« ПредишнаНапред »
tion of the patient was fixed on a certain train of thought, whatever happened to be spoken in harmony with this was heard and appreciated; but what had no relation to it, or was in discordance with it, was entirely disregarded.
What can be more completely in accordance with certain somnambulic phenomena, of which the existence has been stoutly denied, than all this?
But a little careful search in this field may disclose to us points of resemblance more numerous still. It belongs more properly to the next chapter, on Dreaming, than to this, to inquire whether, in exceptional cases, during natural sleep, there do not present themselves some of the most extraordinary powers or attributes, the alleged and seldom-credited phenomena of somnambulism,-such as clear-sight, (clairvoyance,) farsight, (vue à distance,) and even that most strongly contested of all, the faculty of presentiment, the prophetic instinct.
But there is another point of analogy, connected with the renovating influence of sleep and the causes which render necessary to man such an intermittent action, to which it may be useful here to allude.
It would be very incorrect to say that the continued exercise of any function induces fatigue, and consequently necessitates sleep. It is well known that this is true of some functions only. It is not true of the functions of organic life, the automatic or involuntary functions. We tire of walking, we tire of thinking, we tire of seeing or hearing, or of directing the attention in any way to external objects; but we never tire of breathing, though breathing is a more continued action than any of these.
This obvious fact suggested to physiologists, before Darwin's time, the opinion which was first prominently brought forward by that naturalist, that the essential
SUSPENSION OF VOLITION.
part of sleep is the suspension of volition. And some have gone so far as to assert that the only source of fatigue, and therefore the sole necessitating cause of sleep, is the exercise of volition; adducing in support of this theory the observation, that when the muscles of an arm or a leg are contracted under the influence of the will, fatigue follows in a few minutes; while the same contraction taking place involuntarily (as in catalepsy, whether naturally or mesmerically induced) may continue for a long time without any fatigue whatever.
But we cannot adopt unconditionally such an opinion without assuming that there is no waking state in which the volition is suspended or inactive. For we know of no waking state, no matter how listless and purposeless, the continuance of which obviates the necessity, after a comparatively brief interval, for sleep. Nor is it true that men of strong will and constant activity always require more sleep than the indolent and infirm of purpose. Three or four hours out of the twenty-four are said to have sufficed, for months at a time, to Napoleon, the very embodiment of energetic purpose and unceasing activity of volition.
Not the less, however, must we admit the truth and importance of Darwin's remark, that the essential condition of sleep is the suspension of volition. And in this respect the resemblance is striking between sleep. and the various states of the human system during which mesmeric and what have been called spiritual phenomena present themselves. The somnambule, the "medium," are told that the first condition of success in the production of the phenomena sought is, that the subject should remain absolutely passive; that he should implicitly surrender to the action of external influences his will. Indeed, the somnambule is put to sleep, if artificially, not the less
absolutely, by the magnetizer. And when a medium joins a circle around the table, or engages in automatic writing, drowsiness, after a brief period, is usually induced.
Upon the whole, the facts seem to justify the assertion that all mesmeric and so-called spiritual phenomena, so far as they depend on a peculiar condition of the human system, are more or less hypnotic in their character. To obtain a proper understanding of their true nature, and a discriminating appreciation of the results. obtained, this should constantly be borne in mind.
For the rest, it may be doubted whether the popular opinion that it is only during sleep that there is accumulation in the cerebral lobes of the nervous fluid be a correct one, and whether we ought to consider the expenditure of that fluid as restricted to the waking state.
The better opinion appears to be, that, as a general rule, there are, at all times, both a generation and a consumption; that, whether during the sleeping or waking state, that mysterious process which supplies renovating force to the human system is constantly going on,-the supply falling short of the demand upon it, and therefore gradually diminishing, during our waking hours, but exceeding it, and therefore gradually accumulating, during sleep. In other words, we may suppose the supply regular and constant, both by day and night, as in the case of that other automatic process, as little understood, of assimilation; and the demand never wholly ceasing, nor ever, perhaps, perfectly regular in its requisitions, but intermittent as to quantity, usually every twentyfour hours,-making, so long as the will is in action and the senses are awake, its calls at such a rate as must, after a time, exhaust the supply; and then again, during the comparative inaction of sleep, restricting these calls,
HOW IS THE NERVOUS
so that the nervous fluid can increase in quantity and a surplus accumulate before morning.
That, in all cases, a certain reserve fund remains is evident from the fact that, under circumstances of urgency, we can postpone sleep even for several nights. But this encroachment is usually attended with injurious results. Nor does it appear that the brain can be overloaded with nervous fluid, any more than it can be unduly deprived of it, without injury; for there are diseases induced by excessive sleep.
It would seem, also, that the brain can only deal out its supply of nervous force at a certain rate.
For an exercise of violent volition is commonly succeeded, after a brief period, by exhaustion; and rest (which is a very different thing from sleep, being only a cessation from active exertion) becomes necessary before a second such call on the nervous reservoir can be made.
How that reservoir is supplied,-by what precise process there is generated in the cerebrum that store of fluid or force, the most wonderful of all the imponderables, without which, in the human system, there would be neither exercise of volition nor any outward sign of intelligence; whether this mysterious agent is, after all, but a modification of that proteus-showing fluid, the electrical, or, if not electrical, whether it may not be of electroid character:-these various questions how shall we determine?-we who, after the lapse of twentyfive centuries since Thales's first observation on a bit of amber, can scarcely tell, when we speak of positive and negative electricity, which hypothesis is the more correct,—that of a single agent, now in excess, now in deficiency, or that of two electricities, the vitreous and the resinous; we who, indeed, have but learned enough to become conscious that this very agency itself, called by us electrical, must yet be spoken of as unknown,—
unknown in its essence, albeit observed, by thousands of naturalists, in some of its effects.*
Intelligent physiologists and psychologists, it is true, have speculated on this subject; Sir Benjamin Brodie, for example. Speaking of the changes which the nervous system may be supposed to undergo in connection with. mental processes, and in reply to the questions, "Are these simply mechanical? or do they resemble the chemical changes in inorganic matter? or do they not rather belong to that class of phenomena which we refer to imponderable agents, such as electricity and magnetism?" he says, "The transmission of impressions from one part of the nervous system to another, or from the nervous system to the muscular and glandular structures, has a nearer resemblance to the effects produced by the imponderable agents alluded to than to any thing else. It seems very probable, indeed, that the nervous force is some modification of that force which produces the phenomena of electricity and magnetism; and I have already ventured to compare the generation of it by the action of the oxygenized blood
* A few years since, at the meeting of the British Association for the Advancement of Science held at Swansea, a discussion having arisen as to the essence or nature of electricity, and an appeal having been made to Faraday for his opinion on the subject, what did he, the first electrician perhaps of the age, reply? "There was a time when I thought I knew something about the matter; but the longer I live and the more carefully I study the subject, the more convinced I am of my total ignorance of the nature of electricity."-Quoted by Bakewell, in his "Electric Science,” p. 99. "Some of the conditions which we call the laws of electricity and of magnetism are known. These may not improperly be viewed as their habits or modes of action,-the ways in which they manifest themselves to some of our senses. But of what they consist, whether they possess properties peculiar to themselves and independent of the ponderable substances with which we have always found them associated, or in what respects they differ from light and heat and from each other, is beyond the range of our experience and, probably, of our comprehension.”—Rutter's Human Electricity, pp. 47, 48.