The economy of the animal kingdom, considered anatomically, physically, and philosophically

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right auricle . . . bestis On being touched With a Deodie, audsomelimes talies On a peculiar Vibration; one portion frequentlynot vibrating With the portion contiguous to it, but the vibration somelimes follOWing in another and remoter part n. 467). That the action of the auricle talios place thus divisively and conjunctively, is testi sied by iis partition into Winding portions.

That such a mode os action Ahould exist is moreΟVer neceSSRry, because the auricle ought above ali Other paris to be so mobile, that When it receives a generat excitation to motion Dom the Superior cava, it may receive a particular excitation to motionDom every branch of the inferior cava; a circumstance Whichappears to be the proximate cause Why the inferior cava entersthe auricle Without a threshold, dissering in this Dom the superior cava n. 52 I).527. II. The cause of iis diastole or expansion is theblood soWing in Dom the two venae cavae; into this state theauricle comes When iis proper blood also attempis to floW Domitio fleshy ducis into iis motive fibro, and the bl ood of the superficiat vesseis passes Out through its coronary Orifices.-At One and the fame moment the folloWing actions coincide Witheach Other as corioint causes; namely, the action of the two

cavae Upon the auricle, the action of the blood proper to the auricle, or the blood of the fleshy ducis, upon the motive fibres; and the action os the blood of the coronary vesseis of the auricleupon their orifices. of these actions, that of each cava, and consequently the proximate cause of the diastole, is perpetuat. Now it is Doni the efficient causes that the effect floWS, namely, the influx of tho blood tuto tho auriclo, the influx of the blood om the fleshy ducis into every motive fibre, and the essiux

Om the coronary vesseis of the auricle through their orifices; Whetice arises the diastole proceeding Dom the continuous action

takes place in Such a manuer, that When the influx or tho efflux satis, no effect is produced. 528. III. The efficient cause of iis systole or constriction, is, that the nervous Ossseis On the sursace are eXpauded

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With the sursace itfel -Τhis is sulf-evident, and is the case notonly With the nerves Whicli are collected into fascicles, but also With their tWigs and most minutu omeis, in ordor that the forceos expansion may be distributed and duly proportioned to ali ofthem. There is a traction or draWing of the nerve n. 507. 6.12; 508. 7). The spirituous and nervous fluid thus contained, is propelled by every potnt, and the fibre contracts n. 230, 504, 5I6); and with tho fibre, overy arteriai vesset that constituteS

this the cassi With tho nervous fibres Which enter into the muscular substance, but also With the nervolas fibro of the superficies Vesseis, together With the vesseis themselves n. 426, 50 I), and Whicli, taken collectively, constitute the Whole of the Sur- face. Τhis hoWever is Only the cause of the systole; there isas yet no effeci. 529. IV. But the effect of this cause cannot exist, be- fore there is an abundant influx of the blood of the auriclo into the right ventricte, or else of blood DOm SOme Other SOUrce. -In the meantime, besore the effect exists, the cause is in theessori to aut n. 304). As soon as the blood of the auriclo findsan exit, the reaction and equilibrium, or that Whicli suspendsthe effeci, is removed. An esslux is assorded into the right ventricte, and this gives rise to the systole and constriction of the auricle. We have said there must be an influx into the ventricle of tho blood of the auricle, or else of blood DOm some Othersource. FOr With regard to the lalter, in some subjecis there is an influx through the foramen ovale; there is an influx also Domthe Superior cava, through the medium of the auricle, into the inferior cava, With a vieW to preserve the equation of the bicod

n. 521. 5); helice the auricle may be constricted frequently, While the ventricle is constricted only onoe n. 519). Τhis is

n. 428, 429, 430). In natural action, hoWever, the auricle alternates With the ventricie. 530. V. Consequently this reciprocation resulis Solely, and almo8t Spontaneously, froin the pressuro of the blood of tho Vena CRUR.-BeeRUSe DOm What We have premised, it is evident, Τhat the systole of the auricle is the cause of the diastole, and

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tho diastolo the cause of the systole: that the balance of motion is the sursace, or the superficiat vesseis collectively: and that the perpetuatly acting poWer is the tWO Venae CaVae.

