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day, the cristate VeSicles Were composed externalty os a fibrous substance; While their interior cavi ty Was fuit os a fluid orichor. The brain liud become more protuberant, Rnd Wns Containod in the usual coverings; on lacerating Whicli, the ichor solute v fluid was found to have concreted into solid fluments.
Aster tho Sth day, the hitherio Separate VeSicles Were united, and constituted tWo eminences, containing the ventrietes. Aster tho 9th day, the cristate vesicles of the brain, Whicli terminato in the origitis of the Optic nerVes, Were Smaller and more deeplyseated, and inclinen to the Sides. Τhe anterior vesicles Woreseen, and likeWise the originS Os the Optic nerves, running Domthe crisinte vesicles to the eyes. A portion of the infundibulum produced Dom the contiguous VeSicle, gaVe Support anil con
the author's descriptions of his severat figures. 314. Tho solioWing inserenues in relation to Our present subject may be dra uti from this account of the vesicles. I. Thuli ving potui produces by iis animations nil the vesicular sub statice of the fluid of the egg; heiace vesicles around itself, and gones around the vesicles. Thus the Work of formation is gono into in regulni' Order and Leeping. 2. Ait these vesicles and gones, animating correSpondently to the determination os thosirst living potui, modisy and cali sorth DO Other than uti adu- quate fluid, hoWever such fluid may be dispersed throughout thosphore of the egg; and as Soon as the living p0int, by the forco of iis animation, determinately expels iis fluid, a similar othursuid comes in iis place, froin the peripheries of the egg, for thepurpose of preserving the generat equation n. 227), and so oncontinually. 3. The fluid Whicli thus Succeeds, forms passages
are formed, they are alternately expanded aud constricted by the sume generat animation; Whetice a fresti supply of fluid is constantly elicited Dom the albumen in a Way not unlike thalin Whicli tho blood is elicited by the brain through thu medium os a similar animatory motion; On Whieli Subjeci, See n. 349, and Pari II. In this maniter there is no Supply of anything butwhat is suilubie and determined. 4. Τhe vesicles of the bruinare Lept contiguous to the Vesicles of the spine, in order that
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the cerebrum, and the infundibulum; the thalami of the optio nerves, and also the heari, Whicli is primitively a vesicle. Thus nil things ure carried on most distinetly n. 248 , and are formed successively for use n. 249, 250, 25 l). Thus the formative substance draWs the thread froin the srst living potui, and aster- rds continues it n. 253j. Thus tho spirituous fluid is the 1irst cause, the purer blood is the second, and the red blood
produced, then the Vesseis of the puror blood, and finalty the vesseis of the red blood; one of Whicli is prior to the Other, and then RS they ure compounded, one acts With the other n. 272) :not to mention a variety of Other things of Whicli I have spolienabove, and Whicli here also receive confirmation, especialty the position that the sirst animation is most highly determined, and that suit ably to iis representation causes floW in a provisive and given order to the ultimate effect n. 260, 31 l). 6. MoreOVer, a certain most pure fluid enters the red blood as iis principes Substance, und constitutes iis vital essenco n. 37). To this is added various salis that enter into the composition of the globules of the red blood n. 43 . Tho ordor in Whicli this is essected is susticiently evident Dom a contemplation of the pro
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through ille pores of the Sheli n. 53), and then the grosser elements are attracted in order that the red blood may be tempered, copulated, and perfected n. 50, 9 I) ; Whence the sphere os activity bocomes extended to the yolli itself, Where these things liein reserve sor this ultimate use; While ut the fame time thesheli is Wonderfully Opened to the atmosphere, in order that it may be replenished from this fource in additiori, according to the experimental facts related by Bellini in his treatisse, De Motu Ordis, prop. ix. ' 7. We may hence inser that the composition and recomposition of the blood in the vetus is essected in like mannor, that is, through the medium os vesicles n. I99). This conjecture is favored by the nature of venous blood; by iis distension When placed in an exhaustud receiver; by the disser- ence of iis nature Doui that of arterial blood; by the extremely quiescent state of the velias n. 190-I97); and by this consideration, that in Order sor What coexistes to subsist, it muSt perpetuatly exist by the fame modes by Whicli it existed Originalty,
so that subsisterice may be perpetuat eXiStenee. 315. These are nil tho inserenoes Whicli I design to drnwDOm the narrative presenten to us upon the subject of the vesicles, SO sar as it relates to my present subjeci. The facts Whichnre evident are indeed comparatively seanty. It is Only a feWdrops that ive are able to snatch DOm the sathOmless Oeean, and Om these, obscure as they are, is ali Our Wisdom derived. Still Whoever Wishes to admire the Creator in his Work and in the universe of nature, has Only to enter into the animal Ling-dom, as also into himself, and there to contemplate the causes
of things With a destre to trace them Dom their primary Solarce, and Desii Wonders of Wonders Will every moment be burstingiapon his uteW, even though his life should last a hundred times longer than Nestor's, and he should occupy the whole of it in investigating the mysteries Os nature.
