DOI Seite / Zitierlink:
https://doi.org/10.11588/diglit.4812#0016
6 OBSERVATIONS ON THE
contains the same quantity of blood, and, of course, that the arteries with-
in the head are immoveable, like metalline tubes, or want pulsation, or are
unsusceptible of inssammation. For, whilst the heart is performing its sy-
stole, the arteries here, as elsewhere, may be dilating, and, in the mean
time, a quantity of blood, equal to that which is dilating them, is passing
out of the head by the veins.
During the succeeding period of diastole of the heart and systole of the
arteries, the quantity which dilated the arteries of the brain paries into the
corresponding veins and sinuses ; at the same time, as much passes from the
smuses out of the head, as enters into the head from the contracting trunks
of the arteries situated between the heart and the head.
SECT. VI.
Neither does it follow, from nearly the same quantity of blood being at
all times contained within the head, that opening the arteries or veins on
the outride of the head, or in the limbs, can be of no service in the cure of
inflammation, apoplexy, and other diseases of the brain. For, although we
cannot, by arteriotomy or venesecTiion, lessen much the quantity of the blood
within the cranium, we can diminish the force with which it is impelled into it.
The great effecl: of this circumstance needs no other proof than that, in
cases of faintness, brought on by inanition, we are relieved by the horizon-
tal posture, and, in cases of plethora, or of inssammation of the brain, we
are oppressed by that posture. Nay, the less compressible we suppose the
substance of the brain to be, the more readily we understand how the whole
of it may be affected by a plethora, or increased momentum of the blood;
or a particular part of it injured by an inssammation, or by an extravasation
of the blood, or by any other cause of pressure upon its substance.
SEC T. VII.
In phrenitis, apoplexy, and other diseases, it- has been proposed to per-
form the operation of the trepan, in order that the external air admitted
might, by its pressure, lessen the diameter of the vessels. .
But,
contains the same quantity of blood, and, of course, that the arteries with-
in the head are immoveable, like metalline tubes, or want pulsation, or are
unsusceptible of inssammation. For, whilst the heart is performing its sy-
stole, the arteries here, as elsewhere, may be dilating, and, in the mean
time, a quantity of blood, equal to that which is dilating them, is passing
out of the head by the veins.
During the succeeding period of diastole of the heart and systole of the
arteries, the quantity which dilated the arteries of the brain paries into the
corresponding veins and sinuses ; at the same time, as much passes from the
smuses out of the head, as enters into the head from the contracting trunks
of the arteries situated between the heart and the head.
SECT. VI.
Neither does it follow, from nearly the same quantity of blood being at
all times contained within the head, that opening the arteries or veins on
the outride of the head, or in the limbs, can be of no service in the cure of
inflammation, apoplexy, and other diseases of the brain. For, although we
cannot, by arteriotomy or venesecTiion, lessen much the quantity of the blood
within the cranium, we can diminish the force with which it is impelled into it.
The great effecl: of this circumstance needs no other proof than that, in
cases of faintness, brought on by inanition, we are relieved by the horizon-
tal posture, and, in cases of plethora, or of inssammation of the brain, we
are oppressed by that posture. Nay, the less compressible we suppose the
substance of the brain to be, the more readily we understand how the whole
of it may be affected by a plethora, or increased momentum of the blood;
or a particular part of it injured by an inssammation, or by an extravasation
of the blood, or by any other cause of pressure upon its substance.
SEC T. VII.
In phrenitis, apoplexy, and other diseases, it- has been proposed to per-
form the operation of the trepan, in order that the external air admitted
might, by its pressure, lessen the diameter of the vessels. .
But,