| clonal deletion theory | The elimination of certain T-cell populations in the thymus that have receptors for self-antigens. See: immunologic tolerance. (05 Mar 2000) |
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| clonal selection theory | A theory which states that each lymphocyte has membrane bound immunoglobulin receptors specific for a particular antigen and once the receptor is engaged, proliferation of the cell occurs such that a clone of antibody producing cells (plasma cell) is produced. (05 Mar 2000) |
| mnaemic theory | The theory that stimuli or irritants leave definite traces (engrams) on the protoplasm of the animal or plant, and when these stimuli are regularly repeated they induce a habit which persists after the stimuli cease; assuming that the germ cells share with the nerve cells in the possession of engrams, acquired habits may thus be transmitted to the descendants. Synonym: mnaemic theory, mnemism, Semon-Hering theory. (05 Mar 2000) |
| molecular dissociation theory | A theory, pertaining to colour vision, that gray is the earliest of colour sensations, from which are derived, by molecular change, two paired substances that, respectively, detect yellow and blue, and that the yellow gives rise to paired substances for detection of red and green. Synonym: Ladd-Franklin theory. (05 Mar 2000) |
| Warburg's theory | That the development of cancer is due to irreversible damage to the respiratory mechanism of cells, leading to the selective multiplication of cells with increased glycolytic metabolism, both aerobic and anaerobic. (05 Mar 2000) |
| cognitive dissonance theory | <psychology> A theory of attitude formation and behaviour describing a motivational state that exists when an individual's cognitive elements (attitudes, perceived behaviours, etc.) are inconsistent with each other, such as the espousal of the Ten Commandments concurrent with the belief that it is all right to cheat on one's taxes; a test which indicates that persons try to achieve consistency (consonance) and avoid dissonance which, when it arises, may be coped with by changing one's attitudes, rationalizing, selective perception, and other means. See: balance theory, consistency principle. (05 Mar 2000) |
| Cohnheim's theory | That neoplasms originate from various cell rests, i.e., embryonal cells thought to persist in various sites after the development of the foetal organs and tissues. Synonym: emigration theory. (05 Mar 2000) |
| collision theory | <chemistry> A mathematical description of the number of collisions between molecules in a sample of matter per unit time, useful for predicting rates of reaction. (09 Oct 1997) |
| monophyletic theory | In haematology, the theory that all the blood cells are derived from one common stem cell or histioblast. Synonym: monophyletic theory. Origin: mono-+ G. Phyle, tribe (05 Mar 2000) |
| colloid theory of narcosis | That coagulation or flocculation of protein causes dehydration and reduction of metabolism. (05 Mar 2000) |
| Weismann germ plasm theory | <genetics> The theory that organisms maintain genetic continuity from organism to offspring through the germ line cells (germ plasm) and that the other (somatic) cells play no part in the transmission of heritable factors. (18 Nov 1997) |
| pithecoid theory | The theory of human's descent with the ape from a common ancestor. See: darwinian theory. (05 Mar 2000) |
| place theory | A theory of pitch perception which states that the perception of the pitch of a sound depends upon the level or region of the basilar membrane of the cochlea which is set into vibration by the sound waves. See: resonance theory of hearing. (05 Mar 2000) |
| Planck's theory | The theory that the radiation and absorption of energy take place in definite quantities called quanta (e) which vary in size and are defined by the equation e=hv in which h is planck's constant and v is the frequency of the radiation. (12 Dec 1998) |
| Wollaston's theory | A theory that the semidecussation of the optic nerves at the chiasm is proved by the homonymous hemianopia seen in brain lesions. (05 Mar 2000) |