HEA
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HEA
it does now, the Blood never could at firft be put in Mo- the inverfe Method of Fluxions tr Force ,
twnby the Heart. If the Blood conftantly moved forwards, ,„ 7; ' he Venta
with the Motion firft communicated to it; and did the ls fmnA = — X f + + /. But fince z = t; sx=c Coats of the Veffels make no Refinance; the poflerior Blood would not be retarded by the anterior, and the Force of the Blood would equal the intire Force of the Mover. But beeaufe of the Refinance made by the Coats After the like Manner the Force of the right Ventricle, ot the Blood- Veffels, and the Force which is fpenr in di- (noting the fame Things by Greek Letters, which in the tending them, the Blood is continually retarded in its
s
And hence, the Force of the Ventricle =
. + /.
Motion as it circulates, and would in a' fhort Time flop, were not the Motion loll made up again by a frefh Impulfe from the Heart; and therefore the Force of the Heart mult be equal to the Refinances the Blood meets with in its Motion : If it were more, the Velocity of the Blood would be continually increafing; if lefs, it would continually decreafe; and at lad flop : And hence it is evident, that ii the Circulation of the Blood was once flopped, all the Force of the Heart could never fet it moving again.
Thus much for Dr. KeiU's Syftem : — Dr. Jurin char- ges even -this with its Defects; and particularly in that it fuppofes the Weight, whereby the Motion of Water 1
left
are denoted by Italic ones) is found = -? — \.
-\- - — |- A- So that the whole Force of the Heart is
4,1
t s
— + — + " + I + *• S. E.J.
If now we fuppofe f == 8 Ounces, and t to 4 Ounces,
avoird; S = 10 Square Inches, and 2 = to as much;
/ = 2, and \==ij Inches 5 ^ === a Ounces, avoird 5
i== 0,4185 Square Inches, <s =0,583; and t = o 1" :
a The Forces of the Ventricles will be equal to the Weights
out at a Veflcl may be generated, to ,be what generates that underwritten, viz.
Motion : Which, this lafl Author takes for a Mifapprehen- /ion of Sir Jfaac Newton's Corollary; urging, that the Water falling by the Power of Gravity, acquires its Mo- tion of it felt"; and that the Weight falling the fame Time, only receives a Motion equal to that of the Water out of the Vcffel. — There are lbme other Points which he ob- jects againft; and of which the learned Author, has an ex- prefs Vindication in the 'Pbilofofh. TranfaSions; to which nis Antagonist has fince reply'd : But the Author dying in the mean Time prevented any Reioynder.
Dr. Jurin, however, proceeds to give another Compu- tarion, on more unexceptionable Principles; tho' his Advcr- fary has found occafion therein for Recrimination.
He confiders one of the Ventricles of the Heart impelling the Blood, as a given Body impelling another at Rett,
Lib. Oz.
Of the left Ventricle,. — • ■ — ■ 9 — 1
Of the right Ventricle, — . . — . 6 • — 5
Force of the •whole Heart,' ■ — 15 — 4
Which Weights have a Velocity, wherewith they wou'd move an Inch each Second of a Minute.
Cor. Hence it is inferr'd, that when the Pulfe is quicker than ordinary, either the Refiftance is lefs than ordinary, or the Force of the Heart is increas'd, or a lefs Quantity of Blood than ufual is expell'd at each Contraction of the Heart; and vice verfa. — ■ As alfo, that if the Refiftance be either increas'd or diminifh'd; either the Pulfe, or the Quantity of Blood expell'd at each Contraction, will be either increas'd or diminifh'd refpectively, — ■ And that if
with a given Velocity; and after communicating Part of the Force of the Heart be increas'd or diminifh'd, either
its Motion thereto, proceeding with the fame"common Velocity. On which Principle rhe Force of the Heart will either be equal to the Factum of the Weight of the Ven- tricle, and its initial Velocity ere it impels the Blood; or to the Sum of the Motions of the Ventricle and the Blood flowing out of the fame, and the Motion commu- nicated to the Coats of the Arteries and the antecedent Blood.
Now, it is demonflrable : 1°. That the Motion whereby a hollow Machine, unequally contractile, does act in Con- traction, is equal to the Sum of the Faflums of the feveral Particles of the Machine multiplied into their refpective Velocities. Whence it follows, that the Motion of the
the Pulfe muft be accelerated, or the Refiftance diminifh'd. See Pulse.
