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than is requisito, vitiates the silo d. Ait these humors aro but
species of One and the Same gen IS.
342. Therelare suci, viscus, purificatory of the blood, is providen in the embryo and foetus simultaneousty With conception aud groWth; indoed it is innato in tho sceles body itfeis; and the maternat blood, When insected by any discase of bodyor mirid, is carried directly thither through tho umbilicat vos- suis, besore it is transmittod to tho hoari and the braitis. In sceluses, there re, the livor is largor in proportion than it usuallyis aster birth; as also is the sinus and vena portae; the liver is likeWise os a duriter color, and the blood that passes throughtho umbilicat vesseis into the lest hypochondrium, is redder and brighter thau tho blood returned thorice through tho ductus
VenOSus into the vena cava. Heuce We find so considerable a
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course, Or to adopt Only one method ; Daniely, ut every circulation She rejecis to the parietes or peripheries of iis canat ornrtery the substances tess adapted to fluency, While it containsthe blood, With other homogeneous and apter elemenis, in themedian Or axillary line. According to the staternent Of manynnatomisis, und in the wOrds of Boerhaave, In these places i. e. at the minute ends of the vena portae and hepatic Veius there is everyWhere und alWnys a litile canal, arising impereeptibly Doui the acini os the liver; accompanying each branchiudividually of the vena portae; enveloped in the fame Sheath With it, and firmiy and almost inseparably adhering to thatsheath ; gradually enlarging by the confluence of similar pipes ;and finalty terminating ut the trunk of the vena portae in One considerable pipe, termed the hepatio duci, or the porus bilarius, by Which a humor very disserent Dom the bl ood is constantly received, and discliarged under the name of the hepaticbilo. Inst. Med. , 11. 343.) Τhus there is no heaVy, inert, angular, heterogeneous substance rejected Dom the axis to the Circumferetice of the artery, but is derived into the biliary duci; and there is no light, active, homogeneous Substance, but pur-Sues the axillary course as sar as the litile vetus; the vein belligniWVS a continuation Of the canal of the arte . II. I Wisti toconfirm What Was stated in n. 226, namely, that so large is theniimber of the genera and species of Secretions meeting together Dom foretgn sources, even in any one Single gland, VeSicle, or Celi, Composed of vesseis of a threesold Orner, or of the red
any fluid, as in the livor, to produce the bile. Ibid. n. 350. And again he says, In the liver there are simple gland 8; IO-bules are formed of these glands; Iobes of these lobules; and the livor of these Jobes; as proved by the examination os inSecis, fishes, quadrupeds, birds; by the sirst appearance and earlystages of the liver in these subjecis; by disenses, injections, and indeed by common eyesight. Ibid., 11. 342.) Were We thento enumerate the varieties of secretions in the VeSSeis, Celis,
Vesicles and glandes os ali degrees, the secretions floWing Dom
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their oWn vesseis and Dom other disserent vesself, having a disserent sori of blood; Were We in addition to enumerate the mixtures of these secretionS, We Should sind the number of speciesto be infinite, or at least to be One containing innumerable particular species. III. I Wish to confirm What Was stated in
n. 226, namely, that the fluids Whicli are thus mixed, are again conducted through fillers, and after being percolated and discriminated in different Ways, are again united, tili finalty they
potity requires for the Supply of iis necessities, uSeS, Or Contingent emergencies.-FOr ench individual voin that runs by theside os a biliary pore, Sucks in and reabsorbs the matters thatare more suiled to the bl ood and less suiled to tho bile; as do
again, according to Nuchis: thus these substances are reuuited again and again. Neither is anything draWn Osr into the cava by iis sive large and innumerable smali branches but What is homogeneous to the blood; those matters that are homogeneous
to the bile, and heterogeneous to the bl ood, being test bellind. The secretions are united like Wise even in the gall-bladder, is not by the biliary pores, excepi at the exit through the ductus cholidochus, yet by arteries of a not dissimilar origin, and incertain brutes by the hepatico-cystic passages. They are like-Wise reunited aster the circuit made by the blood of the body,
as by the mesenteric veins, the lacteal S, and the VenR CRUR.
