionary (01 Mar 1998) |
| Hailey, Hugh | <person> U.S. Dermatologist, *1909. See: Hailey-Hailey disease. (05 Mar 2000) |
| Hailey, W Howard | <person> U.S. Dermatologist, 1898-1967. See: Hailey-Hailey disease. (05 Mar 2000) |
| Hailey-Hailey disease | Recurrent eruption of vesicles and bullae that become scaling and crusted lesions with vesicular borders, predominantly of the neck, groin, and axillary regions; autosomal dominant inheritance, presenting in late adolescence or early adult life. Synonym: Hailey-Hailey disease. (05 Mar 2000) |
| hair | 1. The collection or mass of filaments growing from the skin of an animal, and forming a covering for a part of the head or for any part or the whole of the body. 2. One the above-mentioned filaments, consisting, in invertebrate animals, of a long, tubular part which is free and flexible, and a bulbous root imbedded in the skin. "Then read he me how Sampson lost his hairs." (Chaucer) "And draweth new delights with hoary hairs." (Spenser) 3. Hair (human or animal) used for various purposes; as, hair for stuffing cushions. 4. <zoology> A slender outgrowth from the chitinous cuticle of insects, spiders, crustaceans, and other invertebrates. Such hairs are totally unlike those of vertebrates in structure, composition, and mode of growth. 5. An outgrowth of the epidermis, consisting of one or of several cells, whether pointed, hooked, knobbed, or stellated. Internal hairs occur in the flower stalk of the yellow frog lily (Nuphar). 6. A spring device used in a hair-trigger firearm. 7. A haircloth. 8. Any very small distance, or degree; a hairbreadth. Hairs is often used adjectively or in combination; as, hairbrush or hair brush, hair dye, hair oil, hairpin, hair powder, a brush, a dye, etc, for the hair. Against the hair, in a rough and disagreeable manner; against the grain. "You go against the hair of your professions." . <anatomy> Hair bracket, the thinnest metal space used in lines of type. Hair stroke, a delicate stroke in writing. Hair trigger, a trigger so constructed as to discharge a firearm by a very slight pressure, as by the touch of a hair. Not worth a hair, of no value. To a hair, with the nicest distinction. To split hairs, to make distinctions of useless nicety. Origin: OE. Her, heer, haer, AS. Haer; akin to OFries, her, D. & G. Haar, OHG. & Icel. Har, Dan. Haar, Sw. Har; cf. Lith. Kasa. Source: Websters Dictionary (01 Mar 1998) |
| hair ball | A hair cast in the stomach or intestinal tract, common in cats. Synonym: hair ball, pilobezoar. Origin: tricho-+ bezoar (05 Mar 2000) |
| hair bulb | Hair bulb, the lower expanded extremity of the hair follicle that fits like a cap over the papilla pili. Synonym: bulbus pili, hair bulb. (05 Mar 2000) |
| hair cast | 1. A cast composed of parakeratotic scales attached to scalp hair but freely movable up and down the hair shaft; found in scaling dermatitis of the scalp, including dandruff, psoriasis, and seborrheic dermatitis. Synonym: pseudonit. 2. A small, nodular accretion of epithelial cells and keratinous debris resulting from failure of the internal root sheath to disintegrate; it appears for 3 to 7 mm along the hair shaft. (05 Mar 2000) |
| hair cell | 1. <biology> Cells found in the epithelial lining of the labyrinth of the inner ear. The hairs are stereovilli up to 25 m long that restrict the plane in which deformation of the apical membrane of the cell can be brought about by movement of fluid or by sound. Movement of the single stereocilium transduces mechanical movements into electrical receptor potentials. 2. <plant biology> Many plant surfaces are covered with fine hairs (Tradescantia stamens are a common source), the hairs are made up of thin walled cells that are convenient for studying cytoplasmic streaming and for observing mitosis. (13 Nov 1997) |
| hair cells | Mechanoreceptors located in the organ of corti that are sensitive to auditory stimuli and in the vestibular apparatus that are sensitive to movement of the head. In each case the accessory sensory structures are arranged so that appropriate stimuli cause movement of the hair-like projections (stereocilia and kinocilia) which relay the information centrally in the nervous system. (12 Dec 1998) |
| hair cells, inner | Bulbous cells that are medially placed in one row in the organ of corti. In contrast to the outer hair cells, the inner hair cells are fewer in number, have fewer sensory hairs, and are less differentiated. (12 Dec 1998) |