This is a question which a medical witness is always called upon to answer. By the term _lucid interval_, we are not to understand a _remission_ of the malady, but a total suspension of it—a complete, although only a temporary, restoration of reason. The question is generally beset with difficulties, and requires all the penetration and experience of the physician to arrive at a safe conclusion; for in many cases the patient is enabled for a limited period to converse rationally, and where he is desirous of carrying any particular plan into execution, to dissemble so completely as to impose with success upon his attendants; of which the following case, related by Dr. _Haslam_,[534] may serve as an excellent illustration. “A lunatic having received, or fancied he had received, an injury from his keeper, at the lunatic asylum at Manchester, threatened to be revenged, for which he was punished by confinement; he was afterwards a patient in Bethlem hospital, and gave _Dr. Haslam_ an account of the transaction, of which the following is an abbreviation. ‘Not liking this situation, I was induced to play the hypocrite; I pretended extreme sorrow for having threatened him, and, by an affectation of repentance, induced him to release me; for several days I paid him great attention, and lent him every assistance; he seemed much pleased with the flattery, and became very friendly in his behaviour towards me; going one day into the kitchen, where his wife was busied, I saw a knife; this was too great a temptation to be resisted; I concealed it, and carried it about with me; for some time afterwards the same friendly intercourse was maintained between us, but as he was one day unlocking his garden door, I seized the opportunity and plunged this knife, up to the hilt, in his back.’” There is a species of insanity which has been called _intermittent_, in which the patient is perfectly rational for a considerable interval; the malady often recurs two or three times in a year, and lasts several weeks, the subject of the hallucination being always the same.[535] Q. 4. _Whether there is a probable chance of recovery; and in case of convalescence, whether the cure is likely to be permanent?_