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

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under the auricle, Surround8 the right ventricle, as marked by the numbers 36, 36, 36, 36, and DOm this ring, tWigs and nerv- Ous Ossseis proceed, Which enter the muscular texture of ea liventricte, so that in this respect the law of action observed by the ventricles is similar to that observed by the auricies. This Occurs, in Order that When each ventricle is sWollen With influent blood, the nervos likeWise may be expanded, but yet not expandod beyond this subcincture, so that the ventricies maybe allowed to bu moved alternately With the nuricles. For

or Dom 36, 36, 36, backWard into the auricie. In this appears thon to consist the astonishingly ingenious mechanism of nature, a mechanism of such a Lind, that hom the mere actionand pressure of the blood of the vena cava, the appendices Ofthe latior are brought into a state Os alternate action. The means by Whicli this is essected, deserve, DOm the importance of tho subjeci, a stili farther examination. 516. Wo have said that tho cause of the alternate motion Ostho heari, is tho action and reaction of the blood and of thenerves; that heuce the proximate cause of the motion os thevontricles is the action of the blood and the nerves in the auricles, and the proximate cause of the motion of the auricles istho action of tho blood and the nerves in the venae cavae. Is noW We Wish to advance sarther into the subject of the continuation os causes, it may be Observed, that the proXimate cause of the motion of the vena cava is each particular branch of it, the proximate cause of the motion of the branch is ench particular tWig of this branch, and cach particular littio iube thetico depending, the proximate cause of the motion os each particular venous tWig is the action of the smallest arteriai vesset annexedio it n. 222, 223ὶ, and the proximate cause of this action is thenotion os the branch, of the trutili, and finalty of the heari; sothat the cause of the motion of the heari is continuous, Rud describes a circle Dom the lest ventricle through the WhOle sanguineous system to the right ventricle; heuce there is no potui in this system Which does not contribute to the motion Os thu

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called Severat, nor can they be called remoto nud proximate, be- cause they are ali in one continuous series, and being thHS con tinuOUS, constitute, and ns it Were successively compotand, thesroXimate cause of the motion of the aurictu, and hunce of the Ventricles. There re, in Order to know the proximate cause Ofthe motion of the right auricie, We must sirst trent of the cauSe of the pressure and action Of the tWO Veme CnVae.

517. With respect to the venae cavae, it is to be observed, Ι. Τhat they bear the sume relation to the right auricle that this auricle bears to the right ventricie. II. Each vena cava iscrepabie of vibrating severat times While the right auricle vibrates Only Once, as the right auricle is capable of vibrating severat timus While the right ventricle vibrates only once. III. The vena cava Superior uetS RA sar RS the nervous ring, 12, I 2, 12, or to the vestibule of the auricle, DOm Whicli a neW mode os motion begins-a motion of the WhOle part that is commonlyculled the auricie. IV. The inserior cava acts as sar as themouit, of the right ventricte, but not like the superior, to any distinet vestibule. V. Without such a disserent extension Osthe motion Os the superior and inferior cavae, the motion os thelieart could not be continued. VI. The tunic of the vena cavamRkeS common cause With the blood iiseis Let iis noW consider these particularS. 518. I. That the cavae bear the fame relation to the right auriclo that this auricle bears to the right ventricie.-We mean in regard to the pressure, action, and influx of the blood, for theoutlying bloon' of the vena cava incites the auricle to aut, in the fame manner as the blood of the auricle incitos the ventricleto aci, the only disseretice being in regard to space and figure. Τhe auricle rapidly enlarges, Dom the culmination Os iis Vauit, into a large sinus Or caudex, the Vena cava likeWise enlarges from a smaller dimension and diameter to a greater, but in a

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to the auricle, res We have above observest upon the subject of the nuricles and ventricles n. 515). Let iis tine sor an examplethe Vena cava inferior, On the fluxion of Whose nerves Lancisi has the fossoWing remata: From each of the sive patrs of nerves . . . ofROtS Rre Sent below the heari, and again ascend throughthe vena cava inferior est the Way to the right Ruriele . . . . From. . . filio renat pleXUSJ We see a number of tWigs inserted into the inserior vena Cava, and Wonder&lly ascending along iis membranes, With an ivied tWine, ali the Way to the right Ruricle . . . . The Derves recurrent Dom the phrenie pair along the eaVa, procoed as follows: large branches are distributen to the nervolis centre of the diaphragm, and send evident tWigs to the vena cava, at the place Where it per rates that septum, Which tWigs ascend, together Mith the Other nerves above deserit,ed as recurrent froni tho lower belly, to the right auricle and ventriete. Τhat these tWigs ascend is evident, hecause their branchesbelou the diaphragm are Os comparatively large Sige, and gradually diministi as they ascend, tili at longili they are obliteratedand disappear in the right auricle, and at the molith of the right Ventricle n. 463, p. 435). I have observed the fame in the

