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during our sleeping than our waking hours ; and that this is the fact, appears in many passages of Mr Macnish's own work. “ When the body," says Mr Macnish,“ is in a state of INCREASE, as in the advance from infancy to boyhood, so MUCH SLEEP is required, that the greater portion of existence may be fairly stated to be absorbed in this way. It is not mere repose from action that is capable of recruiting the wasted powers, or restoring the nervous energy. is. Along with this is required that oblivion of feeling and imagination which is essential to, and which in a great measure constitutes, sleep. But if, in mature years, the body is adding to its bulk iby the accumulation of adipose matter, a greater tendeney to somnolency occurs than when the powers of the absorbents and exhalants are so balanced as to prevent such accession of bulk *.!: hi

I cannot agree with Mr Macnish in his observation that oblivion of feeling and imagination in a great measure constitutes sleep: : Whatever causes sleep, causes also the oblivion with which it is attended. But, to a certain extent, I agree with his

I subsequent observation, that, while one set of organs is laying down particles, another is taking them up with such exquisite nicety, that, for the continual momentary waste, there is continual momentary repair t. This appears to me to require a little qualification to meet the admitted fact of the "renovating influence of sleep † ;" but I should not dissent from the expression “ diurnal waste, and diurnal repair ;"-a form which more ac

"_ curately connects itself with Mr Macnish's observation, that “ this is capable of going on with the strictest equality for half a century II

This renovating influence of sleep is more distinctly explained by Mr Macnish, where he remarks-" That it increases diges tion, and as a natural consequence nutrition, is rendered probable by many circumstances; hence it is the period in which the regeneration of the body chiefly takes place. Were there even no augmentation given to the assimilative function, as is maintained by Broussais and some other physiologists, it is clear that the body would be more thoroughly nourished than when awake; for all those actions which exhaust it in the latter condition are quiescent, and it remains in a state of rest, silently accumulating power without expending any T;" in other words, silently accumulating new particles, or rather masses of particles, without expending the old in the same proportion.

I have already, adverted to the effect of this accumulation on the entire brain ; and, did space permit, I might notice the consequences of partial release of the brain and nerves from this influence-namely, nightmare, somnambulism, and sleep with • Philosophy of Sleep, 2d edit. p. 4.

+ Id. p. 5.
# Id. p. 6.
11 Id. p. 5.

Id. p. 21.

dreams. There is one condition, however, that ought not to be passed over in silence ; that in which the brain and nerves of sense are in a waking state, and the nerves of voluntary motion are still shackled under the weight of the new and unassimilated deposit of the nervous particles. This is a state that but seldom presents itself. These nerves, in our waking moments, appear to be always ready to obey the will, except when they are labouring under paralysis ; but the natural paralysis of sleep is so easily dissipated that it rarely can maintain its power after the mind issues its mandate that the limbs shall move. I should have been without an example of this peculiar condition, if Mr Macnish had not furnished me with a most satisfactory instance, in which he himself is delineator, subject, and sufferer.

“ During the intensely hot summer of 1825," says this gra. phic and lively writer, “I experienced an attack of DaY-MARE. Immediately after dinner, I threw myself on my back

upon a sofa, and, before I was aware, was seized with difficult respiration, extreme dread, and utter incapability of motion or speech. I could neither move nor cry; while the breath came from my chest in broken and suffocating paroxysms. During all this time, I was perfectly awake; I saw the light glaring in at the windows in broad sultry streams ;. I felt the intense heat of the day pervading my frame; and heard distinctly the different noises in the street, and even the ticking of my own watch, which I had placed on the cushion beside me. I had, at the same time, the consciousness of flies buzzing around, and settling, with annoying pertinacity, upon my face. During the whole fit, judgment was never for a moment suspended. I felt assured that I laboured under a species of incubus. I even endeavoured to reason myself out of the feeling of dread which filled my mind; and longed, with insufferable ardour, for some one to open the door, and dissolve the spell which bound me in its fetters. The fit did not continue above five minutes : by degrees I recovered the use of speech and motion ; and, as soon as they were so far restored as to enable me to call out and move my limbs, it wore insensibly away *."