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3I6. VERΗΕYΕΝ. The bl ood of the foetus not only circulates through iis OWn proper paris, as in adulis, but it is also sent throughtho umbilicat arteries to the placenta, a sinali portion being distributedio the membranes On the Way : and it returus froin the placenta throughtho umbilical vein to the vena cava, and so to the cavities of the heart. This is the srst disseretice belween the circulation of the blood in the foetus, and the circulation after birth, When the placenta is separated, and the blood no longer circulates beyond the limits of iis own hodilysystem ; and thus it is that at birili the umbilicat vesseis are cui away and thrown aside, as being of no further use. The blood returning through the umbilicia velit, is mixed with the rest of the blood in the Vena portae, from the Sinus of Whicli a large portion of it is carriod tothe vena cava through a Shori ven ius iube, the ductus venosus, Whichis peculiar to the scelus, and salis into the vena cava immediately under
Another peculiari ty in the foetat circulation is obs0rvable about thelieari, and as in the former case, involves the existence of specialchanneis or passages; by means of Whicli the larger part of the sanguineous mass passes in faci through the lest ventricle of the heari and through the storta, Without previolasty going through the lungs. These Special passages are the foramen belween the vena cava and the pulmonary Vein, and a ShOrt arteriat iube, the ductus arteriosus, J between the pulmonary artery and the descending aorta. The foramen is siluated belween the inferior vena cava and the pulmonary vein ; Opening into the former immediately below a tubercle that lies adjacent to the sirst division of the vena cava ; and into the pulmonary Vein near the lest
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ventricie. It is called from iis figure the foramen ovale. It is so largeat first towards the vena caVa aS to exceed the storta iiself in sigo, butwhere it terminates in the pulmonary Vein it is SomeWhat narrower.
