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the simplo fibre, by means of the vesseis of tho puror and red
ther, Which When it undergoes collapse, the reciprocation of themotion immediately CORSOS. Suthly. The least arteries are more immediately under the govertiment of the nervous fibres, and herice Os the brains, than the largo artories n. 234). For the least vesseis, like motivo fibres, surround even the large arteries and vetus in themannor Os rings, Whetice the nervous fibre acts upon the leastvesseis first, or through them upon the blood of the wholo largo
504. Thoro re tho reat efficient cause of tho motion of thomuscies, is the fluid in the fibres, and the suid in the vessuis; or What amounts to the fame thing, it is the action Or force of the spirituous fluid by the fibres, and the reaction of the blood by iis vesseis. Is then there bo the fame relation of the fibros to thoir fluid as of tho arteries to thoirs n. 472), it follows thattho similarity of relation mill extend to the folloWing particulars. I. That tho spiritu us fluid runs through the fibre just as theblood through iis vesset, but much more perseetly, S Wistly, kc., sinoe it is in an eminent or superior degree. The blOOd runs through iis vesset by undulation, the spirituous fluid, throughiis fibre, by modification; therei ore similarly; because undulation corresponds to modification in iis degrest n. 166 . 2. Thonervous fibre, permeated by iis suid, in the extremes, Where ithas gained iis liberty, because it is no longer compacted into
3. Theresore When the fluid acts in iis fibre, and expands it both Ways, and ut the fame time the vesset, round whicli thos ,re Winds in continuat circles, there being there re roOm sortho blood to 1low in); and vice versa, When the fibre constricis, it then compresses itself around iis vesset, and eXpeis the blood. Τhat tho blood thus expellod continualty repeis and renetS, IS Rconsequence of the equilibrium os generat pressure acquiredaud preserved bu the circulation sit. 178-182 , und without Whicli equilibrium, theresore, no muscular action Would be pOS-
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Sible. This thon is the reason Why the contracted muscle is sale, hard, constricted, and acts on iis tendous according to themechanical direction of iis fibres, and by these tendons uponsaris cap te of being draWn, elevated, or moved. With thesepositions Iaid as a basis, let iis see What is tho cause of the actionos the spiritu us fluid, Whicli onabies it to produce this effect in iis extreme fibrOS. 505. This cause, on the sheWing of generat experieuce itSel and also os ali particular experieuce, is the brain; sor When thebrain Wilis, the muscio at Once rusties into action, nor can themuscle derive iis action Dom any other source than that Domwhicli tho fluid runs out se in iis principies or sirst starting- places along nil iis fibros. It Will be seon When We come to the anatomy of the brain, that overy fibre has iis OWn corculum and cerebellulum prefixed to it, or iis oWn spherule os cortical substance ; that this substance is dividen into iis cortices thalami and congeries, and the8e congeries are so combined and conglomeratoii, that eauli can be distinctly compressed and expanded, oranimate in iis oWn particular locali ty; hetice deep cavities arecut betWeen the serpentine ridges in the brain : When therelare One Or the Other of Such congeries animates, the spirituous suid is determinod into the dependent fibres as Dom littieliearis; those si bres in the extremes are eXpanden or constricted in longili and breanth; consequently the motive SanguineOHS 1ibre also, and through the medium of the sanguineous fibre,
the Whole muscio. For is the spirituous fluid be highly elastic, and is iis fibro bu highly correspondent to it, so that the tWonet RS One and the fame cause, just as We have above observed With respect to the arteries, it sol lows, that no impressed forceperishes, but is the fame at One extreme as at the Other; RS We find to be the casu in tho atmospheres, the paris of Whicli arehight y elastic. Tho tori of the cortical substance are formed in diverSe mauners. Iu One place they are narro' in another
Surface; as SheWn by Ruysch, Epist. Anat. Xli., t . SiV., sig. 2, representing the cavities denuded by the romovat of the tori ofCortical Substance. The fame appears Dom the processes Os pia mater that dis down into the furrows or solds, and as this author describes, crees about in a serpentine manner, Rud not
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in a sulcisorm manner as in the cerebellum. Epist. Anat. vii.)That these tori are cupabie Os being expanded and constricted, both particularly and generat ly, in their places Or Spaces, i S evident Dom the thin, reticular, and expansite membrane that Surrounds them, and Dom the circumscribed space in Whichthey can intumesce; also froin the continuation Os the pia mater Solely into processes of such a nature as do not hinder the elevation of the brain anu more than does the falx of the
