manner described varies of course with the individual case, but
usually less than four weeks is not sufficient, and rarely are more
than six weeks required. In getting up, the patient should begin by
sitting up one or two hours a day, increasing daily, but not too
rapidly, the time of being out of bed and the amount of exertion made.
The electrical treatment should be gradually intermitted: in many
cases massage twice a week seems to be of service even after the
patient is about. In the going back to ordinary daily life great care
is to be exercised to proportion the amount of exertion to the
newly-obtained strength, so as not to lose what has been gained. In
cases of natural or of long-standing acquired {362} severe
neurasthenia the mode of life must be arranged to correspond with the
small daily product of nervous energy.
In dismissing this subject I desire to caution against a routine
employment of this so-called rest-cure, which might readily degenerate
into a species of quackery; and, again, to call attention to the
widespread value of the principles which underlie it, and the
importance of the physician applying those principles with endless
modifications of detail.
{363}
SLEEP, AND ITS DISORDERS.
BY HENRY M. LYMAN, A.M., M.D.
The regularly-recurring incidence of natural sleep forms one of the
most important subjects of physiological investigation. Occurring
ordinarily at stated intervals connected with the diurnal revolution
of the earth, it may for a time be postponed by an effort of the will,
but an imperious necessity for repose finally overcomes all
opposition, and the most untoward circumstances cannot then prevent
the access of unconsciousness. Thus produced, the relation of cause
and effect between weariness and sleep becomes very apparent. The
refreshing influence of such repose points clearly to the restorative
character of the physical processes that continue despite the
suspension of consciousness; it also renders evident the final cause
of that periodical interruption of activity which the brain
experiences in common with every other living structure.
Careful observation of the manner in which sleep invades the body
indicates that its evolution is not associated with a simultaneous
suspension of every mode of nervous function. The sense of sight is
the first to yield. The eyelids close and the muscles that support the
head give way. The body seeks a recumbent position; quiet and
seclusion are instinctively sought. The purely intellectual faculties
are not yet depressed, and the reflex energies of the spinal cord are
exalted. Soon, however, the other senses fail; hearing persists the
longest of all. Released from the control of external impressions, the
internal senses preserve their functions after a strangely-disordered
fashion, dependent upon the progressive suspension of activity in the
various cerebral organs. First the power of volition ceases; then the
logical association of ideas comes to an end. Presently the reasoning
faculties disappear, and judgment is suspended. We thus become no
longer capable of surprise or astonishment at the vagaries of memory
and imagination, the only mental faculties that remain in action. To
their unrestrained function we owe the presentation in consciousness
of the disorderly picture which we call a dream. During the early
stages of this somnolent state we often remark the fact of dreaming,
and an effort at attention may produce a partial awakening; but
usually the subsidence of cerebral function is progressive and rapid.
The fire of imagination fades; the field of consciousness becomes less
and less vividly illuminated; the entire nervous apparatus yields to
the advancing tide; and, finally, the dominion of sleep is fully
confirmed.
{364} During the act of awaking the order of sequences is reversed.
From the end of the first hour of repose the depth of sleep, at first
rapidly, then more gradually, diminishes.[1] Dreams disturb its quiet,
mental activity increases, the power of volition revives; once more
the individual is awake.
[Footnote 1: Kohlschütter, _Messungen der Festigkeit des Schlafes_,
Dissert., Leipzig, 1862, and _Zeitschr. f. Rat. Med._, 1863.]
Sleep, then, is that condition of physiological repose in which the
molecular movements of the brain are no longer fully and clearly
projected upon the field of consciousness. This condition is normal,
and must, consequently, be differentiated from all pathological states
which produce its counterfeit by the more or less complete abolition
of consciousness. This distinction becomes the more necessary because
the presence of the common factor, unconsciousness, in the result has
frequently led to the mistake of supposing a community of antecedents
in the changes by which the passage from sensibility and consciousness
to insensibility and unconsciousness is effected. It needs no argument
to show that the insensibility of artificial anæsthesia is a very
different thing from the unconscious condition which obtains during
natural sleep. Between the stupor of intoxication and the healthful
restoration of cerebral energy which accompanies genuine sleep there
can be no rational comparison. It is therefore in the phenomena of
syncope that the likeness of sleep has usually been sought. The
well-known fact that a copious hemorrhage can speedily develop a
condition of muscular relaxation, insensibility, and unconsciousness
has led certain observers to the belief that natural sleep is, after
all, only a species of physiological syncope. The antecedent
conditions of syncope are so different from the prodromata of sleep
that it is difficult to see how either state can be properly likened
to the other. The bloodless condition of the brain which occasions
syncope is always the result of pathological or accidental causes, and
is not identical with the comparatively insignificant reduction of
blood-pressure which may be observed in the brain of the healthful
sleeper. It is, moreover, worthy of note that sleep is the normal
condition of the unborn child, despite the fact that the growing brain
receives a richer supply of oxygenated blood than the trunk and the
lower limbs—a state of the circulation quite unlike that of syncope.
