As we have said, the function of the brain is duplex; it stimulates and directs, and it is also sentient and conscious, and this second function is persistent in dreams.  Although the brain is no longer directed by a power which dictates psychical acts and phenomena, yet its automatic action is not destroyed, and to this the apparent reality of images seen is owing, since there is no longer any distraction from the external world, or, at all events, its impulses are so attenuated as to be unobserved.  In such conditions past images recur with an appearance of reality owing to the mnemonic and automatic action of the brain; such a tendency exists in the waking state, and the images are associated and dissociated in a thousand ways, by means of analogies, resemblances, former combinations of facts, and series of facts analogous to those of the waking state, and are modified by suggestive impulses.  We have experimental proof, to which I can add my own irrefragable witness, that the stimulating influence exerted by the brain in the waking state is dormant in sleep, and that only its automatic act of representation remains active, with the occasional exercise of an aroused and conscious will.

The following strange and unpleasant phenomenon generally occurs to me once or twice a year.  All at once, in the midst of a deep sleep, I become wide awake; I am fully conscious of myself, of the place where I am, of my position and the like, and wish to move like a person who is fully awake.  Yet for some time this is impossible; the psychical, cerebral faculty is perfectly awake, and master of itself, but not the stimulating faculty, so that the limbs do not respond to the first impulse of the will.  All my efforts are unsuccessful; I only succeed in escaping from this unpleasant situation by uttering with great difficulty some inarticulate sound, which acts as a shock, and I thus obtain the mastery of my body, for the nerves of speech and the muscular movements of articulation also fail to answer to my will.  If this occurs when I am alone, the struggle is severe, and there is a violent shock to the whole body before its equilibrium is restored and the motor function of the brain resumes its office.

It is therefore manifest that the stimulating function of the brain is dormant in sleep and dreams, but its automatic, psychical function persists; it sometimes happens that the stimulus of the will is awakened before the stimulus of motion, and that the brain may be aroused to consciousness for some moments before it has resumed its normal functions as a stimulating organ, which were attenuated and relaxed in sleep.  The abnormal condition of paralysis proves and confirms this fact.