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

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the lest auricle comes to iis nid. Let us consider these par

540. The right auricle is so constructed, that When distended with blood, it opens the orifice into the right ventricie. The systole of the ventricle is the cause of the diastole sit. 530, 531). But no effect follows the cause unless there be an influx

lo the cause, the auricle, sWollen to the proper marti With thepressure of the blood Of the venae cavae, at the time os expan- Sion Opens the orifice of the ventricie. Because the fimbriated

flects the whole of the portion that is contiguous to the Orifice, and thus by a species of resupination, draWs bach the circulartendou so us to Widen the mouili proportionably to the degree of iis expansion; thus the ventricte, merely On the completionos iis SyStole, possesses an open passage for the influx of theblo d. That suci, is the connexion belWeen the auricle and Ventriete, may in Some meas ure be seen Dom the folloWing by Lancisi: Froni the auricles says he, bundies . . . Offibres are sent . . . both OutWardly and Within the cavities : andit is os theso fibres that the compaci substance of the ventricles . . . iS mnde Us. ΤhUS a multitude of lacerti, partly dividod into fascicles, arise externalty DOm the auricles and heads of the vetiis; and after forming, by their greater mutuat adhesion and

contorsion, the loose round tendons of the heari, communicate und are continuous With the series of fibres that malle up theoxternat sursace of the heart. In like manner more tendinous blandies are continued hom the internat sursaces of the headsof the vetus, and of the auricles, and compose the internat structure both of the tricuspid valves, and of the sursaces of the Ventrietes . . . . But nil these things are so done, that thesibros inosculate by diversified and innumerable advolutions, the externat fibres With the internat, and the internat With theexternat, Seeming to constitute a Gordian knot' n. 464, p. 438).Τhis appears to be the cause of the opening of the orifice ou

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the part of the auricle, although there are a variety os other caUSes On the part of the ventricle; and these are employed notonly in retracting the valves and ope ing the large mouth, butalso in opening the s mulier mouilis that lead Dom the lacunae into the fleshy ducis. But these causes so Operate, that What-Over contributes to a particular effeci, contributes also to the generat effeci, sor particulars constitute the general; as theclari OuS enquirer may see, is While sorming a particular idea ofiat the particular tendotis constructed in the ventricies of the beari, he en deavors to comprehend them also under a generalidea. On this subjeci Lancisi says : These mur tendons, dis- posed in the form os sphincters, and applied to the mouilis of the heari, become converten into four Other tubular and very

long tendoris, Whicli are distributed throughout tho body, and

te dotis constructed With amaging iugenuity; some of them common to the ventricles and their arteries' n. 464, p. 437).54I. Aud together With the aorta, contributes to iis diastole.-The auricle contributes to it not only by the infusion ofblood and the expansion of the orifice n. 540), but also When compressed, by relaxing ali the tendons continued Dom the Vena cava, as Weli RS 1DOm iis caudex, into the mouilis, tricuspid valves, and oulside and inside of the ventricle n. 540) ;thus in proportion as the auricle is constricted, it gives the ventricle room to expand, so that although the lalter has an expan- sive poWer Dom the intrusion of the blood tuto tho fleshy ducis n. 527 , this poWer is nevertheless restrained, and iis effect suspended, in proportion to the constriction of the auricle. Moreover the ventricle is capable of being expanded in the fame proportion in Whicli iis superficiat vesseis are enabled to dis-charge themselves through the coronary orifice of the right

auricle. These vesseis aci RS a balance to the reciproces motions sit. 527, 530, 53I), and are enabled to discliarge them-selves in proportion as the auricle is compressed sti. 428-430 . The vorta also contributes to the diastole of the ventricie. We may here refer the reader to our plate, in Whicli L is the right auricle, Gia the aorta, Ρ the pulmonary arte , 35, 50, nervous branches inserted into the coat of the aorta.

