The phenomena of insanity may be arranged under five heads: The first, the insane temperament; the next three the fundamental forms of mental derangement; the fifth, the paroxysmal state. The features of the insane temperament are various; some of them are incompatible with the simultaneous presence of others. When a group of them is present, as a change in natural character, without insanity, insanity is threatened: no form of insanity manifests itself without the presence of some of them. The features of the insane temperament are these: The patient withdraws his sympathies from those around him, is shy, reserved, cunning, suspicious, with a troubled air, as if he felt something to be wrong, and wonders if you see it; he is capricious, and has flaws of temper; being talkative, he is flighty and extravagant; he is hurried in his thoughts, and mode of speaking, and gestures; he has fits of absence, in which he talks aloud to himself; he is restless, and anxious for change of place. Of the elementary forms of insanity, one consists in the entertainment of mental delusions: the patient imagines himself the Deity, or a prophet, or a monarch, or that he has become enormously wealthy; or that he is possessed by the devil, or is persecuted by invisible beings, or is dead, or very poor, or that he is the victim of public or private injustice. The second form is moral perversion: the patient is depressed in spirits without a cause, perhaps to the extent of meditating suicide; or he feels an unaccountable desire to take the lives of others; or he is impelled to steal, or to do gratuitous mischief; or he is a sot; or he has fits of ungovernable and dangerous rage. The third form exhibits itself in loss of connexion of ideas, failure of memory, loss of common intelligence, disregard of the common decencies of life. Each of these three elementary forms is sometimes met with alone; generally two are combined. Sensorial illusions are common in insanity; auditory, unaccompanied by visual illusions, are almost peculiar to it, and to the cognate affection of delirium from fever or inflammation of the brain. To the head of the paroxysmal state belongs the history of exacerbations of insanity, of their sudden outbursts in persons of the insane temperament, of their preferential connexion with this or that antecedent condition of the patient, of their occasional periodicity. VII. In congenital idiotcy and imbecility, the relation of the mind and brain is normal. Often the defective organization is apparent through which the intelligence is repressed. In many countries a popular belief prevails that the imbecile have occasional glimpses of higher knowledge. There is no reason evident why their minds should not be susceptible of the abnormal relation. VIII. In sleep, the mind and brain are in the normal relation. But what is sleep, psychically considered?