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

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muscular action is en led to propel it into the lest auricie, When relaxed, whicli auricle is much smaller than the right, although similarly constructed and silualed,) sor there is nothing to prevent the blood frontentering. SO for a like reason, the blood can be eastly propelled into the lest ventricle When relaxed, through the two mitrat valves, whieli havea similar mechanism to the tricuspides mentioned bes ore ; but it cannotreturn the Same Way. ΜOreOVer, by the action Os the three semiiunarvalves placed at the beginning of the aorta, the blood is again determined straight into the aorta, sor the Same reasons as alleged abOVe, and this, especialty is the aorta be quieScent; and the paSSage is accurately closed against the return of the blood. We are here speahing of the adult subjeci, and of those of our species Who live in the usualma niter. All the pulmonary blood, then, is conveyed Mith a continuat, rapid, and violent motion, froin the lungs into the lest venous Sinus, the lest auricle, and the lest ventricte, and so into the storta. Thismotion is clearly accompavied With the following circumstances in theliving subjeci. I. Both the venous Sinuses are silled, turgid, and red, at One and the fame time ; and so are both the auricles. 2. Both theauricles bec me flaccid at the fame instant, and so also do both the

VenOUS Sinuses. 3. At the very moment that the auricles hecomessaeeid, they a re sillod with blood, by the impulse of that in the vetiis,

and by the contractile action of the ait Oining muscular VenOUS SinuS. 4. At the fame instant, both ventricies contraci, are emptied of blood, become pale, and the two great arteries are filled and dilated. 5. At the moment after this constriction, each empty ventricle is flaccid, elongated, and reddened, and iis cavlty enlarged. 6. Scareely has this happened, When both auricles, and both mUSeular VenOUS SinuSeS, COI tract With a muscular motion, expreSS the blood they contain, and propel it into the ventricies ; and noW the auricles become pale. 7. In

the meantime the venous Sinuses and auricles are again filled, as bes ore; in fine, the Same series of acts occurs again, and so continues tili thestanting animal is just dead. 8. When death approaches, the auricles

and Venous Sinuses palpitate severat times to One contraction Os the Ventricies. At longili the lest ventricte first censes to move, and then iis auricle ; after ard A the right ventricle is stili, and last os ali the right auricle. The animal is now dead, after Which we find the lest ventricle empty, but the right ventricle always fuit os bicod. Thus it appears that ali the bl00d brought bach from every potnt of the body, internaland externat, and from every potnt of the heari, and from the auricles, is driven collectively into the right ventricte, thetice is transmitted through the lungs into the lest ventricte, and theuce is sent ali over the

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body, stom Whenoe it returias again to the heart. And this is the continuat circulation of the bl00d, the glory of Whicli discovery, With the prooss and explanation of it at large, Will confer immortality on thename Os Harvey, Whose doctrine has been confirmed by injection and transfusion, and has received Ocular demonstration se in the microscope. Ibid., D. 155-l60.)461. The heari is also composed os muscular fibres, Whicli ariSesrom four circular tendOns, encompassing the four apertures of the Ventricles, into whicli tendoris most of the fibres are also again inSerted. From these tendoris arise, i. Α smali number of stender fibres, Whichrian in almost a straight line froin the base to the apex on the oulside of the right ventricle Only, serving to Strengthen the muscular SubStance

of that ventricle during iis systole, and to assist it in expelling theblood. 2. Under eath these, in the fame ventricle, arise Other fibres, froni the lost fide of the heari, Whicli ascend obliquely towards theright fide, take a spirat course, and terminate in the base. 3. Under the last fibres again, there are others Whicli ruri froni the right fide os the heari to the lest, encompass and embraee both ventricles, and risingto the base of the lest ventricte, form a contrary spirat to the series mentioned bes ore. These two last classes of fibres are common to both ventricles, and equalty invest both. On ali sides equalty they constringe

stringing both ventricles at once by pressing them against the middie Septum, and dra ing up the apex toWards the base of the heart. In this operation they are assi Sted by another series of fibres, Whicli, 4,pasS in a varied curve round the former, and are implicated With them, serving to bind them together, and retain them in their places. Butthe lest ventricle has in addition two other thicli series of fibres peculiarto itself, the outer of whicli, lying under the former 2, 3, and q), ascend spiralty ali round the lest ventricte toWards the right, and forming part of the septum, terminate in the base of the lest ventricte, the ca-Vity of Whicli they entirely surround, and are also confined Or Secured by other fibres of their own like those mentioned in class 4. Finalty, 5, under the preceding series there is another and a last, Which descend ing in an oblique spirat from the base of the lest ventricte, toward theright fide of the heari, compose the internat substance of the lest ventricte, and after completing the middie septum, are Spent in curves Osdisserent leugilis, variousty contorted. Add to these, that the fleshycolumns, and the excavations in the parietes of the lest ventricie, giveit the poWer of exercising a very Strong and close contraction, both generat and particular : While the other fibres, and the litile columns that

