First Experiment: He caused himself to be tickled with a feather on the lips and inside the nostrils. He dreamed that he was subjected to a horrible punishment. A mass of pitch was applied to his face, and then roughly torn off, taking with it the skin of his lips, nose, and face.

Second Experiment: A pair of tweezers was held at a little distance from his ear, and struck with a pair of scissors. He dreamed that he heard the ringing of bells; this was soon converted into the tocsin, and this suggested the days of June, 1848.

Third Experiment: A bottle of eau de cologne was held to his nose. He dreamed that he was in a perfumer's shop. This excited visions of the East, and he dreamed that he was in Cairo in the shop of Jean Marie Farina. Many surprising adventures occurred to him there, the details of which were forgotten.

1 Paris, 1865. Third edition.

Fourth Experiment: A burning lucifer match was held close to his nostrils. He dreamed that he was at sea (the wind was blowing in through the window), and that the magazine of the vessel blew up.

Fifth Experiment: He was slightly pinched in the nape of the neck. He dreamed that a blister was applied, and this recalled the memory of a physician who had treated him in infancy.

Sixth Experiment: A piece of red-hot iron was held close enough to him to communicate a slight sensation of heat He dreamed that robbers had got into the house, and were forcing the inmates, by putting their feet to the fire, to reveal where their money was.

Seventh Experiment: The words Azor, Castor, Leo-nore were spoken. On awaking, he recollected the last two words, and found he had attributed them to one of the persons who had conversed with him in his dream.

Eighth Experiment: A drop of water was allowed to fall on his forehead. He dreamed that he was in Italy, that he was very warm, and that he was drinking the wine of Orvieto.

Ninth Experiment: A light, surrounded with a piece of red paper, was repeatedly passed before his eyes. He dreamed of a tempest and lightning, which suggested the remembrance of a storm he had encountered in the English Channel in going from Merlaix to Havre.

If these experiments prove nothing else they prove that during sleep the mind is open to the reception of impressions from without, and that external stimuli may either cause or influence the dream. No matter how quiet the night, countless impressions are being made on the brain; these may proceed from rattling windows, the sighing of the wind, noises of the night, etc. Further, impressions may reach the brain from the heart, the lungs and other organs, especially if their functions are disturbed. The fact that impressions can be made on sleeping consciousness does not imply, however, that all these do so, or that they are made use of by the dream. If they are intense or strong this may be the case; but if we believe that thought goes on regularly by night as well as by day, then thought alone may be sufficient to occupy consciousness and prevent outside stimuli from influencing the character of the thought. In waking life we pay little or no attention to feeble stimuli originating outside or inside the body when we are occupied with interesting thought; should the stimuli become strong or the thoughts disinteresting, then these stimuli may engage consciousness and occupy it for a longer or shorter period. Similarly, the thought going on in sleep may be sufficiently strong to prevent outside stimuli from being registered in consciousness.

Practically the only argument offered to support the view that deep sleep is dreamless is the inability of many persons to recall dreams; this is no proof at all. Each of us is aware of the fact that we were thinking an hour ago, but hardly one of us can recall what we were thinking about. Thought is one of the phenomena of life, and sleeping or waking it goes on, just as the heart, lungs and other organs carry on constantly. If we were asked what the mind has to think about all night we might, in return, ask what it has to think about all day. True, in sleep, the eyes are closed, and the ordinary activities of the day, which govern the character of the daily thoughts, absent; yet the mind is well stocked with memories and there is nothing to prevent these from occupying consciousness.

It might be argued that, if dreaming went on through- out sleep, it would be fatiguing, since thought is fa- tiguing. However, just as the physical functions go on at a slower speed during sleep, so does an alteration occur in the mental functions, which promotes mental rest. The thought in sleep differs materially from that of waking life. The thought in sleep makes use of images almost entirely; it reasons by parables, symbols, and in other ways carries out an indirect form of thinking. Directive thinking, as is the waking bent, is fatiguing; indirect thinking, as characterizes sleep, is refreshing. The nearest approach to indirect thinking in the waking state is reverie, which is not only easy thinking and not tiresome, but which often leads to sleep.

If we find it difficult to remember dreams it is largely due to the fact that dreams deal with material lodged in the unconscious mind. In the next chapter we shall take up what is meant by the unconscious mind: here it may be stated that this mind is made up of all past experiences which are not available to waking consciousness, or for recollection. As we go to sleep the door of this mind is, so to speak, gradually opened, and the dream is more or less of a mixture of conscious and unconscious thoughts. We remember these dreams of light sleep, or fragments of them, because we still possess, in part at least, waking consciousness. When deep sleep is upon us the door of the unconscious is well opened and it is with unconscious material that the dream deals. As we awake the door gradually closes; when fully awake the door is fully closed, and with it are shut in the thoughts with which the dream of deep sleep has been dealing. We find an example of deep sleep in hypnotism : in this state thought goes on, the thought taking place in the unconscious mind. On awaking from hypnotic sleep there is no recollection of what occurred during this period.

The question of whether or not we dream all night is not, after all, a matter of very great practical importance. We have good reason to believe, however, that dreaming goes on constantly in sleep and, therefore, no sleep is dreamless. When one speaks of dreamless sleep what is really meant, according to our belief, is sleep followed by no recollection of having dreamt.