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Hunce it is most Wisely provided that tho motion of the brainshali bo coincident With the motion os the heari only When nuniversat concord prevatis throughout the severat paris of thebody, as in embryos and creatures that have never breuthed; in Which cases the lungs, and nil the muscies, remain inactiVO.
sor instance, Dom the first moment of birili and Ospecialty of respiration,-the brain Seems to leave the company of the heari, and to associatu itself With the lungs; producing, instead of an inactivity of the muscies, a voluntary activisy; and instead of an insensibility of the organs, a voluntary sensibility. Helice by
these tWO extreme motions,-for the motion of the brain is the first in ordor and that of the lungs is the last, the intermediate motion, namely, that os the heari, is Wonderfully Lept in astate os perpetuat connection With each, Or in such a state as toallos os an influx of the One into the other. 10. And the generat state os animation cannot be Seen bolter reflected than in the generat state of the pulmonicrespiration. For as Osten as the brain is intent, and thini ingdeeply, or is occupied With anxious cares, the lungs draW theirbreatli tacitly and stoWly, and the breast eithor rises to a fixed
levet, and fears by any deep breath to disturi, the quiet of tho
of air. When tho brain is exhilarated and joyous, the lungs expand and uti ld. When the brain collapses With fear, theliings do the fame. When the brain is disturbed by anger, the
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position be true, ovorything Will pronounce in iis favor; sortite brain, heari and lungs move every potnt in the living
II. I 2. From the very peculiar arteries of the cerebrum and
cerebellum, nam ely, the internat carotid und the vertebrat arteries, it is very evident, that tho sphere of the hestri's activitydoes not extend into the sphere of tho bratu's activity; for onthe confines of the tWo, Whoro the arteries pass out of the bodyand enter the sphere of the brain, by an ingenious provision aboundary lino is effablished to prevent the tWO currenis Dombeeoming con unded with oacti Other, that is to say, to prevent the blood arising Dom tho body Dom rushing Without restraitit in to the hollow of the cranium, and much more into the brain. 13. For Where tho internat carotid separates Dom the trunk, or Dom the externat carotid Whicli it does near the larynx, in the petrous apophysis of the temporal bones, betWeen the great process of the occipiat und the styliform process, a littio belo Nilio Eustachian tube), it suddenly enters an OSSeous Canal, in Whicli it twisis isseis ab ut at various angies, backWard and Dr-Ward in sueti a Wonderfui manner, that to trace iis tortuosities by a draWing and verbal description, Would require a true artist, So Various ure iis angularities. On this subject Morgagni says : I do nos spo hoW a figure that exhibiis the curvatures of the carotid artery, only in referetice to those Whicli solioW a perpendicular line, can bu the best method of expressing them, because When this artery crosses the substance of the cranium, it is curved transversely; Whicli LoWer represents by another figurethat presenis the artery to vioW not lateralty, like Willis's figure, but froni belliud; although ovon this is not the best mode of representation. V Advers. Anat. Vi., Anim. 5.) A clear proof
this, that as soon as the blood of the body arrivus at this sirstpoint of ingress, or last boundary Of the body and first bound-apy of the brain, it Deis that it has passed into another sphereos activity, and alius at disen gaging itself hom the forco and empire of the heari, and at breahing the continuity of iis fluxion. For it is evident that is the heari attempis to propel
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essectualty checked, by the constant curvature Or barrier of thestiores,'' as Willis expresses it. Cerebri Anatome, cap. viii.)And in every part of the body Where the artery goes out tu a perpendicular line Dom the truuli, as the intercostat arteries do rom the aOrta, and also severat Others, it is a sign of the continuous fluxion of the blood being in some measure retarded, and the more so tu proportion as the artery is more frequently reflected at such a perpendicular, as the internat carotid is in the cuneisorm bone, as Weli as asterWard8. I shali Say ΠΟ-thing here of the impori os the faci that this tines place near thelarynx, in the petrous apophysis, a litile belos the Eustachian
iube, Where a litile sesamoid bone is sometimes solanu; kc. 14. Not only the internat carotid, but also the Other common artery of the interior of the head, namely, the Vertebrat, is compelled to undergo similar modes Os reflection and infraction in iis passage to the large foramen Of the occipiat. For as this artery ascends and passes through the transverse foramen of the secOud vertebra, it is generalty incurvated, to necommodato liseis to the particular Obliquity Of thiS foramen; . . . and belWeon this foramen, and that in the first vertebra, ittakes another larger turn, in a direction contrary to the former. Having passed the transverse foramen of the first vertebra, it is considerably incurvated a third time, Dom besere backWards, asit goes through the superior and posterior notch in this vertebra. Such is WinstoW's accurate description Os these Curvatures. p. Anai., Tr. des Arteres, n. 96.) Ridley gives a figure of the uppermost curve, and describes it as folloW8 : . . . The Vertebrat artery . . . entering the brain ut the last and largost foramen Os the Skest, . . . Coming thither on eaoli fide out of the hole in the transverse process of the sirst vertebra Of the Decii, or belWeen the sirst vertebra and the bone of the occipiat, as
