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This is the generat opinion of the learned, as Weli RS OMoWn, and is confirmed by ali the phenomena of the casse. The existence of the animal spiriis is unquestioned, as also that theyare conceived in the brain, and sent down through iis fibros intotho fibres of the body, and ultimately into the motive fibres of the muscies. For Without the ministration of the spiriis, actions corresponding to the decisions of the soles could never be per- rmed, ΠOr could sensations be conveyed to the foui; and there- fore When their descent is impeded, either at the fountain-head, whicli is the brain, or in the sirst streams, that is to say, in the medullary fibres, or in the nerves themselves, Whether the impediment be tho result of compression, di Vision, erOSion, Or
cylinders, as is designed to convey a fluid; besides Whicli, without they had a quid in them, nothing Whatever in the animalbody Would have either origin, progreSS, Order, iam form, Ortise. The nature, hoWever, of the medullary sbre, and also Ofthe nervous, and the mode in Whicli the lalter is connected Withthe former, Will be shewn in the Treatise on the Fibres. NoWsitico it is indubitable that a species of suid, or a Very pure e8Senee, permeates the fibres, the question is, hoW to nume it. In generat it is called the animal spirit, and likened to a most
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It sol loWs by the very connexion os causes, that the animal Spirit cannot be conceived und excluded anyWhero biit in thecortical gland; Which lalter is the beginning and head of iis OWn fibro, and the litile brain of the samo. Is then the fibro Springs Dom the gland, and the animal spirit is the spirit os the fibre, the solantain and Womb of the spirus must be in the gland. The cortical gland then may deservedly be styled the most perfeci modet laboratory and chemicat organ in the
animal Lingdom. Moreover according to anatomisis this gland contains a litile cavity, a simple chamber Or ventricte, and has Within iis structure a pure medullary and cortical Si Stanee, Whereby it is the most perfeci exemplar of the grand brain. There is theresere no doubi that the spirit may be prepared init. The means, hOWever, and the ars, Whereby this preparationis effected, and the nature Os the spirit produced,-these arethe main fastis and dissiculties of Our exploration. The mostlearned an atomisis, as Weli as the best authorities on physios, agree With us so sar, and theres Ore ascribe a glandular characterand construction to the cortex of the brain. For nil the animal humors are elaborated in glaniis; and the finer and simplerthe gland, the purer the humor; Whicli in the highest casushould be callud nos simply a humor, but the bellor anil nobieressenoe of the humors of the body. Theres ore it is designatud by the peculiar and appropria te titie of the animal. SpiritS.
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Such is the correspondence Whicli prevatis throughout theanimal Lingdom, that the nature os one thing may be knoWΠDom that os another; and this mode os inseretice is particularibavallabio for the fluids, Whicli permeate the fibres, vesseis and ducis. The fibro is sorinest With a vioW to iis suid or spirit; the
Vesseis, arteriai and venous, are formest With a vieW to theirs, thatis to say, to the blood; and the ducis are formed With a vieW to the other humors. Ali these paris Dom the earliest insancy are inaugurated into this conformity. SO mutuatly are they accommodated to euch other, the containest fluid to the containingsbre, or the containing tunic of the fibre, that they mae con-jOintly one cause and One determination. But I sorbear this train os argument. Certain it is that tho anatomy of the fibrosii eWs the possibi e character of the spiritu us humor; but iis internat nature We shali noW investigate a litile more deest y.
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and imperfeci substatice. For the frest thon to operate Uponthe last, there must be a middie or intermediate that tu hos iis nature Dom both. In Other Wordes, sor the most persect to actupon the imperfeci, there must be a linii Os intercession, totalie something Dom both the persection of the one and theimperfection of the other. The animal spirit is such a linti; and there re Where the animal spirit is Wanting, the foui is poWerle88 to govern the body in correspondenee to iis OWn operations. This is plain Dom actuat essecis and phenomena; theexperimental demonstrations On the subject being rather Superabundant than deficient. It will, hoWever, be impossibie toeXplain to Ordinary comprehension hoW the animal spirit playsthe part of a mediator belWeen the foui and the body, uni essWe are previousty aequalia ted With the desinition os, and thodistinction belWeen, the foui and the body. We have atready desined the foui, as Weli us the body. But to enable us to perceive the mediation here alluded to, We ought to know What suids and fibres they are Whicli determine the forin and structure of the body. Τhe sirst, the principia, and the properessetice and substance of the kingdom, is that Whicli is tormodihe solit, or the solvis'; the last is the rod blood. The blood-Vesseis produce the ultimate form, i. e., the form of the body. The Orginio Structures ure called into existence, fashionen and conStructed, by mere VeSSeis, and by mere fibres. The animal spirit is theresere the intermediate essen ce belWeen the solitand thu red blood. By this stlone cun the foui aut upon the
The essenco that is intermediate or mediatorial between thesoul and the body, must talie iis nature Dom both. Τho foulis spirituat; the body is materiai. It sollows that this animal
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spirituat could never operate upOn the materiai, Or vice NerSa. But ho v naturos so disserent can be united in One subjeci, re
dissolved, Other globules are set free, Whicli are not red butWhite; and indoed according to the Osten repented and clear experience of LeeuWenhoeli, one globule of red blood gives birili under the above circumstances to Six tesser globules Ofwhite blood or White humor. Not only have the lesser globules beeu Seen, but their peculiar mode os cohesion, and also os Separation, has actually been described, as meli as tho laci os these tesser globules sundering into Others still smaller. Tothis potui at the present day has our vision penetraled, SO that we cati no longer doubt of the existence of the lesser globules. The volume or humor consisting of them We term the whiteand mid diu blood, inasmuch as it arises immediately When thered blood globule is ruptured. This issue os pellucid blood must evidently Spring Dom a fource of iis oWn, inusmuch us itis divisibio and to the lusi degree flexibie, and theresore cannot
Tho identity betweon this purer blood and the animal spirit, We deduce Dom the circumstance of iis permeating the minutest capillaries; of iis Winding iis Way into the cortical glands, Domwhicli it is derived into the fibres, and so accomptishes iis circle; Dom iis being of a sussiciently sost nature, perfectlyyielding, also divisibie, and capille os accommodating iiseis to
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intermediate betWeen the solvi and the red blo d. The lalter, that is to say, each globule of it, is in a manner the repositoryand complex os ali the paris Or forms antecedent to it in exist- ence, and even derives iis principes essence Dom the foui, belligpreeminently animate. Is then the red blood has iis prior essencesrom this pollucid blood, the lalter Would seem to have iis prior essetice Dom the foui Or the primary substance. For it musthave in it some deeper ground , something relatively excellent aud prior, also higher, more intimate, Simple, and persect.
