The remaining medical works of that famous and renowned physician Dr. Thomas Willis ...: Viz I. Of fermentation, II. Of feavours, III. Of urines, IV. Of the ascension of the bloud, V. Of musculary motion, VI. Of the anatomy of the brain, VII. Of the description and uses of the nerves, VIII. Of convulsive diseases : the first part, though last published, with large alphabetical tables for the whole, and an index ... : with eighteen copper plates / Englished by S.P. esq.

Two Physical and Medical EXERCITATIONS, VIZ.

• I. Of the Accension of the Blood.
• II. Of Musculary Motion.

The first Medical and Physical DISCOURSE. Of the growing hot or inkindling of the Blood.

IT is long since I designed to print my Meditations concerning the remaining Pathology of the Brain and Nervous stock: But when many Diseases of that kind affect the animal Spirits, and not rarely the whole Hypostasis of the corporeal Soul more immediately than the Humors or solid Parts; I there∣fore thought it necessary first to publish the Disquisitions of the nature of this Soul, and its manner of subsisting, and also of its Parts and Powers, that from these things rightly known, its preternatural Passions may at length be the better disco∣vered. But concerning these very hard matters, and difficult to be unfolded, when I had begun to frame (as I think) probable and rational Arguments, I saw well that they would be looked upon and laughed at by some as unusual things and Paradoxes; which indeed it becomes me not to take ill, but to let every one freely to enjoy his own sense, and to use in all things his own opinion and judgment. Among the many things conjecturally proposed by me, (which I could not avoid) two chief Arguments are opposed, to wit, that I had affirmed, that the blood for the con∣tinuing of life was inkindled, and that the animal Spirits, for the motive act, were exploded: which terms, though perhaps they may sound rough and strange to be applied to the animal oeconomy; yet if any one shall weigh the Reasons and Ar∣guments which do perswade to the truth of either opinion, I doubt not, but that there will be none who will not give their assent, or easily pardon me for mine. In the first place therefore, because there are so many opinions concerning the growing hot of the Blood, for that some attribute it to an innate heat, others to a flame in the Heart, some also to a fermentation of the bloody mass, and others to its inkind∣ling; therefore I shall endeavour more narrowly to introspect the matter, and as much as I am able, to build upon a more certain Ratiocination, its genuine Cause, though very abstruse.

We have formerly discoursed concerning that Soul, which is common to the more perfect Beasts, with that subordinate or more inferiour of Man, and have shewed it to be indeed Corporeal, and to consist of two parts; the one of these root∣ed in the blood we called a Flame, and the other dwelling in the Brain and nervous stock, Light. As we shall here only treat of the former, I think it will be no difficult matter to make use of the same Reasons and Instances, which truly conclude, or at least very like truth, that in the first place the blood is animate or hath life: second∣ly,

that this Animation is in its accension or inkindling, or consists in an affection most analogical to this.

1. Not only the opinions of Philosophers, but the undoubted testimony of the Sacred Scripture plainly asserts the animation of the blood: to wit, the use of blood was forbidden in the Mosaical Law, for this reason, because the Blood is the Life or Soul; which is also apparent by the observation of the most famous Harvey, for that its motion is to be observed by the eye, shews that it first lives and last dyes. For the greater proof of this, it is commonly known that Animals only live so long as the blood remains in its due plenty and motion; and that they presently dye, if ei∣ther too great a quantity of this be taken away, or its motion suppressed.

But as to the second Proposition, to wit, that the life or soul of the fervent blood depends upon its inkindling; this will appear probable, if I shall shew: First, that the liquor of the blood ought to be very hot in the more perfect living Creatures. Secondly, that this growing hot can be produced or conserved in the blood by no other means besides accension or inkindling. Thirdly, that some chief affections, as it were proper passions of fire and flame, are agreeable to the life only of the blood growing hot. Fourthly and lastly, these being clearly shewn, some other less signal accidents and properties, in which common flame and life agree, are added, and also we will unfold how and in what respect they differ among themselves.

As to the first we affirm, that the blood is perpetually moved in all living Crea∣tures; besides in the more perfect it doth estuate or grow hot in act. Indeed its un∣discontinued motion is required, both for the conservation of the disposition of the blood it self, whose liquor would otherwise be subject to stagnation and putrefaction, as also that being carried about in the whole body, it might be able to give a due tribute to all parts. For that the offices of the blood, at least in the more perfect living Creatures, are divers and manifold, viz. to instil matter in the Brain and nervous stock for the animal Spirits to dispense the nutritious Juyce into all the solid parts, to suggest to the motive parts an elastic Copula, and besides to separate all recrements and worn out Particles, and to put them aside into convenient Emun∣ctories.

But although the mere motion of the Blood in less perfect Animals, or at least its moderate swelling up, such as may be perceived in Wine and other Liquors agitated into Fermentation, is able to sustain and perform the oeconomy of Nature; to wit, for as much as both a crude nutriment is every where received from the river of the blood, though cool, continually flowing into all parts of the whole Body, and that fewer spirits and more thick, as it were separated by percolation or straining, enter the Brain and nervous stock with that plenty, that may suffice for local motion, and the Organs of the few senses to be rudely actuated: yet the blood watering the bo∣dies of more perfect Animals, require offices of a far more excellent kind; for it ought not only to be carried about with a continual and more rapid motion, but very much to swell up, yea actually to grow hot or effervent: to wit, for that end, that its frame or substance being very much loosned, it may more copiously send forth the respective Particles of various kinds, every where falling off from it, and may dispose them here and there for the use and wants of Nature.

But first, for that the animal Spirits are continually to be supplied in great plenty from the mass of blood, and that there is need for the elastic Particles requisite for the locomotive function, to be thence perpetually poured into all the Muscles, it seems very necessary that the liquor from whence these generous and manifold sup∣plements are drawn should be actually hot, or rather should burn forth; to wit, that the aforesaid Particles, not sufficiently to be unlocked but by heat or burning, should freely run out from the substance or frame of the liquor: which truly is ma∣nifest, because from Wine, and also from the same bloody Liquor, and all other spirituous things, a subtil and spirituous humour is copiously drawn, but not to be performed by distillation without heat or fire. Yea the sulphureous Particles, al∣though they are less apt to be exhaled from any Liquor, yet they most readily fly out by inkindling the subject. By these there is an apparent necessity of the blood's growing hot for the perfection of the animal as well as vital function; but that it may appear by what means this is done, to wit, whether by Accension, or by Fermenta∣tion, or by any other way, we shall first in general inquire, by what means, and for what causes any liquid things are wont to grow hot; then we shall consider, to which of these the growing hot of the blood ought to be attributed.

Concerning these we say, that there are only three ways, or so many kinds of causes, by which Liquors conceive a heat, viz. first, by fire or heat being put to them, as when water is made to seeth or boil over the fire, or that it grows hot by the heat of the Sun, a Bath, or Stove, or by the dissolution of quick Lime; instances of all which are commonly known. For the same reason Bath-waters seem to boil. For, that we may instance in our own Baths, to wit, they are impregnated neither with Sulphur nor fixed Salt, as I have plainly experimented, by distilling and evapora∣ting them, and by pouring into them precipitating Liquors; yea by dissolving them with Sulphur, and many other ways. They most resemble Lime-water, and they, as we believe, grow hot from a like cause, to wit, by imbibing the fiery little bodies somewhere hid within the Earth. Of these, unless it had been superfluous, we had here given a fuller description, which may perhaps be done at some other time. Secondly, when saline Corrosives, which are of a diverse kind, being mingled with themselves, or with sulphureous things, work mutually one on another with a great strife and agitation of Particles, and oftentimes excite heat, yea sometimes fume and flame; as when the Spirit and Butter of Antimony are poured to, or mix∣ed with stygian Water, wherein lixivial Salts are melted, or with Oyl of Turpen∣tine, or other distilled things; besides when corrosive Liquors eat metallick Bodies, they often grow hot. Thirdly, and the only way besides (as I suppose) whereby a liquid thing is made hot, is when any humour, being very much imbued with Sul∣phur or Spirit, conceives a burning by putting a flame to it, and so grows hot by burning forth. This is ordinarily seen in oily or very spirituous Liquors, being in∣kindled and inflamed.

