The delusions of some patients are confined to some particular subjects. Upon these their insanity will appear in their conversation, while upon all other subjects they are perfectly rational. A man, who conversed with the utmost propriety on all other topics, on being asked if he believed in Jesus Christ, said at once, ‘I am Jesus Christ.’ A lady, who had very ambitious desires in relation to her husband’s standing in society, became insane upon this point alone, and while she was as rational as ever on all other subjects, she constantly poured a storm of reproach and abuse upon him, because he was not as great a man as she wished and expected he would be. A lady, who had been much fatigued in preparing for house-keeping, upon going into her new abode contracted a feeling in regard to the house, which was something more than a mere dislike—it was a horror. She could not bear to be in it, especially if she were alone. She had an impression, ill-defined but unconquerable and ever present, that something dreadful would happen to her if she remained there. She said that she had rather live anywhere else, even in the poorest shanty. Her friends thought that it was a foolish notion, which she could overcome if she would make the effort. But they were mistaken. She was really insane on that one point. I recommended that she should be permitted to stay away from her house so long as she desired it, and that her mind should be diverted by journeying and visiting. A few weeks sufficed to remove the delusion. I once knew a similar case in which the patient was not removed, and her misery finally drove her to the commission of suicide. It may be remarked of these cases of monomania, as it is termed, that they do not ordinarily retain the same definite and exclusive character which they at first have. If the insanity continue for some length of time, other delusions are apt to be added to the original one. _Moral_ insanity is a form of the disease which is scarcely believed to exist by the community at large, and our courts of justice are very reluctant to recognise it, and will not do so without the most indisputable and abundant evidence. And yet this form of insanity is by no means rare. Many cases of it are found in our Retreats; and the outrages, which such patients commit, are occasionally made the subject of investigation before our legal tribunals. It is an insanity of the moral sense, affecting the intellect little if at all. Dr. Bell in speaking of it says, “There is insanity of _conduct_, but not of _conversation_; the persons afflicted are capable of reasoning with correctness and energy upon premises not only false, but which they know to be false, and frequently display the greatest ingenuity in giving reasons for and explaining away their eccentric and unjustifiable conduct, and accounting for the change which, they will admit, has occurred in the whole tone and temper of their dispositions and propensities.