| dark-adapted eye | An eye that has been in darkness or semidarkness and has undergone regeneration of rhodopsin (visual purple), which renders it more sensitive to reduced illumination. Synonym: scotopic eye. (05 Mar 2000) |
|---|---|
| dark-field condenser | An apparatus for throwing reflected light through the microscope field, so that only the object to be examined is illuminated, the field itself being dark. (05 Mar 2000) |
| dark-field microscope | <instrument> A microscope that has a special condenser and objective with a diaphragm or stop that scatters light from the object observed, with the result that the object appears bright on a dark background. (05 Mar 2000) |
| dark-ground illumination | dark-field illumination |
| Darkschewitsch | (Darkshevich) Li verij O., Russian neurologist, 1858-1925. See: nucleus of Darkschewitsch. (05 Mar 2000) |
| Darling's disease | A fungal disease that is rarely a significant problem in those with a normal functioning immune system. This infection is more common in the southeastern, midatlantic and central states. The vast majority of infections are either asymptomatic or mild and the diagnosis can be difficult. Cough, fever, malaise and typical chest X-ray findings can occur. A serious disseminated form of the infection can occur in the immunocompromised individual (AIDS) that carries a 90% fatality rate. (27 Sep 1997) |
| Darling, Samuel Taylor | <person> U.S. Physician in Panama, 1872-1925. See: Darling's disease. (05 Mar 2000) |
| darlingtonia | <botany> A genus of California pitcher plants consisting of a single species. The long tubular leaves are hooded at the top, and frequently contain many insects drowned in the secretion of the leaves. Origin: NL. Named after Dr. William Darlington, a botanist of West Chester, Penn. Source: Websters Dictionary (01 Mar 1998) |
| darn | 1. To mend as a rent or hole, with interlacing stitches of yarn or thread by means of a needle; to sew together with yarn or thread. "He spent every day ten hours in his closet, in darning his stockins." (Swift) Darning needle. A long, strong needle for mending holes or rents, especially in stockings. 2. <zoology> Any species of dragon fly, having a long, cylindrical body, resembling a needle. These flies are harmless and without stings. Synonym: devil's darning-needle. Origin: OE. Derne, prob. Of Celtic origin; cf. W. Darnio to piece, break in pieces, W. & Arm. To E. Tear. Cf. Tear. (04 Mar 1998) |
| darnel | <botany> Any grass of the genus Lolium, especially. The Lolium temulentum (bearded darnel), the grains of which have been reputed poisonous. Other species, as Lolium perenne (rye grass or ray grass), and its variety L. Italicum (Italian rye grass), are highly esteemed for pasture and for making hay. Under darnel our early herbalists comprehended all kinds of cornfield weeds. Origin: OE. Darnel, dernel, of uncertain origin; cf. Dial. F. Darnelle, Sw. Dar-repe; perh. Named from a supposed intoxicating quality of the plant, and akin to Sw. Dara to infatuate, OD. Door foolish, G. Thor fool, and Ee. Dizzy. Source: Websters Dictionary (01 Mar 1998) |
| daroo | <botany> The Egyptian sycamore (Ficus Sycamorus). See Sycamore. Source: Websters Dictionary (01 Mar 1998) |
| darr | <zoology> The European black tern. Source: Websters Dictionary (01 Mar 1998) |
| Darrow red | A basic oxazin dye, C18H14N3O2Cl, used as a substitute for cresyl violet acetate in the staining of Nissl substance. Origin: Mary A. Darrow, U.S. Stain technologist, 1894-1973 (05 Mar 2000) |
| dart | 1. <zoology> A fish; the dace. See Dace. 2. <zoology> Dart sac, a sac connected with the reproductive organs of land snails, which contains a dart, or arrowlike structure. (07 Mar 2000) |
| dartars | A kind of scab or ulceration on the skin of lambs. Origin: F. Dartre eruption, dandruff. 240. Source: Websters Dictionary (01 Mar 1998) |