In one sleeper, sexual desire evokes libidinous visions, in another, terrifying scenes of violence.
On the other hand, the very close relation observed in thousands of cases between the sleeper’s dreams and his physical condition, invalidates any theory which would revert more or less literally to the belief held in ancient times that dreams were purely psychic phenomena, visions sent by the gods.
Maury whose book, “Sleep and Dreams,” published in 1865, was probably the first serious attempt at deciphering the enigma of dream thoughts, had various experiments performed on himself to determine what dreams would be brought forth by physical stimuli.
He was tickled with a feather on the lips and nostrils. He dreamt that a mask of pitch was applied to his face and then pulled off, tearing the skin.
A pair of tweezers was held close to his ear and struck with a metallic object. He heard the tolling of bells and thought of the revolutionary days of 1848.
A bottle of perfume was held to his nose. He dreamt of the East and of a trip to Egypt.
A lighted match was held close to his nostrils. He dreamt that he was on a ship whose magazine had exploded.
A pinch on the back of the neck suggested the application of a blister and evoked the memory of a family physician.
A sensation of heat made him dream that robbers had entered the house and were compelling the inmates to reveal where their money was hidden by scorching the soles of their feet.
Words were pronounced aloud. He attributed them to some people with whom he had been talking in his dreams.