The stage of dreaming is characterized by the perfect closure of one or more of the avenues of special sense. When this occurs, the harmony between the world and ourselves is broken. The mind is no longer controlled by outward influences, but is struggling under the combined effects of its own innate powers and imperfectly transmitted sensational impressions. We have lost the means whereby the perception of an impression of one sense can be tested by the co-operating scrutiny of another.

Dr. Abercrombie says, that "in dreams, the impressions which arise in the mind are believed to have a real and present existence; and this belief is not corrected, as in the waking state, by comparing the conception with the things of the external world; and that the ideas or images in the mind follow one another, according to associations over which we have no control ; we cannot, as in the waking state, vary the series, or stop it at our will."

The wonderful clearness, at times, of the mind in dreams, must have been observed by all who have given attention to this subject. This lucidity is particularly observed in imaginary conversation, public speaking, and composing, the minutiae of which the individual seldom retains on awaking; but he is astonished at the recollection of the exuberance of his ideas, as well as the ease with which he expressed them. This mental clearness depends upon the passive condition of the external senses, which modifies the impression of external things that would otherwise divert and divide the attention. In this stage, volition is ready for action, but the mental operations are not sufficiently intense to call it into play; and the mind is not controlled by the influences of outward circumstances.

We conceive that every portion of the mental organ is at all times in action; but that the degree differs as regards its various parts, and that their activity is. regulated by existing circumstances. The organs which approach the passive state, exert some influence in moulding the operations of such as are actively engaged, so that although the whole are not at any one time occupied by a single subject, yet there is no part which does not experience in a degree its peculiar mode of activity.

During sleep, the mental organ presents the same phenomena as when awake; for in dreams certain elements only are actively excited - those having reference to the subject of the dream; but the more passive organs are ready to change their state, as circumstances may arise to vary the character of the dream.

On being suddenly aroused, we are generally conscious of having dreamed, with little or no recollection, however, of the subject. But when we awake gradually - the necessity for longer sleep having ceased - the senses recover their functions one after another, until all are fully awake. In such case, the dream is most perfectly remembered. To this general fact, however, there are exceptions, for when suddenly aroused, either by intensity of mental excitement, or from external causes, we retain vividly the strong impression then existing, because the senses of external relation are taken by surprise, and even though awakened, the train of thought cannot be in all cases so quickly arrested. The mind is at all times subject to its proper stimuli; but during sound sleep, that of external relation is cut off by the torpor of the special senses, and it is, therefore, less likely to be actively engaged than when all its sources of communication are open.

From this view of sleep, it may be said, we live in a state of divided consciousness. When the externa senses are in abeyance, our mental existence is clearly distinct from that of wakefulness, and vice versa. But when the senses are partially impressible, then our existence is one of transition. This is the period of remembered dreams.

If it be true, as Combe remarks, that "the senses themselves do not form ideas," yet they do inform the mind of external relations or circumstances out of which ideas are produced. It is not pretended that the mind in dreams does not, or cannot recall ideas of external qualities of bodies, but the ideas which are formed relative to them are the result of internal faculties: - and so it is with the perception of an impression of any one of the senses - in truth, an impression of one may call up ideas which were originally dependent on any one or all combined.

We do not, neither can we, dream of what we possess no knowledge. But memory may, on the impression of a sense, recall to mind a fact or circumstance, and the imagination may take it up and multiply it into a thousand forms and invest them with an endless variety of fanciful creations: - for

"Lulled in the countless chambers of the brain, Our thoughts are linked by many a hidden chain; Awake but one, and lo! what myriads rise, Each stamps his image as the other flies."

The sense of hearing, or impressions made upon the auditory nerve, are most intimately connected with the propensities and sentiments; and the sense of sight, or impressions transmitted by the optic nerve, are more nearly allied to the intellectual operations. The. mental operations, during sleep, are longer controlled or influenced by hearing than by seeing, and dreams are consequently connected more with the animal than the. intellectual constitution in their fundamental elements.

Indefiniteness - a something wanting - is a general quality of mental action in sleep, of which the mind is conscious when it attempts to recall a dream. Combe says, that "in most individuals, the mind has no power of calling up, into fresh existences, the emotions experienced by means of the propensities and sentiments, by merely willing them to be felt; and hence we hold these faculties not to possess memory. The ideas, however, formed by the knowing and reflective faculties, can be reproduced by an act of recollection, which powers are, therefore, said to have memory." This view may account for the imperfect remembrance we have of some dreams which immediately precede the state of complete wakefulness, when, in fact, sleep has been prolonged almost by an effort of the will. For if it requires the sense of vision - which is probably the first to sleep, and the last to emerge from it - to excite the perceptive and reflective faculties, it may solve the problem of imperfect memory of what passes in the mind during sleep. Many of the least distinct remembrances we have of our dreams, with a perfect consciousness, however, of their existence, as well as their almost purely intellectual character, are those in which the individual was engaged in composition or declamation. Another reason for this indistinctness is, that he may have been vacillating between the stages of dreaming and torpor, lying as it were on the confines of each, which would produce confusion in the memory, - remembering what transpired in the one, and forgetting what occurred in the other.