We must believe that the labors of digestion and assimulation do not cease during sleep, but repair losses so that there is a time when the individual having already all the necessities of action is not excited by external objects.
Thus the nervous fluid—movable from its nature, passes to the brain, through the nervous conduits. It insinuates itself into the same places, and follows the old road. It produces the same, but less intense effects.
I could easily ascertain the reason of this. When man is impressed by an external object, sensation is sudden, precise, and involuntary. The whole organ is in motion. When on the contrary, the same impression is received in sleep, the posterior portion of the nerves only is in motion, and the sensation is in consequence, less distinct and positive. To make ourselves more easily understood, we will say that when the man is awake, the whole system is impressed, while in sleep, only that portion near the brain is affected.
We know, however, that in voluptuous dreams, nature is almost as much gratified as by our waking sensations; there is, however, this difference in the organs, for each sex has all the elements of gratification.
When the nervous fluid is taken to our brain, it is always collected in vats, so to say, intended for the use of one of our senses, and for that reason, a certain series of ideas, preferable to others, are aroused. Thus we see when the optic nerve is excited, and hear when those of the ear are moved. Let us here remark that taste and smell are rarely experienced in dreams. We dream of flowers, but not of their perfume; we see a magnificently arranged table, but have no perception of the flavor of the dishes.
This is a subject of enquiry worthy of the most distinguished science. We mean, to ascertain why certain senses are lost in sleep, while others preserve almost their full activity. No physiologist has ever taken care of this matter.
Let us remark that the influences we are subject to when we sleep, are internal. Thus, sensual ideas are nothing after the anguish we suffer at a dream of the death of a loved child. At such moments we awake to find ourselves weeping bitterly.
NATURE OF DREAMS.
Whimsical as some of the ideas which visit us in dreams may be, we will on examination find they are either recollections, or combinations of memory. I am inclined to say that dreams are the memory of sensations.
Their strangeness exists only in the oddity of association which rejects all idea of law and of chronology, of propriety and time. No one, however, ever dreamed of any thing absolutely unknown to him.