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it follows that the nervolas subcincture 36, 36, 36, is rolled bach by the bordor of the auriclo, resupinated as it is, and giving inWariis, and is ruised by the aorta and pulmonary Rrtery together With the Whole cardiac plexus coming DOm thenorta, When the lalter is expanded. For the plexus is placedi, et Neen the artery and the trachea, and is connecten to it bySeverat branehes. The consequenoe is, that the spirituous suid, and the juice contained in those nervous branches, is expelledioWard tho tWigs and os eis; just as When the arteries are CX-

pandeii, the blood is propelled toWard the peripheries of the

sillod with thoir own fluid and juice, at the fame moment in Whicli they are deprived of it in the systolo, the spirituous fluidis pressed forWard by the simultaneous expansion of each nrtery and auricle, froin the plexus into the branches, to Supply What-ever deficiency may have been occasioned. We here thereseresee the reason of this device os nature; sor instance, that theright auricle and large artery ure placod as it Were ut the tWo extremities, the sanguineous Wave sirst floWing into the auricle, and lastly floWing out at the artery, thus animating With their united forces the whole intermediate machine, With a vieW toenable it to reciprocate iis motions, and to induce it to Observea constant habit os action. 542. The auricle moreover extends iis poWer Os action assar as the lest ventricie.-This appears Dom the prolongation oftho tWigs Doni the nervolas substineture 36, 36, 36, even ConSiderably above the lest ventricle isset so that a continui ty ofaction proeeeds DOm this subcincture, and so froni the right auricle ; hence there is no similar nervolis ring between the lestauricle and iis ventricie. This is sileWn by the experietice of Laticisi. In the vivi section Of λWis, V says he, we saW a vermicular motion in the branches of the cava frequently recurring, selloWed at length by a stoW contraction, or fluctuation, of the ample right auricle and ventricte, although there Was noSpontaneous Stroke or pulse in the lest auricle; and whon thel est ventricte Was laid bach, We could observe no motion in iis posterior Wali; although the segments of the heari moved When

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punctured With a needle ; a sufficient pro0 that the occasionalcause fas they say) of spontaneous tension in the right auricleand Ventricte, consisted in the poWerfui pressure of the blood V n. 465, p. 444, 445). The motion of the auricle coincides Completely With the fluxion os the nerves as represented in the plate, for it reaches to the extremities of the foregoing branches; but there is another nervo with iis branches, marhed by figure 3 in the plate, Whicli fines it up ab ut the posterior part of thelest Ventricte, and whicli comes Dom the lest auriclo: for this

reason it is, that no motion can be detected in the posterior partos the ventricie. There is a similar fluxion of the motive sibres, the generat layers of Whicli extend Dom the bottom of One Ventricle over the other. Thore is also a similar fluxion of the tendinous fibres, Whicli are continued Dom the right auricle to thelest ventricio, and Whicli Lancisi thus describes : These cysis, which have a doubie cavlty separated by a partition, are SODamed, that the Osier tWigs, to pursue the comparison, Whichliave begun to constitute the right sinus for instanee, Whenthey have reached the septum, are there tWissed, implicatedand decussated, not in Order to rem ain there, but to be prO- longed onWards to the opposite fide, and lo Weave and enViron the lest cavlty n. 464, p. 439). Is . . . the tendonS that Rre continuous With the auricles and ventricles, he held up to thelight, their Structure appears like a Web, composed Of VariOUS planes of silaments going oss in different directions. Thus onone Sursace the fibres ruti Dom the right of the auricles to thel est of the ventricles; but oti the other hom the lest of the auricles to the right of the ventricles; While many again passSemicircularly, Or are OtherWise dispersed in various Ways With-OUt Observing any ascertained laW, and suppori and strengthenthe proximate planes Ibid., p. 44I . 543. Τhis test ventricte must be constricted at the Same moment as the right, but cannot be expanded unless the auricle comes to iis aid.-See n. 533, VI., 534. Τhis action of Oneventricle With the other, is in accordance With the connection oseach With the nervous, fleshy, and tendinous fibres of the Other n. 542), as also With that os tho fleshy ducis, and superficiat Vesseis; me find it likesisse accordant With experience. It is in Recordanee With the connection existing betWeen the tWo Willi