Fully impressed by the force of such considerations, certain
physiologists[2] have reasoned from the analogies suggested by the
results of muscular fatigue, and have imagined an hypothesis
accounting for the occurrence of sleep by a supposed loading of the
cerebral tissues with the acid products of their own disassimilation
during wakeful activity. The acid reaction of the brain and of the
nerves after exertion suggested the probability that an excessive
presence of lactic acid and its sodic compounds might be the real
cause of cerebral torpor and sleep. Could the hypothesis be proved,
ordinary sleep would take its place in the anæsthetic category and
sodic lactate should be the very best of hypnotic agents.
Unfortunately for this doctrine, the administration of the lactates
has yielded only the most contradictory and unsatisfactory results.
It, {365} moreover, furnishes no explanation of intra-uterine sleep
nor of the invincible stupefaction produced by cold.
[Footnote 2: Obersteiner, “Zur Theorie des Schlafes,” _Zeitschr. f.
Psych._, xxix.; Preyer, “Ueber die Ursachen des Schlafes,” _Vortrag.
Stuttgart_, bei Enke, 1877; and _Centralbl. f. d. Med. Wiss._, 1875,
S. 577.]
Far more comprehensive is the hypothesis of Pflüger.[3] According to
this view, the cortical tissues of the brain are recruited by the
assimilation of nutrient substances derived from the blood. By this
process oxygen is stored up in chemical combination, forming explosive
compounds whose precise composition is not fully understood. Under the
influence of the various nervous stimulations that reach the brain
these unstable compounds break up into simple forms. The motion thus
liberated by these explosions is, in some way at present utterly
unintelligible to us, projected into the field of consciousness where
the mind dwells, and we are thus brought into conscious relation with
the external world. That the capacity for thus signalling across the
gulf which separates matter from mind is the result of a certain
perfection and complexity of material structure is rendered probable
by the utter failure of the infracortical organs of man to impress the
conscious intelligence by any amount of independent activity. It is
also indicated by the unconscious sleep of the rudimentary fœtal brain
and by the brevity of the intervals of wakefulness which mark the life
of the new-born babe. That this capacity is dependent upon the
mobility of the atoms of the brain is shown by the speedy cessation of
intelligence which follows great reduction of temperature, as in
hibernation or during exposure to severe frost. That its exercise is
largely dependent upon the activity of the senses is proved by the
effects of interference with their function. A recent observation,
recorded by Strümpell,[4] is very significant in this connection: A
young man had lost all power of sensation excepting through the right
eye and the left ear. A bandage over the eye and a plug in the ear
arrested all communication between his brain and the external world.
Thus imprisoned within himself, he gave utterance to an expression of
surprise, and sought in vain, by clapping his hands, to arouse the
sense of hearing. At the end of two or three minutes these efforts
ceased; respiration and pulsation were deepened and retarded, and
removal of the bandage exhibited the patient with his eyes closed in
genuine sleep.
[Footnote 3: “Theorie des Schlafes,” _Arch. f. d. Ges. Physiol._, x.
468.]
[Footnote 4: “Beobachtungen ueber ausgebreitete Anästhesien und deren
Folgen,” _Deutsch. Arch. f. klin. Med._, xxii.]
The dependence of the waking state upon the presence and functional
activity of a sufficient quantity of a peculiarly unstable form of
protoplasm in the brain is an hypothesis which presents no great
difficulty of comprehension. But how may we explain the passage from
the vivacity of that waking state into the inactivity of sleep? I have
elsewhere[5] discussed the manner in which artificial sleep is
produced by impregnation of the brain with anæsthetic substances, and
the same general line of argument may be extended to cover the action
of every stupefying agent with which the blood may become overcharged.
