| place theory | A theory of pitch perception which states that the perception of the pitch of a sound depends upon the level or region of the basilar membrane of the cochlea which is set into vibration by the sound waves. See: resonance theory of hearing. (05 Mar 2000) |
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| Planck's 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) |
| Wollaston's theory | A theory that the semidecussation of the optic nerves at the chiasm is proved by the homonymous hemianopia seen in brain lesions. (05 Mar 2000) |
| polyphyletic theory | In haematology, the theory that blood cells are derived from several different stem cells, depending on the particular cell type. Synonym: polyphyletic theory. Origin: poly-+ G. Phyle, tribe (05 Mar 2000) |
| myogenic theory | That cardiac movements are due mainly to stimuli originating in the heart muscle itself and that the heart does not act solely in response to nerve stimulation. (05 Mar 2000) |
| Haeckel's gastrea theory | That the two-layered gastrula is the ancestral form of all multicellular animals. Synonym: gastrea theory. (05 Mar 2000) |
| haematogenous theory of endometriosis | That endometrial tissue is carried, like metastases of a malignant tumour, through the blood stream. (05 Mar 2000) |
| preformation 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) |
| probability theory | The branch of mathematics dealing with the purely logical properties of probability. Its theorems underlie most statistical methods. (12 Dec 1998) |
| Helmholtz-Gibbs theory | An equation expressing the relationship in a galvanic cell between the chemical energy transformed and the maximal electromotive force obtainable. (05 Mar 2000) |
| Helmholtz theory of accommodation | That the ciliary muscle relaxes for near vision and allows the anterior aspect of the lens to become more convex. (05 Mar 2000) |
| Helmholtz theory of colour vision | A theory that there are three colour-perceiving elements in the retina: red, green, and blue. Perception of other colours arises from the combined stimulation of these elements; deficiency or absence of any one of these elements results in inability to perceive that colour and a misperception of any other colour of which it forms a part. Synonym: Helmholtz theory of colour vision. (05 Mar 2000) |
| Helmholtz 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) |
| Hering's theory of colour vision | That there are three opponent visual processes: blue-yellow, red-green, and white-black. (05 Mar 2000) |
| psychoanalytic theory | Conceptual system developed by freud and his followers in which unconscious motivations are considered to shape normal and abnormal personality development and behaviour. (12 Dec 1998) |