| fick's law of diffusion | The principle that a substance put into solution will tend to diffuse towards constant concentration throughout the solution. (09 Oct 1997) |
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| first law of thermodynamics | This law, derived from the principle of conservation of energy, is expressed as E = Q - W, where E is the internal change in energy, Q is the heat the environment transfers into the system, and W is the work the system does. In other words, it means that: The internal energy in a system isolated from other systems remains constant The change in the internal energy of a system that is not isolated is equal to the energy that crosses its boundariesinto or out of other systemsIt can be further extrapolated to mean that despite all the processesgoing on in the universe, the total energy contained in the universeremains constant. (09 Oct 1997) |
| Flatau's law | A law concerning the excentric position of the long spinal tracts; the greater the distance the nerve fibres run lengthwise in the cord, the more they tend to be situated toward its periphery. (05 Mar 2000) |
| Lambert's law | Each layer of equal thickness absorbs an equal fraction of the light that traverses it; Cf.: Beer-Lambert law. The illumination of a surface on which the light falls normally from a point source is inversely proportional to the square of the distance from the source. (05 Mar 2000) |
| Landouzy-Grasset law | In lesions of one hemisphere, the patient's head is turned to the side of the affected muscles if there is spasticity and to that of the cerebral lesion if there is paralysis. Synonym: Grasset's law. (05 Mar 2000) |
| Lapicque's law | The chronaxie is inversely proportional to the diameter of an axon. (05 Mar 2000) |
| Laplace's law | The equilibrium relationship between transmural pressure difference (dP), wall tension (T), and radius of curvature (R) in a concave surface; for a sphere: dP = 2T/R; for a cylinder: dP = T/R. (05 Mar 2000) |
| law | A scientific principle that invariably holds true under specificconditions, for instance, the law of magnetism states that likemagnetic poles repel one another, while opposite poles attract. See: hypothesis, theory. (09 Oct 1997) |
| law of average localization | Visceral pain is most accurately localised in the least mobile viscera and least accurately in the most mobile. (05 Mar 2000) |
| law of biogenesis | The theory formulated by E.H. Haeckel that individuals in their embryonic development pass through stages similar in general structural plan to the stages their species passed through in its evolution; more technically phrased, the theory that ontogeny is an abbreviated recapitulation of phylogeny. Synonym: biogenetic law, law of biogenesis, Haeckel's law, law of recapitulation. (05 Mar 2000) |
| law of constant numbers in ovulation | The number of ova discharged at each ovulation is nearly constant for any given species. (05 Mar 2000) |
| law of contiguity | When two ideas or psychologically perceived events have once occurred in close association they are likely to so occur again, the subsequent occurrence of one tending to elicit the other; this law figures prominently in modern theories of conditioning and learning. (05 Mar 2000) |
| law of contrary innervation | "all living functions are continually controlled by two opposite forces: augmentation or action on the one hand, and inhibition on the other." Synonym: law of contrary innervation. (05 Mar 2000) |
| law of definite proportions | The relative weights of the several elements forming a chemical compound are invariable. Synonym: Proust's law. (05 Mar 2000) |
| law of denervation | When a structure is denervated, its irritability to certain chemical agents is increased; e.g., the greater sensitivity of the pupil to acetylcholine after section and degeneration of the third nerve, and of the nictitating membrane to adrenaline after excision of the superior cervical ganglion. (05 Mar 2000) |