Delirium,[508] in the ordinary acceptation of the word, is the temporary derangement of intellect consequent on acute disease; it may be distinguished from lunacy or madness by the invariable presence of fever, and it ceases as its exciting causes subside; this therefore operates no permanent incapacity; for though the patient cannot be permitted to do any act, or execute any instrument to bind his property or estate, and would not be held responsible for any crime committed during such temporary alienation of intellect, yet he becomes competent to act, and responsible for his actions as soon as the paroxysm and its consequences are clearly over. But there is yet another species of mental disorder which, since it does not incapacitate the patient from performing the ordinary duties and offices of life, does not subject him to the inconveniences of commission of lunacy, or exempt him from criminal responsibility; we mean those partial insanities which are marked by peculiar and unaccountable dislikes, fancies, and apprehensions, a mental idiocyncrasy on some one particular subject.[509] * * * Fuit haud ignobilis Argus Qui se credebat miros audire tragædos,[510] In vacuo lætus sessor plausorque theatro; Cætera qui vitæ servaret munia recto More; * * * * * * * * * * * Hic ubi cognatorum opibus curisque refectus Expulit elleboro morbum bilemque meraco, Et redit ad sese: Pol me occidistis, amici, Non servastis, ait; cui sic extorta voluptas, Et demptus per vim mentis gratissimus error. _Hor. Epis._ 2, _L. ii. v._ 128. To take out a commission of lunacy against such a man would be a greater cruelty than to cure him, and yet occasionally some legal interference may be necessary. When a man suffers under a partial derangement of intellect, and on one point only, it would be unjust to invalidate acts which were totally distinct from, and uninfluenced by, this limited insanity; but if the act done bears a strict and evident reference to the existing mental delusion, we cannot see why the law should not also interpose a limited protection, and still less why Courts of Equity, which, in their ordinary jurisdiction relieve against mistake, should deny their aid in such cases.