There remain indeed some other ways of Calefaction, to wit, Fermentation, Pu∣trefaction, and Attrition, whereby more thick Bodies, or Solids, often conceive a fervour, but they produce not such an effect in Liquids: whilst the mealy Mass or Dough is fermented, the active Particles being stirred up into motion, unfold them∣selves on every side, and lift up the bulk or substance of the subject; in the mean time, for as much as the sulphureous Particles being agitated with them, take hold one of another, and begin to be combined, a certain heat, though more remiss, is excited; in like manner from Putrefaction, Dung or wet Hay get an heat, to wit, for as much as the sulphureous Particles, within included, are very thickly heaped up together, then being combined together, they break out in troops: yet no Li∣quors, either thin or thick, whether they ferment or putrifie, do for that reason at any time grow hot: For Wines, whilst in fermenting they break in pieces the sides of the Tun, or overflow the top of the Vessel with a great noise and ebullition, do not actually grow hot, yea not so much as grow warm. The blood being let out of the Body, and placed in convenient Glasses, either to ferment or putrifie, doth not get any actual heat: yet in truth we grant the Blood in living Creatures to be fermented, and by fermenting to be putrified, yea and some other offices of the ani∣mal oeconomy to perform the same: moreover, we have formerly shewed from its Fermentation being hindred, or too much increased, or otherwise depra••ed, divers kinds of diseases to be produced: yet we deny the heat of the blood to be excited by Fermentation. Because neither the blood of more frigid Animals, nor Wines, nor any other Liquors, though agitated with the highest Fermentation, are for that reason actually hot. And indeed the reason seems evident enough, to wit, because the sulphureous Particles being raised up in the more thick subjects, though they lay hold on one another mutually, and being more thickly heaped together, raise up heat: yet in Liquids, the same kind of Particles, however stirred up or agitated, are imme∣diately disjoyned by the watry coming between, and are hindred from their mutual embrace and combination; so that they cannot of themselves produce an actual heat: For the same reason, hard Bodies being rubbed one against another, or violently knocked or bruised, do not only produce heat, but oftentimes fire; whenas yet Liquids, however shaken and agitated, do not grow warm. Therefore as there are only three ways, whereby actual heat may be begotten in all Liquors, we shall in∣quire to which of these the heat of the Blood may be ascribed.

First, Some say it is the first way, from the opinion both of the Ancients, and of some of the Moderns: the Blood is said to grow hot, by reason of some hot thing put to it, to wit, whilst those affirm an innate heat, and these a little flame to be pla∣ced in the Heart, and to heat the blood passing through it; but either of these opi∣nions easily fails, from which it is clear, that the Heart is a mere Muscle, her doth

contain in it self any tinder or matter for a flame or heat (I know not how) implant∣ed, fit for their continuance. For though it be confessed, that on the continual motion of this Bowel, (which is only animal) the Circulation of the Blood doth de∣pend, yet the Heart borrows heat altogether from the blood, and not the blood from the Heart.

Secondly, As to what respects the second way of making hot a liquid thing, to wit, whereby a great heat is excited by the mixing of saline Corrosives together, or also oily, or by corroding a metallick Body, I think there is none that will se∣riously assert, that the blood grows hot from such a cause; for that its liquor, in its natural state, is always homogene, and although it be stuffed with plenty of Salt, it is however with that which is volatile gentle, and benign only: But there is not to be found, either in the Heart, or in any other place a saline or any otherwise heterogene Mine, whereby the bloody liquor, by working or corroding, may get or conceive an heat: to wit, it behoves either such a Mine or the Body to be corroded, to be perpetually renewed, because the ebullition and heat raised up by the strife of Salts, ceases as soon as the Salts are combined, or the Body corroded. If at any time the saline Particles of the humours in our Body depart from their right temper, and become enormous and unbridled, for that reason the blood, as to heat and motion, enters into some irregularities; yet it seems impossible, that it should originally and perpetually become hot by the congression, and strife, or corrosion of the Salts.

Thirdly, As to the third way, whereby Liquids are made hot, though it may seem an uncouth saying, That the blood is so inkindled, yet since we cannot attri∣bute it to any other way besides, what should hinder from attributing its heat to this Cause? And the rather, for that the proper passions of Fire and Flame are agree∣able to the life of the Blood alone.

For indeed these three things are chiefly and principally Essentials, requisite for the perpetuating flame. First, that there be granted to it, assoon as it is inkindled, a free and continued accession of the Air. Secondly, that it may enjoy a constant sulphureous food. Thirdly, that its recrements both sooty, as also the more thick, be always sent away. So then if I shall shew these things to agree after the same manner with life, as flame, and to those only, without doubt, I think that life it self may be esteemed a certain kind of Flame.

In the first place therefore, that a flame may be inkindled, and remain inkindled, there is need of a free and undiscontinued access of Air, and that not only, that the va∣porous Effluvia's, threatning the suffocation of the flame, may be carried away, and always depart, but much rather, that the nitrous food necessarily requisite for the burning of any thing, may be supplied by the Air. For indeed every sublunary fire, and especially flame, is compounded or made up altogether of sulphureous Particles, breaking out in heaps from a combustible Body, and of nitrous Bodies, which every where flow in the Air, meeting with them: when Particles of Sulphur, breaking out slowly or interruptedly, get to themselves a few nitrous, only planted near them, a fire is usually produced, such as is seen in a burning Coal: But when the former going away more impetuously, either of their own accord, or forced by blowing, presently lay hold on very many nitrous Particles flowing round about in the whole circuit, a flame arises. In truth the whole region of the Air is abundantly stuffed with nitrous little bodies, which are every where ready for the constituting of fire and flame, and they being any where inkindled, meet them after the manner of a stood, although not always after the like manner or measure, because it is observed at some times, especially in the Winter-cold, when the Air abounds more in Nitre, that fire or flame doth more ar∣dently burn, and diffuse farther its heat: on the contrary, in rainy weather, as also when the beams of the Sun shine upon the fire, and so dissipate the Nitre of the neigh∣bouring Air, the fire is so dull'd, as is commonly said, that it is extinguished by the Sun. If at any time the nitrous Particles of the Air are excluded from the sulphureous of any subject breaking out in the inkindling or burning, the fire and flame quickly perish; which appears, because this or that being put into a Glass, after the Air is sucked out or excluded, they presently expire. Further, in the open Air, although a naked fire propagates a fire in a fireable matter by mere contact, yet a flame is hard∣ly inkindled without a flame be put to it, or a very strong fire: because, for the stirring up of a flame very many nitrous Particles of the Air, implanted round about, ought to be inkindled at once; as if Nitre and common Sulphur being pound∣ed

together, be commixed (because both incentives agree) even the least spark falling into such a mixture begets an highly impetuous flame, which desiring no far∣ther a nitrous food, is inkindled or burns under water, in a place void of air, or in any place as freely as in the open air. In like manner the least sulphureous things, as a bit of ponderous wood, being cast into a red-hot Crucible, in which Nitre is fused, the same at first touch presently conceive a flame, and continue till it be wholly consumed: But that fire and flame being included in a place empty of air, expire by reason of the food of Nitre being drawn away, rather than choaked by their own proper smoke, the Illustrious Mr. Robert Boyle hath most clearly de∣monstrated by very many Experiments. For a Candle being lighted, and put into a capacious globe of Glass, and the Vessel stopped up: assoon as the air was sucked out by a wind-instrument, the flame did expire. Moreover he observed, what con∣cludes for our Hypothesis, that the flame contracted it self according to all its dimen∣sions, assoon as ever the Engine began to suck, then after the second or third draught of the drawn forth air, the flame about the utmost extremities appeared very blue, and to go back more and more from the Tallow, till at length getting to the top of the snuff it expired: the same Candle being again lighted, and shut up in the reci∣pient, this worthy Gentleman tryed how long it was able to sustain its light, when the air was not exhausted, and he found it to endure much longer lighted than before. From these it clearly appears, that the flame shut up, expires not so much because it is suffocated by its own proper smoke, as because it is destitute of the nitrous food of the Air. For in the former Experiment the air being exhausted, there was more space for the smoke and fume, that the flame might not be stifled, and yet this dyed sooner, the Recipient being empty, than the same being full of air; besides, the flame dying became bluish, for as much as it participated of more Sulphur than Nitre; and it left the Tallow, and expired at the top of the snuff, for that it followed its most necessary food as far as it was able, to wit, the nitrous Particles of Air. The same Experiment succeeded alike in live Coals, viz. the naked fire, after the food of Nitre was drawn away, suddenly dyed. Here also it doth what the flame of a Candle doth in Mines or Caves under ground, where the nitrous air is wanting or dispelled, at first it be∣comes more contracted and blue, and then a little after expires.

