| Ladd-Franklin 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) |
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| lamarckian theory | That acquired characteristics may be transmitted to the descendants and that experience, and not biology alone, can change and thereby influence genetic transmission. (05 Mar 2000) |
| Frerichs' theory | That uraemia represents a toxic condition caused by ammonium carbonate, which is formed as the result of the action of a plasma enzyme on the increased amounts of urea. (05 Mar 2000) |
| learning theory | Any of several prominent theories designed to explain learning, especially those promulgated by Pavlov, Thorndike, Guthrie, Hull, Kohler, Spence, Miller, Skinner, and their modern followers. See: conditioning. (05 Mar 2000) |
| freudian theory | <psychology> Philosophic formulations which are basic to psychoanalysis. Some of the conceptual theories developed were of the libido, repression, regression, transference, id, ego, superego, oedipus complex, etc. (12 Dec 1998) |
| Freud's theory | A comprehensive theory of how personality is formed and develops in normal and emotionally disturbed individuals; e.g., that an attack of conversion hysteria is due to a psychic trauma which was not adequately reacted to at the time it was received, and persists as an affect memory. See: psychoanalysis. (05 Mar 2000) |
| frontal zone contraction theory | Model proposed to account for the movement of giant amoebae in which cytoplasmic contraction at the front of the leading pseudopod (fountain zone) pulls viscoelastic cytoplasm forward in the centre of the cell and forms a tube of more rigid cytoplasm immediately below the plasma membrane behind the active region. The peripheral contracted cytoplasm relaxes into a weaker gel at the rear and is pulled forward in its turn. Contrasts with the ectoplasmic tube contraction model. (18 Nov 1997) |
| libido theory | Freud's theory that humans psychic life results mainly from instinctual or libidinal needs and the attempts to satisfy them. (05 Mar 2000) |
| Liebig's theory | That the hydrocarbons that oxidise readily and burn are aliments that produce the greatest quantity of animal heat. (05 Mar 2000) |
| lipoid 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) |
| local circuit theory | <physiology> A generally accepted model for neuronal conduction, by which depolarisation of a small region of a neuronal plasma membrane produces transmembrane currents in the neighbouring regions, tending to depolarise them. As the sodium channels are voltage gated, the depolarisation causes further channels to open, thus propagating the action potential. (18 Nov 1997) |
| lymphatic dissemination theory of endometriosis | That endometrial tissue is transmitted by the lymphatic channels. (05 Mar 2000) |