531. That the systole is the cause of the diastole, has beenshewn; sor by the systole the proper blood, Whicli soliciis every motive fibre to receive it, is expressed into the fleshy ducis, n. 410, 412, 427). Τhat the diastole is the cause of the systole,

follows Dom this, that every nervous fibre then becomes expanded, and the expansion is iiself the cause of the constriction n. 528). That the balance of motion is the surtace, Or the Superficiat vesseis collectively, is evident, inasmuch as during the diastole of tho auricle these vesseis are expanded in the

Same manner as the nerves, and their expansion is the cause

case during systole n. 424-427). Whether We say the superficiat vesseis, or the sursace, it amounts to the fame thing, sortite superficiat vesseis are the sursace. But that the perpetuallyacting poWer is the tWo Venae cavae, See n. 514, 516, 527, andali the preceding articles. Henco it is manifest, that in thostructure of the heart there is, as Boerlinave says, a WOnder uland occuli propensi ty to perform reciproces acts of systole and

532. It noW remains sor us to explain, that the auricle expands and compresses iiself in a direction corresponding totho fluxion of the fibros; ot Ouly of the nervous fibres, butalso of the fleshy, and even of the tendinous fibres, ali os whicli, by their direction, determine and shape the Space overwhicli the motion is diffused, or in Other Words, prescribe thelimits of expansion and constriction; for the nervous fibres aut, through the medium of the white motive fibres, upon the fleshys bres, and the fleshy upon the tendinous, in the fame manner RScausus essected aut upon their efficients. From an examinationof the fluxion of the above-mentioned fibres, it is evident, that during diastolo the auricle expands in breadth and longili, and Opens the entrance Dom the superior cava; and that during

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systole, it constricis in breadth aud longili, as Weli as narroWStho inlot Dom the Same CRUR. Τhe auricle expands in euch dimension during diastole: thisis sileWn by the motive fibres themsolves, sor Wo learn by actualexamination, that there is a doubio series of these fibres, WhichsaSs in contrary directions into opposite tendons. When theSesibres are expanded, they relax the parietes in similar directions, that is to say, tengthWiso and breadthWise, ns in the arterieSand Veins ; hence When they are constricted, the reverse is the

rior cava : for the fibres, both nervolas, muscular and tendinous, form a manifest sphincter, or as it Were circular muscie, Whichis expanded, as it WOuid Seem, by sa parto the vena cava; justas me find in the other sphincters of the body, through Whicli,

When operaed, a paSSage is assorded, as in the case of the pharynx, gullet, pylorus, the Orifice of the uterus, rectum, ke. This We may conclude Dom Lancisi's description. In the sirst place, then,'' SVS he, extrem ely minute, and intorted an dagglomeraled fibres, form in this siluation a circular muscle,

not unlike a Sphincter. . . . From this the fibres are continuen

are applied to the superior cava, as to constitute and comprehend within them that uppermost vavit of the vena cava called by us the vestibule, and whicli is the commencement of the right auricle; Whicli auriclo these lacerti beautifully form byprocesses of divarication, multiplication, collection into unequalfascicles, and intermixture With ench other' n. 464, p. 437, 438). But sitico tho definition of the expansion depend8 Solely Uporithe direction of the fibres around the given cavlty lined by them, it follows, that is We Would know the triae form Of expan- Sion, We must first examine the severat layers of fibres, Whicli, considering their great variety, Mould be a tedious underint iug. In generat We may amrm, that res the auricle constricis and the ventricle expands, a sWelling is formed by the pressure of the blood at the confluence of the cavae. Τhis sWelling Lancisi

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llius describes: Every time the whole quadricave muscle of the heari is strained and constricted, the auricles are seen to bedepressed toWard the base, and to descen d; and the ventriolosto bo elevated toWard the base, and to ascen d; so that tho bodyof the hestri, Which be re Was Oblong, becomes Dearly round

subject in the sequet, When I come to speis of the right ventricte, and where the researches of anatomisis vili materially

533. From What we have noW premised on the subject of the right auricie, Wo may learn the nature of the reciprocalmotion os the right ventricte, sor this motion has the Same relation to that of the right auriclo, us that of the right auricle hasto that of the superior cava; and the motive cause of the muscle of the ventricle has also a corresponding relationShip : Where- fore the luWs recitod With respect to the auricle are applicabie also to tho ventricte, for a nervous bolt to the ventricle mari edin the plate 36, 36, 36, 36, runs immediately under the auricle, Dom Whicli bolt the alternate vibration Os the ventricle is externalty deduced as Dom iis stay or ham-string; helice I Wouldhere merely repent the former statemenis, in their applicationto the ventricie. I. That the seld of the action of the ventricio

quently the ventricle is cap te of being moved separalely Domthe auricle, and alternately With it. II. That the cause of iis diastole or expansion is the influx of blood Dom the aurictu. Into this state the ventricle comes, When the blood proper to itatio inpis to soW Dom iis seshy ducis into iis motive fibres, and tho blood of the superficiat vesseis passes Out through theiroriscos into the right auricio and the norta. III. That thoofficient cause of iis systole Or constriction is the expansion os the nervous Osrseis On iis sursace, together With that of the sur- face it self, this expansion taking place in the direction in Whichiis fibros flow. IV. But that the effect of this cause, Or theconstriction, cannot exist be re there is an abundant influx of tho blood of the ventricle into the pulmonary artery, Or elSe Ofblood Dom some Other source. V. Consequently, that iis SyStolo is the cause of its diastolo, and iis diastole the cause of iis systole; that the balance of this motion, is the Sursace Or tho

