Sleeping and Dreaming
Mr. A. E. Durham, in a discourse at the Royal Institution, on these questions, commenced by some remarks on Sleep considered as pleasant, irresistible, and necessary. A Chinese murderer, whose punishment was total privation of sleep, died on the ninth day. The amount of needful sleep varies in different persons, eight hours being the average. John Hunter took four hours’ sleep and an hour’s nap after dinner. General Elliot (of Gibraltar) required only four hours. The conditions favouring sleep were referred to—e.g., silence, warmth, sufficient food, and, especially, a quiet conscience and a mind at ease; and various exceptions were noticed. Considered psychologically, sleep was defined as suspended consciousness, and dreaming as a partial revival of consciousness. Torpor through cold, and coma through disease, are not sleep. After describing the structure of the brain, Mr. Durham stated that he regarded the action of sleep as analogous to a chemical process, during which the brain tissue regains from the blood what it had lost through the activity of the mind. To enable him to ascertain the condition of the brain during sleep, &c., he administered chloroform to a dog, and, while it was insensible, removed a portion of the skull, substituting for it a piece of glass. He found thus that, when the dog slept, the blood-vessels were comparatively empty, the arteries lost their bright red colour and assumed the blue colour of the veins, and the brain tissue collapsed, leaving a space within the skull which was filled with cerebral fluid. When the dog was awakened the blood-vessels resumed their functions, and the brain once more filled the cavity.