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ing circumstances are to be observed, Which also belong to the motions and pulsations of the arteries. I. The time When the tension and contraction of the heari, and the percussion of the breast, take place, is the timo of the systole of the heart. At this time the arteries are dilated, produce the pulse, and are in the state of diastole . So at the Same time the ventricles are contracted, and sorce out the blood theycontain, the arterial vein pulsates, and is dilated together With the aorta and the other arteries of the body. ΙΙ. When the lest ventricle ceasesto move, pulsate and contraci, the pulse of the arteries ceases ; and when iis action becomes languid, the pulse in the arteries is scareelyperceptible ; and in like manner When the motion of the right ventricleceases, the pulse stops in the arteriai Vein. ΙΙΙ. So When any artery is divided or perforated, the blood is thrown Out With force from the wound during the contraction of the lest ventricie. And when the arterial veinis divided, we sed the blood j et out with force at the time of the tensionand contraction of the right ventricie. Ibid., cap. iii.) When the animat' is Dearly dead, the heari ceases to respond With iis motion tothe motion of the auricles ,' and only Slightly nods iis head, movingso faintly that it seems to offer but a sign of motion to the beating auriete. Thus the heari ceases to beat bes ore the auricles, whicli theres ore may be Suid to Survive the ventricies. Fit si os ali the lest ventricle

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43 2

One may See it, after tWO or three pulsations of the auricles, SometimeSin a manner Waliening up and responding, and flowly and with dissicultypers Orming or ess ing a single beat. But We must particularly re- mark, that aster the heari has ceased to beat, although the auricle stilli,eais, is We place a finger tapon one ventricte, each particular pulsationWill be seli in the ventricles; just in the fame maniter, aS We bes Ore Sald, that the pulsations of the ventricles are seli in the arteries ; that is to Say, On account of the distention occasioned by the impulse of theblood. And at this time, When the auricle alone is beating, is Me Sniposy the apex of the heari With a pair of scissors, we shali see the blood1lON Out at every beat. . . . It is to be observed, that When Ι speali os

pulsations in the auricles and heari, I alWayS mean contraetioΠS. . . . Infishes, Dogs, and Similar creatureS, Which have one ventricte, and insteados an auricle have a certain bladder Or vesicle placed in the base of thelieari, and gorged With blood, you Will see this vesicle contraci first, and

heart of the eel, and the hearis of some other sisti and animais, evenWhen removed froin the body, beat without auricles; and in faet, is Fou cut them in pieces, you Uill see these pleces contraci and relax bytheriiselves ; so that in these cases the body of the heari beats and pal

riment in a pigeon, after iis heari had quite ceased to move, and eventhe auricles Uere stili, we found that by Wetting the finger With saliva, and placing it Warui upon the heari, the lalter recovered iis force and lise, and it and the auricles again moved, contracted and relaxed, and

Uere in a manner recalled froin the Stiades Os Oreus . . . . I Observed On

. . . of the Coronary arterieS and Veius, and of the nerves that creepthrough the heari's substance. . . . For When these are in a normal

State, the motions of the praecordia are just and naturat; but Whenthey are depraved, or any irregularity occurs in their siluation, number, figure, and Sige, or in any the least conditions of fuliness, or empti-

