Part 53

Now there are four sources of nervous influence:—the brain and cerebellum, within the skull; the marrow in the spinal canal; and the nervous bundles in the large cavities, termed ganglia.

It is on the independent or unconscious function of the marrow, chiefly, that those mysterious actions, which do not seem to be willed by a conscious mind, depend.

In the day-dream, a thought or form shall present itself, even at a time when the mind is employed on subjects of a contrasted nature. These thoughts, or forms, are usually fraught with a high degree of pleasure or of pain, or refer to events of vital importance, to the dreamer;—such are the objects of the lover’s idolatry, the anticipation of misfortune, or subjects of prospective felicity. Under this excitement, the influence of external objects is often for a time lost; the retina may be struck by a ray, or the membrana tympani by a vibration, but the mind shall fail in its perception,—no internal impression being made. This cannot arise from a point of the retina, or the expansion of the auditory nerve being pre-occupied, as some have supposed. The idea of material impression must fail in explanation; for, on the instant that the mind is awakened, the external impression is again perceived. The external sense, in this case, is not in fault; nor is its direct influence on the sensorium suspended; for we find that a person will continue to read in this state, as it were mechanically; but the attention is diverted by deep thought, so that the reader, at the end of his task, may have no remembrance of what he has been reading.

Let me tell of a curious little episode of Dr. Darwin’s, which will aid me in my illustration. A young lady was playing on the piano a very elaborate piece of music. It was correctly and scientifically performed, although she was agitated during her task; and when it was over, the lady burst into tears. She had been watching all the time a favourite canary in the fluttering of death; and with this catastrophe her mind was almost wholly occupied, but her fingers did not err in their complicated and delicate motions, which they undoubtedly would have done, if the will or mind alone had directed them.

In sanity of mind, and in mania, the most philosophical distinction is based on the health or disease of memory. The ecstacy of madness may not seem perhaps more irrational than an ecstatic vision, but the maniac will not re-word the matter; whereas the mere visionary will repeat the action of the trance as a dream.

ASTR. But there is a sort of somnambulism the reverse of this. In the retreat to Corunna, many of the soldiers, although exhausted by a long march, and having actually fallen asleep, continued to move forwards, leaving their companions behind, who halted and laid down to repose.

EV. This is the continued association of that excitement which has produced muscular motion. The mind was exhausted and sleepy, the brain was inert; but we believe that the spinal marrow does, of itself, effect motion, while the will and consciousness sleep; and we may also stand and sleep. These soldiers did not walk in their sleep, but slept in their walk.

ASTR. I am informed, too, that Richard Turpin, in allusion to his famous flight to York, asserted that Black Bess appeared to gallop unconsciously.

EV. It is true; and when we reflect on this gigantic feat, we may suppose that the mare gallopped the farther, because her consciousness of fatigue was not awake, and her muscular energy was thus concentrated.

Paralyzed muscles will often quiver when the sound limb is quiet; the brain’s influence being, in this case too, inert, sensation is diminished; but involuntary motion continues from a habit in the muscle, or the excitement of unexhausted irritability, as in chorea, spasm, &c. And in some cases of post mortem galvanism, Dr. Dunbar, of Virginia, passed the galvanic aura along the ulnar nerve of an executed negro, and the fingers instantly quivered, and assumed the attitude and action of one playing on a flute or the strings of a violin.

ASTR. It is possible, then, to move without our willing to do so, or being conscious of our act.

EV. There are believed to be, indeed it is almost a demonstration,—four sets of nerves, traced along the spinal marrow. Two to the brain, of sensation and volition, by which the mind feels what the body touches, and transmits its will to the muscles; two others to the marrow, by which it also is stimulated by outward touch, and by which it excites the muscles to motion.

Now when the brain’s influence is kept from muscle, that muscle will still possess irritability, derived from the spinal marrow; nay, that irritability will be greater, because it has not been expended by the acts of that volition, which resides solely in the brain, and which is now cut off. Thus the excito-motory function, and the influence of volition, are in these cases antagonists. And this principle of the incident and reflex spinal nerve is an explanation of the curious dilemma, regarding the suspension of the will in sleep and dream, to which Dr. Stewart alludes.—“Not a suspension of volition, but only of its influence over those organs, which it moves when we are awake.” Decide for yourselves between the physical and metaphysical theories.

Yet, do you not see that all this does not essentially require the direction of mind? If you tickle the palm of a sleeping child, it will close its hand upon your finger; if you awake it, and engage its attention, it will often leave its hold. This is a fact proved by the anencephalous or brainless children. Even the puppy, deprived of its brain, and also the mammary fœtuses of the kangaroo and opossum, fix eagerly on the nipple when it touches their lips. There is a beautiful mechanism in the foot of the roosting birds, adapted to this physiological law. The tendon of the claws is tightened immediately they are touched, by which action they contrive to grasp the bough or perch even when asleep. In cases of paralysis even, the foot will sometimes be instantly drawn up, although it does not possess the least sensation; we may assert, then, that irritability is in an inverse ratio to sensibility.