I have been more large in this Argument, because there is for both the like necessi∣ty of drawing in of the air, after the same manner, for the sustaining the life of the Blood, and for the continuing of flame. For the more hot Animals, if they are hin∣dred from respiration dye quickly, wherefore the same means of killing is most ready and common to shut up the breath, which being wholly obstructed, life perishes as a flame. If it should be objected, that those choaked do dye, because the foot or smoke being retained, blow up and intumifie the bloody mass, which for that reason, the bulk or substance being increased, and made almost immoveable, fills the bosom of the Heart, and hinders its motion: I say, that this is improbable, because if the Arteries, every where in the Limbs and about the Neck, be strained hard together with Ligatures, that the blood being straitned as to the compass of its circuit, be very much stopped about the Praecordia, (more certainly than can happen from the mere retained smoke) yet for that cause death neither presently follows, nor any deadly Symptoms. That this happens in those that are hindred from respiration, be∣cause the vital flame of the blood is wanting of the nitrous food of the Air, rather than overthrown by its proper soot or smoke being detained, the most Famous Boyl also by his Experiments hath put it out of doubt; for he hath observed, that hot living Creatures being put within a glassy Globe, and shut up, did far sooner expire, the air being drawn away from them, than the same being left within it, though in the former case, there was more space left for the receiving the smoke, left the re∣taining of it might constipate the blood: yet however, if the heat of the blood should arise from Fermentation, or the congression of dissimilar Particles, or from an ebulli∣tion, by reason of admitted heat, or from any other cause besides accension, it is so far that that effect could be inhibited or suppressed by reason of the air being excluded, that on the contrary it would rather for that cause become more strong or intense. For it appears, by a common observation, that Liquors chiefly fermentable, the more strictly they are kept in the Vessel, the more they grow hot, and the air being admitted through some vent-hole, they presently cease from their fury. Moreover, Mr. Boyl's Experiments clearly shew, that the effervescencies or growing servent, stirred up by the ebullition of unlike Particles, or by corrosion, also the boiling up of

hot water in a glassie Sphere, are above measure increased after the air is sucked out, Experiment. Physicom. 41, 42, 43. That most ingenious Tract of the aforesaid Author supplies us with many Experiments, whereby it is abundantly manifest, that the intestine motions of those Particles, and almost of every thing, besides fire and life, are very much heightned or made strong in the space emptied of air; but their act, presently after the air is withdrawn, is extinguished: hence we may conclude, the life of a living Creature to be either fire, or something analogical to it. The like to these is yet more clearly observed by the diggers of Minerals, who ordinarily experiment in subterranean Caves, where either the Nitre is wanting, or is driven away by some strange damp or vapour, so that they are in danger of being stifled or smothered, at the same time the flame of the Candle is diminished, becomes blue, and at length expires.

The second thing requisite to sustain a flame, is a constant supply of sulphureous food, whereby it may continually be fed, which being substracted, or by reason of some incongruous mixture depraved, the flame is extinguished; as is perceived in a Lamp, which for want of oyl, or water poured in its place, expires: further, as this sulphureous food is more or less suggested, sometimes more plentifully, some∣times more sparingly, the flame being more or less intense, is sometimes produced clear, sometimes smoaky; in the mean time, the food being constantly consumed by burning, goes away partly into vaporous Effluvia's, and partly into ashes, which are made up of some Particles of Earth, Salt, and Sulphur: But it is much otherwise in Liquors exposed to Fermentation, to which if new Particles be continually admi∣nistred, and the old ones depart, the Fermentation is hindred or disturbed.

In like manner, as in Flame, the Blood of the hotter Animals (and this only in all natural things, besides fire) requires a constant and copious sulphureous food; and that being quickly worn, is for the most part consumed in vaporous Effluvia's, a Caput mortuum being left of Earth, Salt, and stinking Sulphur: In the mean time from its food consumed by burning, it disposes other Particles for other uses. That the life or flame of the blood doth continually want aliment, there is none but daily finds it in himself: For if that be for some time denied, the vigor of the blood is diminish∣ed, yea and consuming the solid parts, it snatches into its bosom their remnants, and other humours of the Body whereby it may be fed. If the nutriment daily sug∣gested from things taken, be too thin and watry, the fervour of the blood, like flame without food, uses to be remitted; but if the food be very sulphureous and swelling with a vinous Spirit, and plentifully taken in, the blood is presently infla∣med, and often breaks out into a Feaver, as it were an open burning. In the interim out of that food of the blood exhausted or consumed, as it seems by accension, hot Effluvia's full of soot and vapour go away, which according to a just account, far ex∣ceed all the other excrements of the Body; and that their nature is plainly fiery, the frequent burning of the mouth and tongue, and infecting them with blackness like the soot or smoke of a Chimney, witnesses; besides, from the inflamed blood adust Feces, like a Caput mortuum, are sent into the Bladder of the Gall, Spleen, and per∣haps into other Emunctories.

Thirdly, That inkindled Flame may for some time continue, there is need of continual ventilation, to wit, that its sooty Effluvia's may still fly away, which else being detained and heaped together thereabouts, will suffocate the fire, because by obstructing the Pores of the inflamed Body, they hinder the eruption of the sulphu∣reous matter to be inflamed. Although this condition doth often interfere with the other more potent, viz. the necessity of nitrous food to be so drawn in from the air, that it can scarce be distinguished from it; yet we may plainly perceive, from the de∣tained soot gathered together about the snuff, the light to be put out: for which cause a Lamp, whose wick is made of plumous Alum or other incombustible matter, will not (as it promises) endure any long time, because the soot sticking to the wick, hinders the access of the oyl to the flame; for this reason blasts of wind from the Air wiping away the sootiness, doth not only render the flame more clear, that is free from fume and thick vapour; but food being sufficiently given to it, it be∣comes more durable.

Even as Flame, the life of the Blood requires also continual ventilation; to which end, besides the greater breathing places of the Breast, innumerable lesser, viz. the Pores of the skin gaping every where through the whole Body, do send forth Efflu∣via's departing plentifully from the boiling blood; which if it happens to be hindred,

or too closely shut up, the blood will grow excessively hot, being as it were beset with fume and vapour: besides, there is need to shorten its circuit, that passing through the Lungs with a more frequent turn, it might there, as much as it can, dispel all its soot or smoak. When the Heavens are heated, the Air seems as it were immoveable and to stagnate, we are wont very much to estuate or grow hot about the Praecordia; for that the blood being fed with a more sparing nitrous food, doth not burn so clearly, but glows with a more suffocating and intrinsick burning: fur∣ther, for that the Particles of the Air being less nimble, when they are inspired and expired or breathed forth, do not so readily convey away the vaporous Effluvia's of the blood; hence it is, that we fan the Air, that it may be made more moveable, and carry away more quickly and plentifully the soot or smoke from our Praecordia.

There yet remain some other smaller Considerations of Fire and Flame, respecting indeed not so much the Essence, as the production and extinction of either, which, whether and how far they may agree with the life of the Blood, we shall briefly in∣quire into.

