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

571쪽

and the corpora pyramidalia, and botween the latior and the

Corpora olivarin. The Spinal marrOW is also very clos ely attachedon iis anterior part by means of iis enuelopes, Where the spinat

artery and vein is Deither solded nor severed, and this is done With tho vioW, that the sirst boginnings of the nerves Which goout lateralty may not be disturbed, and that every action Osthe marrow may be determinod into the nerves, into the venous Sinusos and their sinuli, and into their branches, just besore thel alter pass out of the craniat cavlty through the Same Orifices

565. And at tho moment of such motion transmits iis οWn proper blood, of Whicli it is the mover, luto both vento

CaVae, inferior and superior.-That the spinal marrow is themover of iis OWn blood, just res the cerebrum and cerebellumare of thoirs, is sileWn by the continuation of the nrteries and Vein S, as also by their attachment to iis inner membrane; and indoed to iis chiniis and fissures, as On the anterior pari. Innumerable capillarios run froin the arteries into iis proper cineritious substance, and Dom the fame, innumerable ollaeis paSSinto the vetus; and in the animatory motion are iis proper cineritious spheriales Whicli in the preceding pageS We haVe Compared to so many litile heuris). In the fame animatory motionis every capillary vesset; consequently nil the Various tWigs, branches, and trutilis. The tWigs and branches are so carried through iis integuments, and through the sirst beginnings os the nervos, that in Whatever direction the action extends, theyare in the very stream Of iis motion. It transmits this iis biood into both cavae; for the venous Vesseis project them Selves into the shereth, commonly in the formos a circular spire, niWays taking an exterior direction ns far asthe foramina, Where they malle their exit. The anterior spinnivein projecis iis branches no sarther than into the internat partos the vertebrat sinuses, after first perforating and Stightly permeating the dura mater; but the posterior spinal Vein, Where the expansion and constriction of the medulla tines place, does not project itself into the vertebrat sinuses, but beyond them; namely, into branches that communicate betWeen the ab ove sinuses and the vertebrat vetus, the agygos and cava. In iis course it likeWise receives smali streams from the dura mater

572쪽

extend ns far as the superior cava nud right auricie. MoreOVO CVery Vein is sent out froin the vertebrat sheath, through the Same notches as those traversed by the spinal nerves; and in these Velias, by renson os the reciprocat action, no Other inter-Vals of emux and discliarge can bo assigned to the blood thanthose of the motion of the nervos that simultaneousty pnSS out Osthe Sheath, nor can any other intervias be assignen to the DerveSthan those of the spinal marroW, Dor any other intervals to thespinal marrow than those of the cerebellum and cerebrum. V enre here to observe, that the blood a sed upon by the cineritious substance of the spinal marroW, Whicli is most highly active, is derived Dom the cervical region toWard the vertebralvein, from the dorsal region to varii the agygos, and belOW, through the lumbar vesseis, into the inferior cava. See Vieus-Sens, Neurographia Universalis, lib. it., cap. ii. 566. Into the superior, through the vena agygos, When thebraitis transmit their blood through the jugular vel iis .-This follOWS RS a Consequence Dom the preceding remariis; for While the spinal marroW, at the moments of iis animation, is expellingiis biood as sar as the agygos, the agygos Will at the Same moments be receiving the blood thus expelled; and in Order to en- Sure this result, the intercostat norve is sent into ali the branches of the agygos, and entWines them like ivy, as also the trunk of this Vein, and 8oon aster the vena cava; and While this nerve is Lept in the stream of tho motion of tho brains n. 483ὶ, so also is every branch Of the agygos in the fame stream os motion Withthat of the trunk; as apppars froni the fluxion of the branches of this vetii along the ribs and pleura; hom the siluation of the trianti against the vertebrae; Dom iis passage through the dia-phragm ; Dom iis subnexation to the bronchia and trachea; from iis intimate conjunction With them by the attachments of intervening vesseis und sibros, so as to be sillod and emptied ex- Rctly according to the times of constriction and expansion Of thebronchin and trachen. Thus While the Jungs perform their ani-

