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Chambers, Ephraim, 1680 (ca.)-1740 / Cyclopædia, or, An universal dictionary of arts and sciences : containing the definitions of the terms, and accounts of the things signify'd thereby, in the several arts, both liberal and mechanical, and the several sciences, human and divine : the figures, kinds, properties, productions, preparations, and uses, of things natural and artificial : the rise, progress, and state of things ecclesiastical, civil, military, and commercial : with the several systems, sects, opinions, &c : among philosophers, divines, mathematicians, physicians, antiquaries, criticks, &c : the whole intended as a course of antient and modern learning

Healfang - hemp,   pp. 218-237 PDF (18.9 MB)

Page 219

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Sir Ifaac Newton carries the Thing foniewbhat farther,
*a1 fuppofes Hearing, like Seeing, to be perform'd, not
immediately by the Vibrations of the Air, but by thofe of
1$me other more fubtle Medium, excited in the auditory
Nerves by the Tremors of the Air, and propagated thro'
the folid Capillatnents of the Nerve to the Place of Senfa-
tion. See MEDIUM, VIsION, &c.
The curious Strudure of the Labyrinth, and Cochlea,
tend to make the weakefl Sounds audible; for the whole
Organ of Hearing being included in a fmall Space, had
the auditory Nerve run in a firait Line, the Impreffion
would only have been made on a very fmall Part of it;
and the Strength of the Impreffion being, Ceteris paribus,
always as the Number of Parts upon which the Impreffion
is nade, Sounds which are now low, could not have been
heard at all. - If the auditory Nerve had, like the Re-
tina, been expanded into a large Web, which had covered
or lined Come wide Cavity, the Impreffion of Sounds even
in this Cafe had been much weaker, than they are now
For this large Cavity had given' Room for the Sounds to
dilate; and all Sounds grow weaker, as they dilate.
Both of thefe Inconveniencies are prevented by the pre-
rent Strudure of the Labyrinth and Cochlea, whofe Canals,
by their winding, contain large Portions of the auditory
Nerve, upon every Point of which the fmallell Sound be-
ing at once impreffed becomes audible; and by their Nar-
rownefs; the Sounds are hindred from dilating: And the
ImprefiTons made upon the Nerves by the firfI Dilatations
are always the firongeff.
The Strength of the Impreffion in narrow Canals, is
likewife increafed on Account of the Elaflicity of the
Sides of the bony Canal; which receiving the firfi and
firongefi Impulfes of the Air, do reverberate them  more
firongly upon the auditory Nerve.
It may be obferved, that tho' Air be the ufual Matter
of Sounds; fo that a Bell rung in Vacuo is not heard
at all: Yet will mofe other Bodies, properly difpofed,
do the like Office; only fome more faintly than others.
Thus may a Sound be heard thro' Water, or even thro'
Earth; of which we have various Inflances. See SOUND.
Add, that tho' the Ear be the ordinary Organ     of
Hearing; yet IHagerup, a Danij'h Phyfician, maintains,
that one may hear with the Teeth. - Thus, if one End
of a Knife, or the like, be applied on a Harpfichol, and
the other held between the Teeth ; the Mufic thereof will
be plainly heard, tho' the Ears be ever fo clofely flopp'd.
_  But this, perhaps, may as well be referr'd to the Senfe
of Feeling. ,See FEELING.
Such as Want the Senfe of Hearing are faid to be Mate
or Deaf. See DEAFNESS.
''4The Senfe of Hearing, fays Cicero, is always open;
' for this we have Need of even when afleep.     The
Paffage to it is full of Turns, and Meanders;   that
nothing hurtful may enter or find its Way in.  If any
' little Vermine does endeavour to pahs; it mult flick and
be bemired in the Ceruzmen, or Ear-Wax, laid for that
' Purpofe near the Entrance.' De Nat. Deor. L. a Cap. 5 7.
HEARING, is particularly ufed in Civil and Judicial
Concerns, for a Caufe, being brought before the Judge and
jury, and the Parties being heard as to the Merits thereof;
Such a Caufe was kept off eight Months, e're it was
brought to a Hearing. - We are to have our Hearing the
laft Day of the Term. See ISSUE.
The Hearing of Embaffadors at the Courts of Princes
is ufually call'd Audience. See AUDIENCE and EM-
HEARSE, among Hunters, an Hind in the fecond Year
of her Age. See HU N T I N G.
HEART, Cor, in Anatomy, a mufculous Part, in the
animal Body, fituate in the Thorax; wherein the Veins
all terminate, and from which all the Arteries arife; and
which, by its alternate Contration and Dilatation, is the
chief Infirument of the Circulation of the Blood, and the
Principle of vital Aaion.  See ARTERY, VEIN, BLOOD,
This noble Part is included in a Capfula, or Pouch,
call'd the Pericardium  whofe Struaure and Office will
be explain'd under the Article PERICARDIUM.
The Figure of the Heart is a Cone, or Pyramid re-
vered * the upper, and broader Part whereof, is called the
w~arts* and the lower, the Cone, Apex, or Point; which is
turn'd a little towards the left Side.
Its Magnitude is indeterminate, and different in feveral
