| law of polar excitation | A given segment of a nerve is irritated by the development of catelectrotonus and the disappearance of anelectrotonus, but the reverse does not hold; i.e., excitation occurs at the cathode when the circuit is closed and at the anode when it is opened. Synonym: Pfluger's law. (05 Mar 2000) |
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| law of priority | Use of the earliest published name (senior synonym) of two or more names of an organism as the correct name. (05 Mar 2000) |
| law of recapitulation | 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 reciprocal proportions | The relative weights in which two substances form a chemical union singly with a third are the same as, or simple multiples of, those in which they unite with each other; a corollary of the law of definite proportions. Synonym: law of multiple proportions. (05 Mar 2000) |
| law of referred pain | Pain arises only from irritation of nerves which are sensitive to those stimuli that produce pain when applied to the surface of the body. (05 Mar 2000) |
| law of refraction | For two given media, the sine of the angle of incidence bears a constant relation to the sine of the angle of refraction. Synonym: Descartes' law, Snell's law. (05 Mar 2000) |
| law of regression to mean | In a population mating at random, the progeny of a parent with an extreme value for a measurable phenotype will tend on average to have values nearer the population mean than in the extreme parent. See: law of regression to mean. Synonym: law of regression to mean. (05 Mar 2000) |
| law of segregation | Factors that affect development retain their individuality from generation to generation, do not become contaminated when mixed in a hybrid, and become sorted out from one another when the next generation of gametes is formed. Synonym: Mendel's first law. (05 Mar 2000) |
| law of similars | The homeopathic formula expressing the law of similars, the doctrine that any drug capable of producing morbid symptoms in the healthy will remove similar symptoms occurring as an expression of disease. Another reading of the formula, employed by Hahnemann, the founder of homeopathy, is similia similibus curentur, let likes be cured by likes. Origin: L. Likes are cured by likes (05 Mar 2000) |
| law of specific nerve energies | Each type of sensory nerve ending, however stimulated (electrically, mechanically, etc.), gives rise to its own specific sensation; moreover, each type of sensation depends not upon any special character of the different nerves but upon the part of the brain in which their fibres terminate. Synonym: law of specific nerve energies. (05 Mar 2000) |
| law of the heart | The energy liberated by the heart when it contracts is a function of the length of its muscle fibres at the end of diastole. Synonym: Starling's law. (05 Mar 2000) |
| law of the minimum | Growth and development of plants and animals are determined by the availability of that essential nutrient which is present in the smallest amount. (05 Mar 2000) |
| Le Chatelier's law | If external factors such as temperature and pressure disturb a system in equilibrium, adjustment occurs in such a way that the effect of the disturbing factors is reduced to a minimum. Synonym: Le Chatelier's principle. (05 Mar 2000) |
| frozen-in flow law | <radiobiology> In a perfect conductor, the total magnetic flux through any surface is a constant. In a plasma which is nearly perfectly conducting, the relevant surfaces move with the plasma, the result is that the plasma is tied to the magnetic field, and the field is tied to the plasma. Motion of the plasma thus deforms the magnetic field, and vice versa. The magnetic flux is said to be frozen into the plasma. (09 Oct 1997) |
| Listing's law | When the eye leaves one object and fixes upon another, it revolves about an axis perpendicular to a plane cutting both the former and the present lines of vision. (05 Mar 2000) |