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Superficiat vesseis collectively; and that the common cauSe Orso Ner perpetuatly acting, is both the blood and tunic of thoright auriclo. VI. That tho action os the right auricle and Ventricle extends to the lest ventriclo, Whicli is aided also by the action of the lest auricle. 534. As there is a similitudo and parallelism belWeen thecauses of the constriction and expansion Of the Ventricles, and

535. The only question Whicli here meriis consideration is, what is the modo os constriction and expansion of the right ventricie ; and What is the connection existing betWeen the motions

of the two ventricles : but this can be brought to light only bynicely separating the layers and planes of muscular fibres. Lot us hoWever investigate the fibres upon the principi e that theyelongate during diastole, and contraci during systole n. 230, 472, 504); sor they are so beautifully combined and giri by vesseis,

that the entiro expansion os the fibre is made to talae a longitudinal, and not at least so evidently a laterat direction. 536. Is then We investigate the motive fibres of the heartupon this principie, We have Only to examine anatomicatly the direction of the fibres, and to deduce the mode os expansionand constriction geometri catly and mechanicatly according to the gi ven direction. For 1, the fibres, longitudinalty extended, during SyStole, contraci or elevate the muscle longitudinalty, and vice versa during diastole. 2. The fibres, obliquety extendeddoWnWard S, contraci the muscle in tho fame oblique directionduring systole, and vice versa, extend it during diastole. The two series of oblique fibres, at Whatever angle they decussate, contraci the muscie lateralty, and elevate it longitudinalty during Systole, and alternately expand and extend it during diastole. 3. The transverse fibres simply contraci during systole, and enlargebreadthWiso during diastole, in the fame manner as circular Sphincters. 4. But the spirat fibres, Whether they proceod in asingle direction, or in a doubie direction, the one opposite tothe other, mahe only a perpetuatly oblique plane during Sy8-

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tole, and contraci the muscie simply, and not With a spirat cou- torsion; While, on the other haud, they in like manner expand itduring diastole . For this spirat form produces a poWer os extensionand constriction easy in iis action and almost u resisting. Thismay be proved even to ocular demonstration, by the litile pipes whicli are carried round the heari spirat ly, and tumisy at one and the fame moment, 301, 302). 5. The tendinous fibres also aut in generat as the muscular sibres aut in particular; hence

Whereuer a more generat action is required, or a Simultaneous

action of the particular si bres, in the place of fleshy We have tendinous fibres, combined and disposed according to their modeos acting; for the forces of the muscular fibres verge tOWardes these te dinous fibres as a centre, in Order that by means of the lalter a common or generat effect may result Dom a multipleand most distinet cauSO. 537. From a caresul evolution os the fibros and fascicles and planes os fibres in the heari, We are led to discover iis modeos expansion and constriction. Thus, I, iis ventricles expand in

broad th aud longili during diastole, and constrict during Systole. But this is uot so manifest in the human heari as in that of brutes, Whoro the heari does not lie upon the diaphragm as in man, sor the human heari has soldom or never a perpendicular layer like tho outer layer in the heart of the Ox, kc., but it has common planes, Whicli extend from the baso, and Doni the divisionos the ventricles OutWardly, and Dom their tendinous orifices inWarilly; and these planes running obliquety in contrary directions, decussate variously, and While they constrict the muscle, stightly elovato it to the angle of their direction. The reverse of this talios place during diastole. There are also spirat fibres, and the oblique si bres that are round the cone, become Spiral, and the more horigontalty they run, or the more parallel to thebase, the more do they narroW the enclosed cavlty in brendth, and the less do they rai se it perpendicularly. There are also transverse fibres Whicli only constrict the fides during systole, and expand them during diastole. This laur-chambered muscle,' says Lancisi, alluding to the heari, is madeand constituted os many rolis of fibres, some almost Straight as seen chiesty in brutes that hang down the head) and transverse, and others, and these the greater number, Spiral, and

