“In some types of insanity the patient’s mind is altogether absorbed in the contemplation of a frightful spectral illusion. Under these circumstances the unhappy sufferer is afraid to close his eyes in sleep from an intense fear and dread that he will then fall an easy prey to the horrible phantasms which his morbid imagination has called into existence, and which, he imagines, follow him in all his movements. The patient so afflicted declares he will not sleep, and resolutely repudiates and perseveringly ignores all disposition to slumber. On many occasions he obstinately refuses to go to bed, or to place himself in a recumbent position. He will battle with his attendant if he attempts to convey him to bed. He insists on remaining in the chair, in standing in an erect position all night, and often determinately walks about the room when those near him are in profound repose. In these cases the hallucinations appear to be most exquisitely and acutely vivid when the patient is placed in a recumbent position, on account, it is supposed, of the mechanical facilities thus afforded for the blood gravitating freely to the head. “A gentleman who appeared free during the day from any acute hallucinations, never could lie on his back without being distressingly harassed by a number of frightful imps, whom he imagined to be dancing fantastically around him during the night. Under these circumstances, undisturbed sleep, while in bed, could never be obtained. He was in the habit of sleeping in an arm-chair for some time in consequence of these symptoms. He, however, eventually recovered, and has been for several years entirely free from all hallucinations.” It has frequently occurred to me to notice the increase in the number and intensity of the hallucinations of patients affected with delirium tremens as soon as they assumed the recumbent position. The difficulty of sleeping is in such cases always correspondingly augmented. * * * * * 3d. _An increased amount of blood is determined to the brain, and wakefulness is produced by certain substances used as food or medicine._ Daily experience assures us of the truth of this proposition. In general terms, it may be said that all those substances which, when ingested into the system, increase the force and frequency of the heart’s action, cause also a hyperæmic condition of the brain and tend to the supervention of wakefulness.