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regard to their nervous Abres; for the fame tWigs soWing Domthe Same subcincture, run forWard Over the lest ventricle; Whence the cause of the constriction of the lest ventricle pro- ceeds also froin the expansion of the right ventricle n. 542), to tho aid of whicli the lest auricle comes, When the lalter pourSin iis biood; when the bl ood is not potared in, the ventricte re- maius in a state of constrictio . It is in accordanco With thoconnection belWeen the motive and tendinous flbres of the two,as We learn hom the experience Hready adduced n. 542). Thesesibres pass in common Dom the right sinus over the lest; Where- fore Wheu there is any expansion of the right ventricte, it is notSucceeded by any expansion Os the lest, utiless When the blood soWs in from the lost auricle; but there is only a constriction Ofthis ventricie. It is in accordance also With the connection be-

come Dom the lacu me of the right ventrictu; for there are but

against these, soliciis the fibre to receive it, and instigates it toperform diastole, in Whicli function the expansive poWer of the heari itself consisis, Whicli poWer is thus seen to be no Occultquality. But the fleshy ducis which load toWard the motive fibres of the lest ventriolo, in vain solicit and instigate the ventricle to diastole, When there is no influx of blood hom the lest Ruricle. The cause is indoed perpetuatly acting, but stili it is folloWed by no effect bosore there is an influx of blood into thocavity of the ventricle n. 529). The action is also in aecord-nnce With the connection belWeen the superficial vesseis of the tWO, Whicli cannot equilibrato the bl ood, When there is no blood expelled si om them by expansion, into the storta, or into theright auricle. This We also learn DOm emperience; as that os Fautoni n. 323 , and Harvey n. 544). This is the reasonos What We asserted With respect to the laetus sit. 335 , in Whicli the circulation of the blood is successive, because theright ventricle of the heari can be expanded, but not constricted, besere the lest; so that the systole is simultaneous, butnot the diastole. 544. From these considerations it appears, that the right auricle is like tho Wheel and lever of the whole cardiac machine, or like a crane or axis in peritrochio, and that the other parta

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appended to them, are in a most surprising manner CXCited, each to iis oWn particular motion, by the auricle alone, and that euch ulso involvos iis oWn modo os cooperating: and that theti nil sow to aud fro in the direct ordor of nature, and by Rregular necessity, and this in suci, Wise, that is the auricle stops, the entire heari censes to aut: henoe the auriclo is so connected With iis ventricles, that When the latier a re unable to reciprocatetheir motions, in consequence of any impediment to the en trance of the blood into the arteries, the auricle ean neVeriheleSSVibrate three, four, or sive times, and thus, by perpetuatly repented Strolies, can excite the ventricles to cooperate Willi it n. 5J9). From the plate We have gi veri, it likeWise appears that the auricle dependes upon iis oWn proper nerves; thOSe, forinstance, designated by the figures 12, 12, 12, Whicli proceed

om their trutili 8, 9, 11, as also Dom the branch I4, but nothom that reflected froin the heari, nor Dom the great cardiacplexus. The facts of experience plain ly shes that suci, is tho dependenuo of ali paris of the heart upon this auricle. We may hero indoed refer to the observations of HarVey, Who S nyS :

First of uJl the lest ventricio censes to beat; then the lestauricle; then the right ventricle; and ut last, fas Galen also observed,) Whon ali the others have given up their motion, an dare dead, the right auricle stili benis, so that the life appears toromain in it tho latest. While the heari is gradually dying,