Fire or Flame is produced two ways, viz. either it is kindled from another fire or flame, or begot by an intestine motion of sulphureous Particles. We have largely shewed the Species of either, and the manner of their being made, in our Tract of Fermentation (only we omitted there, that the accession of nitrous food was necessary for the sustaining it) even as flame, the life also of the hot or warm Blood, we have observed to be produced by a twofold way, to wit, it is either inkindled from ano∣ther life or soul, as in Creatures that bring forth alive; or intrinsical Particles pre∣disposed to animation, are at length raised up to life with the blood by a long cherish∣ing of external heat, as in oviparous or egg-laying Creatures.

If it be further demanded, when and how the vital Flame is kindled first in the Blood? I say, some small beginnings of it are laid up from the conception it self in the Genital humour, to wit, when the rudiment of the bodily Soul culled out from the Souls of the Parents, as a little spark stricken from those flames, is hid in a convenient matter; which being from thence raised up by the Mothers heat, begins a little to glow and shine, and afterwards being daily dilated with the blood brought forth, and leisurely increased, is equally extended with the Body, which it actuates and animates. But yet as long as the young one is included in the Egg or Womb, the vital fire, getting very little or scarce any aery food, doth not yet break out into open flame, but like a Brands end covered over with ashes, burns only slowly and very little, and spreads abroad scarce any heat; wherefore both the formation and increase of the Embryo depends very much on the Mothers heat, or the cherishment of some other analogical thing, whereof being destitute it perishes: but as soon as the young one is born in due time, and begins to breathe, the vital fire presently receiving the nitrous food, largely unfolds it self, and an heat or effervescency being raised up through the whole bloody mass, it inkindles a certain flame; and because the blood then first rushing into the Lungs, having there gotten an accession of Air, begins to burn, the flesh of that Bowel, at first reddish, is shortly changed into a whi∣tish colour, like burnt ashes, and the blood it self undergoes a notable alteration; for what did flow of a dark Purple colour into the Pneumonick Vessels from the right side of the Heart, returning from thence presently out of the Lungs, becomes Crimson, and as it were of a flame-colour, and so shining, passes through the left Ven∣tricle of the Heart and the appending Arteries.

Indeed that in Creatures new-born, the colour of the Lungs is so suddenly chan∣ged, I think it ought to be attributed to the blood, there at first more openly in∣kindled, and their flesh as it were somewhat roasted; although the mere inflation of the Lungs in a dead Embryo produces the like effect, because the Membranes of the Lungs and the Parenchyma being distended and increased into a greater capacity, shake off the stagnating blood, and so draw it away into little and scarce to be discer∣ned rivulets.

As to the Colour of the Blood, so variously changed into circulating from a dark purple to a crimson, and from this to that, I say, that the immediate cause of this is, the admixtion of the nitrous Air with the Blood; which certainly appears, be∣cause the change into a crimson, begins in that place where the blood chiefly gets the access of the Air, viz. whilst it is transferred out of the Arteries into the Pneu∣monick Veins; for in those it appears of a dark Purple, in these every where florid, as the most Learned Doctor Lower hath observed. Further, it yet farther appears,

that this alteration of the colour proceeds from the admixture of the Air, because that crimson colour follows in the superficies of all blood, let out of the Vessels by reason of its meeting or mingling with air; and if the flowering or top be taken away, another presently arises. Besides, the blood being let out of a Vein, and very much struck with a switch or rod, it becomes crimson through all: and in like manner the blood of living Creatures shines at first within the Pneumonick Veins, to wit, presently after the influx of the air by the Wind-pipe; and from thence, by reason of the same Particles of inkindled air being yet retained, it passes through all the Arteries still florid; in the mean time, from the Nitre of the Air mingled with the sulphureous Particles, and burning with them, the blood being greatly rarified, and in truth expanded into flame, impetuously swells up within all the passages of the Pneumonick Vein and the great Artery, sending from it self copious breaths and hot Effluvia's; but being dilated towards the ends of the Arteries, and returning towards the Heart, that it may enter more closely into the little mouths of the Veins, it lays aside its turgid and burning aery Particles, and being presently made more quiet and half extinct, and so both its vigour and also its colour being changed, it returns through the passages of the Veins, that at length running into the Lungs, it might renew its burning. After this manner, that the inkindled blood might flame through the whole Body with a perpetual and equal flame, and successively renew its burning in all its Particles, it ought to be carried about by a perpetual course from the nest of its accension into all parts, and from these to that. For this end the Machine or Engine of the Heart was needful, as a Pin or Cock, which being made with a double bosom, might receive in it self from the whole Lungs the blood fresh inkindled, that it might presently drive forward, whilst burning, into every part of the whole Body, and might then receive the burnt and half extinguished blood returning from the whole Body; which being imbued with new inflammable juyce, it might deliver to the Lungs to be re-inkindled.

In performing this task, although the Heart be a mere Muscle, and exercised only with an animal motion, seems to serve alone for the Circulation of the Blood; yet in the mean time, it so much helps to moderate the accension of the blood and its burning, according to the rage of the passions, and to direct other works and uses of the animated Body, that we have thought the vital or flamy part of the Soul to have its chief, and as it were Imperial seat in the Heart and Lungs, in every distem∣per or affection, as of Grief, Joy, Fear, and the like; also in the fits of Diseases, the Heart is disposed after a various manner, and hence it comes to pass, that the blood flowing in fluctuates, and is inkindled with a diverse rage; of which there will be a more opportune place of discoursing, when we shall treat of the Passions.

Whilst we consider that the burning of the Blood, and for that reason the vital or flamy part of the Corporeal Soul doth not appear lively or vigorous in all, nor ever after the same manner or measure; yet it exists according to the various consti∣tutions of the blood, to wit, as it is more or less sulphureous, spirituous, saltish, or watry, yea and according to the divers constitutions and conformations both of the food, with which this flame is nourished, as also of the little spiracles or breathing holes, by which it is eventilated; and further, of the Heart it self, whereby it is agitated and driven about here and there; the accension of blood varies also in every one, by means of several other accidents, to wit, as its flame is sometimes great, clear, and expanded, sometimes small, contracted, or cloudy, sometimes equal and in order, sometimes unequal and often interrupted, yea and it becomes subject to many other mutations; also because the Soul it self having gotten a various nature or disposition, it conceives divers affections and manners, whereof we shall speak here∣after; for as much as it is not a little thing, that the disposition of the whole Soul depends upon the temperament of the bloody mass, and the degree and manner of its accension or inkindling.

It clearly appears, from what hath been said, that Fire and Life do dye or are ex∣tinguished alike many ways, to wit, there is an end of either, if the access of nitrous food, or the departure of Effluvia's be hindred, or if the oily or sulphureous aliment, requisite to either, be consumed, too much withdrawn, or perverted from its in∣flammable disposition; of each whereof it is so clearly apparent, that there needs no farther explication.

Thus far we have shewn, that the Life of the Blood, or that part of the Soul grow∣ing therein, is a certain kind of Flame; let us now see by what means it is disposed

to burning, and how near it comes to the similitude of a burning Candle or Lamp.

A common Lamp, whether designed to give heat or light, for the most part is wont to be made after this manner; to wit, the Oyl flowing perpetually to the wick, gives continual food to the flame; wherefore as there is but one fire-place or hearth only of light and heat, the action of either is limited only to one place, and so as often as there is need of more places at once, or divers parts of the same space or body to be illuminated or made warm, we place here and there divers lighted Candles or Lamps. But if an Instrument made with great artifice (such as is truly an animated Body) with one liquor only contained in it, should be made hot throughout the whole, and to be kept always warm, it ought not only to be lightly inkindled in the wick, but in the whole superficies, and derived by fit Tubes or Pipes to all the parts of the Machine, then the burning liquor ought to enjoy, proportio∣nably to all its parts, an access of nitrous Air, and to lay aside Effluvia's and other re∣crements, and ought also to have a supply of that constant expence: these kind of offices are not to be performed any where up and down, but only in some set places; therefore the burning liquor ought to be carried about through the whole with a perpetual turn, that all its portions might enjoy successively all those priviledges, and at once heat the whole capacity of the containing Machine, to wit, both the in∣ward and outward recesses. Indeed such a Bannian or Bathing Engine, artificially made, might aptly represent the real Divine handy-work of the Circulation of Blood, and what burns in it, the Life-lamp.

