This alarming and dangerous state of the mental faculties, is, fortunately, more frequently the consequence of diseased action elsewhere, or in other words, a symptomatic affection, than the result of an organic or morbid condition of the brain itself. Insanity may arise from any severe constitutional disturbance, or local disease, so long continued as to affect reciprocally the system, hence it is a frequent symptom of all fevers, whether of the nervous or inflammatory type; often supervening upon severe accidents, and very frequently following the shock sustained by the system on the performance of important surgical operations. Insanity may also be idiopathic, or arise without any previous disease, as when the mind has been long kept preternaturally bent on one engrossing subject; or it may proceed from some sudden emotion of the mind, acting on the weakened frame, or from any cause that excites and keeps up a long tension of the reflective powers. It may also arise from organic disease of some part of the brain, or follow from an hereditary taint. Insanity is distinguished from madness, only by the milder character of all the symptoms, and by the subsidence of the incoherency on the suppression of the immediate cause that produced it; whereas, madness is excited by the same causes, and continues for a longer or a shorter time after the subsidence of all the excitement that gave rise to it. The insanity that constitutes what is denominated madness, as a special disease, we shall not refer to in this work, confining ourselves merely to that state which attends or follows ordinary disease. _Symptoms._—Insanity appears in many forms, seldom showing twice alike; but, as a general rule, its characteristics are in the following order: severe pains in the head; noise in the ears; redness of the face; peculiar wildness of the countenance; rolling and glistening of the eyes; grinding of the teeth; loud roarings; violent exertions of strength; incoherent discourse; unaccountable antipathy to certain persons, particularly to their nearest relatives and friends; a dislike to such places and scenes as formerly afforded particular pleasure; a diminution of the irritability of the body with respect to the morbid effects of cold, hunger, and watching: together with a full strong pulse. _Causes._—Hereditary predisposition; sanguineous temperament; violent emotions of the mind; immoderate indulgence in any passion; violent exercise; frequent intoxication; sedentary life; abtruse study; parturition or lactation; tumours compressing the brain; preceding attacks of epilepsy, fever, &c.