| Metchnikoff's theory | The phagocytic theory, that the body is protected against infection by the leukocytes and other cells that engulf and destroy the invading microorganisms. (05 Mar 2000) |
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| Meyer-Overton theory of narcosis | That narcotic efficiency parallels the coefficient of partition between oil and water, and that lipoids in the cell and on the cell membrane absorb the drug because of this affinity. Synonym: Meyer-Overton theory of narcosis. (05 Mar 2000) |
| miasma theory | An explanation of the origin of epidemics, based on the false notion that they were caused by air of bad quality, e.g., emanating from rotting vegetation in marshes or swamps. (05 Mar 2000) |
| phlogiston theory | <chemistry> The hypothetical principle of fire, or inflammability, regarded by Stahl as a chemical element. This was supposed to be united with combustible (phlogisticated) bodies and to be separated from incombustible (dephlogisticated) bodies, the phenomena of flame and burning being the escape of phlogiston. Soot and sulphur were regarded as nearly pure phlogiston. The essential principle of this theory was, that combustion was a decomposition rather than the union and combination which it has since been shown to be. Origin: NL, fr. Gr. Burnt, set on fire, fr. To set on fire, to burn, fr, a flame, blaze. See Phlox. Source: Websters Dictionary (01 Mar 1998) |
| migration theory | An obsolete theory that sympathetic ophthalmia is caused by a migration of the pathogenic agent through the lymph channels of the optic nerve. (05 Mar 2000) |
| Miller's chemicoparasitic theory | That dental caries is caused by microorganisms of the mouth fermenting dietary carbohydrates and producing acids that demineralise the teeth. (05 Mar 2000) |
| cloacal theory | The belief sometimes held by neurotic adults or children that a child is born, as a stool is passed, from a common opening. (05 Mar 2000) |
| 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) |
| 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) |