Page:Cyclopaedia, Chambers - Volume 2.djvu/252

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MUS

and Action don't differ in any thing from thole of other fluid, fubtil Mufcles.

MUSCULAR, or Musculous; fomething that relates to the Mufcles ; or that partakes of the nature thereof. See Muscle.

In thisfenfewe fay, Mufcular Fibre, Mufcular Coat, Muf- cular Heft, Mufcular rein.; Mufcular Arteries, i£c.

Muscular BW are the fine Threads, or Fibres, al- ready defcribed, whereof the Body of Mufcles is compo- fed. See Muscle.

Anatomifts are exceedingly divided as to the nature of thefe Fibres. Some will have 'em Elood-Veffels, viz. Veins, and Arteries ; others Nerves, (gc. See Artery, Nerve, SJjc.

Some retrain Mufcular Fibres to the longitudinal red, c41'd alfo Bejhy Fibres : The tranfverfe, and fpiral Ra- mifications wherewith the former are bound about, they call Nervous Fibres, See Fibre.

Dr. Morgan endeavours to prove, that all the Fibres that enter the Structure and Compofition of a Mufcle, are en- dued with an intriniic Elafticity, Spring, or Power of con- tracting and reftoring themfelves, as a given Weight or Force, by which they may be llrerch'd ; and that this Ela- fticity, or contractive rellitutive Power being a natural in- herent Property of the Fibres themfelves, does not de- pend on the Mixture, Rarefaction, or Effervefcence of any Fluids or Humours whatfoever. See Muscular Motion.

Muscular Membrane, or Memhana Musculosa, a Membrane fuppofed to invert tha whole Body, immedi- ately under the Adipofe Membrane ; call'd alfo Fanniculus Carnofus, (mAMembrana Musculorum Communis. See Panni- culus Carnofus.

Muscular Arteries, are two Arteries proceeding from the Subclavians, and diftributed among the Hind-Mufcles of the Neck ? as alfo to the Arteries of the Loins. See Ar- tery. They are divided into Upper and Under.

The Uffer-Mufcuhrs proceed from the large Artery, and lofe 'emlelves in the Fleth.

The Under-Mufculars are Branches of the inner Iliac Ar- teries.

The Name is alfo given to two Arteries of the Thigh, the one call'd the inter nal-Mufcidar, as being diftributed a- mong the inner Mufcles of the Thigh 5 the other the Ex- ternal-Mufcular, becaufe it proceeds to the outer Part.

Muscular-^/**, is alfo aName given to feveral Veins 5 two whereof come from the Skin and the Hind-Mufcles of the Thigh, and terminate in the Subclavians. See Vein.

There are three others alfo call'd Mufculari, and diftin- guiih'd into upper, Middle, and Under ; the firtt terminates in the Trunk of the Vena Cava, the two others open into the external Iliac Vein.

Muscular Flefl;. See Mufcular Flesh.

Muscular Motion, is the fame with voluntary or fpon- laneous Motion ; thus call'd, becaufe effected by means of the Contraction and Dilatation of the Mufcles. See Mo- tion, Muscle, &c.

The Mechanifm of a Mufcle we have deliver'd at large ; tut how this Mechanifm is employ'd to produce Motion in Animals, is matter of endlefs doubt.

The generality of Writers fuppofe the Belly of the Mufcle to be fwell'd, and thus its Extremes brought nearer ; and confequently the Parts it is fixed to, moved.

TheStrutfure of a Mufcle we have fliewn to be fuch as renders it capable of being fwell'd and contracted, and by that means of having its Extremities brought nearer each other,which is its proper Action : But how the Contract ion is effected, is the Point in difpute.

The generality of Authors account for it from the Influx of fome Fluid into the Mufcular F'ibres : Others folve it from the natural Elafticity of thofe Fibres.

The Retainers to a Fluid, again, are divided as to the •particular Fluid employ'd for this purpofe.

From the Structure and Phenomena of the Mufcles above laid down.we may gather the Properties of the hidden Caufe that moves the Mufcles ; viz. 1/?, That it may either be preient or abfent in a Mufcle ; and therefore, idly, May enter into it, and go out again : i. e. idly. It is derived to it from fome other Place, and paffes from it elfewhere. And, 41%, All this, by an inftantaneous Direction of the Will. JtUy, And in the fame Moment of Time, wherein the Mujcle is contracted, muft pafs from within outwards to every Point of the Surface of the Mufcle ; that is, gtbly, it muft be at once equally diftributed throughout the whole Belly of the Mufcle: And thetefore, ythly, fill and dilate the Membranes of the Fibres, change 'em out of an ob- long into a more fpherical Figure, lengthen their lefs Di- ameter, and diminifh their longer, and fo draw the Ten- dons nearer each other. Laflly, that it muft have its Rife from the Cerebrum and Cerebellum, the Origin of the Nerves and be ftrong enough to overcome thofe Obftacles which here flrongly refill it. To conclude then, it muft be a moil

. active Body, and be apply'd with fo'me Energy wthin the Mufcle.