But it may be objected, that the Blood seems not to be inflammable of its own na∣ture; further, since there is no flame of this heat or effervency to be beheld with the eyes, it may well be doubted, whether there be such a thing or no. I say first, That the Chymical Analysis of the blood shews very many particles of Sulphur and of Spirit, yea a plentiful stock of inflammable Oyl, which are however mixed with other more thick Elements, in a just proportion, to bridle their too great inkindling; to wit, that this liquor might flame out by little and little, and only through fewer parts, for the constituting of a benign and gentle Lamp of life: wherefore the blood being let out of a Vein upon a burning fire, doth in some measure burn, though it is not like the Spirits of Wine, or Oyl of Turpentine turning all into a flame; besides, the whole mass of blood, as the Oyl of a Lamp, ought not to be fired; yea its bur∣ning is instituted for that end, that whilst all the Particles of the Mixture being freed, some sulphureous and spirituous are consumed by burning, others more sub∣til being sent in Troops, might serve for the necessary uses of the animal Regiment; and also others more thick or crass and nourishing, as it were boiled or roasted, might be dispensed for the cherishing all parts; besides, that all the dead, or worn out, and excrementitious may be sent away by fit or convenient sinks, and others constantly substituted in their places by nourishment.

But in the interim, that the vital Flame, which destinated to so many offices, we suppose to be inkindled in the Blood, (otherwise than the common flame, which is plainly conspicuous) appears not at all, a probable reason thereof may be given; as it is most thin, and burns in the Heart, and its depending Vessels as it were shut up in Receptacles, it doth not clearly flame out, but perhaps remains in the form of smoke, or a vapour, or breath; yea, although the blood should openly flame out, yet it might be so done, that its shining being most thin, may not be perceived by our sight, as in the clear light of the day we cannot behold a glowing red hot Iron, nor shining sparks, nor false fires, nor rotten wood, nor many other things shining by night; why then may not the vital fire, even thinner than they, quite escape our sight? Although sometimes hot living Creatures use to send forth a certain fire or flame only conspicuous by night: For we have known in some endued with a hot and vaporous blood, when they have put off their inner garments at night going to bed near a fire or Candle, a very thin and shining flame to have shewn it self, which hath possessed the whole inferiour region of the Body. The reason of which affection seems wholly the same, as when the evaporating fume of a Torch just put out is again inflamed by a light inkindling, and manifestly argues that another flame, the root of this extrinsick one, lyes hid within the Body. For this very cause it is, that from the Mains of Horses, and the Skins of Cats, or other hot Animals being shaken, little sparks as it were of fire leap out, and often flames, only conspicuous in the dark, arise. Besides, we here take notice in a burning Feaver, caused by immoderate drinking of Wine or strong Waters, that the blood, as the flame of it is very much

increased, doth grow excessively hot, and such are wont to emit dry breaths, and sharp Effluvia's of heat, not like those that proceed from fermenting or boiling Li∣quor, but only inflamed. That which some in Feavers have imagined to have seen or observed even burning fires and flame in the eyes, argues indeed that the flame of the blood is very strong, and also that it penetrates the inclosure of the Brain. I knew a certain ingenious Man of a very hot brain, who affirmed, that after a very plentiful drinking of Wine, he was able in the darkest night to read clearly; from hence also may be collected, how the accension of the blood, like that of burning Li∣quors, is to be increased or made stronger, viz. by an agitation of the parts, and a more plentiful affusion of sulphureous food.

But that in the hot blood of living Creatures, the Properties, Affections, and many other accidents of Fire or Flame are found without the manifest form or species of it; what if we should say the cause to be, for that the vital flame of the blood is subjugated, or made subordinate to another form, viz. to the corporeal Soul? Wherefore, although it retains the chief qualities and affections of common flame, yet it loses the species of flame or fire; for in every natural mixture, the superiour form exercises a Right and Dominion over all included Particles whatsoever, how∣ever fierce and untameable they may be in themselves, and stripping them of their species, ordains and disposes them to peculiar actions in that proper Concrete: when the form of fire excels, that bright burning, that it might propagate large∣ly its ends, destroys and consumes all inflammable objects. But if the form of the corporeal Soul be induced upon the fire, kindled within the blood, it burns forth without fulgor or shining, or destruction of the subject, and is invisible, and as it were subjugated flame, is ordained for the sustaining of life and its offices: but truly the Divine Providence, from the very Creation of the World, hath seemed to have predestinated Forms to natural Bodies, to wit, that they might remain as so many Figures or Types, according to which every portion of matter framing the Con∣crete, whether animate or inanimate, might be modificated; so that the Mass, ac∣cording to the virtues of the hidden Seeds, being disposed after this or that manner, happens to have the form of a Stone, a Plant, or Brute, or of any other kind; then the acts and affections, appropriate to such a Species, follow the form it self. When therefore Life or Soul is destinated to these kind of Functions of the more perfect Animals, for the performing of which, the blood, after the manner of burning Li∣quors, ought to be perpetually hot, and as it were inkindled; what should hinder, but that the act of Life, or of that corporeal Soul (consisting in the motion and ag∣glomeration or heaping together of most subtil and agil Particles) may be called a certain Burning or perpetual Fire of the bloody Mass? Wherein although the ac∣cidents and chief qualities of common fire are implanted, yet the form of fire is ob∣scured, as being subjugated to a more noble form, viz. of the corporeal Soul: not much unlike water, which being congealed into Ice or Snow, lays aside the species of water for a time, and may be applied to other uses far distant from fluidity.

But truly, though we affirm, that the corporeal Soul doth stick in the Blood, yet we do not, that it is adequated or limited to it: because whilst the more thick portion of it, as the Roots of some Tree, fixed in the Earth, are sowed in the bloody Mass, the more noble part of the same Soul, as the higher branches, are expanded in the Brain and nervous System; or as we before hinted, when the vital or flamy part of the Soul is contained in the blood, the animal or lucid portion of it is contained in the Head and its Appendix; by which just limit the Sphere of either may be de∣fined, neither may the vital flame impetuously break through the animal Region, the substance of the Brain being more cold, and also shining or bright, is opposed to it, as it were an icy or glassie Bar, whose interiour frame or substance, the small and slender as it were rivers of the blood, for the sake of cherishing heat, can enter: but truly spirituous Particles plentifully flow from its juyce or liquor, every where heaped up near the confines of the Brain, and there disposed as it were to be stilled forth, which being immersed in the Brain, and more exalted, affords matter, out of which the animal Spirits are procreated, to be derived through the Nerves into the various Regions of the Body.

The second Medical and Physical DISCOURSE. Of Musculary Motion.

AS there are two chief or primary Faculties of the Corporeal Soul, to wit, the Sensitive and Motive, we have assigned certain exteriour Powers of ei∣ther of them, which are chiefly acted in the Nervous stock, and others in∣teriour, the Exercises of which lye within the Brain, to wit, such as the Imagination, Memory, Appetite, &c. What we have publickly discoursed of some time since both concerning internal and external Senses, may perhaps hereafter be brought to light and made publick: in the mean time, because I am opposed, con∣cerning both the natural and convulsive Motion, I think it fit at present to publish what I had meditated touching the Motive power, and what Hypothesis I had con∣ceived of so hard and highly intricate a thing.

