In some of his experiments, Sante de Sanctis placed a musical clock under the pillow of his sleeping subjects - the latter his son, a girl, and an imbecile. Pleasant dreams resulted, and the subjects smiled in their sleep. A melancholy air caused the imbecile to ask on waking what had been done to him; and, on one occasion, the girl dreamed the clock was playing martial music. Delicious perfumes (violets, heliotrope,) gave the experimenter's son pleasant dreams. According to Sante de Sanctis, dreams can undoubtedly be influenced in the manner indicated, although a particular stimulus does not invariably produce the same results when repeatedly applied to the same subject, or similar results when a different subject is chosen.

The second kind of dreams are dreams from association of ideas; they are supposed to follow on a primary central act. The memory-image is supposed to be caused by some primary central activity, and not by a peripheral stimulus. We may certainly place by the side of dreams from association of ideas the forms of auto-suggestion which I have frequently mentioned in the foregoing sections, and which I have thoroughly discussed on page 154, and such a comparison is especially permissible in the case of those auto-suggestions by which Hirschlaff considers abnormal hypnosis specially characterized.

Between these two classes of dreams there is another, which I may call suggested dreams. In these no stimulus is applied to the nerves of the subject which he may work out at his fancy; but a dream is suggested to him verbally. An acquaintance of mine told his daughter that she saw rooks, upon which she dreamed of them and related her dream on waking. On other occasions the attempt failed. This was already known to the old mesmerists, and their knowledge must be in nowise underrated Kluge gave an account of such observations: - "Thus mention is made in many places of an English officer who could be made to dream anything wished, by softly whispering to him. On one occasion, he was made to dream of all the phases of a duel, from the beginning of the quarrel to the firing of the pistols which had been put in his hands for the purpose. The report of their discharge woke him." Sante de Sanctis made several experiments on his nine-year-old son when asleep, by whispering certain words in his ear. On three distinct occasions the word "pale" was used and the child woke up a minute after. In two of the three cases there was nothing in the dream which could be attributed to the word employed, with certainty.

Once, however, the child woke up frightened, and when asked what he had dreamed, replied that he had had a horrid dream. "Papa, I thought you were scolding me, and I trembled with fright, because you were quite pale with anger." On three other occasions, Sante de Sanctis whispered the word "task" into the boy's ear. Again, there was no result in two of the cases; but in the third, the boy dreamed that it was time for him to go to school and that he had not finished the very long task that had been set him the previous day. It is also comparatively speaking easy to call up dreams artificially in the case of persons who habitually talk in their sleep; here, we must take it, that the waking person insinuates himself, so to speak, into the sleeper's chain of thoughts, which he is then able to influence in their course. This often succeeds, as we shall see later on. It appears that as far as ordinary sleep is concerned, certain stages are more fitted for suggested dreams than others. The transitional stage between waking and deep sleep, which the French call the hypnagogic state, is particularly noteworthy in this respect.

Havelock Ellis, Manaceine and others have called attention to the suggestibility of subjects in this state, and Delbceuf ascribes to it a role of particular importance in the causation of nervous and mental diseases. He supposes that such maladies are of auto-suggestive originr and that they develop themselves like post-hypnotic suggestions.

As regards the mode of origin, these suggested dreams are identical with the suggested sense-delusions of hypnosis.

But the mode of origin of other dreams in sleep occurs in hypnosis also. I have already spoken of dreams from association of ideas, which are analogous to the auto-suggestions of a hypnotic subject. This is particularly clear when we compare the hallucinations induced by nerve-stimulation on p. 152 with them; these hallucinations are identical as to mode of origin with dreams induced by nerve stimulation in ordinary sleep. I hypnotize X., and repeatedly blow with the bellows close to him, without speaking to him. The blowing causes a central excitation, and X. believes he hears a steam engine. He dreams he sees a train, and believes he is on the platform at the railway station at Schoneberg. This is exactly the same thing as a dream produced by nerve-stimulation, in which the falling of a chair makes the dreamer think he hears a shot fired, and dreams he is in battle. Besides, in hypnosis as well as in sleep, such stimuli are, as a rule, enormously overestimated, as Tissie points out; a slight noise is taken for the report of a gun, and a gentle touch with the hand for the bite of a dog. I drum on the table without speaking; the subject hears and dreams of military music, thinks that he is in the street, and sees soldiers, etc., etc.

Tissie mentions that in sleep visual impressions seldom lead to dreams, since we usually sleep in the dark and with our eyes closed. We can, however, produce dreams in ordinary sleep with the help of any source of light. It is interesting to find, nevertheless, that many investigations on sleep show that the nervous stimulation comes preferably through the ear, as in hypnosis (Mary Whiton Calkins).

One thing is clear from the comparisons I have made: it is a mistake to think as many do, that all intercourse with the outside world is cut off in sleep. Indeed, the opinion that by far the greater number of dreams are induced by sense-stimuli has its adherents (Wundt, Weygandt). This receptivity to stimuli which reach the brain, unregulated by the consciousness and mistakenly interpreted, is a phenomenon of both sleep and hypnosis. Further, it is evident from what has been said that the method employed to make external suggestion in hypnosis often suffices to induce dreams in sleep. At the most, there is only a quantitative difference, since most sense-delusions are directly suggested in hypnosis, while in sleep dreams are caused by some peripheral stimulus which undergoes a special elaboration in the brain of the sleeper. A qualitative distinction is not here possible, although Sully separates sleep and hypnosis on the ground that dreams arise in the former differently from hallucinations in the latter.