hemispheres, but do prevent any divarication of the paris. Moreover, the litile arteries that are put in, traverse the paris
in a reti&rm manner, and then suffer themsolves to be relaxedand constricted. And here and there there are largisti vesseis belWeen the cortical and medullary substance, as SheWn in One
Sanguineous reservOirs in the medullary substance and Ceutre,
StreamS, Or When any particular constriction does not for a long
body Where any motion is soland. That voluntary actions existhom similar constrictions and elevations Of the tori, is proved by experience, as in apoplectie and epileptic persons, and in Others Who suffer under frequent convulsions of their members ;for concretions Os blood Or serum, inflammations, indurations, hydatids, obstructions, and such like, When occurring in thebrain, deprive it of iis faculty os elevation, and cause an inaction Or convulsion of the correspondiug member. But Whentho cortical tori are cui as deeply in as the medullary Substance, tho animal is agitated With extraordinary spasms, RS We learn Dom Ridley. Philosophical Transactions, 11. 287, an. 1703; and Our Pari II., 11. 1 . We noW come to en quire What corticaltori correspond to the respective muscles in the body, and this We cannot RScertain eXcept DOm experiments on living animais,
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by sunetur , Secti Ou, and compression in a varioty of Subjecis, and then observing the offecis producod in the muscies of theb0dy. We may hoWever conjecture, that those are in the great- est activity, in Whicli the largust rivulois of blood are Dund.
ticular sibre, but simultaneously upon the wholo fascicle of si bres, ns is evident hom the anatomy of any particular torus; lar in itthe cortical substance is arran ged tu the forin Os clusters Or acini, and botWeen these there are interstices, bocause When any CO-lored liquid is passest into the torus, the boundaries of these aciniare desinod, and tho tori, is skilfully dividod, exhibit arborescent ramiscations not unlike those in the cerebellum; according to the experience of Alalpighi Ρari II., n. 79). The fibres of allthese ramifications combine, und are then Sent out by the samenumber of peduncles into the medullary Substance, producingin this substance the appearance of strata anu lamellae of sbres. It is theres ore Dom a compound action of the torus upon the fascioles that the effect ultimately produced upon the muscieresulis an effect Which arises Dom a multiplici ty of forces, and
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Vates Or Stretelles it, is a cause of iis spirituous fluid rushingthrough iis extremities, Whicli it cloes even though the continuityof the fibro, or the current of iis fluid, bo intercepted. Τhisi S the case more ospecialty When We considor this fluid to bo in like maniter placen in a state os generat pressure by means of the animation of the bratus and the circulation thenee nriSing, nd tho sibro to havo evoryWhere the forin os a continued brain, just as the artery has everyWhere the resemblance to a Continuestheart. All the fibres of the cerebellum, or ali the nerves arisingsrom iis fibros, such as the intercostes, and the eighth nervo Osthe hoad, nre so distributed to tho viscera of the body, that Whilotho cerebellum distends them by iis spirituous fluid, and as it Were maintains them in the equilibrium os generat pressure, thecauses arising on the part of the body excite the muscies depending upon these fibres and nervos into the motion Whicli is called spontaneous, their natural motion being called involuntary ; for the cerebellum, unlike the cerebrum, cannot animate particularly, since it has no cortical tori cap te of being elevated; henco it cannot animato horti a Will distinctly determined, but has Only a common or generat notion, and inspires nil iis
fibros simultaneOUSJy. 507. Consequently there are causes of muscular motion Onthe part of the body, Whicli causes ure numerous, and indoedas many ns the natural motions. This is evident froin tho phe- nomena of the body. FOr, I, When the stomach is excised, and removed from iis natural siluation, it readily exhibiis the creeping motions peculiar to it, for the solds and gyrations bolongingio iis cavlty it frequently after death presenis in a state Os motion, just as is it Wore stili alive; this Would by no means bothe ense utiless the cause of iis action urose froni the body, forit cannot ariso Doui the cerebellum froin Whicli it is noW separated. Τhis motion may even be produced ad libitum, is thovillous membrane be excited by Warmili, by the potui os aneedie, Or Other stimulus, just as during life it may be excitud