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ness, the motions then very Soon beeome preternaturai. De Motu Cordis, yc., tib i. sec. iii. De I 8is particularibus Cordis.9 Not tomention that severat eminent anatomisis have thought that the hearthaS naturalty no nerves, We may Observe that Thomas Willis, Ρierro Dionis, and Laureiice Bellini, have not feared to assert, that iis nervesare eXceed ingly Smali, and Scarcely deseruing of notice. Aud althoughWe are not ignorant that the accomptished Fallopius Was among the sirst Who furnished a guid ing light to such of his SuccesSOrS RS Wereabo ut to travel in this dark and pathiess Way, and that VieussenS, andespecialty LoWer, as Ueli as Munniciis, and Other more recent alathorS,

are rem0Ved, but particularly on the posterior sursace, a beautis ut nerv-ous network is discerni ble. bid. prop. 47.) There are sive patrS os nerves On each side that supply considerable branches to the hestri; of hicli sive patrs three arise from the root of the spinal marrow insidethe cranium, While the Other two arise also froni the spinal marroW, butoulside the cranium. I. The sirst is the par vagum . . . . II. The Secondis the pair . . . called by Willis and Others, the internat intercostat, but hieli We . . . Shali name the Superior and tendinous intercostal. III. Among those that arise Within the erantum me rechon the Vertebrat,

Whicli fornis the seconii ganglion beside the last cervical vertebra. The first of the patrs that arise froin the spinal marro OutSide the eranium, and that give oss the fourth class of cardiac nerves, is the inserior intercostat, Whicli sortiis the third ganglion. The last pair is the phrenie, Without any visibie ganglion, Whicli arises froin the spinal marro ,

Sometimes opposite to the last cervical vertebrae, Sometimes together With the axillary nerves opposite to the firSi dorSal Vertebrae. . . . Begin-

ning sirst on the right Side, Me see the par vagum running dOWn in com- pany With the jugular vein into the thorax, and there giving oss a branchthat embraces the axillary artery on the Same side, and then becomeS recurrent. Aster this it seuds out various tWigs On ali Sides, quiad penetrating the pericardium in company With the vena cava, putS sortii abranch that goes to the right auricle, and afterWards another that runs bach under the pulmonary artery, but Seniis iis larger Omeis to a large plexus, that lies posteriorly in the base of the heari, betWeen the pulmonary artery and the storta, just in faet where the ductus arteriosus passes betWeen those two great vesseis. Τhis plexus meriis the mostparticular attention. For a multitude os nerves froni euch of the fixo

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patrS concurs to produce it, nud it again gives Osr innumerable nervOUS filaments to the inner substance of the heart. . . . From the ganglion Osthe Superior intercostes nerve, Whicli ganglion is siluated belWeen thesrsi and second cervical vetebrae, near the internat carotid artery, and under the jugular voin and the par vagum) in addition to many as it Were tendinous branches that are supplied to disserent paris of the nectiand longue, and to the upper paris of the thoraX, three Very conspicu- OuS branches proceed under the carotid artery, and asterWards Withinthe thoraX, Inount up Over the aorta; and then penetrating the peri- cardium, One Os them runs Over the pulmonary artery, and is distributed directly to the anterior substance of the heari, and accompanies a branch of the coronary artery, and piunges With it into the muscular lacerti of the lidari. The two others just as ure observed Of the par Vagum,) reach the plexus abovementioned, from Whicli they a re distributed largely and abundantly to the muscular substance of the heart. The third or vertebrat nerVe, . . . after coming hom the Second ganglion, divides into severat branches, the clites of whicli proceed through theright fide of the thorax, along the descending cava, to the pericardium, and go by the Same course as the superior nerves to form the pleXus; DOm Whicli aster artis, as from a larger Duntain, rivuleis of nerves penetrate and irrigate the heari itself. The fourth, or inferior intercostat nerve, ... is furnished With the third ganglion, from Whicli branches nota seW, passing through the pericardium, creep OVer the Superior Cava and right auricle, and are distributed to the heari, to assist in forming the abovementioned plexus. Finalty, the fifth nerVe is the phrente, . . . Whicli aster penetrating the thorax, closely embraees part of the Superior Vena cava, and externalty the peri cardium itself, the membrane os Whicli it supplies With certain nervolis fibres, and Dom this membrane creeps through the annexed trunk of the superior cava, not only to theright auricle and ventricte, but also to the plexus above alluded to. Thenerves that proceed froni the sive foregoing pairs, direct their course ontho test fide in a similar inaniter, and terminate in the heRrt. . . . Fromthe lest triank of the par vagum, a litile below the recurrent branch, another Ossset proce0ds, whicli is reflected, and dips both into the les tauricle and into the plexus We have so osten mentioned; hom Whichas terWards nervolis fibres are dis used into the substance of the ventricles. Aud it is Worthy of particular remark, that on the lest fide, stoin the seconii pair of nerves, that reach pertingunt to the heari, a large branch issues froin the superior ganglion, and descending along

coat, and penetrating the pericardium besides the os set that it sendsover the externat sursace of the heari, to accompany the coronary

