Sleep and Its Derangements

by William A. Hammond

“1. That the power of volition is not suspended during sleep, appears from the efforts which we are conscious of making while in that situation. We dream, for instance, that we are in danger, and we attempt to call out for assistance. The attempt induced is in general unsuccessful, and the sounds that we emit are feeble and indistinct; but this only confirms, or rather is a necessary consequence of, the supposition that in sleep the connection between the will and our voluntary operations is disturbed or interrupted. The continuance of the power of volition is demonstrated by the effort, however ineffectual.

“In like manner, in the course of an alarming dream we are sometimes conscious of making an exertion to save ourselves by flight from an apprehended danger; but in spite of all our efforts we continue in bed. In such cases we commonly dream that we are attempting to escape and are prevented by some external obstacle; but the fact seems to be that the body is at that time not subject to the will. During the disturbed rest which we sometimes have when the body is indisposed, the mind appears to retain some power over it; but as even in these cases the motions which are made consist rather of a general agitation of the whole system than of the regular exertion of a particular member of it with a view to produce a certain effect, it is reasonable to conclude that in perfectly sound sleep the mind, although it retains the power of volition, retains no influence whatever over the bodily organs.

“In that particular condition of the system which is known by the name of incubus, we are conscious of a total want of power over the body; and I believe the common opinion is that it is this want of power which distinguishes the incubus from all the other modifications of sleep. But the more probable supposition seems to be that every species of sleep is accompanied with a suspension of the faculty of voluntary motion; and that the incubus has nothing peculiar in it but this—that the uneasy sensations which are produced by the accidental posture of the body, and which we find it impossible to remove by our own efforts, render us distinctly conscious of our incapacity to move. One thing is certain, that the instant of our awaking and of our recovering the command of our bodily organs is one and the same.

“2. The same conclusion is confirmed by a different view of the subject. It is probable, as was already observed, that when we are anxious to procure sleep the state into which we naturally bring the mind approaches to its state after sleep commences. Now it is manifest that the means which nature directs us to employ on such occasions is not to suspend the powers of volition, but to suspend the exertion of those powers whose exercise depends on volition. If it were necessary that volition should be suspended before we fall asleep, it would be impossible for us by our own efforts to hasten the moment of rest. The very supposition of such efforts is absurd, for it implies a continued will to suspend the acts of the will.

“According to the foregoing doctrine with respect to the state of the mind in sleep, the effort which is produced on our mental operations is strikingly analogous to that which is produced on our bodily powers. From the observations which have been already made, it is manifest that in sleep the body is in a very inconsiderable degree, if at all, subject to our command. The vital and involuntary motions, however, suffer no interruption, but go on as when we are awake, in consequence of the operation of some cause unknown to us. In like manner it would appear that those operations of the mind which depend on our volition are suspended, while certain other operations are at least occasionally carried on. This analogy naturally suggests the idea that all our mental operations which are independent of our will may continue during sleep; and that the phenomena of dreaming may, perhaps, be produced by these, diversified in their apparent effects in consequence of the suspension of our voluntary powers.”

A very little reflection will suffice to convince the reader that Mr. Stewart has altogether mistaken the nature of sleep. There is no evidence to support his view that the body is not subject to the action of the will during sleep. No change whatever is induced by this condition in the nerves or muscles of the organism. The first are just as capable as ever of conducting the nervous fluid, and the muscles do not lose any of their contractile power. The reason why voluntary movements are not performed in sleep is simply because the will does not act; and Mr. Stewart is again wrong in asserting that volition is not then suspended. We do not will any actions when we are asleep. We imagine we do, and that is all. The difficulties which encompass us in sleep are, it must be recollected, purely imaginary, and the efforts we make to escape from them are likewise the products of our fancy. Herein lies the main error which Mr. Stewart has committed. He appears to accept the dream for a reality, and to regard the seeming volitions which occur in it as actual facts; whereas they are all entirely fictitious.

An example will serve to make this point still clearer.

Not long since I dreamed that I stood upon a very high perpendicular table-land, at the foot of which flowed a river. I thought I experienced an irresistible desire to approach the brink and to look down. Had I been awake, such a wish would have been the very last to enter my mind, for I have an instinctive dread of standing on a height. I dreamed that I threw myself on my face and crawled to the edge of the cliff. I looked down at the stream, which scarcely appeared to be as wide as my hand, so great was the altitude upon which I was placed. As I looked I felt an overpowering impulse to crawl still farther and to throw myself into the water below. I imagined that I endeavored with all my will to resist this force, which appeared to be acting by means altogether external to my organism. My efforts, however, were all in vain. I could not control my movements, and gradually I was urged farther and farther over the brink, till at last I went down into the abyss below. As I struck the water I awoke with a start. During my imaginary struggle I thought I experienced all the emotions which such an event if real would have excited, and I was painfully conscious of my utter inability to escape from the peril of my situation. Here were circumstances such as, according to Mr. Stewart, demonstrate the activity of volition, but at the same time show its inability to act upon the body. But clearly they show no such thing, for the imaginary volition was to refrain from crawling over a precipice which did not exist, and over which, therefore, I was not hanging. Such an act of the will if real, could not in the very nature of the real conditions of the situation have been carried out—the volition was just as imaginary as all the other circumstances of the dream.

Again, it is not always the case that the imaginary acts of the will are not executed during sleep; and hence it would follow from Mr. Stewart’s argument that the power of the will over the body is not then suspended. Assuming for the moment that the volitions of sleep are real, as Mr. Stewart supposes; if it can be shown that they are satisfactorily performed, it results from his line of reasoning that the will has power over the body during sleep. Every one who has ever dreamed has at times had his will carried out to his entire satisfaction. He has ridden horses when pursued, and has urged them forward with whip and spur so as to escape from his enemies. Or he has executed the most surprising feats both with his mind and body, and has performed voluntary deeds which have excited the admiration of all beholders. Such acts are of course entirely the product of the imagination, and all the volitions which accompany them have no firmer basis than the unbridled fancy; but, according to Mr. Stewart, they would be evidence of the power of the will over the body,—a power which in reality does not exist; not, however, as Mr. Stewart supposes from any impediments in the nerves or muscles, but because it is never exerted.

So far as relates to movements performed during sleep, such as turning in bed and assuming more comfortable positions, they have nothing whatever to do with the will. They are dependent upon the action of the spinal cord, an organ that is never at rest, and the functions of which were not known as well when Dr. Darwin and Mr. Stewart wrote as they are now. The same is true of more complex and longer-continued actions, such as those already mentioned of individuals riding on horseback, or even walking, during sleep.