573쪽

maiorv motion ni the Same moments Witti tho brains, and the

is discliarged into the superior cava, When the bl ood of the sinuses of the head is dis harged into the jugular vetus, and theblood of the jugular vetiis is dis harged into the Same CRUR. Τhis is the reasou Why ali the bl od of the spirat ry sold of the lungs, or nil the blood that flows Doui the muscies acted on in respiration, is derived into the agygos; and since the respirationis so varied n. 368 that ali the muscies of the thorax and abdomen may be culled into notion to elevate the lungs, this veluis theresere ut the sume intervals constrat ed to receive theblood Dom the intercostat, intracostat, infracosint, and Supra-COstia muscies, and DOm uJl the vertebrat muscies; Dom the triangularis sterni; DOm the serrati and pectorales; Dom the - dominal and diaphragmatic muscies, and consequently Dom themammary, emulgent and spermatie Veius; DOm the trachen, Pleura, adipOSe membrane, ke.; in a Word, froin the wholo fioldio Whicli the pulmonary potion extends, Whether this actionnriSe DOm n previOus exercise of the will, or otherWise. This is the reason Of the wonderfui communication Whicli these branches

cles, to the Stomach, intestines, anus, bladder, pubes, loWerribs; or to every potnt DOm Whicli, While the respiration is carried On, the agygos can draW the expressed liquid. Thus Domthe anastomoses of this vein With Others adjacent und remote, We may inser, What Was the natural and accustomed mode os respiration in this subjeci. 567. And in ordor that there may be a continuous chnin Oscauses from the first to the last, the agygos is a single Vein, and unites With the superior vena cava beside the right auricle, andis lied up to the trachea.-Besore entering upon this Subjeci, Which touehes very closely upon the cause of the continuationof the motion of the heari, I Will give a brief description of the

574쪽

RZygOS, compiled from Lancisi, Eustachius, Morgagni, WinSJOR, nud VieUSSens. The Vena nZygos, Or vena sine pari, ObtainS itSbl00d principalty froin the vertebrat sinuses, the intereOStat Vein S, the Spinal nerves, and from a grent number of muSCles. In man it is a single velit, and placed on the right Side, ruri ning Dear the vena cava and the right auricle of the heari; though in s me subjecis there is a lesser vein,-the SeminZygOS, -On the lest fide. The vena agygos is also single in themonkey, the dog, the horse, und some other animal s. It lieson the lest fide in the hedgohog and the mouse. There aretWO Veins corresponding to it, in the Ox, the goas, and thesheep; also in the pig; but in the latior tho lust voin is so dis- posed that it receives iis bloon uiso Dom the loWor ribs of the right fide. In gallinaceous foWis there are mur Such vetus, tWOOn euch Side. The vena agygos of the human subject joius the Vena cava OutSide the peri cardium, and upon the right bronchium, round Whiel, it turns; it is also uniten to tho trachea bystrong fibres and minute ve88eis, Whicli penetrate ali the Way totho internat sursace of the lalter. In the monkey, dog, and cat, it inosculates With the superior vena cava inside the pericardium, and near the right nuricle of the hoart. In the horso, iton fers the base of the right auricle by one orifice; in the Ox

other by an intermediate muscular septum. In birus, ali the Vein8 RD8Wering to the vena agygos discliarge themselves into the right und test axillary veitis. The human SemiaZygOS, When present, rutis to the lest subolavian vein. The vena agygos lies inside the thorax, opposite the roots of the ribs, along the right si de of the vertebrae, und belWeen the membraues of the pleura,

that is, in the posterior mediastinum. It has valves, like

Other vetus; und ut iis in osculation With the vena cava, it is furnished With a muscular semicircle or semisphincter, Which is

supplied by a particular branch of the spinal intercostal nerves.

A similar muscular guard is observed in the semiagygos Or lenVein, When present, at the place Where it joius the subclavian. At iis loWer elid, the vena agygos Sometimes communientes Withthe inferior vena cava, somelimes With the right emulgent Vein, Sometimes With one of the lumbar vetus; aud in iis ascent itinere es very greatly Dom receiving ten branches, into Whicli,