Vena caVR Superior, Where the descending branches are, but theygo no sarther doWn than the vestibule, Or nervous cincture Ofthe auricle, as marhed in the plate by 12, 12, 12. The vena

cava then has to the auricle a relation similar to that Whichthe auricle has to the ventricie. For the notion of each of theseextends DOm every branch, in the fame manner as the nctionos every branch extends Dom ali the tWigs of this branch throughwhicli tho influx of the blood talios placo. So that there are thesame number of Spheres, or is I may SO Speah, the Same number of joints of motion in One continuous series, Whicli constitutes

the proximate sphere of the right auricle, or is Fou please, the proximate sphere of the right ventricie. 519. II. Each vena cava is cap able of Vibrating severat times While the right auricle vibrates ouly Once, as the right auricle is capable of vibrating severat times While the right ven-

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triele Vibrates Only once.-For as I have suid, the joint of themotion begins Dom the nervous stay, and terminates With the tWigs of this stay in the muscular substance. According to this arrangement, every joint can severalty exhibit frequent vibrations, as is testified by the experiments made by Steno, Whosays, that While the right auricle Was beating soldom and 8loWly, I saW at longili a motion of the cava, both in the right

after tWo Or three pulsations of the auricles, somelimes in a

520. III. The vena cava superior acts RS sar RS the nervous

ring, I 2, 12, 12, or to the vestibule of the auricle, hom Whichn neW mode Os motion begins-a motion Os the Whole part thalis common ly called the auricie. IV. The inferior cava acisas sar as the molith of the right ventricte, but uot like the superior, to any distinet vestibule.-This is manifest Dom the experience adduced n. 518 . For, according to Lancisi, the tWigssent up along the inserior vena cava are obliterated aud dis- pear in the right auricle, and at tho mouit, of the right ventricte' n. 463, p. 435): but not so the nerves of the Superior cava, Whicli only reach the top of the vavit of the auricle n. 518 . This is confirmed by the evidelice of sense, sor belWeen the Su-

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perior cava and the auricle there is a plain tendon, Os Which. Weshali sponti in the sequel, and whicli is placen here in Ordor that Some motion may commenee afresti. But the case is not thesame in tho inferior cava, Whicli Leeps enlarging With one continuous belly Dom iis superior pari as far as the division os tho tWo cavae, and DOm iis inferior pari as far as the auricle properlyso called and the ventricie. The action Os the superior cava thenreaches as sar as the tendon Of the vestibulo, and the action Osthe inferior cava as sar as the auricle itself or tho mouili os theright ventricie. 521. V. Without such a disserent extension os the motion Of the superior and inferior cavae, the motion of the heart coulduot be continued.-The reason is, 1. Because the Superior Vena cava carries doWn the blood derived more particularly Dom thebratus and medulla Oblongata, and the inferior cava carries Uptho blood collected Dom nil paris und corners of the body. The Same quantity cannot flOW through One cava as through theother; the greater quantity frequently comes froin the bodyWhen the muscies are in Strong reciprocation; SOmetimes, hoWever, the greater portion comes DOm the braitis, in Whicli casu Were there DO Such diverse extension os motion as We have referred to, the quantity of blood in otio cava Would excite thenuricles and ventricles to aut more than the quantity of blood in the Other. 2. In Order there re alWays to effect an equilibrium os tho blood of either region, the inferior cava is so siluate dunder the superior, that When the auricle is compressed, that pari os tho blood that does nos 1loW into the ventriclo, son scillior into the inserior vena cava, Or et Se prevenis any slOWingin there rom, untii an equation Or equilibrium of the pressure of tho blood si Wing Dom each cava be obtained. 3. This uras more eSpecialty nece8Sary in the Successive circulation of thoblood Oxisting besore birth n. 331-334); from this successive circulation the simultaneous circulation, Whicli is subsequent tobirili, is derived; so that ali the blood of the vetus theu flowsinto the right ventricte, and ali the blood of the body 1lowsthrough the foramen Ovale into the lost ventricie. In this state, tho action of the blood of the inferior cava vas subject to the notion os the blood of the superior, Which Would not have beenthe casu is the inserior cava entered by a similar tendinous

