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

461쪽

Our sormer cli ters, We may inser the cause of the variation Osthe pulse. The causes of it, in generat, ure internat and externat; both of Whicli classes may bo further subdividen intonatural und preternaturai. But the doctrine of tho pulse is thelast that cari be givon and completed as iis importatice deSerVOS. 469. Refore we attempt to frace out the prooeimate and remote causes of the motion of the heari, it is necessary,-in addition tot hat has hilherio been suid respecting the blood, the arteries andveins, the primitive structure of the heari, the proper and coronary et esseis of the fame, and the foetat circulation.-TheSe arenearly uti the subjecis that belong to the particular experience by Which We gain instruction respecting the hestri's motion, undwithout Whicli me in vain aspire to a true linowledge of it. Tounderstand this motion, and trace it up to iis causes, i S a Work of uo litile perplexity, and one Which may veli enlist Our bestnitempta to solve it. Particular experietice, or that busied sim- ply abolit the heari, Will not be of mueli assistanee; We muStalso know the intimate relations of the heari, and iis primevalstate; and indeed, tu generat, everything Whatever that causes the animal Lingdom to live and move : in ShOrt, Ue muSt ΡΟSSeSs a generat anatomical knowledge n. 12-IG). The reason Why so many of the learn ed have entertained different opinions ou the otio potnt of the origin of this motion, is, that theyliave proceeded and judged DOm particular experienee Rione :but these opinions I sorbear to defati, because I am resolved tobe contrary to no one, but simply to fix my attention upon data and facis, and to solioW Where I see the truth, Or the cause Supported by experieuce Rud reRSOn. 470. Mean Khile, the nature of the blood, of Which We troated in Chapter I., must be sheWn besore We caii demonstrate thecause of the hemi's motion; for the heari is framod sor theblood, and appropriates to iis OKn litile arteries and fibros thepurest, SpiritHOUS, Simple, recent blOOd,-itS firSt-coming guest, in order that iis life may have precede ce of that of othororgans n. 453-456 . Again, be re Me can understand the

462쪽

precede the knowledge of iis compound structure. The condition Os accidenis and essentinis comes successive v. and DOm the

spolieti os in Chaptor IV. But especialty of the proper veraeis of the heari, the subject of Chapter VI; for these vesseis are What Joad tho blood directly into the motive fibres, or the

mena, although I tacitly admit and grant, that another principieof this motion may bo soliud, sar higher than tho body, and Dom

463쪽

472. One thing only should be premised in reseretice to the

particular subject We are noW considering, or to the motion Ofthe heari; namely, that the nervolis fibre, regavded in iis simplicity, cannot be better compared With anything than with thuartery; sor the artery of the brain is continued into the medullary fibre through the medium of the cortical or cineritious Spherule, so that it may Without doubt be concluded, that tho

464쪽

catly expandod by iis liquid, is both dilatod and elongated n.

That each has muscular action; the fibro, because it is a simple motivo sibro, or a fibro of the sirst degree; the artery, carrying the purer blood, and particularly the conglomerate artery, be- cause it is a motivo fibre of tho second degree; and the arte of the red blood, Whicli is further complicated, because it is nmotive fibre of the third degree; as an entire muscle is, of the laurili degreo. That tho artery is nothing but a compound fibre; for the nervous fibre Winiis round the arteriai vesset in a perpetuat circlo, just that the fibre may pass Doni the superior degreeto the inferior, While it bucomes the artery, or the motive fibre of the seshy muscie; for the purpose of boing enabled to aut conformably upon the fluid of that degrue, or upon the blood. There re there is no truly vital solid in the wholo body but thesibre; and there is no truly vital fluid but tho spirituous fluid intho fibro and in tho blood, and Whicli is the one Only animal substanee : so the b Ody is nothing more thau the appendix of thebraitis, for their's is the fibre and spirituous suid, or Whatevertives in tho b dy. The fibro, With iis enclosed spirituous suid, assumes every affection that the litile heari or cortical spherulo prefixed to it, receives; almost as the artery With iis biood receives every affection that the heari impresses iapon it, ns is manisost Dom the pulse: so that the si bre has the fame state as iis parent brain. The reason os Whicli is, that in elastic substances nothing perishes, but the state communiented to One is communicatsed to nil n. 100, IOI). Almost the fame rule holds good analogicalty of the red blood, in Whicli the fame qualities exist, but more imperfectly according to the degrest of composition n. 102). Meanwhile ali nervo, Whilo it is produced in iis natalsoli, is formed With a vieW to ultimates, Or regards the use thalit is to assord in extremes sit. 25 I). For this reason it is various in iis maniplos and fasciculations; and it comes sortii hard orsost; and as it ruris on, it exercises processes Os exuition and separation to fuit it for uses in intermediate things also; and finalty, in ali the ultimates, it salis almost into simple fibres, justas it Was in the primus; and tuto more simple fibres When it hasto receive sensations; into less simple fibres, When it has tonitemst anu effect motion : there re it is preti y nearly similar

