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

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unequat saeculi, Or ostener Stili, Os One large Sacculus, or is you please, os a signi id but narroW valve, or aS Verheyen calis it, a large sinus,)the orifice of whicli sometimes looked do nWarils, and frequently for--rds ; and admitted a large probe, and even the end of the handio ofa scalpet, betWeen ii and the wali of the velit, to such a depili, that What Verheyen saW in calves of disserent ages appears to be true also in regard to man; namely, that the valve, While it is uniten to the wali of the pulmonary vein on the fide facing the lungs, stili increases and is extended where it looks to ward the heart. Ι have most certainly Observed that Dearly the whole of that part of the valve which was stillloose, hau beco me much thicher aud firmer than it Was in the foetus. At the very bottoni of the sacculus, betWeen ii and the front and upperborder of the foramen Ovale, I have frequently Seen a minute paS- Sage stili operi for the blood, and once of such a Linil as to admit thepoint of the handie of a scalpet without any difficulty into the vena cava. This passage I found in a semate subjeci, and the like also oncein that os a male at least sorty years old, in Whicli case it was so Wideas almost to admit the tis of the litile finger on the fide toWards the

vena cava; for the farther the passage Went to the orifice of the sacculus, the more it contracted, and assumed the form os a conical iube.

This last observation satly contradicis that Which you say that Litire

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INDUCTION.

324. FROM the anatomy of the chich in the incubated egg, it appears that the circulation of the rod blood passes throughthree remarkable changes and vicissitudes. The sirst, When theprimitive heari or punctum saliens propeis the blood received, through certain vesseis upWards toWard the bratiis; and thebrains express it domnWards into the umbilices vesseis. Atthis period the bratus are the principes cause of the circulationof the bl Ood. The second change talies place When the aorta is extendeddo Wards to the region of the abdomen. The blood is thencarried aWay by the inferior vena cava, aster traversing the Cardiac vesicles, toWard the bratus; and thetice it is carried doWn by the Superior vena cava, after again traversing the cardiae vesicles, through the descending uorta into the abdominat region ; Dom Whicli it returiis through the inferior vena caVa asbesore. The circle whicli the blood thus describes, is as it Weredouble, and reflex, but yet continuous. So long as this circulation continues, tWo motions must exist successively in theauricles, and tWo in the Ventricies. The mode and determination of the circulation in the unitedor conical heari, besore the lungs begin to respire, is similar tothe above. Thus the blood carried down Dom the brain sthrough the superior vena cava into the right ventricte, is propelled there rom through the ductus arteriosus into the descend-

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ing aorta, and so into ali the provinces of the inferior region. Τhen it ascend s through the inferior vena cava, and is dri Venthrough the foramen ovale in to the lest ventricte, and Domthence toWards the braitis; and so On continuatly : the heari it-self distinctly determining tho stream in both cases. This is

the purpose of the foramen Ovale and ductus arteriosus, Without Whicli such a circulation could not be carried On.

The third change occurs after birili and exclusion. Fortho blood is then driven Dom the superior vena cava and Domthe inserior vena cava simultaneously, into the right auricle and Ventricte, and traversing the lungs, into the lest auricle and ventricte, and thetice into the trunk of the aorta: Dom Whichthe braitis talio ovi and attraci no more bl ood thau their state

demands. At this time there ure no longer tWo succeSSive motions in the auricles and tWO in the ventricies. Thus, as the Order of circulation is reversen immediatelyaster birili, so the foramen Ovale and ductuS arteriOSUS Rre necessarily closed . Nevertheless, in a variety of cases, this

foramen may for a long time be Lept open Dom the right auricle toWards the lest, and in sonae cases even 1 om the lestauricle tOWards the right.325. I dare not profess to treat of the circulation of the spirituous fluid, and of the circulation of the White or purerblood antecedently to the appearance of the Ped blood; because

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production as far as the heari Was not yet visibie.' Ibid. Τhecorculum then is traversed by the white blood besore tho redblood, and by the spirituous fluid bosore ei ther; iis lissue, lihethat Os every other viscus of the embryonio body, being formedout of the fibres of tho latior suid. Hen e the circulation Ofthe spirituous fluid is the most universat n. 150-154). But it may be advis te besore procoeding furthor, to recur to the circulis performed by the rest blood, Whicli are not so concealedDOm ObServation, being clearly indicated by the red color of the fluid; and then after irenting of the red circulation, to addsomething on the subject of the white circulation, or that of the purer blood, and finalty, on the circulation os the spirituous suid.