“ Upon the whole," continues Mr Macnish, “ I consider DAYMARE and NIGHTMARE identical. They proceed from the same cause, and must be treated in a similar manner t..” It must be admitted that they are nearly, but not altogether, identical. In both, if I am right in my views, the nerves of voluntary motion are under the influence of the new deposit of nervous matter. In nightmare the nerves of sense are under the same inAuence. In daymare they are not ; they are perfectly awake, and the individual is in full communication with the external

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world. Both of these instances differ from common dreams in this peculiarity. In these instances, the mind actually issues its mandates whether obeyed or disobeyed. In common dreams, a current of thought passes through the mind like a train of reali. ties, but the mandates of the mind and the motions of the limbs are equally imaginary.

In his chapter upon Trance, Mr. Macnish details a similar case, but in which the symptoms were much more 'aggravated and protracted. Both cases differ altogether from the six cases of protracted sleep detailed in Mr Macnish's eleventh chapter. There is no reason for supposing that these persons were not uuder the influence of intense slumber, during the greater part of the interval engaged in the paroxysm. Nor is there any reason for rejecting as its cause the continued deposition of new nervous substance to an unusual extent. “ The right hand and arm of Mary Lyall appeared completely dead and bereft of feeling; and even when pricked with a pin, so as to draw blood, never shrunk in the least degree. At the same time she instantly drew back her left arm whenever it was touched by the point of the pin. After an interval of seven days she began to move her left hand, and, by pointing to her mouth, signified a wish for food. She took readily what was given to her; still she discovered no symptoms of hearing, and made no other kind of bodily movement than of her left hand. ***

Thus, according to my theory, every kind of nerve connected with the organs of digestion, and the nerves of volition of the left arm, were occasionally released from the oppression of the assimilative particles, while the other nerves of the body continued under their influence, and particularly the nerves of sensation of the right arm. As to those last mentioned nerves, I would not be understood as maintaining that this cause alone occasioned the numbness of the limb in question.

The case of Elizabeth Perkins differs from the others in its fatal termination. After a profound slumber of eleven or twelve days, she “ awoke of her own accord, to the great joy of her relatives, and wonder of the neighbourhood. On recovering, she went about her usual business; but this was only for a short period, for in a week after she relapsed again into a sleep which lasted some days. She continued, with occasional intervals of wakefulness, in a dozing state for several months, when she expired."* Is it not natural to suppose that, in this case, the secerning vessels of the head were in such a diseased state as to effuse upon

the brain much more than the quantity of nervous matter usual in the healthy state? If the torpor bad arisen from the pressure of overloaded bloodvessels, or an effusion either of

* Philosophy of Sleep, p. 209.

+ Id. p. 210.

а.

water or blood, it would have been called apoplexy, and not sleep.

Mr Macnish observes, that the cause of drowsiness, or the “ constitutional disposition to doze upon every occasion, seems to be a certain want of activity in the brain, the result of which is, that the individual is singularly void of fire, energy, and passion. He is of a phlegmatic temperament, generally a great eater, and very destitute of imagination. Such are the general characteristics of those who are predisposed to drowsiness. The cases where such a state coexists with intellectual energy, are few, in number.”* Every word of this description reminds you of the assimilating process, and its effects, and affords a marked difference to another cause, which he notices, of a similar re

a sult, yiz. that “ drowsiness sometimes proceeds from a fulness of blood in the head, or a disordered state of the digestive organs.”+ It sometimes, however, arises from both these causes,

”'t as in that instance which Mr Macnish, but without reference to either of them, adduces from Boerhaave, of an eccentric physician who took it into his head that sleep was the patural state of man, and accordingly slept eighteen bours out of the twenty-four, till he died of apopleay, a disease which, according to Mr Macnish, is always apt to be produced by excessive sleep. I

Mr Macnish adverts to many facts, tending to support my theory, and particularly those respecting the use of food, the very material which supplies and puts in motion tbe assimilating process.