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by stinging particles, acrid bitter substances, emeties and PurgatiVes. 2. The gullet also When excited by a voluntary act Ofthe Pharyn X, fauces Or longue, moves the cardiae orifice of the stomach together With iis ingesta, this part of the StomachmoVes again the stomach in general n. 496 , and the stomachrolling est things in iis spires, urges them through the pylorus into the intestinos. 3. Through the excitations Of these paris, the chyliferous vetus at the fide, and at the fame time the ductus cholidochus, and osten the gall-blander, and other of the vesseis of the abdominal kitchen connected With them, are by means of the nerves and plexuses put into a persectly facile and superabundant degree of action. 4. And the phrenic nerve, WhichWhen chased is suid to excite the muscle of iis septum,) and WhichoWes the cause of iis action principalty to the three cervical nerves, Dom Whicli it depends, When acted upon by the elevationos the ribs, clavicte, and sternum, and also by the expansion Osthe lungs, and in like manner by the constriction of the thorax, causes the expanse Os the diaphragm to adapt itself to the respiration Of the lungs, and acts in consequence iis OWn part in determining the pulmonary space.' 5. In like manner the re- Spiratory muscies of the lungs, Or those Whicli naturalty constrictthe thorax, suci, as the intercostat, and even the sternat audVertebrat, the nerves of Whicli arise Dom the dorsal region of the Spinal marroW, are excited to aut not only by the action of
the marros itself and iis hordisorm ganglia, but also by the friction of the nerves in the foramina Of the vertebrae, to thebodies of Whicli they aro stted inferiorly and superioriy, So that
Ipse nervus diaphragmaticus qui dicitur etiam frictus musculum sui septi excitare , qui causam suae actionis praecipue tribus nervis cervicalibus, a quibus pendet, aque cOStarum, claviculae et sterni elevatione, tum etiam a Pulmonum eXpanSione, Sic constricto thorace, acceptam debet, essicit actus, ut expansum diaphragmatis Secundum pulmonum respirationem applicetur, et Suam quoque causam in Spatio pulmonario determinando agit.
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pands and stretches the bronchia, the plexuses ulso With their continued tWigs and Osrseis are rat sed and extended, producingan effect upon ali the vesseis dependent upon them. 7. The large arteries und vetus of the body preserve the modo os actionwhicli is natural to them, even though the nerves Supplying them be separased DOm them, as We learn DOm an eXperiment
Wave Which by expanding iis vesseis excites the circular muscleos the tunic. Consequently here also is a cause of action Whicharises On the part of the body. 8. The fame laW holds With
in consequence of their rupture, lives in itS OWn proper causesas long as any fluid remaliis in iis nervolas fibro, and is enabledio flow into it in place of that Whicli has been expellen Dom thenerve; lienee When the vesset Or fibre, Whicli is the predominant part of the organigation, is touched, the fluid belonging to it is
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With Such particular determinations descend into ali the multitudinous motions in tho body, and Dom iis first principies dis-Ρ08e itself tuto conformity With tho causes Whicli meet it Onlyin the body, and of Whicli it is asterWards rendered coΠSCiΟUS. 10. Τhis is the reason Why even is the par vagum be compreSSed in the nech, Or iis branch be anyWhere cui Osr, or be rendereduseless by iis inclination to beeome tendinous, or by any Other cause, nevertheless is it be associaled With the intercostat nerve, it Will, in iis middiu and extreme paris, continue the nnturni motion Of the viscus. II. The par vagum therefore, together Withiis intercostat nervo, is transmitted Dom the cerebellum into nil those viscera of the body Whicli are governed by natural instinci, in order that it may net everyWhere Dom causos arising DOm thebody, and likeWise upon the extremo ramisi ontions os iis severatoisseis; the cerebellum uiso has no Other superintendence overit, than such as is requisite for infusing into it iis spirituous fluidat the periods of iis animatory motion; On the cessation Oswhicli infusion the action Os the nerve censes, because the life of the nervo is iis fluid, in the sume manner as the lise of the artery is iis biood; the artery dying Whenever the heari dies. 12. The extreme sinen ess of the fibres can be no obstacle to the progress of the fluid, for it Will only correspond to the sinenessand volume of the fluid itself. Because tho fibro is made insuch conformi ty to iis fluid, that tho fluid travols as Deely us isit Were not propelled through iis medium ;' there being a perfectly reciprocat correspondeuce belWeen the fibre and iis fluid, just as thero is belWeen the blood and iis artery n. 134, 135):whorosoro is the fluid of the fibre is enabled, at the mere Will of the brain, to aut upon the muscle proper to it, so is the fibre ableto aut upon iis oWn fluid, and this fluid to aut upon the musciesrom a Cause derived DOm a solarce disserent hom that of thebrain, Whicli is done Without any distinction belWeen the tWo; for traction itself Whenover it is dono by traction) never extend8srom the trunk in to the branches, and thetice into the Osrseis, uniess there be a similar action upon the Ossset, and One that is in conformity With the sueuess of the fibre; is it be extended
' Nam ita est conformata fibra ad suum fluidum, ut sive ipsa contingatur, Sive fluidum immediate propellatur, idem resultet essectus.