Could the hypothesis of Obersteiner and Preyer be accepted, it would
be an easy matter to explain the advent of sleep when it gradually
supervenes; but we cannot thus explain the rapid and intentional
passage from wide-awakefulness into the profoundest sleep, such as
becomes a matter of habitual experience with sailors and with others
who have formed the habit of going at once {366} to sleep at
regularly-recurring periods of time. Certain writers have endeavored
to account for this fact by imagining a special mechanism at the base
of the brain (choroid plexuses of the fourth ventricle, etc.), by
means of which the current of blood through the brain may be
voluntarily diminished, with a consequent arrest of conscious
activity. But, still adhering to the hypothesis of Pflüger, we shall
find a clearer explanation of the facts by considering the phenomena
connected with the succession of impressions upon the organs of sense.
It has been ascertained[6] that such impressions must persist for a
certain measurable length of time in order to excite conscious
perception. A sound must be prolonged for at least 0.14″, a ray of
light must agitate the retina for 0.188″–0.2″, ordinary contact with
the surface of the body must continue during 0.13″–0.18″, in order to
produce any knowledge of sound and light and common sensation. For the
simplest act of perception 0.02″–0.04″ are necessary. It is therefore
perfectly reasonable to suppose that when the explosive material of
the brain has been sufficiently reduced in quantity and quality by
prolonged cerebral effort, the impression of sense may no longer
suffice to excite in the cortical substance vibrations of sufficient
length, or following each other in sufficiently rapid succession, to
sustain the conscious state. The cortex of the brain may then be
likened to the surface of a body of water into which bubbles of
soluble gas are introduced from below. When the bubbles are large and
succeed each other rapidly, the surface is maintained in a state of
continual effervescence. But if the size of the bubbles be diminished
or if the solvent capacity of the liquid be increased, its surface
will become almost, if not quite, perfectly tranquil. In some such
way, without any great amount of error, may we picture forth the
molecular changes that determine the advent of sleep.
[Footnote 5: _Artificial Anæsthesia and Anæsthetics_, pp. 15-17.]
[Footnote 6: Carpenter's _Physiology_, 8th ed., p. 852.]
Returning now to the subject of the rapid induction of sleep, we find
that it usually occurs among people who lead an active life in the
open air, like children and laborers, and are perhaps compelled to
endure frequent interruptions of their rest. The sailor who is trained
to sleep and to work in rapidly-successive periods of time—four hours
on deck and four hours below—has virtually become transformed by this
habit into a denizen of a planet where the days and the nights are
each but four hours long. His functions become accommodated to this
condition; his nervous organs store up in sleep a supply of protoplasm
sufficient only for an active period of four or five hours, so that
when his watch on deck is ended he is in a state as well qualified for
sleep as that of a laborer on shore at the end of a day of twelve or
fifteen hours. Moreover, the majority of those who manifest the
ability thus to fall asleep are individuals whose waking life is
almost entirely sustained by their external perceptions. So soon,
therefore, as such excitants are shut out by closing the eyes and by
securing shelter against the sounds and impressions of the air,
comparatively little remains for the production of ordinary
consciousness, and sleep readily supervenes, especially if the
excitable matter of the brain has been already depleted by active
exertion.
It is well known that a predisposition to sleep may be very quickly
induced by extraordinary expenditures of force; witness the effect of
the venereal act and the consequences of an epileptic fit. That
analogous {367} predispositions may indeed be very rapidly developed
by modifications of cerebral circulation is shown by the sudden
reduction of cerebral excitability during the act of fainting. But
this does not prove that cerebral anæmia should be elevated to the
rank of the principal cause of natural sleep. In all such cases the
nervous process is the primary factor and the direct cause of change
in the circulation.[7] The character of these changes has been
admirably illustrated by the observations of Mosso.[8] By the aid of
the plethysmograph this experimenter was enabled to compare the state
of the circulation in the human brain, laid bare by erosion of the
cranial bones, with the movement of the blood in other portions of the
body. The occurrence of sleep caused a diminution in the number of
respirations and a fall of six or eight beats in the pulse. The volume
of the brain and its temperature were at the same time slightly
reduced through the diversion of a portion of the blood-current to
other regions of the body. If during sleep a ray of light was allowed
to fall upon the eyelids, or if any organ of sense was moderately
excited without waking the patient, his respiration was at once
accelerated, the heart began to beat more frequently, and the blood
flowed more copiously into the brain. Similar incidents accompanied
the act of dreaming. The renewal of complete consciousness was
followed by an immediate increase in the activity of the intracranial
circulation.
[Footnote 7: W. T. Belfield, “Ueber depressorische Reflexe erzeugt
durch Schleimhautreizung,” _Du-Bois Reymond's Archiv_, 1882, p. 298.]
[Footnote 8: _Ueber den Kreislauf des Blutes im menschlichen Gehirn_,
Leipzig, 1881.]