In the upper pari, to ards the right ventricte, it has a raised borderio prevent the blood Dom eastly passing it by; but at the lower partit is comparatively fiat and even, to mahe the entrance of the blood more easy. Besore the ouilet Os the foramen in the pulmonary vein, there is a large valve, whicli toWards the lungs is attached to the wallos the vein, but towards the ventricle of the heari is entirely free. Τhis valve serves principalty to prevent the blood Whicli passes throughthe foramen horn the vena cava, and the blood whicli passes stom thepulmonary vein toWards the lest ventricte, Dom impeding each other in their course. Through this soramen then a large portion of the bloodos the vena cava that would otherWise pass to the right ventricte, runsos necessity to the lest: immediately, when the lest ventricle is open, and when it is not open, mediately through the correSponding auricle, Dorn whicli the foramen almost directly opens. I say a large portion Osthe blood, this bding sussiciently indicated by the fige of the foramen; although What the actuat quantity is, I bellove it to be impossibie to determine. But perhaps a dolabi may exist . . . as to how the blood of the Vena cava can pass into the pulmonary vein through a simple seramen, sor it may be thought that the two vetus are distant Dom eachother, as being adjacent to disserent cavities of the heari; herico that inorder sor the blood to pass froin the cava to the pulmonary vein, a tubemust be required, to effect a communication belween them. But this dolabi Will cease, is we only consider that these two vetiis are inserted into the ventricies ori the posterior pari, so near together that theircoats join, and serm as it Were a complete Wali perforated by the fora
The ductus arteriosus arises hom the pulmonary artery, near iis commencement and immediately before iis division into a right and lost branch: in faci, We may say that this artery divides into three branches, namely, into the two already mentioned, and into the very canal ofwhich We are speaking. This duci, canat, or iube, terminates in the descending aorta not sar frum iis commencement. It is of much largercalibre than the great branch of the pulmonary artery ; in laci, nearly one hals of the whole artery is expended iapon it. A great portion of the blood sent frona the right ventricle of the heari into the pulmonaryartery, passes immediately through this iube into the descending aorta, and is distributed by the twigs of the lalter through the loWer paris of the bo , and through the SecundineS.
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The circulation in the scelus is theres ore performed as soll0Ws :A great part of the blood passes se in the inferior vena CRUR nearthe heari, through the foramen ovale into the trunk of the pulmonaryxeiri; thetice into the lest ventricte, immediately is the ventricle beopen at the time, but through the lest auricle is the ventricle be notopen. But that portion of the blood of the inferior vena cava that does nos paSS through the foramen ovale, ruris together With that Whichcomes through the superior vena cava, into the right ventricte, in partimmediately, and in part mediately through the auricle, just as in Our-selves : Doui the right ventricle it is expelled into the pulmonary artery, and a great part of it passes thetice immediately through the ductus arteriosus into the descending aorta; the other part purSues itS courSethrough the pulmonary arteries and vetus illi it comes to the lest ventricie, Whicli it enters, s metimes immediately, and somelimes mediately through the auricle; and then, together With the blood that arrives at the fame moment through the foramen ovale, it is drixen into thenorta by the constriction Of the ventricie. But since the descendirignoria is much occupied by the blood conveyed through the ductus arte-riosus, it is evident that it cannot receive much bl00d froni the lest ventricte, and there re that nearly the whole, or at least by far the greater portion of the blood of this ventriete, is distributed through the superior paris of the body. The blood that passes through the descendingaorta, circulates not Only through the inserior paris of the saetus, butalSO through the secundines, as We besore Observed . . . . And althoughthe pulmonary arteries after their division are collectively someWhat more capacious than the ductus arteriosus, it does not there re followthat a less quantity of blood passes through the lalter than through the Pulmonary arterieS ; but rather a larger; for the transit of the bl odthrough the lungs of the foetus is exceddingly dissiculi, inasmuch asthey are collapsed by reason of having no respiration, and there reconsiderably compress their blood-vesseis rp. tium. Anat. , lib. it., tr. V., cap. XiX.) The foramen ovale remaliis longer open toWards the ventricle and auricle than On the other fide, as I have somelimes observed in the humansubjeci, and very frequently indoed in brutes . . . . NOU RS thiS foramenis closed on the fide of the pulmonary vein, but not on the fide of the vena cava, there re we find that in the latior siluation there is alWaysa large sinus test to mark the place of the foramen; and this sinus is soland even in old subjects ; DV, even in the bodies of those Who have dieit os old age. V Ibid., cap. xx.) Cors. Num. Anat. , lib. i., tab. XX., fig. li, repreSentS the vena cava opened, she ing the soramen OVale,