On thefc Principles, Dr. Jurin proceeds to demonftrate the three following Theorems.
i". That the whole Motion of Refiftance made to the Blood, iffuing out of the Heart in the Syftole, or the whole Motion communicated to the antecedent Blood and the Coats of the Arteries, is equal to the whole Force of the Heart, quara froxime.
2°' That the Motion communicated to the antecedent Blood in a Syflole, is to the Motion communicated to the Coats of the Arteries, as the Time of the Syftole is to the Time of Diaftoie. Whence if, with Dr. Keill, we fuppofe
Machine is equal to the Factum of its Weight into fome the Syftole perform'd in one third of the Interval between
mean Velocity between the Particles moved fwifteft, and thofe moved ffoweft. — 2°. That if the Water be exprefs'd out of the Qrifice of fuch a Machine, the Motion of the Water, burfting out of the fame, will be equal to the Sum of the Facta of any tranfverfe Sections' of all the Threads of Water, feverally multiplied into their refpective Lengths and Velocities : Whence it follows, that the Motion of the Water is equal to the Factum of the Water iifuing out at
two Pulfes, the Motion communicated to the antecedent Blood will be I of the whole Motion of the Heart 5 and that communicated to the Arteries f .
3 . In different Animals, the Force of the Heart is in a Ratio compounded of the Quadruple Ratio of the Dia- meter of any homologous Veflel, and the inverfe Ratio of the Time wherein the Heart is contracted; or a Ratio compounded' of the Ratio of the Weight either of the the Orifice into fome mean Length between that of the Heart, or the whole Animal; the fubtriplicate Ratio of longeft Thread and the ftiorteft. Hence, alio, if there be the fame Weight, and the reciprocal Ratio of the Time.
feveral fuch Machines full of Water, and contracted alike, whether equally or unequally, the Motion of the Water, burfting out at the Orifice of one of them, will be in a
Hzh-RT-ftum, a Difeafe, among Phyftcians ufually call'd Cardialgia. See Cardulgia.
The Teftaceous Powders, as Oyfter-Shells, Crabs-Eyes, ISo.
Ratio compounded of the Quadruple Ratio of any homo- are the ufual Remedies. See Testaceous.
logous Diameter of the Machine, and the reciprocal Ratio of the Time wherein the Contraction is effected.
From thefe Data is drawn a Solution of the Problem, 'To find the Force of the Heart? — For, calling the Weight of the left Ventricle, or the Quantity of Blood equal to the fame, f; the inner Surface of the Ventricle, S; the mean length of the Filaments, or Threads of Blood expell'd from the fame, I; a Section of the Aorta, S; the Quantity of Blood, ccntain'd in the left Ventricle, q; the Time wherein the Blood would be thrown out of the
Heart of a Tree, the middle Part thereof, taken longitudinally, is called fo. See Tree and Timber.
Heart, in the Manage. — ■ A Horfe that works in the Manage, with Conftraint and Irrefolution, and can't be brought to confent to it, is faid to be a Horfe of two Hearts.
HEARTH, Focus. See Fire, Chimney, ($c.
HB.&-B.ru-Money. See Chimnev-^/cik^v.
lizbR'tH-Stoues. See FiRE-Jroae.
HEAT, Calor, one of the primary Qualities of Bodies 5
Heart, were the Refiftance of the Arteries and antecedent oppofed to Cold. See Quality and Cold Blood removed, t; the variable Velocity, wherewith the Blood would flow thro' the Aorta, if the Refiftance were taken away, v; the variable Length of the Aorta, pafs'd
over by the Blood, x; and the Time wherein the length x is run, z. — • The mean variable Velocity of the Blood contiguous to the Ventricle, or the mean Velocity of the
Ventricle it felf will be = —; the Motion of the Ven- tricle, = f X — j the Motion of the Blood iffuing out, = stx l-\- x; 'and their Sum, or the Force of the Ventricle, = sv x 4 + I + *. But, v = — • whence, by
Or, Heat may be defined a Phyfical Being, whofe Prefence is known, and its Degree meafured, by the Expanfion of the Air, or Spirit, in the Thermometer. See Ther- mometer.
Heat is properly a Senfation, excited in us by the Action of Fire : Or it is the Effect of Fire on our Organ of Feeling. Sec Sensation and Fire.
Hence it follows, that what we call Heat, is a parti- cular Idea, or Modification of our own Mind; and not any Thing cxifting in that Form in the Body that occafions it. — Heat is no more in the Fire that burns the Finger, than Pain in the Needle that pricks it. — In Effect, Heat, in the Body that gives it, is only Motion; in the Mind, only a particular Idea, or Difpofition of the Soul. See Idea.
Heat,
