In simple dreaming, as there is a loss of voluntary control over the current of thought, so is there an absence of control over the muscular system. Movements expressive of emotions, however, may still take place, and may afford to the by-stander an indication of what is passing in the mind of the dreamer. The indications of fear, horror, or disgust, or of hope, rapture, or desire, —laughter or weeping, smiles or frowns,— may all display themselves, when there is an absolute cessation of all vo luntary movements. This is remarkably the case in attacks of incubus, or nightmare ; in which the dreamer is oppressed by intolerable distress, from which he makes vain attempts to free himself. His distress may be expressed by moans, or by the agitation of his coun tenance ; but none of his fancied efforts are indicated by any respondent movements. This condition may subside into a state of tranquil slumber, or the agitation may increase to such a pitch as to awake the sufferer ; and as the first act or the waking state is usually to cry out or kick violently, it has been supposed that the return of volition has been the cause, instead of being the effect, of the cessation of the op pressive dream. There are cases, however, in which the dreamer executes movements in consonance with ideas passing through his mind, —such as would, in the waking state, be termed voluntary ; but these must be con sidered as belonging rather to the category of somnambulism than to that of simple dreaming.
The direction of the current of thought in dreaming is often given by impressions on the organs of sense, which influence the mental operations, by calling up associated ideas, without being recognized and perceived as distinct sensations. Thus, Dr. James Gre gory, having applied a hot bottle to his feet on going to bed, dreamt that he was walking up Etna and finding the ground intolerably hot. On another occasion, he dreamt of spending a winter at Hudson's Bay, and of suffering much distress from the intense frost ; this evidently the consequence of his having thrown off the bed-clothes in his sleep, and of his having been reading, a few days before, a very particular account of the state of the colonies in that country during winter. Dr. Reid, having a badly-dressed blister on his head, dreamt that he was being scalped by Indians ; and a man in a damp bed, that he was being dragged through a stream. A gouty man, when beginning to feel his pain in his sleep, may dream he is on the rack before inquisitors. The sound of music may excite delightful dreams. M. Girou de Buzarein gues* made some curious experiments on this point, and. directed at pleasure the-cha racter of his dreams. In his first experiment, having allowed the back of his head to be uncovered during sleep, he thought he was at a religious ceremony in the open air ; the custom of the country in which he lived being to keep the head covered excepting on some rare occurrences, among which was the per formance of religious ceremonies. On waking he felt cold at the back of the neck, as he frequently had when present at the real cere monies. Ile repeated the experiment in two days, with the same result. In a third ex periment, he left his knees uncovered, and dreamt that he was travelling at night in the diligence; and all travellers know, he observes, that it is chiefly at the knees that they feel cold when travelling by that conveyance at night. The very remarkable degree in which this influence of external impressions is ex erted, when sleep is being indueed by the agency of certain narcotics, will be presently noticed. By the use of the term " external " is here meant that which is external to the mind itself. The dream may originate in im pressions derived from any part of the bodily frame. Thus we find that indigestion is a very common cause of nightmare, and that an irritable state of the genital apparatus provokes lascivious dreams. When the ex ternal impressions are recognized as sensa tions, and the dreamer's current of' thought completely follows their guidance, so that even the meaning of spoken language is ap preciated, the condition approximates to that of Somnambulism.
One of the most remarkable of all the pecu liarities of the state of dreaming, is the rapidity with which trains of thought pass through the mind ; a dream in which a long series of events has seemed to occur, and a multitude of images has been successively raised up, being often certainly known to have occupied but a few minutes or even seconds. This is best seen in those cases in which the dream has obviously originated in some sensory impres sion, which has also had the effect of arousing the sleeper. A very interesting example of this, in which a similar dream was produced in two individuals, husband and wife, from the same cause, came within the knowledge of the late Dr. James Gregory. It happened when the public mind was much excited in regard to the alarm of French invasion, and the gentleman who was the subject of it was himself a zealous member of the Edinburgh volunteer corps. Whilst asleep, between two and three o'clock in the morning, he dreamt of hearing the signal gun: he was immediately at the Castle, witnessed the proceedings fOr displa3ing the signals to alarm the country, and saw and heard a great bustle over the town, from troops and artillery assembling, especially in Princes Street. At this time he was roused by his wife, who awoke in a fright, in consequence of a similar dream, connected with much noise and the landing of the enemy, and concluding with the death of a particular friend of her husband's, who had served with him as a volunteer. The origin of this remarkable occurrence was ascer tained, in the morning, to be the noise pro duced in the room above by the fall of a pair of tongs. How long the dream had continued in this instance is uncertain ; evidently not for a period in the least comparable to that required for the actual occurrence of the events that had passed through the mind of each ; and it is probable, from many similar cases, that the lady was awoke by the noise rather than by the fright. Thus a gentleman dreamt that he had enlisted as a soldier, joined his regiment, deserted, was apprehended, carried back, tried, condemned to be shot, and at last led out for execution. After all the usual preparations, a gun was fired ; he awoke with the report, and found that a noise in an adjoining room had both produced the dream and awoke him. The same feeling of duration, arising out of the number of images passing in succession through the mind, is often experienced when we are well assured that the whole duration of our sleep has not exceeded a few moments. We have known a clergyman fall asleep in his pulpit during the singing of the psalm before sermon, and awake with the conviction that he must have slept for at least an hour, and that the congrega tion must have been waiting for him ; but on referring to his psalm-book, he has been con soled by finding that his slumber has lasted no longer than during the singing of a single line. There would not seem, in fact, to be any limit to the amount of thought which may thus pass through the mind of the dreamer, in an interval so brief as to be scarcely capable of measurement ; and this view is confirmed by the circumstance, now well attested, that it is a common occurrence in drowning for the whole previous life of the individual to be presented instantaneously to his view ; with its every important incident vividly impressed-on his consciousness, just as if all were combined in a picture, every part of which could be taken in at a glance. This, again, is connected with the fact that the operation of the associative principle inay re produce in dreams the remembrance of facts long since forgotten in the waking state. Such, however, is by no means peculiar to the state of dreaming ; for in the waking state we often retrace involuntarily and unexpectedly some thing, which we have in vain attempted to recall at will, and which might be said to have passed from our mental grasp.