| Semon-Hering 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) |
|---|---|
| sensorimotor theory | In the developmental theory of Piaget, the postulation that during the first 18 months of life there occurs a transformation of action into thought; at first there is a gradual shift from inborn to acquired behaviour, then from body-centreed to object-centreed activity, ultimately permitting intentional behaviour and inventive thinking. (05 Mar 2000) |
| humoral theory | The ancient Greek theory of the four body humors (blood, yellow and black bile, and phlegm) that determined health and disease. The humors were associated with the four elements (air, fire, earth, and water), which in turn corresponded to a pair of the qualities (hot, cold, dry, and moist). A proper and evenly balanced mixture of the humors was characteristic of health of body and mind; an imperfect balance resulted in disease. Temperament of body or mind also was supposed to be determined, e.g., sanguine (blood), choleric (yellow bile), melancholic (black bile), or phlegmatic (phlegm). Synonym: fluidism, humoralism, humorism. (05 Mar 2000) |
| hydrate microcrystal theory of anaesthesia | A theory of narcosis pertaining to nonhydrogen-bonding agents; postulates the interaction of the molecules of the anaesthetic drug with water molecules in the brain. Synonym: Pauling's theory. (05 Mar 2000) |
| side-chain theory | Ehrlich postulated that cells contained surface extensions or side chains (haptophores) that bind to the antigenic determinants of a toxin (toxophores); after a cell is stimulated, the haptophores are released into the circulation and become the antibodies. See: receptor. Synonym: Ehrlich's postulate. (05 Mar 2000) |
| somatic mutation theory of cancer | That cancer is caused by a mutation or mutations in the body cells (as opposed to germ cells), especially nonlethal mutations associated with increased proliferation of the mutant cells. (05 Mar 2000) |
| Spitzer's theory | An interpretation of the partitioning of the heart of mammalian embryos primarily on the basis of recapitulations of the adult structural pattern of lower forms; most frequently cited in relation to the partitioning of the truncus arteriosus to form ascending aorta and pulmonary trunk, which is achieved by the phylogenetic development of the lungs. (05 Mar 2000) |
| Nernst's theory | That the passage of an electric current through the tissues causes a dissociation of the ions, with consequent concentration of salts in the solution bathing the cell membranes, the electric stimulus being thereby effected. (05 Mar 2000) |
| neurochronaxic theory | Theory stating that variations in pitch of the human voice are produced by active muscular contractions synchronised with cycles per second of pitch, no longer believed to be true. (05 Mar 2000) |
| stringed instrument theory | A no longer tenable theory stating that in human voice production the vocal cords function in a manner similar to the strings in a stringed musical instrument. (05 Mar 2000) |
| darwinian theory | The theory of the origin of species and of the development of higher organisms from lower forms through natural selection (survival of the fittest in the struggle for existence), and of the evolution of humans from an ancestor common to himself and the apes. (05 Mar 2000) |
| nursing theory | Concepts, definitions, and propositions applied to the study of various phenomena which pertain to nursing and nursing research. (12 Dec 1998) |
| de Bordeau theory | That each organ of the body manufactured a specific humor which it secreted into the bloodstream. (05 Mar 2000) |
| decay theory | A theory of forgetting based on the premise that an engram or memory trace dissipates progressively with time during the interval when it is not activated. (05 Mar 2000) |
| decision theory | A theoretical technique utilizing a group of related constructs to describe or prescribe how individuals or groups of people choose a course of action when faced with several alternatives and a variable amount of knowledge about the determinants of the outcomes of those alternatives. (12 Dec 1998) |