A lady informed me that upon one occasion she had gone to bed very tired, but was suddenly startled from her sleep by a voice calling her by name. Without stopping a moment, she arose, put on her shoes and stockings, lit a candle, took a loaded pistol from a shelf near her husband’s head, cocked it, and was leaving the room, the pistol in one hand and the candle in the other, when she was seized by her husband. She turned, recognized him at once, and would have fallen to the floor had he not caught her in his arms. Her husband, who slept in the same bed with her, had heard one of the children cry in an adjoining room, and had called her. She, hearing his voice, had partially awakened, but had conceived the idea that he had called to her from another part of the house, where some danger menaced him. She had acted upon this supposition, and was perfectly conscious of every movement she had made. It does not appear that some persons are more liable to attacks of sleep drunkenness than others. Neither do I know of any means by which its occurrence could be prevented. It is a natural phenomenon, to which all are liable. It is more important in its medico-legal relations than any other. APPENDIX. ADDITIONAL OBSERVATIONS RELATIVE TO THE PHYSIOLOGY OF SLEEP.[151] Since the chapter on the Physiology of Sleep was written, I have, by additional experiments, satisfied myself that the theory then enunciated is correct in every essential particular. By means of an instrument adapted to show the extent of cerebral pressure, and which I first described nearly two years ago, I have been enabled to arrive at very positive results. In every instance the pressure was lessened during sleep and was increased during wakefulness. The experiments were performed upon dogs and rabbits. Briefly, the instrument consists of a brass tube, which is screwed into a round hole made in the skull with a trephine. Both ends of this tube are open, but into the upper is screwed another brass tube, the lower end of which is closed by a piece of very thin sheet india-rubber, and the upper end with a brass cap, into which is fastened a glass tube. This inner arrangement contains colored water, and to the glass tube a scale is affixed. This second brass tube is screwed into the first, till the thin rubber presses upon the dura mater and the level of the colored water stands at 0, which is in the middle of the scale. Now, when the animal goes to sleep, the liquid falls in the tube, showing that the cerebral pressure has been diminished,--an event which can only take place in consequence of a reduction in the quantity of blood circulating through the brain. As soon as the animal awakes, the liquid rises at once. Nothing can exceed the conclusiveness of experiments of this character. No mere theorizing can avail against them. FOOTNOTES: [1] See the author’s Treatise on Hygiene, page 92. [2] La Théorie des Songes. Paris, 1766, p. 206.