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pressure of the heari, test the brain, or ruther the medulla spinalis, medulla oblongata and cerebellum, should be compelledio rise at every beat of the heari, or every momentum of theblood. But to return to the internat carotid artery. I 5. Τhis artery, on passing through iis foramen, and entering the hollow of the cranium, does not immediately climb to
at the posterior clinoid processes; it nexi passes doWnWard into
the receptacula cavernosa of Vieussetis, φ and even in these ithas a Sinuous course. Such a number of inflexions in every
direction inade by a single artery in iis progress as One and the Same trunti, sussiciently indicate that iis biood, as propelled by the heari, cannot invade the province of the brain, unless thebratu allos it to do so; that it consequently rids itself of thestroke of the heari, is not in the Osseous foramen, at least aster-Wards in the cavi ty of the skuli. 16. Nor is this the ODly precaution taken With a vieW of Separating the sanguineous current of the inferior region Domthat of the superior, for the very tunic of the artery is itselfadapted to cooperate in producing this result, since the artery is suid to divest iisseis of iis muscular tunic as soon as it enters the foramen, and to procure another more sultabie, and which shali comply With the motion of the brain. For it is the musculartunio continued Dom the large muscle of the heari, that alone propagates the pulse through the arteries; so that Whereuer this tunic is, the heari is virtualty present. Heuce Without this auxiliary fibre disposed into annular forms, or continued by the Same method, the pulse ceases to aut, sor it cannot extend be-yond tho termination Of this tutile. 17. The carotid artery subjecis isseis to the dura mater Uponiis first arrivat at the ent rance of the cranium, and again, in thereceptacles, to the duplicatures of the dura mater, to the upper of whicli oti the fide of the sella furcica it somelimes seems totvisti to unite by means Os vesseis and intercommunicatingsepta; finalty, before reaching the brain it perforates this membrane. There is also a Lind of foramen coecum, covered Solelymith this membraue, upou Whicli the artery lies, and of WhichHeister mines mention. Comp. Anat ., n. 100.) Τhus in place of the muscular tunic, this artery horroWs as it Were an Outer
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tuuic hom the mater of the brain, in the place Where this mater, proceeding DOm the circumferenoe und processes of the matres of both bratus, is concentraled abo ut the middie of thosphenoidal bone or sella equina With the Whole os iis generalvibration. The pia mater also receives the ad Vancing artery after it has crossed another foramen, according to Ridley, Who
mater; . . . but not Mithout the mediation Or intervention of the pia mater, Whicli membrane nil the branches of the a resaid. . . more Or IOSS Pros themSelves up On, besore they enter on
there re, thus stripped Os iis muscular motive tunio, is invested With other tunios more sultabie, and Which, as We haVe Sald,
Wepser had previousty given a plate of ths sigmoid curvature of the internal
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ance of a Lind os blandor placed at tho sidos of the sella turcica, and are largor in sige than a nutmeg, and fili the Whole space under the dura mater in this siluation.' Observationes Anatomicae eae Cadaveribus eorum quos sustulit Apoplewia, p. 39 ; I2m0., Schasrhus., 1675.) That the samo is the case in the vertebrat
iS contrary to the usage and nature os ali the other arteries in the body, Whicli as they recede Dom tho heari, do ΠOt incrense in Width, but alWays flowly decrense in the form Of a Cone, ta- pering to the finest and most delicate potnt. Whereuer theybegin again to enlarge, as in the vetus, they immediately losetheir pulsisu force; a clear indication that in this place princi
of Malpighi, Whicli I Will in pari cito in illustration of this phe-
carotid artery p. Cit., p. 38 , in Whicli plate the fides of the artery are Some hat separated Dom each Other, in Order the better to display iis sinuous and tortuous Ourse : hetice in the passage cited by Swedeliborg, he spealis of the paris While theyare stili in their natural siluation.- Tro
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fore it passed into the chrysalis state, the motion Os the heari, previous to the Opening of the belly, Was directed Dom bolowupWards, but aster the opening, the potnt of departure Waschanged, and 70 pulsations ensiaed, Deely traversing the entire
19. It is thure ro tho right of the brain, sortisiud with theso
Only at the stased moments in Milich it malles iis demand, asindeed experience testifies. Τhus Wepser says : More than onoe I have injected Water colored With satyron into the carotidbefore iis division into iis externat and internat branches, and Iliave remarked that tho arteries of the dura mater Were rapidlycolorest anil silled With the injection, While ulmost noue of itappeared in the internat carotid, on account of the curve Whichthat artery malles near the stylisorm process as it is about toenter the osseous canal. F. Cit., p. 102, 103.) Ι am notignorant that Vieussetis, Willis and Ρacchioni arrived at asomeWhat disserent result, but nono Os these Writers mentions Whether the tincture Was injected on the Oulside of the foramen of the cranium, or on the inside, Or in What subjeci the experi