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artery on the bach part of the same) is immediately inflectod whonit comes in contact With the pulmonary artery, and like a neW staybiniis d0wn the trunk of the aorta, Where it is attached internalty to the pericardium; and then becomes recurrent to the traehea and oesophagus; a circumstance Whicli Ι am not aWare that any anatomist has hitherio described. Ibid., prop. 48.) From What We have suid of the wondersul communication belWeen the nerves of these sive brancheson both Sides . . . the reason may be gi Ven Why When the par Vagum,sor instance, or any Other of the nerves On one Side, is lied, the motionos the heari, although disturbed, does not cense entirely; sor We Should have to ite the nerves of ali the patrs at once, Whicli nerves, as We haVeSheWn, are ten in number, in Order to produce this esseet; an operationWhicli is scarcely possibie, at any rate Without the animal be dead pre-viously. Ibid. , prop. 49.) Fr0m each of the siVe patrS Of nerVeS, . . . os seis are sent below the heari, and again ascend through the vena cava inferior ali the way to the right auricie. Certain it is . . . that the nerves of the par vagum, the intercostat nerves, both superior and inferior, and the vertebrat nerves also, after paSSing out of the thorax, below the diaphragm forin the renat plexus, or as Others cali it, thestomachic plexus, although it is found belWeen the renat capsules. From this plexus We see a number of twigs inserted into the inserior Vena cava, and Wonderfully ascending along iis membranes, With anivied twine, ali the way to the right auriete. . . . But the nerVeS r Current stom the phrenic pair along the cava, proceed as follows: large branches are distributed to the nervous centre of the diaphragm, and send evident tWigs to the vena cava, at the place Where it persorates that septum, Which tWigs ascend, together With the Other nerves above described as recurrent froni the lower belly, to the right auricle and

ventricie. That these twigs ascend is evident, because their branchesbelow the diaphragin are os comparatively large Sige, and graduallydiministi as they ascend, tili at longili they are obliterated and disappear in the right auricle, and at the molith of the right ventricie. Ibid.,

prop. 50). The nerves that are sent over the externat and anterior sursace

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lalter have in dedit sonte minute nervous tWigs, but Deither So many in I Umber as thoge of the arteries, nor adherent from the base to the apex, With the wonderfui and winding intert inement Whicli the membranes of the arteries present: sor in the vetiis they appear to creep

and mesh of them in every pari, and particularly in the internat paris, and in the vieinity of the mouilis of the large veSSeis. Ibid., prop. 52.)See also Ibid. , tab. Vii. 464. That the heari is a mn sole suspended in the thorax has been admitted by all. . . . For is the breast be ever so litile opened, and the pericardium be cui, the heari immediately presenis itself, appended toitS VeSSel S, Whicli are l0osely connectod both With the lungs, and withthe throat, head and axillae. Ibid., prop. 27.) AS SOon aS We touchthe heari, we discover four lacertous and fleshy bellies, and in these bellieS Separate and distinet sinuses, whereos two, Whicli are comparatiVelysaeeid, are called auricles, and the rest ventricies: the right soonestyleliis to pressure, the lest is rather hard and resisting. When theentire heari is stripped of iis externat membrane and adipose follicles, We immediately see, even frona the ouiside, Dur tendons, culled the circular tendons, whicli are variousty and separalely locateit With regarit toeach other. In the base of this viscus there are at least tW0 ; by one of Whicli, placed antoriorly, the right ventricle is sirinly bourid, and continued to the pulmonary artery; by the other, Whicli is for the most pari placed posterioriy, the lest sinus is similarly connected to the noria. We then See two Other tendoris, although much lo fer, at the Sides of