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apex on the oulside of the right ventriete only. . .. 2. Undernentii these, in the fame ventricle, arise Other fibres DOm the

right fide, talio a spirat coursu, and terminate in the base. 3. Under the last fibres again, thero are others Whicli run Domthe right fide of the heari to the lest, en compass and embrae both ventricles, and rising to the base of the lest ventricte, forma contrary spirat to the series mentioned buforo n. 461 . Weshali bo bolter ablo to jud ge of this subjeci, is me consuli the various anatomicat plates in Whicli the layers of the heari aresheWn, and particularly the figures in CoWper's Anatomy tab. xxii., fg. 2, 3, 4, yc.). There is then during diastole an expansion Of the ventricles, and during systole a constriction of the ventricles, and this falles place in disserent hearis in a greater orless degree according to the disseretices in the oblique or spirat course of the fibres. 2. There is also a direction of the fibres toWards the apertures of the ventricles; for instance, of thesib res of thu right ventricte toWard 8 the pulmonary artery, and of tho fibres of the lest ventricio toWards the aorta; so that thereare Wedges of fibres that inflect themselves Dom the externalsursace to the internat, Dom Which also fhey again return; theyare aidest moreover by other particular fibres, in order that theconstriction Of each ventricle may be in the direction of the common apertures; and they also inflect them selves Dom the orifices betWeen the auricles and ventricles toWard the surtace, and arethetice reflected. These Jayers of fibres,V says Lancisi, tahea direction more or less inclined to the longitudinat diameter of tho heari; so that s me of them form With it4 an acute angie, Some almost a right angie. But these as it Were bound fibres,do DOt run SO as to pass through the apex tuto the cavities, but

439). 3. In like mannor niso fibres run DOm the auricles OVertho ventricles to the mouilis belWeen the auricius and ventricles,

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on Whicli subjeci Lancisi says : Τhe fibres are drawnJ Domthe externat sursace of the auricles, and of the heads os tho Veius, Obliquely, and as it Were Spiralin through the externalpart of the ventricles, ali the Way to the apex: Whicli fibres, consequently, alWayS enlarged in bulli, make up the thicli cortex

Os the ventricies. . . . Dut When the Spirat fibres reach the apex, they mahe a Single and loose turn Upon them SelVes, and are

carriod inWards, and beautifully constitute the inmost sursaceos the ventricles, and especialty of the lest ventricte, together vitii thoir tricuspid valves n. 464, p. 438, 439 . 4. There arealso layers of particular fibres Whicli are prolonged froin theirown proper and also hom their generat origin, in Order to construct the fleshy columns or particular ventricles, being thenee extended sor the purpose of directing the bl ood into tho fleshyducis. For it is evident enough,V says Lancisi, that the internat paris of the ventricles, aud the tendinous cords of the

liave begian to constitute the right Sinus, for instance, Whenthey have reached the septum, are there tWisted, implicatedand decussaled, not in Order to remain there,V ke. n. 464, p. 439.) This is done, in ordor that When the Ventricies by means of their constriction propel the blood into the large arteries,

ducis, sor they are compressed both in generat and in particularioWard the septum Where the lacunae open Mith their litile ducis. Certain fibres, V says Boerlinave, constringe the entire heari, . . . . ConStringing both Ventricles at Ouce by pressing them against the middie Septum, and draWing up the apex toWarda

then, that there are as many particular directions concurri gwith the one generat direction, as there are inleis and ouileis of the blood, that is to say, as there are orifices, lacunae, fleshy

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cular texture of the heari, and the motion arising theresrom, according to the foregoing rules, must have a distinet Comprehension Os uti the channeis, and the equalty numerous directions of the fibres; otherWise the multiplicii y of their particular Wind-ings Wili cause him to lose his Way, and be to him an inextricabie labyrinth. For the most particular fibres are so subordinaledio, and coordinated With, the more generat, that ali of them

Simultaneoiasty cause a generat motion, like So many partS COmbining to sortii a compotind. What a stupendous Chain Of connection is thus exhibited in the animal economy l Discourse asWe may Upon the subjeci, Stili, after ali, What is suid Will be asilothing in comparison With What remnius unsaid. 538. The cardiac machine is so constructed, that iis alternale molion depensis Uon, and is determined by, the auricles, and particularly the riphi auricle, as it8 wheel and lever; consequently et on, and by, the intumescenoe of this auricle, when the blaod presses, recis, and sow8 in; and upon, and by, iis detumescence, when the nerves are ewtended. It Was SheWn above, that thelieari is not unlike a machine put in motion by a lever, Wheel, pendulum, or Spring, and that On the motion of this alone,

iis appendages 1lo , according to rute, into their respective alternate motions n. 514 . That the diastole is the cause of the systole, and vice versa, and that it is the sursace only thatacis as the balance of the motion sii. 530, 53I). Also that the

provided sor the contained blood; this emux naturalty taking place into the subjacent ventricle n. 529); that hence the ventricle is expanded When the auricle passes into systole, and thatit is thus that the alternation os motion exi sis n. 529, 533). But let us approach stili nearer both to the manuer and effectos the alternation.

539. I say that the right auricle is so constructed, that wheu distended With blood, it opens the orifice luto the right ventricie. And together With the aorta, contributes to iis diastole. Nay more, that it extends iis poWer Os action as saras the lest ventricle; Whicli ventricte must be constricted at thesame moment as the right, but cannot be expanded unless