IV. Again I Wish to confirm tho position stated in n. 205,namely, that such things only are imported to, and allocaledat, the litile mouilis and lips of the minute veitis, as are to beseiged and sWallowed; consequently that there is a cauSe operat-ing Dom a disserent quarter in producing such an apposition Ofalimenis, antecedently to any choice exercised by the VeiΠS.-We shali say nothing of the various modes os apposition and conVeyance in the biliary pores, in Whicli those things are reabsorbed that are not suiled to the bile; sor be re the mind is illustraled and confirmed by What is palpable We cannot argue Dom What is impalpabie. But it is manifest to the senses, that the biliary pores them selves continuatly pour the bile of the liver
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Phagus, palate, gums and longue, pOur the severat humors thatare proper to them ; and ali these heing mixed With the extracts of the laod, are placed in apposition With tho lacteias and me- Senterie vetiis, With the mesenterius at least in birds. That thocause of this apposition precedes, and arises si om a disserent SOurce, is Very evident Dom the causes of the discli arge of bile, Whicli are ei ther external or internat n. 216). The externat arethose of the stomach and intestines, as When they are either too much relaxen or toO much irritated; moreover the discli getines place according to the quantity or quali ty of the laod, oros Whatever elso may be received into the system; for the gallduci joitis the biliary duci at an acute angie; the common duci descending obliquely, and applied to the duodenum ut acute
the discliurgo of bile, arise Dom the State of the intestines; asindesed may be clearly inferred from the hepatio plexus, Whichis connected With the stomachic plexus. The internat causes os the dis harge of bile, are the affections Of the brain When act-ing very Strongly on the fibres of the body, as in anger, cholerand sudness. V. I Will also confirm the position os n. 227, that there is a certain equation of quantity and quality of the fluids, pervading the system, and to Malch nature, as is for the saliuos equilibrium, tends and aspires With nil her might. For Wheu more os one species of liquid is demanded, consumed, or eliminated, in one extreme than in another, a nes liquid of theliind must immedia tely run thither to supply the want, Dom ali
This is very manifest in the liver, Where the two bilos the hepatio and the cystic) considerably increase in quantity accordingio necessary or contingent HSe; as in those persons Whose stomach and intestines lose their natural tension, and in chOlerio and melancholy subjecis, Who are frequently amicted With jaundice and Other diseases, arising Dom blach bile, and Whose
intestines, Whether OWing to externat Or internat causes, requirea large quantity of bile, in place of Whicli a neW Supply imme-
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fhis is With a vieW to the establishment of that natural equilibrium Whicli is to be produced by an equation in the quantityand quality of the liquids. For this reason a number of passages are prepared, Which lead to this organ, and whicli are adapted to mine the assiux Os bile correspond with the essiux.Τhus it is that use or habit hecomes nature n. 227 . TheseremarkS, hoWeVer, are intended only as cursory: the subject Willbe more fully trealed Wheu We come to spein of the Liver ind
344. But these thinos take place with a disserenoe in ovisurous and viviparous animala respective . The disserenoe arises Domthe circumStanee, that viviparous animais are furnished Withtheir beneficent store in the mother anu her blood; While Ovi- parous animais derive theirs DOm a provision os appropriate matters most methodicatly coordinated in the ogg. Hence vivi- parous animais are provided With a placenta, sitiing the solds,pores ind open Vesseis Of the uterus ; and on the other haud Oviparous animais lime WaVing Superficies, ZOnes and VeSicles,
by means of Whicli the chosen Dod is emulged in the ordor in Whieli it lios prepared and laid iis in the ogg. In viviparous animais, theresore, first the most spirituous blood, then themore simple blood, and lastly the red blood, are respectivelyconVeyed, in order to be purifled, sirst through the root of the ovum, then during iis descent through the Fallopian iubes, eve Where by virtve of the poros and the viseid substance of the seed there collected; then through the uterine placenta, and the umbilicia vesseis Whose roots are there, to the liver. Thecase is disserent in oviparous animais, in Whicli the liver does Π0t appear tili the 6th or pth day; for est things contained in the egg are pure, and are called into activity by the simple heatos brooding, While in the womb the materinis are osten contaminated, namely, by the emotions and heats of the animal and rationes mitid of the mollier. Heuce in vivi parous animais theblood has as it more a disserent gyro; sor being attracted throughthe umbilicui vesseis Mone, the form os iis gyration is changed. Stili hoWever the circulation, considered in iiself, seems to be
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three ld; sor there is the primitivo circulation, as in the eggbefore the existence of the heari, and whicli is perhaps Dom theliver to the braitis; thoro is anothor in lilio mannor to the head, after first passing the heari; and there is the circulation that
