| 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) |
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| 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) |
| surface tension theory of narcosis | That substances which lower the surface tension of water pass more readily into the cell and cause narcosis by decreasing metabolism. (05 Mar 2000) |
| systems theory | Principles, models, and laws that apply to complex interrelationships and interdependencies of sets of linked components which form a functioning whole, a system. Any system may be composed of components which are systems in their own right (sub-systems), such as several organs within an individual organism. (12 Dec 1998) |
| Dieulafoy's theory | An obsolete theory that appendicitis is always the result of the transformation of the appendicular canal into a closed cavity. (05 Mar 2000) |
| dipole theory | A theory in which the activation current of the heart is conceived as a single net moving dipole, the positive pole leading. (05 Mar 2000) |
| DLVO theory | <cell biology> Theory of colloid flocculation advanced independently by Derjaguin & Landau and by Vervey & Overbeek and subsequently applied to cell adhesion. There exist distances (primary and secondary minima) at which the forces of attraction exceed those of electrostatic repulsion, an adhesion will thus be formed. For cells there is quite good correlation between the calculated separations of primary and secondary minima and the cell separations in tight junctions (1-2nm) and more general cell cell appositions (12-20nm) respectively, although it is clear that other factors (particularly cell adhesion molecules) also play an important part. (18 Nov 1997) |
| double bind theory | Contradictions in verbal and behavioural communication between parent and child (patient) which entrap the child because he is unable to comment on the incongruity or to escape from the situation. (12 Dec 1998) |
| duplicity theory of vision | That the cones of the retina function in bright light and the rods function in dim light. (05 Mar 2000) |
| implantation theory of the production of endometriosis | That, at the time of menstruation, cells of the uterine mucosa pass through the fallopian tubes and escape into the pelvic cavity where they implant themselves on the peritoneum. (05 Mar 2000) |
| incasement theory | Archaic theory that the embryo was fully formed in miniature within a gamete at the time of conception. See: homunculus. Synonym: emboitement, incasement theory. (05 Mar 2000) |
| quantum 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) |