Epileptic born criminals and the morally insane may be classed as lunatics under certain aspects, but only by the scientific observer and professional psychologist. Outside these two forms, there is an important series of offenders, who are not criminals from birth, but become such at a given moment of their lives, in consequence of an alteration of the brain, which completely upsets their moral nature and makes them unable to discriminate between right and wrong. They are really insane; that is, entirely without responsibility for their actions. Nearly every class of mental derangement contributes a special form of crime. _The Idiot_ is prompted by paroxysms of rage to commit murderous attacks on his fellow-creatures. His exaggerated sexual propensities incite him to rape, and his childish delight at the sight of flames, to arson. _The Imbecile_, or weak-minded individual, yields to his first impulse, or, dominated by the influence of others, becomes an accomplice in the hope of some trivial reward. The victims of _Melancholia_ are driven to suicide by suppressed grief, precordial agitation, or hallucinations. Sometimes the suicidal attempt is indirect and takes the form of the murder of some important personage or their own kin, in the hope that their own condemnation may follow, or it is to save those dear to them from the miseries of life. Persons afflicted with _General Paralysis_ frequently steal, in the belief that everything they see belongs to them, or because they are incapable of understanding the meaning of property. If accused of theft, they deny their guilt or assert that the stolen articles have been hidden on their persons by others. They are inclined to forgery and fraudulent bankruptcy, and when their misdeeds are brought home to them they show no shame. Unnatural sexual offences and crimes against the authorities are also common. While they are seldom guilty of murder, they frequently commit arson, through carelessness, or with the idea of destroying their homes because they think them too small, or wish to get rid of the vermin in them, such as rats. The sufferer from _Dementia_ forgets his promises, however serious they may be. Cerebral irritability often leads him to commit violent acts, homicide, etc. In some cases, mental alienation is manifested in a mania for litigation, which urges the sufferer to offend statesmen, state lawyers, and judges. A common symptom of _Pellagra_ is the tendency to unpremeditated murder or suicide, without the slightest cause. The sight of water suggests drowning, in the form of murder or suicide. Young persons at the approach of puberty and women subject to amenorrhea often exhibit a tendency to arson and crimes of an erotic nature. Similar tendencies are sometimes displayed during pregnancy, and an inclination to theft is not uncommon.