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the base of the ventricles; one, Whicli occupying the place On the right, connecis and unites the right ventricle With iis sister auriclo, and withthe stem of the vena cava; the other, Whicli occupying the lest butflightly posterior Siluation, connecis and unites the lest ventricle Miththo lest auricle, and with the stem of the pulmonary vein. But thesseshy sibres that constitute the four Walis of the sinuses, terminate sorthe most part in these tendoris . . . . It is plain, theres ore, that both theseshy and tendinous fibres, are so disposed sadvolvi on the auricles aud ventricles, and so decussate With other fibres, as to forin the tissueos but one organ,-the s ur-cliamberest muscle of the heart. Vet Ιthiuli it should here be observed, that these four tendoris, dispoSed in the forin os sphincters, and applied to the mouilis of the heari, hecome converted into four other tubular and very long tendoris, Whicli are distributed throughout the body, and denominated arterieS Rud Vein S. . . . TO the tendoris abovementioned, we do not adit the long but uot hollowtendon described by some writers, and Whicli running externalty fromthe base to the apex, tines up and collecis Only the externat fibres of

the heari; for this long whitisti fillet is not a legitimate tendon, and infact is no more than the Strong externat membrane of the coronaryartery, Whicli descen Is frOm the base to the apex, and has been an OceaSion Of mistahe to severat anatomisis. But the heari is seen to bea quadricave Or four-chambered muscie stili more clearly, Rhen We Opentis sinuses, for We then finit Within the ventricles eleven other tendous constructed With amaging ingenuity; some of them commou to the Ventricles and their arteries ; while they ali tend principalty to connect to-gether the s ur internat vatilis of the heari, and to make them Stronger. Ibid., prop. 28.) The hollow muscies in the body are produced by avarie 1 twisting of villi and fibres round determinate cavities, and moreor tess by the application of the spirat forin eSpecially.' . . . That nature has applied this Wondersul law of formation to the heari particularly, no one Will deny, Who observes that this four-chambered muscle is madeand constituted of many rolis os sibi es, sonae almOSt Straight as Seenchieny in brutes that hang down the head) and tranSverse, and OtherS, and these the greater number, spirat, and for the most pari decussatingWith, and intersecting each other. Ibid., prop. 29.) We Shail beginfroni the trunk of the vena cava, Where it is . . . jOined Uith the pericardium and the diaphragm. In the sirSi place, then, eXtremely minute, and intorted and agglomeraled fibres, form in this siluation acircular muScle, nOt Unlike a Sphincter. . . . From this the fibres are

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the Superior cava, as to constitute and comprehend within them that uppermost vavit of the vena cava called by us the vestibulo, and whichis the commencernent of the right auricle ; Whieli auricle these lacerti beautifully forin by processes of divarication, multiplication, collectioninto unequat fascicles, and intermixture With each other. In like man-ner the vestibule of the pulmonary vein, and the vavit of the lest auricle, is produced by the varied application and intertexture of sibi es ; although in this place the fibres . . . do not constitute so evident a Sphincter, and

Rre not SO numerous Or Strong, as in the vena cava and right auricle,

through whicli the blood is sent With less velocity, and there re needsa greater circumpulsion from the fibres. Anil as On the anterior sursace of the heari, whicli is the Dearest, bundies of fibres are sent froni the Vena cava and right auricle, so On the posterior sui sace, bundies of the Same are sent frOm the pulmonary vein and lest auricle, both outWardly, and within the cavities ; and it is of these fibres that the compaci substance of the ventricles, and particularly of the lest ventricte, is madeup. Thus a multitude os lacerti, partly divided into fascicles, ariseexter alty from the auricles and heads of the vetiis; and after forming, by their greater mutuat adhesion and contorsion, the loose round tendous of the heari, communicate and are continuous With the series offibres that mae up the externat Sursace of the heart. In like mannermore tendinous blandies are continued froni the internat sursaces of the heads of the vetiis, and of the auricles, and compose the internat structuro both of the tricuspid valves, and of the sursaces of the ventricles; folio tig a similar mode of propagation to that observed in the formation Of the semilianar valves and larger arteries. But est these thingsare so done, that the fibres inosculate by diversified and innumerable advolutions, the externat fibres With the interual, and the internat withthe externat, seeming to constitute a Gordian knot, and suggesting to the minil What Hippocrates says, that When a circle is Once deserit,ed, iis beginning can no longer be soland .' Ibid., prop. 30.) Τhere arethree principat arran gemenis, and modes thereO Whereby a Strong contexture of sbres, and One Whicli poWerfully resisis disruption, is produced around the ventricies of the heart. The srst lies in the contrivance of draWing the fibres froin the externat sursace of the auricles, and Ofthe heads of the vel iis obliquely, and as it Vere spirally, through theexternat part of the ventricles, ali the way to the apex : Whicli si bres, ConSequently, alWays enlarged in bulli, malle up the thich cortex of the Ventricles; eXcepting only n feW that penetrate as it Were directly iu-