Τhus the dissoronce of circulation is a disseretice Only in sorm, Which does uot prevent the circulation being the fame in Lind.But these rem lis are Only hypothetical, and must necessarilypartae of this character in proportion as experienee does notgo haud in haud With inductive reason. 345. The third change occurs after birth and exclusion. Forthe blaod is then driven Dom the superior vena cava and froni the inferior vena cava 8imultaneous , into the right auricle and ventricte, and traversing the lunos, into the lest auricle and ventricte, and thenoe into the trunk of the aorta. Τhis circulation of theblood, and the pulse of the beari thence arising, are trented of throughout in Chapter VII., as is also the following lemma: That at this time there are no longer two successive motions in theauricles and two in the ventricies. Let us proceed therelare toanother part of the subjeci. 346. From which the brains take out and attraci no more blaod than their state demanda. For aster birili they are rotased, is I may use the expression, to the exercise of thinhing, perceiving, knoWing, and Willing; they are aWaliened as Dom a
tho cerebrum is intimately busted With cares Or rensons, auddeeply exercises iis organic forces and faculties, and causes iis animal minu to ouille the bodily senses and to marry the rationat mitid. The case is otherWise When the cerebrum has no
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blood, or borrow Dom the heari or body such portion of it astheir State requires, inasmuch as this Would appear to implythat they exercise a species of attraction. Hetice, although this subject does not properly belong to the present Part, yet as, in case I Were silent, I might be supposed to have committed an error in regard to the most essentini laWs of nature, I am under the necessity of briefly explaining my position. In n. 217, it is shewn, that the arteries of the brain completely emancipatethemselves Dom the heari and blood of the body ; the internalcarotid, by perpetuat contortions and inflections, continued Domitio first throshold of the cranium to the base of the brain, asalso by divesting itself of iis muscular coat. The vertebrat artem likeWise emancipales itself by the fame expedient as the internat carotid, as is clear Dom the solioWing description; to Wit,
that as soon as it gaius the support Of the vertebrae, it entersthe foramen in the transverse processes of the cerVicat Vertebrae, and giving oss branches On every fide to the spinal marrOW audiis integuments, und the neighboring muscies, it climbs by asteep acclivity to the superior condyles, Where it malles tWOturus and then a third; first, round the second of the cervical vertebrae called the epistrophaeus, then bach again round the first vertebra Or atlas, and then OutWards in a large lunar arcti, Dom Whicli it immediately returns. Thus aster sending branchesto the occipiat, and to the occipital and cervical arteries, it en- ters the great occipital foramen, Where the sirst pnir of vertebralnerves, Or the last pair os nerves of the head, paSSeS Out, undWhere the spinal accesso nerve enters. Being theu providedWith a coat Dom the dura mater, it inflects itself Within tho crinium, describing a stiori circle, toWard the posterior part of the medulla oblongata, and uuites oti both sides to sortii a littio trunk, Whicli is called the posterior spinat artery. Τhe auteri
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branch of this artery first retiarns directly Dom the basilar orsphenoidal apophysis of the occipiat, thon after a stight oblique ascent meets iis selloW approaching Dom the opposite fide, and both combino into a common trutili, salmost ut the srst Stepos iis progress Dom tho cerebellum), whicli trutili is then called
the cervical or basilar artery. From the potnt Os coalition, Orfrom each crus, springs the anterior spinat artery. Thus it appears that not Only the internat carotid, but also the vertebrat, and With theso the anterior and posterior spinat arteries, entirelyrelease themselves Dom ad continuity with the hoari and iis un-dulations ; and this the more evidently, because as SOOΠ RS theyenter the cranium, they become eularged, and do not, like thearteries of tho hody, diministi and continuatly sprean into ramifications, utilii the carotid artery has first reached the cerebrum, and the vertebrat artery the tuber annulare, as their motoryorgans sti. 192. 5 . It noW only remaius for me to explain themanner in Whicli these arteries, emancipated Dom the controlof tho heari, and subjected to that of the brains, dispense theirblood, and procure it in accordance With their state, Without being compelled to receive it unitivi ted. 348. Αll these arteries and vetus, as Weli as the SimSOS, Geso placed in the stream of the cerebrat motions, as not to alloWthemselves to be expanded or constricted by any other motorylarce than that of the animation of the braitis. The large OrSuperior sinus of the falx is attached to the hemispheres of thebrain, by the fibres, lacerti, vesseis, prolongations of the pia mater, and by the muscular potnis that Ρacchioni calis glandular congeries, that is to say, Where they are present, or thenece8Sity of the case requires their assistance. This sinus is attached also to the hemispheres of the brain by What are denominatod the chords of Willis, Which so regulate and restore iis natural mode Os tension and expansion, as not to alloW it to beOpened and closed by any other motory force than that of thebrain acting Dom both sides upon the dura mater and the falx, Or Upon the membranes that invest the sinus. Τhis is plainlyadmitted by Ridion Who says that the action of this sinus is derived froin the motion of the brain alone. Anatomy of the Bruin, Chaptor VI.) In like manuer the laterat sinuSeS Rre ut-tached to the hemispheres of the brain, sor at their sirst Ouiset