Mow all the Fluids in the Bodythat have any Preten- tions to thefe Properties, that are any way qualified to pro- duce the Phenomena above; or that have been alledged as the Caufe of Mufcular Motion, are the Animal Sprits,, (or, as our later Writers call it, the Nervous Juice) and the Blood ■ but as each of thefe fingly fcarcc appears adequate to the Effefl, hence Authors have fuppoled 'em to mix in the Mujcles, and each to contribute to the Aftion of the other. But the Animal Spirits feem to have the greateft. number of Advocates, tho' their Exiftence was never yet fully prov'd ; beiides that the manner of their Aflion, as affign'd by Authors, feems to be arbitrary and precarious.

Some, with the great Dr. Willis, make the Tendons a ReceptaiL tor the Spirits, which are rais'd at the Inftiga- tton ot the Will, and fent thence into the Belly of the Mujcle, where meeting with the active Particles of the Blood, they ferment, and caule an Intumefcence, and fo conn-aft tho Mufcle.

Others, amongft whom Des Cartes and his Followers, al- low no Receptacle for 'em but the Brain, fend 'em thence thro' the Nerves like Lightning at every Summons of the; Will ; becaufe they can't allow the Tendons to be a pro- per Lodgment, on account of the Clofenefs of their Con- texture, nor can believe that the Animal Spirits fhould re- main there unactive.

Others, among whom M. da Ferney, imagine this Intu-< melccnce may be without Fermentation by the Animal Spi- rit, and a Juice from the Arteries running into the Tendons and Flefhy Fibres, and extending them, as Ropes, U>r. fwell in moift Weather.

Dr. Chirac, and others, maintain, that every Mufcular Fibre, beiides its Vein, Artery, and Nerve, has alfo from Space to Space, feveral little Cavities, or Pores of an ob- long Figure, when the Mufcle is flack or flaccid ; but the Blood circulating thio' the Mufcle, is continually depositing into ihofe Pores a fulphurous Recrement, abounding with Alkaline Salts, which meeting with the Spirits that flow by the Nerves into thofe fame oval Pores, their Nitro-Aerial Particles ferment, with the faline ones of the Sulphurous Recrement, and, by a kind of Explofion, fo diltend the Pores, as to change the long oval Figure into a round one J and thus the Mufcle is contracted.

llorelli takes the Fibres of a Mufcle to coniift of a Chain of divers Rhombus's or Lozenges,whofe Areas are enlarged or contracted as the Nervous Juice, with the Lympha and Blood, are let into, or forced out of 'em, at the Inftance of the Soul.

Dr. Croon fuppofes every Flefhy Fibre to confift of a Chain of little Bladders, or Globules, communicating with each other; into which the nutritious Juice, and one or two more Liquors entering, do, by means of the natural Heat, make an Effervefcence ; by which the Body of the Mujcle is extended, l£c.

Dr. Cheyne takes the fmall FibrilU of the Mufcle; to be fo many ilender elaftic Canals, bound about by fmall rranfveri'e parallel Threads, which divide the hollow Ft- brilU into fo many elaftic Cyjies or VeficuU, which are orbi- cular, being formed of two concave Segments of a Sphere ? into every one of which VeficuU, an Artery, Vein, and Nerve enter ; the two firft to carry and bring back the Blood, the latt to carry thither the Liqiudum Nervoftm, or Nervous Juice, which mingling in the VeficuU with the Blood, does, by its acid pointed Panicles, prick and break the Globules of the Blood, fo as to let out the imprifoned elaftic Air (contained in the Globules) into thofe little VeficuU ; whereby the elaftic Cells of the Fibres will be blown up, and thereby their Longitudinal Diameters from Cell to Cell ftraimed : and this muft contract the Length of tho whole Fibre, and fo move that Organ to which one of the Tendons is fix'd.

Dr. Keil, not contented with this Theory, fets up an- other, wherein the fame Structure of the Mufcle is fup- pofed, and the fame Fluids ; viz. the Blood and Nervous Juice, the Agents or Inftruments of Contraction : but in- ilead ol the pungent Particles of the Nervous Juice piercing the Globules of Blood, and fetting at liberty the im- prifon'd elaftic Jura, he accounts for the Whole from the Doctrine of Attraction.

He endeavours to Jhew, that the Diftenfion of the Ve- ficles of the Fibres is not owing to their being fill'd with a greater Quantity of Blood and Animal Spirits than before their Contraction 5 but to a Rarefaction arifing from the Mixture of thofe two Fluids, by means whereof they come to peffefs a greater Space.

To account for this Rarefaction of the Blood and Spirits in the Veficles of the Mufcular Fibres, he fuppofes a fmall Globule of Air between the Particles of a Fluid, which Particles have a ftrong attractive Force, whereby they en- deavour to come together : By pretUng every way equally