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326. From the anatomy of the chiest in the incubated eis, it oppears that the circulation of the red blood passes throughthree remarkable changes and vicissitudes. For at ille Commeneement of sormation the blood cannot be drivon into a gyrationsimilar to that whicli it asturWards describes Whon the litile bodyis formed; because ali things come and grOW successively : be- cause the heari has sirst to bu initiated into the laws of iis motionunder the auspices of the bratus : and because it acis ut 1irst usa triple vesicle, not as a cone : and also beenuse the Sanguineous Stream cannot be transmitted through the lungs untii they areopened. The circulation then goes through three remari ablevicissitudes, the generat fountains os motion being also three

means of the humor driveti through the veitis, Was evidently into the auricle; Dom this the expressed juice Was propelled through a narrowed tubeJ into the ample right Ventricte, by the constriction of Whicli it Was again protruded into a conti-ΠuOUS appendage, DOm Whicli there Was a direct passage into the noria. The norta sent upWards certain considerable branchesto the head, and was continuod doWnWardes in the form os atrunk, Whicli, after dividing, extended as sar as the extremity of the carina n. 242). And Lancisi says : At the end of the 2nd Gy, the rudiment of the heari is seen as a Crooked, Continuous, yet irregularly constricted and diluted vesset, Whichbeginning Doui the junction Os the umbilicat vetus, Or DOm thevena cava, is first dilated into an ovat vesicle, . . . and ulti- mately opens into the continuous aud proportionably narroWtrunk of the great arte , whicli here and there divides into

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various branches, but more particularly into tWo, Whicli ultimatoly sorm the umbilicat arteries. These terminate in a reticular plexus at the cireumferetice of the cicatricula, und theumbilicat vetus there begin, and constitute an orbit of motion in the blood of the foetus, running DOm the circumferenee throughthe veins to the praecordia, and Dom the praecordia through the arteries to the circumference' n. 245ὶ. But this subject canhardly be understood by a bare description: is me examine Mal-pighi's plates representing the process of formation and the gyre of the sirst circulation of the blood, it Will be seon to the lise, that ut this period certain branches proceeding Dom the last

cardiae vesicle, convey the bl Ood into a certain arteriai sinus notunt ille the sinus of the porta, and whicli sinus being inflected ove the head, and then stretching doWn toWard the inserior paris, is sunderest into minute branches, and terminates in theso-callud umbilicui vesseis. Not a trace of the descending aortais yet seen; is there be any trace it is too flight to be visibie. 328. And the brains e ress it downwarri inlo the umbili alve88eis, Or into the bOrder, area, Or reticular pleXus, Where theblood in a manner disappears, but so u fhews isseis in the Veliis, by means Of Whicli it again arrives at the heuri. Thisfirsi and most simple circulation, there re, is uniform, pro Oed-ing froin the heart upWards and then doWnWard s. In this epochos the circulation me have to notice, I. That the arteries intowhicli the litile beari now propeis iis biood, do not decrense in diameter, like the arteries that are formed in the body, butulti mately terminate in a certain large holloW or sinus, silualedhigh up, or above the head. 2. That tho blood is dotruded Dom this channei or trunk into the smaller vesseis, and finalty into the smallest. At the end of 3 days,V says Malpighi, . . . the bl od received by the auricle hom the Vein, Was propelled through a duet into the right ventricte, and thetice into the lustventriete, and at length in to the arteries, Dom Whicli it passedinto the trunk. From this trutili proceeded the umbilicat branches, Whicli terminated in tWigs at the border, forming a reticular plexus'' n. 243). 3. That in this border or periphery the bl ood in a manner disappears, and then reappearing in the vetus, floWs bach again into the heart. It Would thus seem that this farterialJ trunk of the head is at One extremisy, the area