To the end that the murringe of the foui and the body may have issue, and that the progeny may inherit the nature of both the parenis, the lalter must os necessity meet and combino in that chemicat organ Where the spirit is prepared. Τheorganic form of the cortical gland, as specised above, containsa minute chamber Or ventricle; also a medullary substance of the purest Liud; and this, tWO-sold, or vasculis and fibrous; and moreOver a simple cortical substance, Whicli is the originand beginning os simple fibres. By comparing the cortical gland in these particulars With the brain, Which itself is a glandand a great chemicat laboratory, We may to a certain eXtentillustrate the generation of the animal spiriis; or at ali evenisso sar est listi it, that When the causes of the phenomena coincide, the above potuis Will go a long Way to perSUnde HS.
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Τo understaud illese positions, it Will be necessary to malle Oursolves familiar With the construction of the cortices gland. We have given a description Os it above, Where We lime SheWΠ, that the simple substance termed the foui, is conceived and bornby a transcendent process in the simple cortex ; and that thesimple fibres are iis chinneis Os determination, Or the rnys of iis intellectual light. Is then this firsi substance is conceived in the simple cortex, it must be carried stlong iis fibres Where-over the luiter are determined. NOW that a very large part of the simple fibres terminates in the extremely minute cavlty Of
the glaud, is rendered highly probably by the analogy of the
Τhis position of Swedent,org appears to be borne Out by modern reSearch, Rithough his deduction has not yet been dra n by others. It is now generalty admitted that each nervous fibre, including also the medullary fibres of the brain, proceedsSingly, i. e. , Without real anastomosis, DOm iis origin to iis termination. But is me regard the whole brain as a cylinder, and compare iis calibre with that of ali thenerves Which issue DOm it, and of the spinal marro , the proportion Will probablybe as more than 100 to 1. Α vast body of fibres must theti terminate in the brainitself; and where therein but in the ventricles, the walis, fides, Or ends of Whicli consist for the most part of medullary substance Z This consideration throws important experimental light on the existence of the animal spirit, as weli as indeedupon the functions of the brain generally. - Tro
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posit their spirituous essenee. The portion os fibres Whichdoes not terminate there, runs toWards the medulla oblongata, to give origin to the nerves. The fame appears to be the casewith tho simple fibres in the cortices gland, that most minutebrain. Moreover the lalter is a considerable mass relativelyto the fibro to whicli it gives birth, Which shews that it is notali spent iapon the fibre. Is then so large a portion of the fibre terminates in the litile chamber of the gland, it follows that the very substance that is born in the simple cortex, must bederived to that chamber, and be polired thereinto; nil indeed but the part that goes to forin the medullary fibre. The analogy of the brain shews likewise that the purest elements and sulphureO-saline principies of the Serum, are conveyed into the fame chamber by their oWn proper Vesseis. The medullary substance of the brain is tWOsold, Vig., vascular and fibrous. In the lateria ventricies moreover We have the choroidplexuses, Whicli consist entirely of vesseis, Or Os interlacemenis and mesties of litile arteries. From these a quantity of serum
exudes into the ventricles, Whicli mingled With the spirituous essenee of the fibres, prepares the animal spirit to pass Withfacili ty tuto the red blood. Α similar mode os construction and function reppears to obtain in the cortical gland. The vascular substance that ramifies through the gland, terminates of necessity in the cavlty thereos; for the beginning of the fibros is
coincident With the end of the arteries. Is then both the medullary substances, the vascular as Weli res the fibrous, terminate in the simple ventricte, chamber or cavlty of the gland; aud isthe fibrous substance carries the purest animal essenee, Or the substance of the foui, and the Other or medullary carries thesulphureO-Saline or ethereat principies and elemenis, it follows that the contenis os eneli are married in the litile cavity, togivo birili to that most nobie of spring, the animal spirit, Whicli
parta kes at once of a spiritual and a material essenoe. But it will be asked Where the subile vesseis come Domwhicli are inserted into the gland. Nom according to the idea We have suggested Os the cortical gland, not only does the arterint vesset pass into the body of the gland with the purerblood, but the litile coat of the fame vesset also presses thitherusilli the minute stamina or threads of Whicli it is composed.