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UI PRAEcESSERANT, NON PRAERIPUISSE MIHI VIDENTUR QUAE DICI POTERANT, SED APERUISSE . . . . SCIENTIAJ CRESCIT IN DIES, ET INVENTURIS INVENTA NON OBSTANT. V-SENECA, EPIST. LXXIX.
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I. BEFORE We approach the subject Os the moments Or intervals of motion observed by the tWo braitis and medullae, Whicli motion me cali animation, it Will be requisite as a foundation to prove the motion Of this viscus by experienee. Wemust not trent of these moments besore We have ascertainediheir existeneri nor enquire into quali ty be re We are certainos actuality. For the ancients ulterly dented the existence of this motion, as also do certain of the moderns, thoughit has at last been clearly detected by severat great anatomisis, such as Ridley, Vietissens, Baglivi, Fantoni, Bellini, Pacchioni, and Others; and so clear is the evidence of iis existence that Whoever doubis it at the present day must doubi the senses offight and touch. In asserting the existence of this motion, it Will be requisite merely to cite the experimental facts recorded by the above illustrious authors; these facts being WOrth innumerable arguments. Τhus Ridley says, that having opened thehead of a living dog, he observed a systallic motion of the
dura mater and longitudines Sinus, . . . analogOUS to the PHISR-tion of the heari, Which Was quicker than usual, and exactly corresponding With it in pOint of time. . . . When One blade ofa blunt piar os scissors Was cautiousty introduced into an aper- ture made in the membrane, and the lalter Was stit open, thebrain covered With the pia mater protruded through the aper-
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ture, iis motion' stili continuing strong to the tOUCh. . . . OnasterWards gently smearing over the dura mater With a seW drops of Oil of vitriol, no vibration of the membrane, Or at least onlyan insignificant and Obscure vibration, Was percei Ved, ... thoughon applying the finger, the pulse of the brain iiself Was very
the animal manifested sigiis os great pain; and when the blade Of a knise Was passed right through to the opposite fide of the
thrusting their fingers into the brain, observed that iis systoleand diastole mere carried on in spite of the great resistance thus opposed.V Philosophical Transactions, an. 1703, p. 1481 1483.) And Vietissens says : We asseri that the whole massof the brain, especialty Where it is at some distance Dom thebones of the skuli, has a natural motion Os intumescetice and detumescenee, and We prove it by the single faci, that When meopen the head os a dog, or of any Other animal, traces of the severat externat convolutions of the brain are found accuratelyaud deeply engraved upon the boues of the shuli. Such traces of the exterior figure of the convolutions of the brain, could never be imprinted upon the inner sursace of the situli, is thebrain Were enti rely destitute os motion; for no One, We preSume, Will assirm, that the dura mater, as it lies betWeen the skuli and the brain, is capable of producing depressions in the shull.V Neurographia Universalis, cap. Vi., p. 41; fol., Lyons, 1685.)Baglivi says: Whoever Wishes to be assured upon this matter, has only to inspect and consider the anterior part of the cranium in a neW-bOrn child; for the bones being exceedin y sost, by placing the palm of the haud upon them W0 shali feel a strongaud regular motion Of systole and diastole. . . . But is We Wishto perceive stili more clearly the systole and diastole of the dura mater in iis Whole extent, We may do so in Wounds of the head whicli are accompanted by fracture of the shuli, and penetrate to the brain, such as We Ourselves have seen in severat of the
Italian hospitais,) and we shali then sind that the entire portionos the dura mater Iaid bare by the Wound, pulsates equabb and
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sorcibly, and not ouly in those channeis and surroWs that arehollowed out by the litile arterius distributed through it: as Would bo the case is the motion os the dura mater dependedupon these litile arteries; supposing Which, should convulsive motions supervene DOm the wOund, We should be quite at a Jossio account for the strong and evident pulsation discerniblothroughout the dura mater, and distinguished by iis oWn properinterVals and spaces, so that One Would reatly think it Was thelieari that Was pulsating. Τhis phenomenon the author has Witia essed Osten und in the presence of others.J V De Fibrci Motrice Specimen, lib. i., cap. iv.) And Fantoni says: Nothing in the brain is more conspicuous, than iis alternate sWell-ing and subsiding, or dilatation and contraction : these motionesare visibie in cases of Wounds of the head, and in the vivisectionos brutes . . .. We find it recordest of Zoroaster, the celebrated Κing of the Bactrians, . . . that on the very day that he Wasborn, his brain palpitaled to such a degree as to repet a liandWhen placed upon it. . . . It is Well known by experimenis, that in living animais, When the brain is Wounded, and the fingerthrust Weli into it, a very strong diastole aud Systole of iis sub-Stance are perceptible. TO state a generat opinion, not a particle of the brain is destitute of this motion : uJl the gland sand ali the littio iubes eHoy an alternate and regular CompreS-sion. Epist. ad Pacchionum, in Pacch. Operibus, p. 171, J72;4to. , Rome, 1741.) I say nothing of Other observations to thosame effeci, draWn directly Dom living subjecis, and recorded by a great number of celebraten authors, as Pacchioni, MayOW, and particularly Bellitii in his opuscula, Where he spealis of the systallic motion os the brain and the natural contractili ty of the