575쪽

and particularly the uppermost, subordinate branches ruit Domthe trachea and bronchia. On the lest fide it receives fix OrSeven branches, the uppermost of Whicli, insinuating itself under the right bronchium, and the great artery, at the lest fide of the thorax, climbs Over the axillary artery, and ultimately salis into the lest axillary veiti. The laurili in ordor of the lest branches beginning Doui the lower en d is larger than the rest, and may be rogarded as a litile trutili Of union; it comes Originalty Doui the testes, and in semeses Dom the uterus; and increases by streanaleis joining it as it ascend s. The vena agygoSosten joius the vena cava, at Other times the emulgent Vein, and the mammary vetiis; but it derives the greatur part os iis biood froin the intercostes muscies, both of the right and test fides, Dom the serrati and pectorales, Dom the lumbar and vertebralmuScles, DOm the diaphragm, up the fide of Whicli it creeps, om the sinuses of the spinal marroW, Dom the pleura, Domthe adipose membrane, si Om the sternum, and DOm Other SOurces. Thus it receives Dearly ali the inferior intercostat vetiis

of the right fide, Which in their turn communicate With therest of the thoracic, and with the mammary veitis); also the lest intercostat veitis, though soldom the whole of them; sor thesuperior veins ruti osten to the lest sub elavian Vein. Inferiorina branch of considerable sige arises Dom the two last intercostulveins, and from those of the abdominat muscies, and rising to the vena agygos, unites With it abolit the last rib : and some- times branches come froin the straight lumbar veitis, and Domthe inserior diaphragmatic velit. But the variety exhibited by this vein While it is serming iis trunk,-the variety both in

power to dWeli upon ali the particulars thereos. We must addio the foregoing, that this vein receives no blood Dom the three superior ribs, but for the first time Dom branches between thethird and murth ribs. It is Woll Worthy of observation, that the intercostat nerve puis forti, a trutili in the neok Dom bothiis inferior ganglionio plexuses, Whicli trutili divides on eaeli fide into branches, ab ut the fourth or fifth dorsat vertebra;

576쪽

nate motion. We see Why it is connected and lied up to thebronchia and trachea, to Whicli it is so united by insertud fibres and by vesseis, that it can vomit out iis liquid Only at the alternate periods in Whicli the lungs respire; that is to say, in Whichthe bratiis und medullae animate. Thus there is a concatenationos causes Dom tho srst to tho last, tho last linii in the chainbeing formed by this velit, Whioli not only superadds the latest nid toWard the continuation of the motion of the hestri, butheeps nil the causes in a state of concatenation and mutuni connection by forming them as it Were into a circle. In Order, moreOVer, that the spinal marros may assist in executing thistask, it likeWisse transmits tho blood Dom itself and Dom part of the cauda equina into the inferior cava, so that When the muscular fibre is at rest, the motion of the cava may be called into existence from n living solarce; this likeWise the spinal marroWis enabled to do hom boing placed in the ultimate boundary of

in birds, thon they could not be inserted into the trachea, but

577쪽

on eaoli fide into the axilla , subclavian, or jugular vein, in Whicli case the last cause Would not correspond with the first,

uniess the vena cava ran in Some Other manner into the auricle;

and that it dous so may be demonstraten Dom the anatomyos birds. Thus the agygos itself confirms the laci, that therespiration Of the lungs coincides With the animation of thebratus n. 280, 283) ; as also that in the foetus, be re the lungsRTe opened, the heart so voraciotasty sWallows the blood of thebrains, and that Of the spinal marrow, as to hurry ali the blood of this velit toWard the right auriclo, Whicli is the wheel of the cardiac motion n. 514, 538, 544ὶ : nor does it allow of a Semi-ngygos inosculating With the lest subclavian vel , excepi in those subjecis Where a due quantity of blood is potared into the sub clavian vein from the jugular voltis. Helice in those animais in Whicli the agygos is dolablo, Wo may infer that the greatest partof tho blood of tho longitudinal sinus is derived in to the right

arm of the laterat sinus, and heuce into the right jugular Vein. Whether or not this bo the laci, the experience of another age wili best ascertain. 569. And it is not necessary, that the moments of animationin any of these paris should coincide with the alternate moments of the heart. It is enti rely the action of the blood of the vena cava, as eXercised principally upon the right auricle, that produces the alternate motion of the heuri n. 514, 516). This action is continuous; in other Words, the blood soWs into tho cava Domone branch at perions disserent froni those in Whicli it flows intoit Dom another; for instance, froni distant branches at periodsdisserent Dom those of the proximato branches n. 190-198, 523 . Τhe vena cava may vibrate frequently While the auricle Vibrates only Once, and the auricle may vibrate frequently Whilethe ventricle vibrates Ouly onco n. 519 . Hence it is of no consequenee at What moment the blood is potired into the vena cava, provided iis action be continuo iis . The mechanism bywhicli this is essected may in some meastare bo illustrated in the folloWing manner. Suppose two bladdors to be tied together,