One may See it, after tWo Or three pulsations of the auricles, Sometimes in a manner Waliening up and responding, and SlOWlyand With dissicut ty performing or essaying a single beat. ButWe must particularly remarii, that aster the hestri has censed tobeat, although the auriclo stili benis, is We place a finger taponone Ventricte, eneli particular pulsation mill be soli in the ventricies ; just in the fame manner, as We belare suid, that thepulsations of the ventricles are soli in tho arteries; that is to Say, On account of the distention occasioned by the impulse of the blo d. And at this time, When the auricle alone is beating, is Wo suis oss the apex of the heari With n pnir Of Scissors, We

545. All the other paris are so mutuatly connected, that which-ever comes into molion, contribules to iis reciprocation. We havetaready Observed thnt the vena cava excites the auricle to motion;

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that the auriclo excites the right ventricte, and that the right ventricte together With the auricle excites the lest ventriclo n. 543). The storta iiself and the pulmonary artery, by actingilpon the nervous Subcincture, Serve as Wings to the ventricles;

thus they reaci in the Same proportion as they are acted On, and when thdy drive their blood on into the subsequent VeSSeis, compei it to precipitate iis course into themselves Dom the antecedent vesseis. Nay, more, ali the litile arteries proper to theliearl-ali the fleshy ducis contribute to the reciprocation os motion; for these, as they receive the blood, eaeli into iis oWΠlitile tubo, impol tho fibre to a reciprocation of motion; CVery superficiat vesset also contributes in like manner to this reciprocation ; so that Whether We consider the heari as a Whole, orvieW it as to iis severat paris, there is nothing but conducesto the generat purpose of this reciprocation. 546. Consequently each, tosether ruith the whole, is kest insuch perfeci equilibration, that the smallest thino inveris the hinge of the molion, and the resistance, which in the natural state is very slight, is east overcome. This is evident Dom the severat articles contained in the present Ρari, since the diastole is thocause of the systole, anu vice versa, the systole the cause of thediastole, and the Only balance sor reciprocating the motion is that of tho blood-vesseis and capillaries of the Sursace, the resistance of Whicli is immediately overcome, in Order that ample

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and reaction, assist iis ventricle to reciprocate iis motions n. 545), but also on receiving the wave, it accepis it RS itS OWn, and spontaneously, that is, by means of iis muscular Coat, Propeis tho blood toWard the extremities of the branches; thus Whatever be the portion os the Wave it receives, it expels it Domitself, and by the forose of the heuri seuds it nWay in the Same Order os succession in Whicli it Was first broughi in; for every

lest Ventriclo, moreover, is endoWed With iis strengili os muscle, Only on account of the frequent changes in the equilibrium os the generat pressure of the arteries, Whicli Changes Rre OCCR-Sioned SO many times in the course of a d y or nn hour by the assections of tho body und mind. For When the arteries by theSe means are toO mueli constricted, they refuse to admit Domthe heuri So large a volume, and consequently, in Order lar itto pass through them, it must needs be 1irst pressest ovor thenortic inreshold; as in case of Wresiling, figlitin g, panting, Striving, and Other disserent obstructions offerest at disserent times to the passage of the blOOd. MoreOver nature, Or rather the formative substance or solat, in Whicli the si si ends, as Wellas the middie and ultimato ends, a cording to Whicli causes fol- ΙοW in provisive and gi ven order illi they nrrive ut the ultimate esseCt, are present and inherent, simultaneousty aud instantly) n. 260 , seems to have providest this strength of muscie tooppose the frequent changes of this kiud, and in order that in the advance nud decline of age, When the channeis in the heurthave a tendency to obstruction, and the fibres begin to groW tendinous and to decrense in purity, number, and integrity, the bodymay in no respeet suffer Dom Want of iis usual supply of blood, butthe heari may, by reason of iis Strengili, continualty have poWerto recover iis equilibrium, and never experiencing any lo88 of iis forces, may endure to the latest moment of liso, and bo thulast organ to die. Theres Ore, according to our proposition, theresistance is eastly surmounted, being in the natural state extrem ely slight. 548. Main, when the fame sub eis are rightly considered, Melearn what are the remote e scient causes of the hearlys molion, numely, that the lunos, the cerebrum, the medulla oblongata, the