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When the right ventricle is filled, fas it is Whon the current Ofblood through tho lungs is interrupted,) the right auricle beats

522. VI. Τhe tunic of the vena cava mines common CRUSOmith tho blood iiseis. For one is so suiled to the Other, thattho tunic is the tunic of the blood, or of iis mode of acting, and the blood is tho blood of the tunic, and Dom the tWo combinedresulis One single determination n. 134, 135); so that by one We may judge of the other. As therelare the bloon auis, sodoes the tunic; especialty since the very nerves themselves enter the tunic, and dispose and impet it, at the fame time as theblood, to aut in such and in no Other manner. That One is thus an assistant cause to the Other, is evident Dom experienee. Steno Observes, that in a yOung COrmorant, . . . When tho right Ventricle was laid open, and emptied of blood, a motion stili continuod in the conis of the vein, although ΠOW completelycollapsed, and the transverse fibres, One aster another, Were stightly elevated thereby, so as to present the appearance of athread carried transversely over the Vein, and proceeding t0Wards the beari: this motion had not censed at two o'clock in the asterii Oon, although I began the vivi section ut Dine o'clockin the moruing n. 466, p. 446). HOW this is effected by the determination of the nervous and motive fibres, is best demonstrated Dom the anatomy of the auricle and ventricte : a similarphenomenon being seen in the auricle; for Steno again Says: Sometimes the motion crepi in the border of the auricle, Dom

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the inferior corner toWard the superior; SometimeA the Sameborder Was moved in the contrary direction, or from the Superior Coruer to the inferior; Sometimes When the border Was entirelynt reSt, a contraction Was observed in the middie plano as it

and the manner in Whicli the tunic should aci, must be determined by the nerves. Hence When We Say that the proXimate cause of the motion of the heari is the pressure and action Ofthe blood of the vena cava, We understand this vein taen collectively With iis tunic, as Wo fhail also do in the ensuingremartis On the pressure and action of the blood of the auricle. Ιt is a question Worth investigation, since ali the branchesnspear Simultaneousty to appropriate to themselves the Whole auricie, Whether each particular branch influunt into the vein, does not appropriate to itself somo sitare in the plane of the Ruricle, as Steno's observation Would Seem to imply. 523. From these observations We may learn hoW the Superior Vena cava, and hoW the inferior, acts upon the right auricle; for instance, that the action os each is not distinguished into intervais, but is continuous, and coincides, is I may So Speah, With active pressure or living conatus. At first sight indoed itWould appear, as is Some vermicular motion, Or Some motionsimilar to that of the intestines, were in the cava iiself,-n circumstance Which We might infer Dom the experiments related by Lancisi, Who says: In the vivisection Os foWis, We SaW nvermicular motion in the branches Of the cava frequently recur

alone beat below the heari, exhibiting two enti rely distinet mo-tious, One of Which Was Seen On the Oulside, in the remoter pari, the other on the inside, in the pari nexi to the heart n. 466). But is We examine the causes of the action of the cava, We shallfind that whilo the animal is alive, there is no such Verminatingmotion in the trunk itself, for the inferior cava is incited to actby oach of iis branches; the branches floW, Or are inserted, into

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the trunk at disserent distances Dom each Other, netther doesthe blood rusti into it Dom one branch at the fame moment RS DOm another, the branches being sit uated at disserent distances Dom the main trutili in disserunt regions of the body; and thus the blood dous not rusti into the trunk Dom the illac and other

emulgent, diaphragmatic, intercostat, &c.; in other Words, it

iliacus, pectineus, triceps, Obturator, Serratus, or nneoneVS, ut

the time When either ali or some of them aut disserently Domench other at the mandate of the brain. Hence, inasmuch RSthe beginning of the motion of the vena cava originateS Domeach respective branch, and the branches do not pour tho blood into their vein at one and the fame moment, it necessarily sol loWs, that ali the causes that effect the motion os the vena