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from tho trutilis, it is meroly friction, not traction, Whieli is continuod in to the extremities of the fibre. 13. At every infusionthere is only an extremely smali lo8s of the spirituous fluid, in-nsmuch as no more is expressed than can in the branches thus
und the heari or brain most absolutely present. Wheresere When any potnt of a separated fibre is tOuched, compressed, or OtherWise modissed, a similis modification instantly flowsalong nil tho litile succeeding branches to the extremities, Withthis only differetice, that touch here modises but a smali numberos branches; namely, those Only Whicli are bel0W the potnt of
contreet; While the cerebrum Or cerebellum modifies ali universally, as the heari modisies est the arteries n. 570).508. The externat acting causes, therelare, ure nil the Various species of contaci that at any time excito the fibro in aWay conformabie to iis Simple Or compound structure. Thoentire nerve aeis in One Way, iis fasciole in another, tho fibroitself in another; and the acting causes must ausWer to the ordor and degree of the fibres. The cauSes are, I. Any puncture or tWitching arising Dom Shars corpUSculeS, large Or Smali, as in the intestines and stomach, nny, in the aeSophaguS, fauces, longue and gums. 2. Any irritation produced by heat or cold, in Whicli casu the sensibie fibres immediately constrici or expand, corrugate Or SmOOth themSelves; as everyWhere in any fibraled membraue. 3. Vibration produced by cauSes exciting a tremor,
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as in the trachen. 4. Teusion and relaxation, such as ta ke place When the intestines excite the bile of the gall-bladder. 5. Reciproces friction and traction Os a nerve, Or of iis tunic, or faScicle, as of tho dorsal nervos in the foramina of the vertebrae. 6. Elevation and depression, as in the phrenie nerve, When the brachial nervos, or the ribs, or the diaphragm itself, are acting, or the lungs aut upon the diaphragm. Atid everyWhere in thosenerves that depend upon the cartilages Or Other tendinous eXtremities of the ribs, clavi cle and sternum, by means of the muScles acted iapon by the Will. 7. The intumescence eXtendingand expanding the Whole nervous and fibrillary fissue os acavi in as in the heari and lungs. According to Lancisi: When ... the nerves of the heart are in a normat state, themotions of the praecordia are just and naturat; but Whon theyare depraved, or any irregularity Occurs in their siluation, number, figure, and Sige, or in any the least conditions of suliness,
sit. 463, p. 432, 433 . In another place he says, Sometimes When the vena cava isJ only punctured With a needle or Withthe potui os a lancet, the intermitted motion is again reneWed : and when the experiment succeeds, the cava moving like the intestines) mines reciprocat peristallic constrictions and vibrations
toWard the heart. . . . But What We have Stated of the vena cava,
during vivisections, censing DOm ali motion, and recoxering iis benis When priched With a needle, or stimulated by the application os a Warm body, tines place also equalty in every part os the heari, in the auricles as Weli as ventricles; a single prich, or the frusti contact of a Warm body, being sussicient to cause irregular palpitations and fluctuations there also; provided in Ways that the heari has nos grown cold and stissV n. 465, p. 444 . But more on this subjeci presently. 8. When either