In all these variations it is worthy of note that the nervous
impression was the primary event. The changes of blood-pressure and
circulation were invariably secondary to the excitement of
nerve-tissue. Sleep, therefore, is the cause, rather than the
consequence, of the so-called cerebral anæmia which obtains in the
substance of the brain during repose. This condition of anæmia is
nothing more than the relatively lower state of circulation which may
be discovered in every organ of the body during periods of inactivity.
Every impression upon the sensory structures of the brain occasions a
corresponding liberation of motion in those structures. The movement
thus initiated arouses the vaso-dilator nerves of the cerebral vessels
and excites the vaso-constrictor nerves of all other portions of the
vascular apparatus. Hence the superior vascularity of the brain so
long as the organs of sense are fresh and receptive; hence the
diminishing vascularity of the brain as its tissues become exhausted
and unexcitable; hence the unequal and variable vascularity of
different departments of the brain as sleep becomes more or less
profound. These modifications of the brain and of its circulation are
well illustrated by the effects of a moderate degree of cold applied
to the cutaneous nerves of the body, as not infrequently happens when
the night air grows cool toward morning. Such moderate refrigeration
of the skin excites its sensitive nerves, which transmit their
irritation to the brain. The excitement of this organ causes
dilatation of its vessels, with increased irritability of the cortex,
vigorous projection into the field of consciousness, and the
consequent occurrence of dreams denoting imperfect slumber or even
complete awakening. The remedy consists in the application of gentle
heat to the surface of the body. By this means the transmission of
peripheral irritation is checked; the brain becomes tranquil; sleep
{368} supervenes. A similar wakefulness is in like manner produced by
unusual heat. The remedy here consists in the employment of measures
calculated to reduce the temperature of the skin to the normal degree.
Sometimes wakefulness is maintained by some less general irritant. The
feet alone may be cold, either because of previous refrigeration or
because of local hyperæmia occurring elsewhere in an anæmic subject.
There, again, equalization of the circulation—that is, the removal of
cerebro-spinal irritation—may be all-sufficient to procure sleep.
Noteworthy also is the tranquillizing effect of foot-baths or of the
wet sheet in many cases of cerebral excitement and wakefulness. In
like manner, that form of sleeplessness which often follows intense
mental activity may generally be obviated by a light supper just
before going to bed. Activity of the stomach is thus substituted for
activity of the brain, and the consequent diversion of blood is
sufficient to reduce the production of excitable matter in the brain
to a point that permits the occurrence of sleep. A morbid exaggeration
of this process is sometimes witnessed in the soperose condition that
accompanies digestion in patients whose blood has been reduced by
hemorrhage or by disease. In such cases the nutrition of the brain
proceeds at so slow and imperfect a rate that any considerable
diversion of blood toward other organs produces a syncopal slumber
which resembles normal sleep only by the fact of unconsciousness. If,
however, food be taken in excessive quantity or of irritable quality,
the consequent indigestion will produce nervous excitement, reaching
perhaps to the brain, and preventing sleep.
Dreams.
The most interesting question regarding sleep concerns the condition
of the mind during repose. We know that while the body is awake the
mind is always active: does this activity entirely cease during the
period of sleep? The phenomena of certain varieties of trance indicate
that the mere semblance of death is not incompatible with great mental
activity. In like manner, the phenomena of dreams serve to prove that
various intellectual processes, such as memory, imagination,
attention, emotion, and even volition, may still be exercised while
every external avenue of special sense is closed by sleep. The result
of the exercise of mental activity under such conditions constitutes a
dream. The fact that observers who have made trial in their own
persons have always found themselves engaged with the details of a
dream when suddenly awakened from deep sleep has been supposed to
afford valuable proof of the proposition that the mind is never wholly
inactive during the deepest sleep. To say nothing of the significance
of certain somnambulic states (double consciousness), in which
intelligence evidently exists for a long period of time without
leaving any subsequent trace in memory, the mere fact that we remember
very few of the events that occupy the mind in dreams cannot be urged
against the doctrine of continuous mental action, for we remember very
few of the images and ideas that have stirred the depths of
consciousness during the waking state. Our recollection of dreams is
exceedingly variable. Sometimes we retain in memory all the events of
a long and complicated vision, but usually, though entranced by the
vivid {369} beauty of the spectacle that unrolls its splendor before
the eye of the mind in sleep, and though the intensity of its seeming
action may be sufficient to awaken the dreamer, who recalls each
incident as he reviews the picture during the first waking moments,
the impression soon fades, and the coming day finds him incapable of
reproducing a single scene from the nocturnal drama.