CRUR, Rre ContinuouS, Or malle One common cause, Whicli is One and the fame as continuous pressure aud action; helice

also as the equation and generat pulseless circulation of the blood in the veins n. 190-19S . The fame thing takes place With regard to the superior vena cava, into Whicli indeed theblood soWs at stated moments froin the bratus and spinat mar-rOW, but this action is reduced to one common action by theblood of those vertebrat vetus Whicli come Dom the region os the necti, especialty by the blood of the subclavian and axillaryVeius, Whicli floWs Dom the entire longili of the arm in disserent Ways, according to the disserent distances and actions of the muscies. This appears to be the reason Why the jugular vetusinosculate With the si clavian, and the agygos With the superior cava; Dr Were the action distinet, the heari itself might bo impelled tu obey it, and to pulsate according to the animation os the bratus. We must not deny, hoWever, but that the greatestor proXimate action procelds Dom the blood that soWs out of the jugular vein and vena agygos. Is any Vermicular motion proceeded Dom these, there Would no longer be sueti a circulation as there is in the arteries, but in consequence of this Lind of vibration, there Would be a propulsion of the blood in the Velias in every direction, and more particularly in that direction Where an escape sor the blood Was assorded; as, lar instance,

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into the auricle, in order that an impletion Os ali the vesseis, and an equation of the blood, might With the more certainty be ob tained, and that the continuo us action Of the vetus might itsolsbe maintained under the auspices Of n universat motion, as istho case With ait the Other organs of the body. To animais Whicli are dead, or immediately after death, these observations do not apply; sor in these, Some branch or other inosculatingWith the vena cava stili survives, and when it acts Without theothers, Occasions a certain distinet motion, hecause it is notcon unded With them, nor is it compounded by them into one

tinctly as possibie a motion toWards the auricle ... in ali thebranches of the cava n. 465).524. But let us approach Dearer to the cause of the alternate expansion and constriction of the heari, and indeed of the alternate expansion and constriction Os the right auricie, Whicli noWimmediately sollows. We have said that the cause of the diastolo of tho auricle is the continuous action of the Vende CaVae, and that the proximate cause of iis systole is the action os iis nervo us fibres upon iis muscular fibres. But hos the blood reciprocates these actions With the nerves, is nos eastly comprehended, utiles s we have sirsi learni Dom Chapter V., hoW theblood of the lacunae of the auricle is pressed into the fleshyducis of the lalter, thetice into iis motive fibres, and Dom both

these into iis superficiat vesseis, lar ali these particulara con- cur as associale causes to produce the effect of reciprocation, and indeed in such a Way that When the common blood, or theblood of the venae cavae, presses sorWard and floWs into theentire cavlty of the auricle, the blood also Whicli is proper tothe auricle, and whicli is in iis fleshy ducis, presses sorWard and flows into cach os iis motive fibres; ali iis paris being arrangedio this end n. 423, 427). For utiless the blood proper to ei ther

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cRVa Were pressing into the fleshy fibre at tho fame moment in Whicli the common blood Were pressing into the large caVity, the muscie could by no means hecome dilated, as may be Seensi om the principies buforo laid doWn on the subject of the muS

525. It solioWs, there re, I. That the fiuid of notion os theauricle is froin the nervous beli 12, 12, 12, ali the way to iis

extreme horder, and hetice that the auricle can be moved separalely and alternately. II. That the cause of iis diastole Orexpansion is the blood floWing in Dom the two venae cavae; intothis state the auricle comes When iis proper blood niso nitem pisto floW Dom the fleshy ducis into iis motive fibre, and the blood of the superficiat vesseis passes Out through iis coronary Orifices. III. That the efficient cause Os iis systole Or constriction, is, that the nervous Ossseis On the sursace are expanded With thesursace iiseis; the expansion taking place in a direction corresponding to the fluxion of the fibres. IV. But that thoosrect of this cause cannot exist besore there is an abundant influx of tho blood of the auricle into the right ventricte, Or elseos blood Dom some other source. V. Consequently that this reciprocation resulis solely, and almost spontaneously, hom thepressure of the blood of the vena cava. Let us nOW considerthese propositions in detail. 526. I. The sold of action os the auricle is Dom the nerv-ous boli 12, 12, 12, ali the Way to iis extreme horder, and hetice the auricle can be moved separately and alternately.-Τhis has atready been shewn n. 515 . For the action of the nerve, bocause the fluxion os iis fluid, as in the case of the arteries, is onWards along the branches, and there re Dom the nervOus bolt to the extremities of the Osrseis. Consequently it extendsalso Dom every branch to the extremities of the branch, so that the common action Os the auricle is subdivided into as many particular actions as there are Ahoois and tWigs. This is indi-cuted likeWiso by the natural vibrations of the auricle, for the