20. But in most brutos that hang tho head und feod on herbage, animal nature, in prohibiting the incursion of the bl odinto the head, has recourse to a method disserent Dom that Whicli is adopted in man, and yet even in these the contrivanceis Wondersul to prevent tho blood Dom 1lowing into the brainaceording to the pulsatory movements of the heart. For in Such animais, as sOon as the internat carotid passes into thecranium, it spliis into tWigs, on whicli it is almost spent, Withthe exception of a smali residual canal; being accompanted With
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titile bands Whicli are produced principutly Dom the dura mater,
Whicli et ther constitutes or in vesis the parietes of the recepta-cles, according to Morgagni. Advers. Anat. Vi., Anim. 18.)But the greater part of these ramifications unite again into oneartery before they climb tho brain. We find, theresore, that in this manner likeWise the pulse of the heari is compelled to stopat the potnt Where the pulse of tho brain bogins. This is theorigin of the rete mirabile, Whicli exhibiis three generic varieties in three classes os subjecis. The Frst is that notWork calledrete mirabile by Way of emineiace, as also rete Galenum, although Galen appears to use the term in a Wider sense. This kind of netWork is Very conspicuous in the receptacles, interWoveri Withlitile membranous bauds and cords, and with vesseis Wonderi ullyt Wissed like ropes. The second Lind is formed When the carotidariery does not carry round the Osrseis hoWever numerous that proceed Dom it, in the receptacles, but hides them in tho duplicatures of the dura mater, especialty at the posterior fide of the Sella equitia, near the circular sinus, at the beginnings of the basilar Sinuses, and likeWise at the fides, where the carotid runsciose to the pituitary gland, and perhaps also ab ove, RS VieUSsens seems to intimate. Neurographia Universalis, lib. i., cap. vii. 3ὶ The third kiud os rete exists When there are either notraces, Or no Vi Sible Ones, of iis appearance, but only some tWigstaken Dom the carotid are insinuated into the gland, the rete thus existing in the gland alone; according to the statemetit ofRidley. But these observations are only by the Way. 21. But let us pursiae this artery further, for the salie ofuscertaining Whether the heari can claim any poWer Over it Whenit hecomes an internat Or cerebrat arte . For as SoOn RS itreaches the brain, it disposes iis largor branches betWeen thelobes thereos, or in the fissures of the iobes ; iis smaller branches and of eis belWeen the convolutions, furrows and ridges; ittheu carries them on more deeply into the substance of thebrain, and in deed to every individual cortical and cineritious
spherule in Whatever corner and intimate recess it lies concented. For this reason Ruysch maintaius that the whole of the cortical substance is vascular, Thes. Anat. i., ass. iii., 11. 19, et in Oper.
passim ., in and thus it is everywhere most obvious that while thebrain is animating the system Dum this iis substance, and tWiSt-
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ing in and out iis Winding gyres and labyrinthine mages, QVery artery is at the fame time undergoing iis alternation os expansion and constriction, is deriving iis biood by alternations fromthe carotid, and propelling it into the great und smali sinuses of the mater. The anatomy of the brain abound 8 in prooss
is siluated in the stream of the generat and particular motion Ofthe viscus, and in deed so siluased, that when the two braius perform their systole, the blood-vesseis of both persorin their diastole, and vice versa. Henco that the brain is the mover of
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SheW8 De Motu Cordis, c., tab. vi., fg. I). From this parallel Welearn that the arterial blood does not enter the brain, and that the venous blood does not leave it, Without the consent of thebrain, and that it is in tho power of the brain, and soWs Domiis mode of acting, ei ther to admit or to emit the blood; soreVeryWhere in the extremes We snd receptacles Dom Whicli an dio Whicli the brain, Whicli acts as an intermediate, extendS theboundaries of iis activity. 23. As it is noW quite evident, that the arterial blood canby no mentis be potared into the homispheres of the brain by
the mere poWer anu force of the heari, so in like manner the venous blood of the brain cati by DO means rusti into the chambers of the heari at tho moments in Whicli the heari performsits diastole, or the auricle iis systole. For a bolt Or muscular sphinctor is interposed bellind the superior Vena cava, the con
of the spinal marroW,) and be re the right auricle of the heari, but no suci, barrier exisis belWeen the right auricle and inserior cava, Whicli collecis the bl Ood hom nearly the whole body. Thus abundant precaution is talien to prevent the bl ood os oneorgau Dom disturbing the vibrations of another, and converting
sussicient to prove that tho motion Os the brain, is it doos notcoincide With that of the heari, coincides nevertheless With thatos the lungs. Let iis therelare come nearer to the potui. III. 25. We may learn froin the blood of the spinal marroW more cloarly than Dona the blood of the bruitis, What are the intervalsos iis influx und 01flux, and more particularly We may learn this froin tho blood of tho dorsal and thoracic portion of the spine, Whicli lies close along the pulmonary region; Where re is thecerebrui and pulmonary motions coincide With cach Other, Weought to sud more evident proose of it here than above aud