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and bestile it a tubercle seen also in some animais) near the orifice of the corona vein, Whicli orifice in the sheep is sald to be common to the coronary and the bronchial vein. 3l7. LoWER. It remaliis sor us to observe, that while the foetus is in the womb, Where respiration cannot be carried On freely, and
where consequently it is not necessary that the whole of the blood should pass through the lungs, it is Wisely ordered that the greater part of the bl00d shali be carried in another direction. For in the foetus, immediately below the tubercle above mentioned,' a foramen, called the foramen Ovale, Opens into the nearest pulmonary Vein, justbes ore the entrance of the lest ventricie ; and through this foramen, thegreater part of the blood returned to the heart by the vena cava, immediately be re the entrance of the right ventricte, is p ured into the pulmonary vein, and together With the bl od that has served for the nutrition of the lungs, is sent into the lest ventricie. But lest the bl odshould return the Same Way, a peculiar membrane is attached ali round, excepi at the bottom, to the margin os the foramen, and loosely han like a veil in the trunk of the pulmonary vein, falling below the inserior border of the foramen; so that it eastly yields to the blood coming froni
other hanil, When by any chance the bl od is urged to return froni the pulmonary vein into the Vena cava, this membrane, by the first impetus of the blood of the pulmonary vein, is closely applied to the fide of the
foramen, and thus essectualty prevenis the retiarn. . . . And as there isas yet no necessity sor ait the blood that flows into the right ventricte, and thetice into the pulmonary artery, to pasS through the lungs, Sowe frid a provision made to divert a part of it froin the lungs, in the existence of an arteriai canal running froin the pulmonary artery to theaorta. Thus the blood expelled froin the right ventricle is transmittensor the most part through this canal into the storta, and distributed With tho rest of the blood throughout the body. But aster birth, and
when respiration begitis, the foramen OVale Rud arterint canat . . . gra
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egress stoin the liver,) exhibiis a laterat anastomosis, that is to Say, a large, open foramen, of an ovat figure, and pervious froin the cava into the Venuus artery so called by the ancientsJ : so that the blood is ena-bled to sow sortii frooly and abundantly through this foramen, RSthrough a single vesset, froin the vena cava into the venous artery and test auricle, and thus into the lest ventricie. More ver, in this foramen OVale, On the fide to ards the venous artery, there is a thin, firm membrane, SerVing RS an operculum Or cover, and larger than the foramen ;and whicli asterWards in adulis so covers the foramen, and unites On ali Sides so essectualty With the surrounding paris, as entii ely to obstruct an dalmost to obliterate the passage. This membrane, I say, is So placed,
the foramen Ovale and the canalis arteriosus. . . . The former Opens Domthe right auricle into the end of the pulmonary velit, or the beginning of the lest auricle ; in stiori, into the confine belween the two: and poursthe blood into the lest ventriolo without alloWing it to approach theright. The canalis arteriosus begitis a litile beyond the sigmoid valves in the pulmonary artery, and runs transversely to the aOrta, being Some-What finalter than it, but certainly larger than the arterial vein Domthis pollit to the lungs. The canalis arteriosus is more capaciOUS nearthe heari than near the aorta. It is evident froin the above circumstances, that this canat is a b road or royal road by Whicli the circuit of the blood is per rined so long as the lungs are unopened. Disquisitio Anatomista de Formato Foetu, cap. V., p. 107, I 08; l2mO.,
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320. MVNNICKS. In the ascending Vena cma, near the heari, there is a large mouth, ΠOW generalty called the foramen Ovale, throughwhicli a passage leads stoin the vena cava to the pulmonary Vein, and whicli is guarded by a membranous valve toWards the lalter vel . Thereis also a stiori canal running from the pulmonary artery to the aorta, and called canalis arterioεus by reason of the thichness of iis coats. Thus the blood that comes through the ascending vena cava stom thelower paris, passes through the foramen Ovale into the pulmonary Vein,
and ali oriters the lest cavlty of the heart. But the blood that comes through the descending vena cava stoin the upper paris, is ali sent into the right ventricie ; whence it is expelled partly through the pulmonaryartery into the lungs, and purgues iis course through the pulmonaryvein to the lest ventricie ; and partly through the pulmonary artery, into
the canalis arteriosus, and by this route into the storta. In process ostime nature gradually obliterates both these passages, namely, thesoramen Ovale and the canalis arteriosus, and neVer Opens them againin adulis, utiless serious obstructions occur in the ordinary channeis.
