Year: 1868

the brain are in intimate connection, so
that when the blood-vessels contract during
sleep, the fluid rises into the brain by at
mospheric pressure; when they become
turgid, the fluid is partially expelled from
the brain into the spinal column. If the
base of the skull is fractured, this fluid
does not flow out while the patient is asleep,
but begins to flow again from the orifces
when he awakes. The cerebro spinal fluid
abounds in the brain of idiots, and others
prone to sleep, and is in much smaller
amount in the brain of persons of active in
tellectual habits.


"a For long time sleep was supposed to
be a state Of congestion in the brain, pro-
duced by tureidity of the vessels. This
is incompatible with recent observations
already referred to, which have shown that
there is much less blood in circulation in
the brain during sleep than in the waking
state. The old experiments supposed to
prove congested state of the brain in re-
ality only produced a bloodless condition
Of it. Magendie injected hot water into
the brain and induced sleep. But, in do
ing SO, he necessarily expelled blood, by
introducing another fluid into the closed
undulating cavity of the skull. For the
same reason, sleep eusues when the aorta
of an animal is tied, or when arterial blood
is removed from the body by bleeding, but
not to an extent which produces convul-
sions. The compression of the carotids in
men occasions sleep amounting to stupor
as has been long known"


=" IT," says Dr. Lyon Playfair, whom the
North British Rerie,U quotes, % the brain
suffers changes, as do the other organs OF
the body by their exercise, there is as
much necessity for repose in the action of
the brain as there is for vegetative state
Of existence to reinstate in their full integ-
rity its various parts. Hence the necessity
for that quiescent state Of the mind known
as sleep, when its manifestations cease
The waste of cerebral substance could on
ly have been occasioned by oxygen, which
is the only ultimate cause of waste, as far
as we are aware, in the animal economy.
a deficiency in its supply would, therefore.
retard waste, and allow vitality to remodel
its impaired structures.


Such, then, is the state into which the
body is thrown by the periodical diminution
! in the action Of the heart and lungs The
less rapidly that the heart beats, the less
rapidly can the blood be aerated and the
oxygen-bearing fluid be supplied to the
brain. The slower that the lungs act, the
slower must oxygen enter the system to
supply the diminished circulation. And
as the brain in sleep is not in state in
which it can change, from q deficiency in
the supply Of oxygen, the consequence is,
(if it be admitted that the manifestation of
thought and sensation is accompanied by
changes in the material substance Of the
brain,) that the manifestations Of the mind
are prevented, and it becomes no longer
apparent to the external world. This,
then, is sleep"


All experiments show clearly that any
cause which increases the flow of arterial
blood in the brain produces cerebral excite
ment; while any cause which diminishes
the action of oxygen produces depression,
sleep, or torpor, according to its degree Of
action


The impression of Psychologists ct pres
ent is that night is the chief period for
storing up oxygen in the blood, to be used
during the day in the production of work.
when volition finds it ready at hand TO ex-
ecute the voluntary motions, and to enable
the mind to make its manifestations through
changes in brain matter. The importance,
then, Of sleeping in well-ventilated rooms
cannot be too strongly insisted on. The
workman has to store up his force during
the night, and should take every precaution
to assist nature in fulfilling this important
function