depend upon the animatory vibration os the subjacent Or interjacent brain, and in part also the dura mater, Whicli is theuniting medium belWeen the motions of the brain and heari,as Will be seen in the Sequel. 2. We must in the first placo bear in mind, that it is a very
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dissiculi task to Oxplore accurately in living subjecis the distinctintervias of the elevation of the bratu; for in order to perceive them, a considerable portion of the skult must first be raised; the dura mater Whicli adheres to the situli beside the futures must then be separaten Dom it, and this mater must be divided, in Order to Open a passage for the finger to the substance of thebrain. The folloWing obstacles to a just observation os effecis
Elther in consequetice of the dura mater being delached om the bones, and divided, the force and abi lily of the brainto reciprocate iis motions proportionably fail; for iis faculty of
regular and distinct respiration of the brain. Or elae the sinus of the dura mater, especialty the Superior longitudinal sinus, and perhaps also the two laterat sinuses, sill With blood. For as the arterial blood then rusties immediatelyinto the sinuses, and a fuit egress through the jugular vetus is dented it, in consequetice of the contractiou of the brain, and iis cessation Dom motion, the brain becomes quiescent, or elSemith great effori labors to mahe an intimate motion, and as it vere to Overcome itS OWn substances. This likeWise tines place Whenever the necti Or chest is tightly bound with a ligaturo in the manner somelimes adopted sor destroying dogs. Or elae there is some hindrance arising Dom extravasated blood and serum. It generalty happens in vivi sectionS, in consequence of the contractions and essoris they produce, that thechanneis are clogged and the interstices siled that oxist both without and within the substance of the bratus and marro , RS a provision for the Dee exercise Of expansion and constriction. Or elae it we do not reach the brain iiself, We perceiveoither by sight or touch the motion of the dura mater Rione, and concludo Dom it to that of the brain. But here me aredeceived by sirst appearances; for there is a miXed Or compOundmotion in the dura mater,-one motion OWing to iis arteries, whicli communicate immediately With the arteries ou the oulside
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of the head, and another motion received Dom the brain through the medium of the three great sinuses. Τhis is thoreason, as I think, Why Baglivi, Pacchioni, and ali other anatomisis, so far as I knOW, founding their assertions upon What appears to them to be experimental faci and evidetice, assertiliat the moments or pulses of the brain and heari are SynchrOnous. But that this is nos tho case With tho bratu itsolf Willappear Dom a closer investigation Os the phenomena. 3. Let us nexi proceed to arguments; first, to Such as areprobabie, nexi, to Such as are more demonstrative. The Subject is so Wide, that is What We have stated be true, We shalliind clear and ample confirmation not only Dom the whole ofanatomy, but hom the Whole circle of medicat experience an danimal physiology. Indeed it is a subject Which, as We proceed, cannot remain long in obscurity; for the brain considered in iis Widest acceptation, that is, as comprising the cerebrum, Cere- bellum, medulla oblongata, and medulla spinalis, reigΠS universalty aud particularly in the fibres of the body; and thelieari, in iis arteries and vesseis. Hence Whereuer there is a fibre associaled With an artery, or an artery Mith a fibre, thatis to say, throughout the whole body, manifest sigus must existio decide the question Whether or not the action Os One soWAconcordantly into the action Os the other. But let us come to
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or undiae quantity of the blood Or Serum, SOme aneuriSm, poly-POUS accretion, Or Other incidental malady, the brain Would as- Sume and imitate the inconstant motion of the heari; Which could not but be attended mitti imminent danger to this most nobieorgan, and particularly to iis cortical substance, Whicli requires the most refined blood, because it requires iis purest essenee. 5. Were the motioris of the tWo organs synchronous, in this case, either the motion os the brain Would floW into the motion
of the heari, or the motion of tho heari tuto that of the brain; is the former Were the case, then the brain could not be moved by causes originating in the body, as atready indicated: is thelalter, then the brain Would be moved by ali tho causes that assect the pulso. This likeWise appears to be repugnant to the
constant a d certain IaWs Os nature, and of the animal economy,nV, even to the laWs of subordination; for the brain is priorto the heari, hetice iis motion is prior to the motion of the hestri; as is evident Dom the observations of Malpighi and othors oti the chich in the incubated egg. What is prior does not in the order of nature suffer isseis to be commanded by What is posterior; nor What is superior by What is inferior; Dor What is interior by What is exterior; just as in civit order, themaster must not be under the controi of the servant; that is tosay, the brain must not be under the controi of the heari, utiless the brain purposes to live under the jurisdictiou of the crasser blood, Or to lead a Lind of mere corporeal life governed