The foramen ovale is ci sed by no other means than by iis valve, Whichin potnt of substance, tenuity and translucency, alWays retains iis original valvular character. The lungs in the foetus are comparatively red,
and during the early period os formation very heavy and dense ; butsrom abolit the third monili they become datly thinner and lighter, and
pulmonary artery into the aorta through the canalis arteriOSUS; . . . buthe dentes that the fame blood, in the naturat course, is again conveyed through the foramen Ovale Dom the vena cava into the pulmonary Vein ;but thinks rather that by a change in the laws of nature it flows bach froin the pulmonary vein into the vena cava, to Supply the absence of air in the foetus. . . . Litire asseris that he found the foramen ovaleopen in a maia os forty, and this, in Such a manner, as to alloW a passage froin the pulmonary vein to the vena cava, but not vice verδa ; fortho orifice of the soramen Mas thrice as large toWards the pulmonaryvein as toWards the vena cava ; from whieli it seemed to him that thesrst impulse of the blood must be on the part of the pulmonary Vein, and that there must be an introduction os the blood into the vena cava. V Theatrum Anatomicum, tom. it., p. I95 ; DL, Geneva, l7l6.)322. ΜοRGAGNI. Does the bl od flow through the anastomosis whicli Ι besore described as existing in the foetat heari, from the vena cava into the pulmonary Vein, according to the common opinion ; or
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d0es it pass frona the pulmonary vein into the vena cava i I investigated this pollit in the suetat calf, . . . and made the sollOWing ObServations. In the 1irst place, the valve in this siluation was so large andremari able On the si de to ards the pulmonary vein, that I do not SeehOW those Who refuse to cali it a valve, can consistently cali any other structure in the body by that naine. On applying a probe to it on the Side nexi to the vena cava, the probe passed on Without any dissicultyos iis own accord into the pulmonary Vein. On the other haud, When Ι tried to pass the probe stom the pulmonary vein into the Vena caVa, the valve presented an impediment, and the probe did not glide on withthe fame freedom and sacility. Among the various causes of the delay and impediment thus experienced, Were certain litile cords connectingilio border of the valve to the front part of the pulmonary Vein, and whicli I find were known to Ridley, Who aster arils looked for them invalii in the human scelus, as I did likeWise in the scelus of the dog. Among these cords there Was one much thicher than the rest. Theywere ali exceed ingly like those fibres by Whicli the borders of the mitraland tricuspid valves are attached to the columns of the heart. Andthere is nothing, so sar as Ι know, to militate against the idea, thatthey correspond also in function and ossice to those fibres ; that is tosay, are Stretched during the diastole of the auricles, and draWing uponthe valve, admit the blood, but on the other haud are let bach during the systole, and relaxing the valve, alio K the blood lo close the passage, testas ter having come from one of the auricles, it should immediately flowbach again into the sanie. Be this as it may, certain it is that these fibres Would not be placed on the fide nexi to the pulmonary vein, is the
Although, Alanget, ' you have brought forWard Dur passages from disserent Writers, on the subject of the arteriat iube, yet from not One of them can the reader understand into What part of the aorta the blood is carried by that tube. Who indeed could conjecture stom your citations, that it is carried into the beginning of the descending aorta, after that vesset has given Osr ali iis branches to the superior regions: a factfrom Whicli certain ingenious inferetices have been draWn by recent
We have very frequently seen, that that part of the valve whicli extended beyond the anterior and inferior margin os the foramen Ovale in the foetus, even in old subjecis Was not only not united to the wallos the pulmonary Velia, but presented the appearance of tWO Or more