| Hill's phenomenon | <clinical sign> In aortic insufficiency, greater systolic blood pressure in the legs than in the arms; normal arterial systolic pressure in the leg is 10 to 20 mm of Hg above that in the arm, whereas in aortic insufficiency the difference may be 60 to 100 mm of Hg. Synonym: Hill's phenomenon. (05 Mar 2000) |
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| hip-flexion phenomenon | When a hemiplegic attempts to rise from a lying posture, the hip on the paralysed side is flexed first; the same movement takes place on lying down. (05 Mar 2000) |
| hip phenomenon | Twitching of the glutei muscles when firm pressure is made on the nates, in cases of spastic paralysis. Synonym: hip phenomenon. (05 Mar 2000) |
| psi phenomenon | A phenomenon that includes both psychokinesis and extrasensory perception; the extrasensory mental processes involved in the alleged ability to send or receive telepathic messages. (05 Mar 2000) |
| Hoffmann's phenomenon | Excessive irritability of the sensory nerves to electrical or mechanical stimuli in tetany. (05 Mar 2000) |
| Purkinje's phenomenon | <ophthalmology> In the light-adapted eye, the region of maximal brightness is in the yellow; in the dark-adapted eye, the region of maximal brightness is in the green. Synonym: Purkinje effect, Purkinje shift. (05 Mar 2000) |
| hunting phenomenon | An unusual reaction of digital blood vessels exposed to cold; vasoconstriction is alternated with vasodilation in irregular repeated sequences, in an apparent hunting of equilibrium of skin temperature. Synonym: hunting phenomenon. (05 Mar 2000) |
| Hunt's paradoxical phenomenon | In dystonia musculorum deformans, if an attempt is made at plantar flexion of the foot when the foot is in dorsal spasm the only response is an increase of the extensor, or dorsal, spasm; if, however, the patient is told to extend the foot which is already in a state of strong dorsal flexion, there will be a sudden movement of plantar flexion; the same phenomenon, mutatis mutandis, is observed when there is a condition of strong plantar flexion. (05 Mar 2000) |
| Sherrington phenomenon | After the muscles of the leg have been deprived of their motor innervation by sectioning the ventral roots containing fibres for the sciatic nerve, and allowing time for the degeneration of the fibres to occur, stimulation of the sciatic nerve causes slow contraction of the muscles. (05 Mar 2000) |
| shot-silk phenomenon | The appearance of numerous wavelike, glistening reflexes, like the shimmer of silk, observed sometimes in the retina of a young person. Synonym: shot-silk phenomenon, shot-silk reflex. (05 Mar 2000) |
| shwartzman phenomenon | A two-stage reaction in which a first encounter with endotoxin produces intravascular fibrin thrombi whose clearance results in reticuloendothelial blockade which prevents the clearance of thrombi caused by a second encounter with endotoxin, resulting in tissue necrosis and/or haemorrhage. In pregnancy gram-negative septicaemia during delivery or abortion may serve as the first or provocative encounter. The phenomenon is non-immunologic and is known to occur only in rabbits and man. (12 Dec 1998) |
| Somogyi phenomenon | A rebound phenomenon of reactive hyperglycaemia following a period of relative hypoglycaemia, which may be subclinical and difficult to detect; the hyperglycaemia induces use of more insulin, thus aggravating the problem. Synonym: posthypoglycaemic hyperglycaemia. (05 Mar 2000) |
| Soret's phenomenon | In a solution kept in a long, upright tube at room temperature, the upper part, being the warmer, is also the more concentrated. (05 Mar 2000) |
| sparing phenomenon | The manner in which a nonessential nutritive component, by its presence in the diet, lowers the dietary requirement for an essential component; thus, nonessential l-cysteine spares essential l-methionine and nonessential l-tyrosine spares essential l-phenylalanine. Synonym: sparing phenomenon. (05 Mar 2000) |
| Splendore-Hoeppli phenomenon | Radiating or annular eosinophilic deposits of host-derived materials, and possibly of parasite antigens, which form around fungi, helminths, or bacterial colonies in tissue. (05 Mar 2000) |