The motive Faculty of the bodily Soul is wont to be exercised with another kind of Action than the sensitive, viz. with a diverse aspect and tendency of animal Spi∣rits. For that every Sense is a certain passion, wherein the Soul, or some portion of it, being outwardly struck, is forced to nod or shake, and a wavering of the Spirits being inwardly made to look back towards the Head; but on the contrary, every Motion is a certain Action wherein the Soul seems to exert it self whole, or part of it self, and by a declination or fluctuation of Spirits being made to bring forth a Sy∣stasis, and to extend something as it were its member. Further, whilst the Soul so exerts it self, or some part of it self, that the works then designed might be perfor∣med, an heap of animal Spirits being every where disposed in the motive parts, some∣times one, sometimes more are raised up by the Soul, which by that means being expanded with a certain force, and as it were exploded, they blow up the containing bodies, and so the same being increased as to their thickness, and made short as to their length, are made to attract the adjoyning member, and stir up local motion.

1. In every motion, these three things ought to be considered: viz. First, the original of the Action, or the first designation of the Motion to be performed, which is always in the Brain or Cerebel. Secondly, its instinct or transmission of the thing begun to the motive parts, which is performed by the commerce of the Spirits lying within the Nerves. Thirdly, the motive force it self, or exertion of the Spirits im∣planted in the moving parts, either into a contractive or elastick force. From this threefold Fountain, viz. as the business is performed in every one of these in a various manner, very many kinds and differences of Motions are deduced.

1. As to the original or beginning of Motion, we shall take notice, that that which proceeds from the Brain, with a knowing and auspicious appetite, may be called Spontaneous or Voluntary; but that which is wont to be excited from the Cerebel, where the Law of Nature presides, such as are Respiration, the Pulse, with many others, may be called merely Natural, or Involuntary: either of these is either di∣rect, which is stirred up of it self, or primarily from this or that beginning, as often as the appetite requires this or that thing, out of a certain proper, and as I may say, intestine deliberation, and chuses out respective motions; so in like manner, when the ordinary offices of the natural and vital Function are performed, according to the solemn Rite of Nature; or the motion of either kind is reflected, to wit, which depending on a previous sense more immediately, as an evident cause or occasion, is presently retorted; so a gentle titillation of the Skin causes a rubbing of it, and the more intense heats of the Praecordia stir up the Pulse and Respiration.

2. As to the Vehicle of the Instinct, which we suppose to be wholly done by the Nerves, for as much as it is performed by a single Nerve, or by more at once, it is called either a Simple or Complicate Motion; then for that some Nerves help mo∣tion more or less than others by sooner or later moving, this or that member is said to be moved first, or by it self, and another by consent: yea, and that consent is

wont to be acted or done with neighbouring or more remote parts, and that with a diverse respect: But we have in another place largely shewn instances of these kind of sympathetick motions, as also the causes of each of them, and their manner of being made.

3. There is another, and that a remarkable distinction of Motions, taken from the various constitution of the moving parts: to wit, parts endued with nervous Fibres, and in which the motive Spirits dwell; either they are Muscles, which per∣form local motions; or membranaceous bodies, the motions of which are terminated in themselves, which therefore we call Intestine. As to what belongs to local mo∣tion, of which only we treat at present, although it be confessed by all, that the Brain or Cerebel, and the Nerves and Muscles together one or more, as it were with joynt forces, do contribute to this motion; also, though it may be sufficiently un∣derstood, that the beginning of the motion to be performed is designed in the Brain or Cerebel, and that its instinct is conveyed wholly by the Nerves; yet by what means the Muscles perform that work, far exceeding any mechanick virtue or operation, seems most hard to be made plain.

That local Motion is performed by traction, and doth depend upon the contra∣ction of a Muscle, is not only a vulgar Opinion, but is also plain by ocular demon∣stration; yet it is very much disputed and variously controverted among Authors concerning the manner of Contraction and efficient Cause; some think it enough to say, that the Soul it self, by its presence, doth actuate the Muscle, or contract or draw out here and there its Fibres, as it were a net spread forth. But indeed this is to attribute to the sensitive Soul a supernatural, and as it were Divine virtue. To wit, that the same, by its mere Spirit, was able to bend and force heavy and very great bodies whither it pleases. Further, for what end are the motive Organs fra∣med with wonderful artifice and manifold difference, unless that after the manner of Machines, they might perform their operations by an orderly structure, and as it were mechanical provision of parts? Truly it will be no hard thing to apply the ex∣ercises of a Muscle and of the whole nervous Function, and to explicate them accord∣ing to the Rules, Canons, and Laws of a Mechanick. Before I enter upon this, I think it not amiss first to speak something of the make, conformation, and use of a Muscle in general. The ancient Anatomists, almost all with one consent, did divide the body of a Muscle into Head, Belly, and Tail; taking for the Head the extre∣mity of the Muscle connexed to the part, to which contraction is made; for the Tail, the end or portion of the Muscle inserted to the part to be moved; for the Belly, the part of the Muscle coming between, which is beheld more tumid, with a bulk of flesh; then for the performing of motion, they did suppose the Muscle to swell up about the Head and Belly, and so to grow short as to its length, and to at∣tract nearer to it self the hanging part; yet by what means, and for what cause the belly of the Muscle swells up, none yet hath clearly unfolded.

Moreover, although the Doctrine of the Nerves hath been much described by the most skilful Anatomists of every Age, so that the Muscles of the whole Body (as it is thought) have been exactly recounted, and offices assigned them, and monstrous names fitted for the expressing them, yet the true frame of a Muscle, not yet shewed by others, first began to be delivered lately by the most ingenious Doctor Steno. He hath found out in every Muscle two opposite Tendons, into which both the Fibres go; yea, and hath taught, that the same Fibres wholly, which compose strictly on one side, the Tendon of the knitting being more loosly joyned, do constitute the flesh; yet so, that some being laid upon others, compose the thickness or profundity of the Muscle, and some laid nigh to others, its breadth or latitude: he calls the former Fibres Ordines or Orders, but the other Versus or Turnings; then the parts and composition of a Muscle being after this manner laid open, he aptly reduces its Figure to Mathematical Rules, and according to Canons thence taken, shews the action to be unfolded: because he advertising, that in a Muscle with a simple right line, all the fleshy Fibres, parallel within themselves, and for the most part equal, are car∣ried from one Tendon obliquely into another; and that those Tendons are sowed in the opposite ends or angles of the flesh, whereby he most ingeniously describes a Mus∣cle to be, a Collection of moving Fibres, so framed together, that the middle flesh constitute an oblique angular Parallelopipedum, but the opposite Tendons compose two quadrangular Prisms or Figures. The Instrument which Painters use for the describing many Exam∣ples of the same thing, fitly represents the figure of this delineated in a plain: because

the styles being fixed to the opposite Angles, express the insertions of the Tendons and the Parallelogram it self the fleshy part of the Muscle: for when the opposite Angles are diduced to a great distance from one another, and made sharper, the two sides come nearer together, and render the Area or middle of the Figure longer, but narrower, a Muscle not contracted is denoted: But if the same Angles are brought nearer, and made more obtuse, the two sides go farther apart, and so make the mid∣dle of the Muscle shorter, but also wider, a contracted Muscle seems to be repre∣sented. In the mean time, in either site of the aforesaid Parallelogram the quantity or longitude of the sides is not changed, but only their position, and the largeness of the Angles is varied: whether it may be also so in a Muscle, shall hereafter appear. In the mean time we shall take notice, out of the observation of the same most Lear∣ned Steno, that a Muscle is either simple, which consists of one belly and two Ten∣dons, of which sort there are many in the Arm and Leg, which are the movers of the fingers and toes, yea and almost every where in other parts of the Body; or com∣pounded, that hath many bellies, to every one of which, two opposite Tendons are hung; yet so, as when those compounded Tendons, to wit, two together, shall be joyned, one compound Tendon enters the middle of the flesh, and the other embraces the middle on both parts. This is evidently discerned in the Masseter or Throat-muscle, the Deltoid, and divers others, in all which, even as in a simple Muscle, whilst the fleshy Fibres (to which only the motive power belongs) are contracted, the opposite Angles are enlarged according to the insertions of the Tendons, and so the bellies being made shorter, and at the same time thicker, do swell up.