465쪽

to itsolf sit both oxtremes; and in the intermediates, Or Mongiis course, it is a conglomeration, or properly a nerve. But it vere useless to carry the parallel sarther; lar the comparisonthroughout presupposes the existence of a spirituous suid, and

ness cannot reach them, he deprives of their causes ali the eL fecis that nature operates in the animal kingdom. 473. We observe in generat With regard to the Derves, that the specific function Os any nerve cannot be eXplored, uni SSWe eXplore also at the fame time the ossico of the muscies thatit enters and per rates; the office of the glands that it moves; of the nervos With Whicli it communicatos; and of the arteries and voltis that it comes in contact With: ail Whicli must be collected in one sum; thon the compound and simultaneous actionos ali, and tho simple and particular action Of each, must be Con-

bers or syllabies, as in the algebraic analysis, and We are ignOrant of iis value, utitit it is resolved into analogies and ratios, Or into various forms Os subordinate equations. Atid in theu animous body, ali the actions possibie in any one subjeci,are repreSented by the nerves, and subsist as it Wore in equation, SO long as they do not represent any distinet action. Isthen an action be like an equation, and eaeli fibrii, Or conteX- ture os fibriis, bo like a number Or ratio entering into the equation, it is evident that the tWig of a single nerve can be used asa pari or ratio in innumerable actions n. 15 ; for Whether We Speis, Sing, ery, Dat, Cough, gape, Sneege, figlit, or embraee, the twig of One nerve cati talie some sitare in ali these actions, although every nerve has iis oWn proper function. But is Wowould resolve the Whole of this naturat equation, We must havea linowledge not Only of every nerve specifically, but of eve nerve genericalty al8O. The trunk is analogous to the generat ; the branches derived Dom it, to the particulars under that general; While ali are universally under the most generat. Mean While, in Surveying the astonishing connexion Os ali paris, scarcely any seeling remains but mere WOnder. Το considerthum severalty Would be to Write volumes. Nature is alWays in

466쪽

ministrant cerebellula in the places Where they are Set; moreOVerthoy consist os a mixture os cineritious and medullary Substance. The cardine nervos themselves, RS already Observed, and RS Wemay See from the plates of Lancisi and Vietissens, proceed sorthe most pari Dom suci, ganglia, and principalty froin the great cervical ganglia of the intercostat nerves on both fides. Thohighest of these ganglia on the lest fide gives out Dom iis bosoma large frutila toWard the praecordia, and a considerable proportion Os the others also is spetit On the cardine plexus. ΝOW RSit is our present object to explore the action Of this plexus, Nemust begin our enquiry Doui this potui. The highest cervical ganglion On the lest fide, Dom Whicli as iis genuine beginuing, and also DOm an almost similar ganglion On the right fide, the intercostes nerve proceeds, and determines itself both upWardsu ad dOWnWard S, may serve as the exemplar sor est the rest. Τhis ganglion, according to the exquisito dissection institutud by

467쪽

Lancisi, and tho minute description Which he has given, is en closed Within three membranes, a litile increased and thichenodby an accession Os fibres.' The exterior of these membranos Ioosely invests the ganglion, as the tunica vaginalis testis investsthe testes, and the enclosed body may be squeeged out like a

