LUCID INTERVAL (Lat. /ucidus, bright, from /ucere, to shine). The true definition of lucid interval, according to the alienist. is: A period of time, of from an hour's to a few days' duration, during which an insane per son appears sane in speech and act, and in general manner and conduct. The forms of in sanity in which a lucid interval occurs are gen erally characterized by exaltation or perversion. There may thus be a cessation or suspension of the fury in Mania ; there cannot be repair or en lightenment of the obscurity in idiocy or demen tia. It may consist in the mere substitution of clearness and calmness for violence and con fusion: in the occasional recognition of his actual condition and external relations by the lunatic; or in the reestablishment of intelligence and natural feeling so perfect and complete as to differ from sanity solely in the want of perma nence. There invariably exists an undeneurrent of unsoundness. It is found to be extremely dif ficult to distinguish this state from real and trustworthy restoration to reason. except by ref erence to duration. Legally, these conditions have been held to he identical. A will executed
during a lucid interval, although that was ex tremely transitory, and although the testatrix unloosed the straps by which her hands had been confined. in order to execute the document, has been held to be valid: all that appears to be required, under such eircumsta is to prove that the conduct of the individual bore the aspect of rationality and health. It has been observed that. immediately before death, a small pn por tion of the insane regain lucidity. and die in pos session of emnparative sense and serenity. This change is supposed by some to depend the failing powers of the circulation. Consult: Shel ford. .I Pre etirel Tnatise on the Lair Concern ing Lunaties, Ninny, and rsons of I nsemnd .hind (London. 1833) : Taylor. The Principles and Praelire of lleelicol Jurisprudence (London. 1873) ; Reese. 1/cdica/ Owl Toxi cology (Philadelphia. 19021 : Spitzka: ltspmon of insanity kNew York. 1S-;71: Hamilton. .t Jla»ual of Medical ern York. 1sq71. See INSANITY.