In a simple Muscle, according as one Tendon or both together, or either by turns, ought to be drawn; besides, according as the part to be drawn is thin, or broad, or planted near or far off, and for several other respects the fleshy belly is diversly for∣med; and as the Rhomboides is its chiefest regular figure, yet that also is some∣times triangular, sometimes trapezial or quadrangular, pyramidal, spiral, semilunar or like an Half-moon, or of some other irregular form. But in all these kind of Mus∣cles, the fleshy Fibres, according to all their positions, whilst they are contracted, at the same time intumifie or swell up, and are shortned from either end towards the middle, though in all Muscles not always in a like manner and dimension; for if ei∣ther Tendon be to be drawn at once, the contraction from either fleshy end, is for the most part equal; but at the same time, if one only be drawn from the others that are immoveable, the contraction is made less, and sometimes, viz. where the flesh immediately sticks to the bone without any notable Tendon, almost none.

The compounded Muscles are distinguished with a far greater variety; for besides their diversity of figures, all which would be an immense labour to enumerate, accor∣ding as they are more or less compounded, or have their bellies more or fewer, with a manifold Series stretched out here and there, with Fibres sometimes of the same, sometimes of a divers order, they are very much differenced.

The more thin and less compounded Muscle, when perhaps it is sorted into two or three bellies, disposed in the same being plain, hath the series of fleshy Fibres for the most part looking diversly, all the exteriour Tendons embracing one end of the Muscle, and hath the others intermediate or that come between immersed about the other end; so that the several fleshy Fibres of every Belly lye parallel between the one extreme Tendon and the other intermediate Tendon. The thicker and more compounded Muscle, that it might perform at once quick, hard, and long motions, hath many bellies planted in divers plains, and the series of fleshy Fibres (which are all short) looking many ways. The frame of them, although it be very intricate, that one can scarce number all the bellies, much less observe their habitudes, mutual depen∣dences, and means of connexions among themselves; yet they may in some sort be reduced to this common Rule in most, to wit, in the great compounded Muscles, such as are those round ones which contribute mighty strength and elastick force to the middle of the Arms and Legs, we may take notice, in one end of two vast exte∣riour Tendons covering almost the whole superficies of the Muscle, which being di∣vided presently into many fissures or clefts, are stretched out between a broad shoot or claw to the other extremity of the Muscle; then on the opposite side, about this other end, a great Tendon enters the middle of the flesh, which also is cleft or divided pre∣sently into many laps, distributed through the whole interiour belly of the Muscle. And as these interiour lamens or laps meeting with the exteriour, and being stretch∣ed out almost to the opposite end, look many ways, and have their superficies turning

on every side, some every where are destinated to others opposite, and are committed or sent through the intervenient series of the fleshy Fibres: such a Muscle, whose very many bellies being planted in divers plains, do look many ways, can by no manner or way be cleft or pulled asunder, but that the other series of fleshy Fibres must be broke asunder in the midst. The bellies of a Muscle, so very much compounded, although manifold, yet are very slender, so that the fleshy Fibres thereof being most short, and having their Angles always equal, but oblique, with the tendinous laps, for that cause make a most strong attraction. Because the numerous series of fleshy Fibres seem as it were so many distinct posts or supporters set together for the moving of any weight, or rather, for that either great Tendon is presently so cut into many lappets, it is like, as if a mighty draw-rope, hung for the drawing up a body, should be presently divided into many little ropes or cords, by which many men might draw at once. For whilst the several series of the fleshy Fibres are shortned at once, they draw the opposite Angles of all the tendinous lappets together, and so the belly of the whole Muscle being intumified or swelled up, they strongly draw either end, or that which is moveable towards the middle.

On every Muscle, both simple and compound, there is stretched on every side a membranaceous covering; besides, other little Fibres transverse, to wit, membra∣naceous, are woven between the direct moving fleshy Fibres of every one, which clothe each of them, and keep or fasten them together, yea (as it seems probable) they both communicate to all the fleshy Fibres the same instinct of obeying the mo∣tion, and also carry to the Tendons, the troops of the inflowing Spirits, received from the Nerve.

The Arteries and Veins, inserted in the middle of every Muscle, send forth little branches on all sides, obliquely cutting the moving Fibres, from which lesser bran∣ches dispersed between the Interstitia of the flesh, water them all with a flux or re∣flux of the blood. But the Nerve entring the fleshy belly of every one, distributes some smaller circles only in the neighbouring parts, as it were bearing only the Sym∣bol or mark of the commanded action, commands the execution of it to the Guard or inferiour Company of the fleshy Fibres and membranaceous Fibrils.

I had designed Figures, almost of every kind of Muscles, to be engraved accord∣ing to the natural appearances: but the Printer making haste, I had not the oppor∣tunity to dissect an humane Body, having only taken some few Muscles from the Leg of an Ox, we have caused them to be delineated to the life, which are to be seen at the end, although the famous Steno hath already accurately performed this task. Which Figures, if any one think too much bending to Mathematical Rules, he may with an easie labour behold the same Conformation of a Muscle, as he hath de∣scribed it in the flesh it self. For if a simple regular Muscle be cut out of any Animal, and so placed, that the Tendons here and there be held on the sides, the fleshy Fibres between them intercepted in oblique and equal Angles, be pressed upon an Horizon∣tal plain, the flesh will be exactly like a Rhomboides or an oblique angular Parallelo∣pipedum. Then if the site of the same Muscle being changed, and its Tendons placed above and below, you shall cut long ways the inferiour Tendon, and pull the parts one from another, and divide by tearing the whole Muscle into two parts, you shall presently see a most elegant spectacle, all the fleshy Fibres disposed in one series, yea and parallel between themselves, and of the same longitude, to proceed from one Tendon into another, and to make both Angles always oblique and equal; although we cannot cleave after this manner the compounded Muscles, whose manifold bellies have a diverse plain, yet it will easily appear, to one curiously cutting them, either raw or boiled, two Tendons to be fitted to each Parallelogram of the flesh.

As to what respects the action of a Muscle, we plainly saw in dissected living Crea∣tures, (which only shew this) that it is contracted, yet not so as the old Opinion declared, to wit, that the Fibres being contracted from the end towards the begin∣ning, one extremity of the Muscle was carried towards the other; but the fleshy Fi∣bres only and their ends are seen to be contracted towards the middle, the Tendons being still unchanged and altered neither as to their longitude or thickness: which thing also the most Learned Steno did first of all observe long since. This is clearly perceived in the Diaphragma and the Muscles dedicated for Respiration, which are moved with a constant change: for as often as the Muscle is contracted, you may behold all the fleshy Fibres, in either extremity, to be pulled together at once, and as if they would enter on either side one another to be carried nearer, and so at once to

become shorter and thicker, then from that constriction to return loose to their wont∣ed longitude and slenderness. Whilst you behold this to be so done, you will easily think, that something, to wit, spirit or subtil matter doth flow from the Tendons into the flesh or fleshy Fibres, which entring them on either side, blows them up, and at the same time draws them together nearer within themselves, that presently all the Fibres are made shorter and intumified; then when that matter recedes from the flesh or fleshy Fibres into the Tendons, the Fibres being emptied and loosned from their corrugation or wrinkling, are restored to their former longitude, and so by turns: whether this in truth be so done or no, shall be discoursed anon.

In the mean time, that we may proceed to other appearances of Musculary Mo∣tion, if that the Membrane of the Muscle being drawn away, you shall separate some fleshy Fibres from others by cutting the little fibrils, whereby they are joyned, and loosen them quite, you will see them so singular and free, to be wrinkled or drawn together in every motion like the others compacted together.