A heavy meal" (he says), “ especially if the stomach be at the same time weak, is apt to induce sleep."" Those who eat heartily, and have strong digestive powers, usually sleep much. The great portion of sleep required by infants, is owing, in part, to the prodigious activity of their digestive powers. The majority of animals sleep after eating, and man has a strong tendency to do the same thing, especially when oppressed with heat, In the summer season, a strong inclination is often felt to sleep after dinner, when the weather is very warm. A heavy meal, which produces no uneasy feeling while the person is awake, will often do so if he fall asleep." || Besides the effects of the assimilating process, may we not, in the two latter instances, look to the effects of heat and of a heavy meal as increasing the velocity or the quantum of the blood, and thus creating a pressure more than natural on the substance of the brain, and partaking more of the character of apoplexy than of sleep?

His contrast of Dr Reid with General Ellict has also the same tendency. The former “ could take as much food, and immediately afterwards as much sleep, as were sufficient for two days." The latter “ never slept more than four hours out of

• Philosophy of Sleep, p. 205, + Id. p. 206. $ Id. p. 16.

|| Id, pp. 35, 36,

# Id. p. 206. Id. p. 32.

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the twenty-four. In all other respects he was strikingly abstinent; his food consisting wholly of bread, water, and vegetables."*

The very purposes which he ascribes to SLEEP, correspond in every particular with my theory. “Its main object is to restore the strength expended during wakefulness, to recruit the body by promoting nutrition and giving rest to the muscles, and to renovate the mind by the repose which it affords the brain. Action is necessarily followed by exhaustion ; SLEEP, by checking the one, restrains the other, and keeps the animal machine in due vigour.”+ The strength expended during wakefulness can only be restored by replacing, with new particles, those carried off by the wear and tear of exertion. Nutrition can only recruit the body by replacing the substance it has lost--the mind can only be renovated in a metaphorical sense; it is the brain which is really renovated, and that by means of the assimilating process. Action is necessarily followed by exhaustion ; but the very operation which causes sleep remedies the exhaustion, while it restrains the action, and, by repeatedly renewing their composition, keeps every nerve, every muscle, every bone, every organ of the animal machine, in due and healthy vigour.

He throws considerable light on the subject when he observes, that " where there is no excitement, sleep is sure to follow. We are all kept awake by some mental or bodily stimulus, and when that is removed our wakefulness is at an end.”I 6 The finished gratification of all ardent desires has the effect of inducing slumber. Hence, after any keen excitement, the mind becomes exhausted, and speedily relapses into this state." those stimuli which keep it employed, and sleep ensues at any time."S Not that these stimuli can prevent or interrupt the usual progress of the assimilative process. They merely urge into the vortex of their influence each particle as it is deposited, and do not permit the accumulating matter to paralyse the energy and activity of the thinking brain. But when these stimuli are withdrawn, when desire or reflection ceases, then the new and scarcely-assimilated substance acts with a dead weight on the living nervous texture,-every moment adds to its mass and power, and the seat of thought and feeling feels and thinks no longer-it is paralysed-IT SLEEPS.

All that I ascribe to the presence of the ASSIMILATING PROCESS, Mr Macnish attributes to the absence of the SENSORIAL POWER,—all that I attribute to the diminution of the former, he ascribes to the increase of the latter. In this respect we are like Lavoisier and Stahl, contending for the presence or absence of oxygen and phlogiston in their respective theories of combustion. Thus, in his chapter on Sleeplessness, he says, “ Sleep takes

• Philosophy of Sleep, p. 33. + Id. p. 39. # Id. p. 13. & Id. p. 15.

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