vesseis that pervade the sursace of the brain, or iis proximate membrane, have such a degree of Strength, and 8Weli to so great an extent, as to elevate the entire subjacent mass of the brain;
sor according to the experietice of Ridlen Fantoni, and others n. I), the pulse of the brain is perceptibie internalty, and sWelisus Dom beneuth the dura mater, so that the truces of iis arteries and of the furrows of the brain appear accurately imprintest upon the inner tables of the sinciput. Wepser also doubted Whether the arteries possessed this poWer, and Candidly expresses himself on the motion of the bratu : That thebrain is moved by the arteries,V says he, although it be furuished With very many, and although considerable Ones lie under
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iis base, is more than I can venture to assori; considering the inadequasty of tho arterint pulsu to elevate so large a maSS RS
aud Π0t only this, but also upon iis inmost substanee and Very Core. Epi8t. cit., p. 172.) Hence Wo may infer that in ali probability, the arteries themsolves are not the cause of themotion of the brain; but that iis origin must be fought elSe-Where, that is to say, in the brain iiseis; and consequently ina8much as the origin os iis motion is different hom that of thelieari, it follows that tho tWo may either coincide Or not coineide. For in ordor that the two origitis of tho motion of tWo bodies may constantly unite Wit, euch other in thoir progress, it is requisite that there bo a third uniting and intermediate b Ody,
eontinue under the fame necessity os reciprocating iis motion ,
as the impulsive causes of both the hodies. 7. That the origin of the motion of the brain is voluntary, or in the Will, Wo may plainly infer Dom this, that the brain knows What it Wilis, and Wills What it knows, and lienee iS Casa ble of being the cause of iis oWn motion or animation. Τhat itis the cause a d author of iis motion in particular, is sufficiently evident si Om iis active poWer ovor tho muscios of the body. Isit has the power of uti liiing itself and iis substances in eVery particular see fari II., 11. 132 176), it follows that it has thep0Wer of doing the fame thing in generat. This folloWS RS amalter of COUrse, because every particular tali en collectively is identical With the gonorat. Similis is the origin os respirationor pulmonary motion, for every one linows that it is voluntaryduxing the da . Is theros oro tho origin of tho motion of thebrain be voluntary, and is that of tho lungs be also volunta , it Would appear, that tho animation or rospiration of the brainis coincident With the motion of tho lungs rathor than With that of the heari, Whose systole and diastolo are entirely SpontaneOUSOr naturai. There is indoed an animation of tho lungs Whicli is sartly Spontaneous, as during sleop, but such also appears to bethat of the cerebellum, Whicli assumes the govertament ni Digbi, When the cerebrum fleeps in respect to any exercise of Wili UpOH
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iis paris, and the cerebellum draWs a deeper and more regularinspiration uni terrupted by any voluntary animations of the cerebrum. Thus this voluntary motion, mixed With the naturalmotion, appears to be reserable to both braitis, for the motionos the cerebellum and tho tWo modullae is coincident With the
8. AS We may argue DOm the origin os the motion of thebrain, SO may We argue likeWise hom the final cause, and Domthe effect of this motion. The effect is, by the animation Ofthe brain, to propol the purest fluid or animal spirit Dom thecortical substances through the medullary fibres into the nervous fibres of tho body, and thus to animate iis Whole Lingdom, and malle it live, at every successive moment, by means of the transmission of this fluid. In ordei for this effect to extend to
agent in the body having a motion concurrent With iis oWn; and this agent is no other than the Iungs, Whicli appear to play the fame part in generat as the brain does universalty in particular. FOr the pulmonary action plainly extenda to every single potnt of the body, and even is it does not aci upon ali, stili itis in the effort so to do, as observation and experiment might sufficiently attest, Were this the time to adduce them. NoW is these tWo motions are concordant in their intervias, then bymeans of this generat auxiliary, the spirit, Whicli is the life of
the body, Will be disrused rapid ly and in iis natural vehicle
brain not consocialed with the motion os the lungs, but Withthat of the heari, in those creatures Whicli respire; for the heartacis solely upon the red blood, the brain acts more universalinand With each lung, upon the purer Or White blood, and at thesame time also iapon the spirit of the blood, or the exquisitelysubtile juice of the nerves. Is the circle of the red blood gere
performed in the arteries at the fame intervals as the circle of the nervolis suid in the nerves, I scareely knoW Whether any
muscio in the body, With the exception of that of the listari and arteries Whicli are stimulated to action solely by the influent blood , would suffer itself to be incited to stet; sor in proportion