578쪽

570. A similar observation holds With rogard to the Derves that traverse the sursace of the heari, for it is not necessarythat tho spirituous suid should bo potired into them Dom thecerebellum at the fame alternate periods as those in Whicli thelieari pulsates, but only that they be supplied With their juice at

Stomach, intestines, liver, arteries, c., Whicli are in the highest state os mobility eveti after being separaten froin the great nerves n. 506-5IO . For by the intumescetice of the hear tho fluid is eliminated solely froni those ultimate litile branches of the nerves Whicli are then extended, and into Which When relaxed a Desii quantity flows D in thoir largor branches an dirutilis; und lest there should ever be a deficiency of the sup-pJy to those omeis, it has besen shewn that in tho heart this supply has been provided for by the auricle and storta in a peculiar manuer n. 54I, 545). We may Observe, moreover, that in the arteries With Whicli the Derves, or rather the fibres of the DerVes, may be compared,) this may be proved to ocular demonstration D. 472). For is the great trutili of the artery be taken,

579쪽

e et iis Osten as We relax or compress the nrt ery With the finger. The effect is the samo Whether the compression he made ut the Same moments With those of the motion of the hestri, whicli isti OW ns it Were separated froin the artery, Or Whether it be made

ad libitum at anu other time. Os the samo kinil also is the

n. 506-508, 56 I). For in the doctrine of muscle, artery and fibre, the following rule is of the sirsi and last importanee, namely, that in every particular pOint Os an artery there is a liken ess of the hestri, and in overy particular potnt of a fibrethere is a likeness of the brain, and this, in suci, vise, that there is no pollit in an artery and no potui tu a fibre, but propulsits suid, just res is tho beginning Were there, and the beari Orbrain most absolutely present. Where re When any potnt of ns parated fibre is fouebed, compressed, or OtherWise modisied, a similar modification instantly flows along ali the litile succeedirigbranches to the extremities, With this only differetice, that touch here modisies biit a smali number Os branches; namely, thoSeonly Whicli are below the pollit os contact; While the cerebrumor cerebellum modifies ali universaliv. us the heari modifies allthe arteries n. 507 . 571. Since then these are the remote incient causes, it foli0w8, that the molion of the hearl may be continued for a lime without the assistance of any of them; but this time wiu be longer orshorter in proportion as the a bovementioned hodies are in the series and connection os causes: in sile, just 80 long as the nervous sbres of the heari can be maintained in their integrity and porseros actino, to preserve them in which is the peculiar ince of tho cerebellum; and so lano as the blood can be poured from thetivino fountain into the vena cava. Is it be asked by What connection Os causes the heari mav be enablud to continue iis

580쪽

Among the wOnders of natural and unatomicat history, Mesud it told, that the motion of the heari may bo continuod sister the cerebrum has been excised, and Separated DOm the cere- bellum and medulla oblongata; nny, after it has become ab SO-lutoly hardoned into stone. And that the fame may be the casein subjecis horn Without brains ; and tu insects after their headsure cui Oss. And finalty in persons Whose lungs have been longcolla Sed. 572. The motion of tho heari mav be continued uster thecerebrum has been excised, and separated DOm the cerebellum and medulla oblongata.-This Wo snd in the experiment made by Vietissens to Which We have atready alluded n. 559 , and Where the render may likeWise see the causes of the fact; namely, that suci, is tho connection of the cerebrum With the cerebellum, that although tho cerebrum stoWly and tacitly animRtes, esse-cialty in man, the cerebellum may nevertheless be expanded and constricted; and that the cerebellum extends iis sphere of activity to the sinus of the falx, Whicli sinus properly belongs tothe cerebrum; to the laurili sinus, or torcular Herophili, Whicli carrios out nil tho blood froin the penetralia of the cerebrum ;to the region of the testes, nates, and pineat gland, or to theso-called isthmus of the ancients, but refleXively; nay, CVen to the organs of the chemicat laboratory of the brain, and to the laterat Sinuses, Or syst aud second sinus of the ancients, bothos Whicli lie upon the cerebellum. Consequently as long a8 the cerebrum is ut rest, the blood is p ured in to the jugular vetus by the action Os the cerebellum, Whonce arises that lixing Spring