Lernet by compressing it betWeen the fingers. Iis fissile is made up externalty of red fibres; internalty it is moistonodwith a light lubricating 1luid, liko that of the pericardium. Theother tunic invests the ganglion stili more closely, and consi Sis of tendinous fibres, but more solid stud complicatud. The third membrane, called by Lancisi a circular tendon, is composed ofa tendinous substance strongly united to the body of the gau-glion, and has iis fibres continuous With fleshy fibros. So that the whole ganglion is formed principalty of tWo tendonS ; I, of a

branes, and of the litile nervos di sed through them; Whichtendon not Only covers the Whole mass of the ganglion, but also enabies it to exercise muscular action force. 2. Os anothertendon, Whicli descends through the middie axis of the ganglion from the head to the tali, and givos oss penniform fibres. In this ganglion, boiled and stripped of iis tunius, Lancisi discovered onthe ouiside a Liud os nervolas rete closely implicated With iis membranes, and under it fleshy fibres rutining in beauti ut order om top to bottom, as in the riud os a meton divided by surrowsinto equat segments. In addition to this, innumerable fibriis, uuited With the internat tunic, emerged Dom the intermediate

commissures of the fibres, and Which Were torn nWay as theganglion Was stripped of iis membranes. The superior VerteX of this ganglion is attached by nerves and membranes to the fulcra of the vertebrat und craniat bonos. In to this ganglion, as indoed into the others, not one Only but Severat nerves are

admitted, Some of Whicli run in straight by the vertex, Otherstransversely at the belly and sides, Others insinuate themselves obliquety; most of them reacti as far as the internat substance, but some are dispersed solely through the membrane. Such aspenetrate to the internat substance, seem to be Alightly tingedwith a blood color, but the rest are White. The blood in thointernat substance is derived Dom the trutilis of the neigh-

Dissert. de Ganyllia Nereorum, fg. 2, 3, 4.

468쪽

boring arteries and vetus, and entering the ganglion, together With a farrago os nerves, contributes, with them, to mine Us iis bulli; a bulli Whicli novertholoss alWays appears grenter than is proportionen to the various bodios and vesseis that enter it. Thenerves that issue Dom this ganglion proceod in disserent directions ; for instance, to the pharynX, larynX, tongue, membranes, trachen, bronchia, nay, even to the carotid artery, the vorta, and jugular Vein, and to severat muscies; but the nerve that proceeds toWard the praecordia, descends belWeen the mediastinum and the pericardium. 475. From the evisceration and anatomy of this principalganglion Of the intercostat nervo, We decided ly learn, that theganglia in generat are constructed for the purpose of promotingilie progress of the nervous liquid and spirituous suid. For the fibres in the nerves are so compacted Within their tunic, and the fascicles os fibres With in theirs, that unless they are utilat dedand relaxed on their Way, they cannot potar sortii their liquid in

tid artery, and jugular vein; ali of Whicli are in a state Os perpetuat activity, and require a continuous and unimpened 1low of blood, inasmuch us their life consisis in their action. Notindoed that the above-mentioned fibres and fascicles depositaught of their liquid in the ganglia themselves, or terminate in them, and run Out DOm them again as Dom neW stations; butaster being previolasty constricted, they here relax their bands, and enjoying a Deer expansion, suffer the fluid to be propelledonWardS, und ut the Same time themselves propel it. Τhat theydo propel, is manifest Dom their muscular character; that isto Say, DOm their membranes, their blood, their fleshy fibres, thoir tendinous extremities, their belly, and their oblong figure; so that When they contraci, they dra upon the continuous DerVes, and When they unsold, they relax these nerves; and indoed the whole nerve distinctly, the fasciclos of the nerves distinctly, and tho fibres of the fascioles distinctiy; sor the Outer-

Within, through whicli tho fascicles ruti out in disserent Ways, though for tho most part in a right lino, and whicli is likeWise

469쪽

invested with a muscular tunic. There are Smali meShes, Or asit Were rotisortii plexuses of fibres, that either creep in Ono integument, and there sold themSelves Up, Or et Se intervene beatween the integuments. Hence the litile ganglia are themselvos vehicles of nervous fluid, and are consequently auxiliaries of the cerebellum, medulla oblongata und medulla spinalis, Without