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imate cause, as We besere Sald, is the netion Os the venae cavaeupon the auricle; the more ,remote cause is that Whicli produces this action of the cavae; that is to say, both the action of theirblood and viso of their tunius. Heuce Whatever contributes tothe quality and existence of the proximate cause of the motion of the hears, Whicli is the action of the cava, in the Order Ofcauses is the more remote. Thus is the muscular tunic be thoproXimate cause of the circulation and action of the blood, thon the motive fibres, and consequently the nervolis fibres constituting and determining the motive fibre, hence also the cerebrum and the cerebellum, are the remoter causes. Thus What-ever is prior, Superior, and Constituent of the cause of a cause, Or os the cause efficient of an effeci, is in this respeet more remote, and this, in an ascending and descending order. Τhere

coordinate or bolonging to the fame degree, though properly

549. The lunos, since they admit und transmit the blood of the right fide of the heari, and kees the proecordia in the universalmotion. The lungs do not immediately cause the action of thelieari, but merely allow the bl ood to be transmitted, net therdoes the norta cause the action of the hemi, but serves only tosen d out the blood. The pulmonary vein, and the action os iis biood upon the lest auricle, is the proximate cause of the diaStole of the lest ventricte, and consequently the associale cauSe of the diastole of the venae cavae; the primary cause being that whicli incites the right auricio to aci n. 542, 543). Τhus the pulmonary Vein is an administrant cause, and is brought into association With the cava, in ordor stili sarther to promote the progress of the blood that has once been setit into the heart. It is thus a primary cause in the series of those Whicli propeltho blood through the heart. 550. There is belweon the lungs and the heari a conjunctionand relationship so intimate, that We may readily pardon the Very natural error Os those Who presume that the lungs are a part of the proximate cause of the alternate motion Os the heari; for the right cisterii of tho huart dous not open excepi only into

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Were of the lungs; and consequently When iis passages of ingreSS RIad egress are closed, or When the recesses of the lungsare Constricted, the right ventrictu beats in vain, and so does

the muscular fibro of tho right fido of the beari does not terminate illi it traversos tho lungs and arrives at the lest ventricte, besides Whicli tho inmost membrano of the heari invests theiramost membrane Of the pulmonary arteries. The pericardium,too, as a distinct bag, invests the pulmonary vesseis, and also the bronchial branchos as far Dp as the sursace of the lungs, and to the trachen. The heari, moreover, lies in a carved recess in the bosom of the lungs, and Over the aponeurotic centre Of the di aphragm, the peripheries of Whicli are pressed and moved by the concave Jobes of the lungs. Again, the Outer membrane of the pericardium is continuous With the outer membrane of the tranSverse Septum, and the lalter With the mediastinum, in the duplicature of Whicli tho heart lies; hetice it is continuous Withthe pleura, and ali iis processes anil folds, and thus also Withthe Outer sursace of the lungs. Nerves also prooeed DOm theplexus Os One of these organs into the other. FrOm this ex

proXimate cause of the alternate pulsation or motion Os theheari, When neveriheless the reat faut is otherWise; for the reception by the pulmonary artery of the bl ood of the right ventricte, is the cause of the motion of the heari only in the fame manner as the noria is the cause, Whicli admits tho blood of thelest ventricle; and as the potiring by the pulmonary vein of thoblood into tho test cavity, is the cause of tho motion Of the

heari, Only in the fame manner as the vena cava Whicli infuses

tho blood into the right sinus is tho cause; With this differetice, that the right ventricle acis iapon the lest, and nos the lust uponthe right n. 542, 543 . Stili, hoWever, doubi is not remove luntii One porceivos the proximato cause of the motion Os the