From the foregoing and other similar facts it has been argued, that all our dreams really take place in the act of falling asleep or of awaking ; so that even when we fancy that we have been dreaming all night, our uncon sciousness has been really complete, except at these momentary intervals. That this doctrine cannot be altogether true is obvious from the fact, that we can frequently detect the character of a dream, and even in some degree trace its progress, by the expression of the sleeper's countenance ; so that dreams certainly may occupy time, and occur during ordinary sleep. On the other hand, it may be freely admitted that the apparent duration of our dreams does not afford the least measure of the time they have really occupied; and that it is probable that even when our sleep has seemed most disturbed by them, we have really passed a larger portion of the night in a state of complete unconsciousness than the mere impression left by our dreams would allow us to believe. But it has been questioned by some, on the other hand, whether there is ever such a state as that of complete unconscious ness. It is affirmed that the mind can never be entirely inactive ; and that every body, in fact, does dream throughout the period of sleep, although the dreams may not be re membered in the waking state. This state ment is rather based upon the hypothesis with which it commences, than upon any positive facts ; and as it requires us to give up the simple teachings of ordinary experience, for the reception of a mere metaphysical dogma, the physiologist need not concern himself with the discussion.
On the whole, it may be said that dreaming indicates that sleep is imperfect ; and this view harmonises with the fact that between dreaming and the waking state there are various connecting gradations. Thus, reverie or day-dreaming differs from the dreaming of the sleeper, not so much in the condition of the mind and its instrument the cerebrum, as in that of the sensorium, which is not so com pletely withdrawn in the former.case, as it is in the latter, from the consciousness .of external itnpressions. In sleep, on the other hand, the dreamer may have a consciousness of the un reality of the images that arise in his mind, and may even make a voluntary and successful effort to prolong them if agreeable, or to dis sipate them if unpleasing ; thus evincing the presence of that power of control over the current of thought, the want of which is one of the best characteristics of ordinary dreaming, as it is also of insanity, and indicating, there fore, an unusual approximation to the vigilant condition.
The action of narcotics on the nervous system presents many curious illustrations of the foregoing statements regarding the nature and phenomena of dreaming. There are some which have the power of inducing every con dition intermediate between an unusual activity of the thoughts and a state of complete stupor, accordina to the dose taken. This is the
case to a certain degree with opium; but still more decidedly with the extract of Cannabis Indica, a preparation of whch, known under the names of Hachisch and Dawamesc, is much used in the East for the production of a species of agreeable intoxication. The first effect of a dose of this substance is usually to produce a moderate exhilaration of the feelings and an unusual activity of the intel lectual powers ; but this activity gradually frees itself from voluntary control. The in dividual feels himself incapable of fixing his attention upon any subject ; his thoughts being continually drawn off by a succession of ideas which force themselves (as it were) into his mind, without his being able in the least to trace their origin. These speedily occupy his attention, and present themselves in strange combinations, so as to produce the most fantastic and impossible creations. By a strong effort of the will, however, the original thread of the ideas rnay still be recovered, and the interlopers driven away. These lucid intervals successively become of shorter duration, and can be less frequently procured by a voluntary effort ; for the internal tempest becomes more and more violent, the torrent of disconnected ideas increases in power so as completely to arrest the attention, and the mind is gradually withdrawn altogether from the contemplation of external realities, being engrossed by the consciousness of its own internal workings. There is always preserved, however, a much greater amount of self-conscionsness than exists in ordinary dreaming ; the condition rather corresponding with that just referred to, in which the sleeper knows that he is dreaming. The succession of ideas has at first less of incoherence than in ordinary dreaming, the ideal events not departing so far from possible realities ; and the disorder of the mind is at first manifested in errors of sense, in false convictions, or in the predominance of one or more extravagant ideas. These ideas and convictions are generally not altogether of an imaginary character, but are called up by external impressions, which are erroneously interpreted by the perceptive faculties. The error of perception is remarkably shown in regard to time and space ; minutes seem hours, hours are prolonged into years, and at last all idea of time seems obliterated, and past and present are confounded together as in ordinary dreaming : and in like manner, streets appear of' an interminable length, and the people at the other end seem to be at a vast distance. Still there is a certain con sciousness of the deceptive nature of these illusions, which, if the dose be moderate, is never entirely lost.