sensory paths from the outer world were shut off. When we wish to sleep we are wont to strive for a situation resembling the one in Strümpell's experiment. We close the most important sensory paths, the eyes, and we endeavour to keep away from the other senses every stimulus and every change of the stimuli acting upon them. We then fall asleep, although we are never perfectly successful in our preparations. We can neither keep the stimuli away from the sensory organs altogether, nor can we fully extinguish the irritability of the sensory organs. That we may at any time be awakened by stronger stimuli should prove to us "that the mind has remained in constant communication with the material world even during sleep." The sensory stimuli which reach us during sleep may easily become the source of dreams.
There are a great many stimuli of such nature, ranging from those that are unavoidable, being brought on by the sleeping state or at least occasionally induced by it, to the accidental waking stimuli which are adapted or calculated to put an end to sleep. Thus a strong light may force itself into the eyes, a noise may become perceptible, or some odoriferous matter may irritate the mucous membrane of the nose. In the spontaneous movements of sleep we may lay bare parts of the body and thus expose them to a sensation of cold, or through change of position we may produce sensations of pressure and touch. A fly may bite us, or a slight accident at night may simultaneously attack more than one sense. Observers have called attention to a whole series of dreams in which the stimulus verified on waking, and a part of the dream content corresponded to such a degree that the stimulus could be recognised as the source of the dream.
I shall here cite a number of such dreams collected by Jessen36 (p. 527), traceable to more or less accidental objective sensory stimuli. "Every indistinctly perceived noise gives rise to corresponding dream pictures; the rolling of thunder takes us into the thick of battle, the crowing of a cock may be transformed into human shrieks of terror, and the creaking of a door may conjure up dreams of burglars breaking into the house. When one of our blankets slips off at night we may dream that we are walking about naked or falling into the water. If we lie diagonally across the bed with our feet extending beyond the edge, we may dream of standing on the brink of a terrifying precipice, or of falling from a steep height. Should our head accidentally get under the pillow we may then imagine a big rock hanging over us and about to crush us under its weight. Accumulation of semen produces voluptuous dreams, and local pain the idea of suffering ill treatment, of hostile attacks, or of accidental bodily injuries."
"Meier (Versuch einer Erklärung des Nachtwandelns, Halle, 1758, p. 33), once dreamed of being assaulted by several persons who threw him flat on the ground and drove a stake into the ground between his big and second toes. While imagining this in his dream he suddenly awoke and felt a blade of straw sticking between his toes. The same author, according to Hemmings (Von den Traumen und Nachtwandeln, Weimar, 1784, p. 258) dreamed on another occasion that he was being hanged when his shirt was pinned somewhat tight around his neck. Hauffbauer dreamed in his youth of having fallen from a high wall and found upon waking that the bedstead had come apart, and that he had actually fallen to the floor....Gregory relates that he once applied a hot-water bottle to his feet, and dreamed of taking a trip to the summit of Mount Ætna, where he found the heat on the ground almost unbearable. After having applied a blistering plaster to his head, a second man dreamed of being scalped by Indians; a third, whose shirt was damp, dreamed of being dragged through a stream. An attack of gout caused the patient to believe that he was in the hands of the Inquisition, and suffering pains of torture (Macnish)."
The argument based upon the resemblance between stimulus and dream content is reinforced if through a systematic induction of stimuli we succeed in producing dreams corresponding to the stimuli. According to Macnish such experiments have already been made by Giron de Buzareingues. "He left his knee exposed and dreamed of travelling in a mail coach at night. He remarked in this connection that travellers would well know how cold the knees become in a coach at night. Another time he left the back of his head uncovered, and dreamed of taking part in a religious ceremony in the open air. In the country where he lived it was customary to keep the head always covered except on such occasions."
Maury48 reports new observations on dreams produced in himself. (A number of other attempts produced no results.)
1 He was tickled with a feather on his lips and on the tip of his nose. He dreamed of awful torture, viz. that a mask of pitch was stuck to his face and then forcibly torn off, taking the skin with it.
2 Scissors were sharpened on pincers. He heard bells ringing, then sounds of alarm which took him back to the June days of 1848.
3 Cologne water was put on his nose. He found himself in Cairo in the shop of John Maria Farina. This was followed by mad adventures which he was unable to reproduce.
4 His neck was lightly pinched. He dreamed that a blistering plaster was put on him, and thought of a doctor who treated him in his childhood.
5 A hot iron was brought near his face. He dreamed that chauffeurs4 broke into the house and forced the occupants to give up their money by sticking their feet into burning coals. The Duchess of Abrantés, whose secretary he imagined himself in the dream, then entered.
6 A drop of water was let fall on his forehead. He imagined himself in Italy perspiring heavily and drinking white wine of Orvieto.
7 When a burning candle was repeatedly focussed on him through red paper, he dreamed of the weather, of heat, and of a storm at sea which he once experienced in the English Channel.
D'Hervey,34 Weygandt,75 and others have made other attempts to produce dreams experimentally.
Many have observed the striking skill of the dream in interweaving into its structure sudden impressions from the outer world in such a manner as to present a gradually prepared and initiated catastrophe (Hildebrandt)35. "In former years," this author relates, "I occasionally made use of an alarm clock in order to wake regularly at a certain hour in the morning. It probably happened hundreds of times that the sound of this instrument fitted into an apparently very long and connected dream, as if the entire dream had been especially designed for it, as if it found in this sound its appropriate and logically indispensable point, its inevitable issue."
I shall cite three of these alarm-clock dreams for another purpose.
Volkelt (p. 68) relates: "A composer once dreamed that he was teaching school, and was just explaining something to his pupils. He had almost finished when he turned to one of the boys with the question: 'Did you understand me?' The boy cried out like one possessed 'Ya.' Annoyed at this, he reprimanded him for shouting. But now the entire class was screaming 'Orya,' then 'Euryo,' and finally 'Feueryo.' He was now aroused by an actual alarm of fire in the street."
Garnier (Traité des Facultés de l' Âme, 1865), reported by Radestock,54 relates that Napoleon I., while sleeping in a carriage, was awakened from a dream by an explosion which brought back to him the crossing of the Tagliamento and the bombarding of the Austrians, so that he started up crying, "We are undermined!"
The following dream of Maury48 has become celebrated. He was sick, and remained in bed; his mother sat beside him. He then dreamed of the reign of terror at the time of the Revolution. He took part in terrible scenes of murder, and finally he himself was summoned before the Tribunal. There he saw Robespierre, Marat, Fouquier-Tinville, and all the sorry heroes of that cruel epoch; he had to give an account of himself, and, after all sort of incidents which did not fix themselves in his memory, he was sentenced to death. Accompanied by an enormous crowd, he was led to the place of execution. He mounted the scaffold, the executioner tied him to the board, it tipped, and the knife of the guillotine fell. He felt his head severed from the trunk, and awakened in terrible anxiety, only to find that the top piece of the bed had fallen down, and had actually struck his cervical vertebra in the same manner