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of the umbilicat vesseis at the other, and the heari in the mid die ; Hl Within the sphere of the brain's activity. 329. At this period the brains are the principut cause of the circulation of the blood, but not the heari, as is evident homthe mere description. For, I. The arterial trunk of the head, immediately receives in a suli stream tho blood ducted Dom theheari or corculum; and by iis constriction and expansion, Whicli probably arise froin the animation Of the living potnt, of the Vesicles surround ing the brians, and of the gones, protrudes it stili farther. 2. Sinco the trunk of the head is ut one extremisy, and the area of the umbilicat vesseis at tho Othor, it foems that this area is Within the Sphere of the fame animation that is thecauso by Whicli the blood is driven through the vetiis toWardstho heart. 3. The heni t then, thus placed in the middie, exercises no Other action than to receive the arriving blood, and tothrow it out When received; ali Other matters boing under theauspices and gOVertament of the bratiis. 4. Tho heari is thus initiaton into iis future ossice; and afterWards, When it has acquired a certain degree of strength, it is taen into consori, tominister in a subservient Way in the formation of the body. 330. The seconii change takes place when the aorta is extendeddownwards to the region of the abdomen. While the sirst circulation of tho blood continues, there is no appearance, aS We OVOsaid, of the descending aorta, Whicli is at any rate too salut tobe notice te. At the end of 2 Gys and 14 hours V says Mal-

ing toWards the middie of the abdomen, producod tho umbilicat

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blood: novortheless the beari is so far hept in subservionco totho brains, that it Send8 iis emissaries to no Other place, at noother time, and in no Other quantity, than the bratus diroci. Thus the whole and the paris groW in mutuat concord. Thiscirculation appears to be of the follOWing nature: 33 I. The blood is then carried away by the inferior vena cava, after traver8ing the cardiac vesicles, toward the brains; and thenee it is carried down by the Superior vena cava, after againtraversing the cardiac vesicles, through the descendino aorta into the abdominat region; from which it returns thro h the inferior vena cava af before. Aster a consideration Of the facts presented by Malpighi and Lancisi, it cannot be advanced as certain, that sill tho blood that is carried Dom the heari to the brains, descenus Dom the bratus through the superior cava, inasmuchas it appears that a considerable portion os it is immediatolyderived into the border and peripheries, in Ordor to ascendthrough the inserior cava. Be this as it may, bes ore the sirst circulation can be changed into the second, there must it foems be this intermediary process; namely, one part of the blood descending froin the brutus must be carried into the peripheries; another pari must be carried toWard the heari, as a centre, towhicli indosed ali tho blood retiarns On completing iis Circulation:

in the meanti me, the vena cava ascendens and descendens are

provided, as Weli as the norin, Whicli carries tho blood both up-Ward aud doWnward. The heari is in the umbilicat region, DomWhicli it maintaius a relation to the superior and inferior regionS; so that being localed in tho mitist, it contains With in iiself tholaW of the consequenis, and likeWise refers itself to the ante

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the blood Doui the vetiis, pulsated With a Lind of double motion, as though distinguished into tWo chambers, and thus theblood Was propellod into the heari in a peculiar Way, Whichrequires further investigation n. 242). That a similar circu

of tWO ventricles, as it were contiguous Saeculi, uni ted togetherat their upper pari, and Mith the body of the auricles placedupon the top of them; and there Were two successive motion Sin the ventricles, and the fame number in the auricles. Ibid.

The mystery os nature, Which Μalpighi says is in Want of sur-ther investigation, is pininly revenled, is We weli examine thegyre of the second circulation n. 33I), and diligently compareit With that of the first circulation n. 327). For is the blood, after receiving iis determination Dom the brains, be conveyed into the littio heart through the superior cava, nearly the Wholeos What is thus convoyod is sent doWn tuto the descending aorta and the inferior regions os the body; but nil that arrives throughthe inferior cava, after passing the heari, is pumped up in the

direction of the brains. Aud since this is done in a continuous Stream, Or Successively, it folioWs, that the auricle and ventricle pulsate With a double motion; the auricle pulsates, Dr inStanee,srst Whon the blood onfers it Dom the superior caVa, and again When tho blood senters it Dom the inserior cava. The ventriete PutSates in consequence of iis connection With the auricle; fixStly, there re, When the blood is driveti into the descenditignoria, and secondiy, When it is driven into the ascending aorta; according to the author's description. 333. This successive circulation then, being performed by

the heari, it hecomes iis to inquire into tho modo by Whicli it is essected, in Order that we may seo that a circulation of the Lindis practicable; sor at sirst sight it Would appear, as is the blood,