Whicli the extreme fibres, Whose activi ty is perpetuat, Mouldsoon bo destitute of their vital fluid; a circumstance to Whichthe cardiac machine Would be especialty liable, acting as it dous unWeari ed ly, and never permitting iis muscie to subside tuto

476. But in ordor to explore ali the uses of the ganglia, Weought to en quire into every delati respecting them; into ali thenerVOS, arteries, and Veins that enter them; nud into the modo in Whicli these run through the Gordian knot: and into thosethat pass out froin them; and What muscies they enter; and then in to the generat and particular action Of the muscies, inn8much ns it proceens Dom the nerves of the given ganglion ;Whicli notion again should be compared With the origins of enchnerve, and With the usu and office it is dedicatod to from iis very infancy n. 473) : an investigation Which Would be exceed- ingly complicated, utiless ali things Were considered in Ordor. But such an enqui belongs rather to neurology a8SocialedWith myology, and to both as applied to the natural and voluntary actions of the body and members. Meantime it is evident, 1. That the ganglia serve as auxiliaries und vehicles for moving the nervolis fluid OnWards. 2. And in faci thuy distinctly moveonWarus that Whicli soWs belWeen the fascioles of the fibros, and that Whicli flows belWoen the fibres, and that Whicli sows in the fibres n. 157). 3. Αnd by a proper muScular larce, Rud aforce analogous to muscular, they drive hom poliat to pollit tho fluid that intervenes between, and the fluid that traverses, the fascicles and the fibres; and thus perform an assistant functionto the bratus. 4. They receive the reflex motions both of thoentire nerves, and also of the fascioles, and extinguisti those motions, to prevent them Dom penetrating up to the brains, and disturbing the principies; sor the ultimate enVelope SUr- rounds them loosely. so as to duli a d restruin the impetus of the disorderly verve. 5. They reduce the Various, and even

470쪽

Subordinate natural motions, to one universat motion, Whicli is that of the bratus. 6. Τhey finalty combine into a single centreos action, the severat nerves contributing to any common Orparticular action, so that Out of this centre os action the nervesare en led again to emanate With a similar sorce and animus; at least in respect of tho fluid and lise of the nervos that produce the very notion in the muscies. But under What serm OfSociety the nerves potir forti, to the sield of this action, and hoWthey mingle So as to conspire, is a secret Which no acumen Os Sight can penetrate, und Whicli cun be ascertained only Dom the CXtremes Where the nerves again un&ld themsolves into fibros; in Shori, Dom the mutuat and distinet survey os essecis. 477. And into the cause of the action of the intercostat nerve.

Α specific knowledge of this nerve is requisite, for it, together With the par vagum, has the govertiment of the heart. Fromnearly ali iis ganglia placed in the necti, it seuds considerablebranches, Some to the peri cardium, some to the great reticularplexus, and distributes another entire branchJ over the ventricles of the beari; so that the heari seems to be ontrusted to iis guidance particularly. Where re, Without a previ Ous description of it, and an understanding of iis mode Os action, We cannot trent of the motion of the heari Dom the ground of

478. The intercostia or great sympathetic nerve, ConStaΠtly increasing Dom nerves passing to it out of the spinal marroW, is Supposed to derive iis origin Dom the fifth and si xth piars of cerebrat nerves. Whether it ariso Dom these, or Whether itterminate in them, it is Weli ascertained that One, tWΟ, Or more threads ascend at the inside of the fixili patri or that a fascicleos severat issues forti, obliquely, and contrary to the flux of thesibres. But the mode, condition, obliqui ty, and number of theluosculating filamenis, varies according to the Vari OUS characterSof subjecis. Eustachius places iis origin or en d in the fixilisair alone. Vieussens, Ridley, Heister, Willis, and Other penetrating anatomisis, derive it se in the fifth and fixili patrs con-jointly. Indeed it is evident, that notther the fifth nor fixilisnirs, When traversing the receptacles of the sella equina, dis-Ρ0Se themselves to form tho intercostat nervo; but that the lat-ter, by sen ding Out flendor cord8 and Statiling 1 OOtS, connectS