| germ theory | The theory, now a doctrine, that infectious diseases are due to the presence and functional activity of microorganisms within the body. (05 Mar 2000) |
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| mass action theory | That large areas of brain tissue function as a whole in learned or intelligent action. (05 Mar 2000) |
| gestalt theory | A system which emphasizes that experience and behaviour contain basic patterns and relationships which cannot be reduced to simpler components; that is, the whole is greater than the sum of its parts. (12 Dec 1998) |
| Reed-Frost theory of epidemics | A mathematical theory to explain how epidemics originate and continue. (05 Mar 2000) |
| reed instrument theory | A no longer tenable theory stating that in human voice production the larynx functions in a manner similar to a reed musical instrument. (05 Mar 2000) |
| reentry theory | That extrasystoles are due to reentry of an impulse initiated by the sinus impulse, to which the extrasystole is coupled, into the ectopic focus. (05 Mar 2000) |
| catastrophe theory | A branch of mathematics dealing with large changes in the total system that may result from a small change in a critical variable in the system; an example is the change in the physical properties of H2O as the temperature reaches zero or 100 |
| Pauling's theory | 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) |
| cell theory | <biology> The theory that all cells come from previously existing cells, and that cells are the most fundamental structural units of all living things. (26 Mar 1998) |
| cellular immune theory | A concept, put forth by Elie Metchnikoff, that cells, not antibodies, were responsible for the immune response of an organism. (05 Mar 2000) |
| celomic metaplasia theory of endometriosis | That endometrial tissue arises directly from the peritoneal mesothelium. (05 Mar 2000) |
| resonance theory of hearing | That the basilar membrane of the cochlea acts as a resonating structure, recording low tones from its apical turns and high tones from its basal turns. Synonym: Helmholtz theory of hearing. (05 Mar 2000) |
| Golgi's theory | <physiology> The scientific theory that there are interconnections between the axons of Golgi cells and the axons of Deiter cells (both are types of neurons) which play important roles in neurotransmission. (09 Oct 1997) |
| membrane expansion theory | That adsorption of anaesthetics into membranes so alters membrane volume and/or configuration that membrane function is affected in such a way as to produce anaesthesia. (05 Mar 2000) |
| chaos theory | A branch of mathematics dealing with events and processes that cannot be predicted precisely on the basis of conventional mathematical theories or laws; some biological processes, e.g., spread of malignant disease, appear to conform to chaos theory, at least sometimes. (05 Mar 2000) |