$ubjeffs, according to their refpeaive Dimenfions. - Its
ordinary Length is about fix Inches, its Breadth at the
Bafis four or five; and the whole Circumference fourteen.
Its Place is in the middle of the !rboraxv between the
two Lobet of the Lungs ; and it is faflen'd to the Aedia-
flinumv and Rericardium, and fupported by the great
91 f] lEA
Blood-Veffels, to which alone it is immediately connee 3
being, for the Conveniency of its Motion, difengaged from
any other Impediments. - It is cover'd with a thin Meni-
brane, which, about the Bafis, is guarded with fat 3 and
which is no other than the common Membrane of the
Mufcles. See MEMBRANE.
It has two great Cavities, call'd Ventricles, fomewhat
unequal; the right being larger, capable of containing
between two and three Ounces of Blood. - They are di-
vided by a flefhy Partition, confifing of the fame mufcular
Fibres with the Parietes themselves, and called the Sept,~M
the Figure whereof is Concave towards the left Ventricle,
and Convex towards the right. - There is no immediate
Communication between the Ventricles; but for the Blood
to pafs out of one into the other, it muld fetch a round
thro' the Lungs. See SEPTUM, &CI
The Parietes, or Sides of thefe Ventricles, are of a
Thicknefs and Strength very unequal; the left much
exceeding the right, becaufe of its Office, which is to
force the Blood thro' all the Parts of the Body; whereas
the right drives it through the Lungs only, and is therein
greatl affifled by other Parts. -The right Ventricle; in,
Effec, feems only intended with a View to the Lungs ;
whence, in fuch Animals as have no Lungs, we only find
one Ventricle, which is the left. See LUNGS.
In the Ventricles are little Mufcles, called Columnme
Carnee, or Lacertuli, derived from the 'Parieties, and
connecaed, by tendinous Extremities, to the Valves of the
Heart hereafter mention'd. See COLUMNA.
The Ventricles are capped each with an Auriclej or
little Mufcle, confifing, like the Ventricles themselves, of a
double Order of flefhy Fibres. See AURICLE.
The Veffels, either arifing from, or terminating in the
Heart, and its Auricles are two Arteries, viz. the Aorta,
and the Pulmonary Artery, which have their Origin from
the two Ventricles, viz. the Aorta from the left, and the
Palmonary from the right: And two Veins, which ter-
minate in the Auricles, v2iz. the Cava Vein in the right;
and 'Pulmonary Vein in the~igl See AORTA, CAVA* l
At the refpeaive Orifices of thefe Vefels are placed
Valves. See VALVE.
Particularly, at the Orifice of the Arteries, within each of
them, are three femi-lunar Valves, or Membranes, of a femi-
lunar Figure, which clofe the Orifice of the Artery, and hinder
the Relapfe of the Blood into the Heart at the Time of
its Dilatation. - At the Mouth of the right Ventricle, juft
at its Junaure with the Auricle, are three others call'd
7-ricIfides, from  their three Points being falen'ad by
tendinous Fibres to the C'olumne Carne6'; fo that upon
the Contraaion, or Syflole of the Heart, they clofe the
Orifice, and hinder the Blood from recurring into the great
Vein. - The fame Office do the two Mitral Valves, at
the Exit of the left Ventricle, flopping the Return of the
Blood into the Pulmonary Vein. See SEMi-Lpnar, Tki-
The Subilance of the Heart is entirely flefhy, or muf-
culous. - The Antients, indeed, generally took it for a
Parenchyma; but Hippocrates had a jufler Sentiment;
and after him Steno and the Modern<, have evidently found
it to confift of a continued Series of proper mufculous Fibresk
varioufly contorted, or wound up, and ending at the Orifices
of the refpeaive Ventricles, where they form their Tendons;
In di{eaing the Heart, after taking off the proper
Membrane, there appear, on the outer Surface of the right
Ventricles, fome flender firait Fibres tending to and end-
ing in the Bafis. -  Immediately under thefe is a double
Order of fpiral Fibres, the exterior whereof afcend ob-
liquely from the Septum to the Bafis, and form  a Sort
of Helix, or Cochlea :  The interior take a contrary
Courfe; winding obliquely from the right Side towards the
left, fo as to encompass both Ventricles, and ending in
the Bafis on the left Side, form likewife an Helix of an
inverfe Order. - Under thefe appear the Fibres of the
left Ventricle; and firfi, a fpiral Series running to the lefts
under which, as in the other Ventricle, lie another Ordei
running the contrary Way, which not only extend to the
outward Paries, but encompaffing the whole Ventricle;
make the Septum more immediately appertain to, and be
a Part of, the left Ventricle. Stme of them, inflead of
terminating, as the repf do, in the"Tendons of the Heart,
run inwards, and form the Columne Carneee; while othersi
reaching down to the Cone, are wound about it, and
form the Circle called the Centre of the Heart. See
The Fibres of the Heart appear to be the fame with fhorle
of the other Mufcles; whence the Part now =enerally papes
for a real Mufcle; tho' fome think the Interece not over
jull, inafmuch as the Aorta has the fame Claim to be
reputed a Ma4ple. See MXVscr and AORTA,

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