| rule | A statement of conditions, effects, or phenomena typically observed in agiven situation or process. (09 Oct 1997) |
|---|---|
| rule of bigeminy | Rule that a ventricular premature beat will follow the beat terminating a long cycle. Sudden prolongation of the ventricular cycle, by changing the refractoriness in the conduction system, causes a peripheral region of bidirectional block to become transiently unidirectional and thus opens potential pathways for reentry to occur. (05 Mar 2000) |
| rule of nines | Method used in calculating body surface area involved in burns whereby values of 9 or 18 percent of surface area are assigned to specific regions as follows: Head and neck, 9%; anterior thorax, 18%; posterior thorax, 18%; arms, 9% each; legs, 18% each; perineum 1%. (05 Mar 2000) |
| rule of outlet | An obstetric rule for determining whether the pelvic outlet will permit the passage of a foetus; the sum of the posterior sagittal diameter and the transverse diameter of the outlet must equal at least 15 cm if a normal-sized baby is to pass. (05 Mar 2000) |
| Clark's weight rule | An obsolete rule for an approximate child's dose, obtained by dividing the child's weight in pounds by 150 and multiplying the result by the adult dose. (05 Mar 2000) |
| M'Naghten rule | The classic English test of criminal responsibility (1843): "to establish a defense on the ground of insanity, it must be clearly proved that, at the time of committing the act, the party accused was laboring under such a defect of reasoning, from disease of the mind, as not to know the nature and quality of the act he was doing, or if he did know it, that he did not know he was doing what was wrong." (05 Mar 2000) |
| weigert-meyer rule | <radiology> Applies to duplex collecting systems, upper-pole ureter, obstruction most likely to be hydronephrosis, inserts more inferiorly and medially in bladder, may insert into urethra, vagina, etc., males not incontinent: insertion above ext. Sphincter, associated with ureterocele, lower-pole ureter, reflux most likely to be pyelonephritis see also: drooping lily sign (12 Dec 1998) |
| Cowling's rule | An obsolete rule for a child's dose: that fraction of the adult dose obtained by dividing the age of the child at the nearest birthday by 24. (05 Mar 2000) |
| Haase's rule | The length of the foetus in centimeters, divided by 5, is the duration of pregnancy in months, i.e., the age of the foetus. (05 Mar 2000) |
| Haldane's rule | <genetics> if one of the two sexes is missing, sterile, or rare in a population of first-generation hybrids between two different species, then that sex is the heterogametic sex (has two different sex chromosomes, such as XY as opposed to XX). (09 Oct 1997) |
| Prentice's rule | Each centimeter of decentration of a lens results in 1 prism diopter of deviation of light for each diopter of lens power. (05 Mar 2000) |
| Schutz rule | The rate of an enzyme reaction is proportional to the square root of the enzyme concentration; applied specifically to pepsin within a limited range. Synonym: Schutz' law. (05 Mar 2000) |
| His' rule | The duration of pregnancy is calculated from the first day of the first omitted menstrual period; obsolete. (05 Mar 2000) |
| Huckel's rule | <chemistry> The number of depolarised electrons in an aromatic ring is equal to 4n + 2 where n is zero or any positive integer; l-tyrosine, l-phenylalanine, l-tryptophan, and l-histidine (when the imidazole ring is deprotonated) obey this rule. (05 Mar 2000) |
| Nagele's rule | Means of estimating date of delivery by counting back three months from the first day of the last menstrual period and adding seven days. (05 Mar 2000) |