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tior again We find the laurili sinus attachen to the cerebrathemispheres, and 8o lying betWeen the cerebrum and cerebellum, that When either of them expands, and particularly tho cerebellum, the Sinus is compressed and contracted like a press, and is asterWards opened and expanded by the inWard recedingof the brians. The fame remarii applies to the smaller, both longitudinal and laterat sinuses, When they are preSent. Thecasse is som0What disserent With the Dur shorter Or longer sinuses of the sella equina; of Which we shali speah in the sequet. All the sinuses are so secured to the hemispheres of thebrains by fibres analogous to those Os muscie Or nerVe, and by vesseis and sineWs that aut as straps, that they necessarily per-Drm their systallic motions in accordance With the animatOrymotion of the brains. This Will be mund explained at sume longili in the Pari oti the Sinuses of the Bratu. Moreover, thevertebrat artery itself, and particularly the united artery termed
the cervical, Where it traverses the semi-Orbicular protuberance
of tho medulla oblongata in the chanuel excavatod for it, is placed under similar fellers, so as to expand and contraci RC- cordi g to the alternate and mill-like motion of that protube rance. The Same remark applies to the anterior and posterior spinat arteries; to the vertebrat sinus; and to the vetus in thespinal marroW. It applies likeWise to the carotid artery, andio every one Os iis branches and tWigs; for this artery is largerbetWeen the lobes, Amalter belWeen the Serpentine promineΠCOS, and smallest between the litile surrows and ridges. In this respect it is not unlike the larger, or longitudinal and laterat sinuses betWeen the hemispheres, Whetice iis branches may becassed arteriai sinuses or sinuli; and they are subtended by the pia mater, as the great longitudinal sinus is subtended by the dura mater When passing into the falciform process. Non e of these arteries can be expanded Or constricted excepi according as thebrain, With iis lobes, prominences, and ridges, opens and ShutS. They are consequently sO enclosed ita, and annexed to, thebrain by most minute fibres, by prolongations of the membranes, and by Vesself, that they are Opened When the brain collapses, and constricted When tho brain expand s. Τhis is
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essected by an externat force, by means of the vesseis insinualedinto the cortical substance of tho brain, and their fibriis bind-ing ali these funios in such a manner, that in proportion as theyare lateralty expanded they are at the samo time longitudinalty contracted, Or Shortened; so that in proportion as the canat is lateralty draWn a pari, it is longitudinalty relaxed. I shali notmention the other arteries and veitis Within the brain, as those in iis ventricles, ducis stud crannies, ali Whicli are so siluated in the stream of the motion os the brain and ventricles, &c., RS tObe expanded and constricted in unison With each other. Helicethere is nothing more palpable thun the nature of the motion Osthe brain and iis members,-nothing more clear than the particular use of eaeli pari and the generat use of all. 349. Let us noW return to the consideration of the modo in Whicli the brain obtutus iis blOOd, Or, according to our theorem, subtracis the quantity Whicli iis state requires. Is the arteries, vetus and sinuses of the bruin are Opened by iis animatory motion,
it sollows that a Desti supply of blood must then floW into them, and this by continuity Dom the carotid artery and iis tortuouschanuel in the cavernous receptacles, and into this channei, bycontinuity, DOm the ventricose and circumflex cistertis of this artery Whicli precede it, consequently DOm the externat carotid, and thetice Dom the aorta and the heari; this is the reasoti that the carotid arises as a branch Dom the aorta. The case is thesamo as is Wo took a bladder Or siphon fuit os mater, and immersed One end Os it in a vesset of Water; for is we then dilatustiis Walis or iis externat Surface, especialty is in so doing Weshortened the longili of the siphon, Desii Water Would soW into
this is tho result of the tenden cy to naturat equation n. 227), by means of Whicli, according to mere physical laWS, nature aspires to her equilibrium, With a vieW to avoid a vacuum, in Which she peristi es or is nothing. Such theti is the mode in whicli the brains aci and fili their arteries, and it may Wellbe denominated physical attraction: not that it is attraction in the proper sense of the term, but an impletion Os vesseis by the draWing of their tunics farther apari and then clOSer tO-gether, or causing them to exercise a species of Suction, SUChas We See displayed in pumps and Syringes.