| Jordan's rule | <genetics> An evolutionary rule that states that the closest genetic relatives of a given species are found very near it, but the two groups are isolated by some kind of natural barrier (such as a river) that neither species can cross easily. (09 Oct 1997) |
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| Young's rule | An obsolete rule to determine a child's dose: 12 is added to the child's age and the sum is divided by the age; the adult dose divided by the figure so obtained gives the proper dose. (05 Mar 2000) |
| Le Bel-van't Hoff rule | The number of stereoisomers of an organic compound is 2n where n represents the number of asymmetric carbon atoms (unless there is an internal plane of symmetry). A corollary of their simultaneously announced conclusions, in 1874, that the most probable orientation of the bonds of a carbon atom linked to four groups or atoms is toward the apexes of a tetrahedron, and that this accounted for all then-known phenomena of molecular asymmetry (which involved a carbon atom bearing four different atoms or groups). See: stereoisomerism. (05 Mar 2000) |
| Liebermeister's rule | In adult febrile tachycardia, about eight pulse beats correspond to an increase of 1캜. (05 Mar 2000) |