The polype, in which we trace no brain or nerve, exists and moves by its irritability, and without sensation or consciousness. We know also that the vis insita, or vis nervosa of a muscle, that is, its irritability, exists even after the animal life has ceased. The turtle will live and move long after its brain has been removed. The heart itself, an involuntary muscle, is stimulated also to action without sensation. The heart of the assassin, Bellingham, beat long after he was cut from the gallows.

If I have made these things clear, I am now prepared to explain, with some anticipation, those two curious contrasts, somnambulism and incubus. If the spinal or motive nerves be asleep, and the cerebral or intellectual, or volition nerves, awake, we shall have night-mare; if, on the contrary, the motive nerves are in excess, beyond the sensiferous or volition nerves, we have sleep-walking.

ASTR. I believe the philosophy of Leibnitz affirms two perceptions; one with, and another without, consciousness. I do not recollect if he distinguishes the seat of these perceptions; but, if the brain be that which perceives, I presume consciousness will follow that perception sometimes in so slight a degree as not to excite judgment or reflection. Am I correct?

EV. You have adopted the common error of metaphysicians. If, in the abstraction of waking moments, some persons talk to themselves, as it were unconsciously, so, from the reflex influence, may volition and motion occur, with as little self-feeling. That the immediate impression, however, and a necessity of action, may combine, is illustrated by Dr. Beattie’s case of the officer who could be thus excited in his sleep. By a whisper in his ear, he was induced to go through the whole ceremony of a duel, and did not completely wake until the report of his pistol roused him. This gentleman was also told that he had fallen overboard, and he began to imitate the motions of swimming; then that a shark was following him, when he would dive off his couch upon the floor; and when he was told that the battle was raging around him, he proved himself an arrant coward by running away.

Somnambulism may be induced by congestion or irritation of that point where the incident nerve blends with the grey matter of the spinal marrow, producing internal irritation, as the tickling of the foot does through the cutaneous nerves of a senseless limb.

CAST. We are thankless creatures, dear Evelyn, but all this reiteration bewilders me, does it not you, Ida? Yet, in my simplicity, I can but think it unphilosophical entirely to disregard the will as the spring of our actions.

EV. If I must EXPLAIN, fair lady, I cannot avoid prolixity. But to your question I will answer, no; for somnambulism may be excited by the memory of an intention. In the experiment made by the committee of the physical society of Lausanne, on the Sieur Devaud, of Vevay, it was proved that on the evening before the fit of somnambulism, his head was heavy, and he had a sense of oppression on his eye-lids. If, at this time, the mind was impressed by some legend, or story, or incident, the actions of the sleep-walk were perfectly coincident with such a subject. If a romantic tale of banditti were related, his alarm would be apparent in his subsequent sleep. In this somnambulist was beautifully illustrated the effect of permanent impression on the brain, rendering, for a time, the sense of vision useless; for having once perused his paper, it was so imprinted on his mind, that the exact spot for each letter was exactly fixed on by the finger. And we have heard of one more interesting case, in which the somnambule, remembering that he had made errors in his writing, traced, on a blank paper substituted for that written on, the corrections, in the very places corresponding to the erroneous writing. And that here was memory was proved in this, that during the time his eyes were shut, the pen was dropped on the very spot where the inkstand stood; but this being removed, no ink was obtained, and the writing was blank.

Now we believe that there are certain vessels which contribute to nervous energy, perhaps by secreting a nervous fluid in the brain, or by concentrating electricity, which Dr. Faraday believes may constitute the animal portion of the nervous system. This influence may be profusely accumulated in a waking state; the resolution to act has been formed; or, there may be a rapid production in sleep of this energy. Then, when sleep occurs, this impression becomes uncontrolled. The third form of insanity of Spurzheim, irresistibility, exists, and the night-walk takes place. And indeed it may form an interesting analogy to that satiety of the voluptuary, “Childe Harold,”

“Who e’en for change of scene wou’d seek the shades below,”

and to one unhallowed story related in “Salmonia.”

From this excess there is the stimulus of pain to move; one of the most powerful motives of human action. Cardan, if we may believe in his “Opera et Vita,” was at least a monomaniac; and he “was wont instinctively, as it were, to relieve this tendency of his mind by the excitement of bodily pain.” I may assure you that I have, during my professional studies, often witnessed (and indeed have sometimes suggested) a remedy on this knowledge: you may be aware, that a severe and painful disorder will mitigate, if not entirely dissipate, that apathetic misery which springs from a vacant or unoccupied mind.

In contrasting childhood and age, we witness these curiosities in the restless activity of youth and early manhood, for at these periods we are very constant somnambulists; not so in the passive state of old age, in which sleep-walking is very rare. Something of this we see also in the growing pains and fidgets of girls and those whose duties are sedentary. Exercise is the relief for all this.

Now when the sleep-walk has exhausted this excess of irritability or electricity (if it be so), the dreamer returns to bed and sleep. A hint is here thrown out to us, that if powerful exertion be employed previous to sleep, the night-walk might not ensue. Lethargy often terminates in somnambulism.

If I may for another moment still prose over the intricate, but deeply interesting question of the pathology of somnambulism, I will observe, that we often find it one symptom of madness or idiocy, and we know that somnambulism not seldom terminates in epilepsy.