Further, I advertise you, that these Fibres so loosned and freed, some cut off in one end, and separated from the Tendon, did yet contract themselves to the motion of the Muscle, together with the other Fibres, about the other whole end, without that cut off in the mean time growing flaggy or loose. After this I divided with a pair of Scissers, a certain fleshy portion of the thinner Muscle, in three or four pieces transverse, the bigness of an inch: which being done, the portions cut off in either end, only entred into, for a short space, some light and inordinate corrugations, and presently became immoveable. The other extreme portions of the Muscle so cut, sticking to the Tendons, continued to be much more lively and longer contracted, but irregularly and convulsively, to wit, with a certain intortion of the Fibres. Truly, in the Fibres so cut off, some small footsteps of contraction did remain for a little while, partly by reason of the Instinct of Motion delivered through the membrana∣ceous fibrils, by which they did yet cohere with the whole flesh, and partly because the animal Spirits, implanted in the fleshy Fibres, now divided from the rest, and left without influence, did exert or put forth their utmost contractive endeavours after the usual manner. For this reason sometimes in the Heart taken out, and in a piece of it cut off with a Sword, as also in other Muscles, after the Nerves and san∣guiferous Vessels are cut off, a contraction and relaxation continue for some time. The other Fibres cut off only by reason of the access and recess of the Spirits from the Tendons, were able still in some measure to be contracted and relaxed.

When in the Diaphragma I had freed many singular Fibres from the knittings of others, I tryed what Ligatures put in several places of them might effect. Some of them then being bound about the middle, were contracted even as the whole fibres, but with some little swelling about the Ligature. When I had bound others about the ends, where they cohere to the Tendons, now one, then another, the motion was chiefly and almost only continued about the free end. Further, in the fibres bound at both ends at once, the contraction wholly ceased.

Contraction and Relaxation are not only seen, and indeed probable, in the Heart, but in the Diaphragma and other Muscles appointed for Respiration, which use to be performed in all, acting vicissively, according to the Instincts of Nature, and for the most part equally (though there are not the like intervals of motions in all) yea, and the Muscles serving to the voluntary function, enter oftentimes into spontaneous Contractions, unless they be hindred by their Antagonists, as it appears, for that the Spasm or Cramp of one Muscle comes upon the Palsie of another. Contraction and Relaxation are iterated more swiftly in the Heart, than in the Muscles of Respi∣ration, and so perhaps in these, than in several others. In those ready to dye, the fleshy Pannicle every where trembling, clearly shews their changes by innumerable beatings or leapings.

As to what respects the Humors, whereby all the fibres of a Muscle, viz. the fleshy, tendinous, and membranaceous, and what lies between them, seem to be watered, filled, or blown up, we ought to take notice of them, at least two of them, (to wit, the bloody and nervous liquor) if not more. And in the first place it is clearly ma∣nifest to the sense, that the blood doth wash all the fleshy and membranaceous fibres which are interwoven with these: because, if the Spirit of Wine, tinctured with Ink, be put into an Artery belonging to any Muscle, the Vein in the mean time being tyed close, the superficies of all the fleshy fibres and transverse fibrils are dyed with black∣ness, the Tendons being then scarcely at all changed in their colour; it appears from

hence, that the blood doth every where outwardly water all the flesh or fleshy fibres, and only those. We have not yet found by any certain mark, whether the blood enters more deeply the fleshy fibres, or instils into them the subtil liquor falling from them, although this last seems most probable; but indeed we affirm, that all the fibres, viz. the fleshy, tendinous, and membranaceous, are perpetually and plen∣tifully actuated by the implanted and inflowing animal Spirits, and constantly imbu∣ed with the nervous liquor, which is the Vehicle of the Spirits. But how far, or how much the aforesaid humors conduce to the exercise of the animal Faculties, doth not easily appear; but because the animal Spirits cannot consist without the nervous liquor, and depend very much upon its disposition, we may conclude, that it doth serve something to the actuating the motive power; for that reason also, that the continual afflux of the blood is nevertheless necessary, an Experiment cited by the Ingenious Steno, and proved of late by others, plainly confirms. He hath observed, that in a living Dog, the descending great Artery being tyed without any previous cutting off, the voluntary motion of all the posterior parts have ceased, as often as he tyed the string, and as often returned again as he loosned the knot.

These are the chief Phaenomena to be observed concerning the frame and action of a Muscle in the dissection of Animals, both of such as were living, as also of the dead and dying. From which, however placed together and compared among themselves, how difficult a thing it is to constitute the Aetiology of the animal motive faculty, ap∣pears even from hence, that the most Ingenious Steno, after he had very accurately deli∣vered the Elements of his Myology, by himself first invented, nevertheless he wholly avoided that Hypothesis which might be founded out of them; for that he yet doubt∣ed, whether the explication of a Muscle by a Rectangle were convenient to Nature in all; wherefore when many run to the manner of musculary Contraction, by the re∣pletion of the fibres, and others from their inanition, and some to both, he inge∣nuously professes, that the true causes of this thing do not clearly appear to him.

And as to this abstruse matter, although I do not believe that I am able to bring to light, or shew any thing more certainly than others; yet as in mechanical things, when any one would observe the motions of a Clock or Engine, he takes the Machine it self to pieces to consider the singular artifice, and doth not doubt but he will learn the causes and properties of the Phaenomenon, if not all, at least the chief: In like manner, when it is brought before your eyes to behold and consider the structure and parts of a Muscle, the conformations of the moving fibres, their gests and alterations whilst they are in motion, why is it that we should despair to extricate the means or reasons of the motive function, either by truths or by what is next to truth? Where∣fore I think it may be lawful for me here to bring before you our conceptions and no∣tions concerning this thing, indeed not rashly taken, or to comply with our former Hypothesis, or to oppose any other; which if they shall not satisfie all, may at least excite others to find out better.

But we shall here repeat what we have mentioned before, viz. that the power or virtue by which a Muscle is moved, proceeds from the Brain, is conveyed through the Nerves, and is performed by the fleshy fibres contracted, and by that means abbre∣viated. This latter is proved by ocular demonstration, yea it appears by it, that the motive force doth depend also upon those former, and is so transferred by a long passage, that the influence of the Spirits being suppressed in their beginning, or inter∣cepted in the way, for that reason the exercise of the designed motion may be hindred. Further we notifie, that the motive force is far greater in the Muscle, or in the end, than in the beginning or middle: because the Brain and depending Nerves are made of a tender and fragil substance, and can pull or draw nothing strongly; but the Muscle putting forth strongly its contractive force, seems almost to be equal to the strength of a Post or Crow, or of a Pully or Windlace. Sometimes the local motion is a compound Action to be performed of many Organs, which consist in divers places, and as its virtue is far more strong in the end than in the beginning or way, we will inquire by what means, as it were mechanical, the motive force may be so augmented or multiplied in its progress, then what is brought to the motion from the several Organs.

As to the first, in Artificial things, when for the facilitating of motion, and the increasing the moving force, many Instruments are invented, all of them, or at least the chief, may be reduced to these two Heads, viz. first, either the same force or impression may be continued, without the addition of any new force, from one term

or end to the other, or from the first mover to the thing moved, which notwith∣standing may be much increased in the way, as the Centers of Gravity are farther off or multiplied; for the farther the motion is begun from the first Center of Gravity, the stronger it proceeds, as is beheld in a Crow or Leaver, and in other things redu∣cible to a Leaver. Then if other things be disposed beyond the first Center of Gra∣vity successively before the end of the motion, as in a circular Wheel, the same mo∣tive force is wont to be increased very much. But to this there is required, that the instruments of motion be sufficiently strong and tenacious in their whole tract; for otherwise the motive force being increased, the same breaking falls down before the designed action be performed. Secondly, there is another way of multiplying the motive force to a great degree, and also at a great distance, which is performed with the addition of new forces or of fresh supplies, to wit, when the elastick Parti∣cles, or those making the force, being disposed and shut up in private places, as it were little Cells, afterwards, as occasion serves, are sent forth by a light contact or blast of a remote Agent, into the liberty of motion, which they readily perform. By this means, Air compacted and shut up, when it is permitted to get out, impe∣tuously forcing a Bullet or other object, sends or drives it out a great way. It is sufficiently known what mighty and often horrid forces Gun-powder yields about the end of the Explosion, when in the beginning or first inkindling, the force being transmitted through the fiery fume, as yet weak, might be restrained by a light im∣pression of the hand. There are also other explosive little bodies of a various kind, which being hid in convenient Boxes or Cells, when they are raised up into motion by an inkindling, or irritament, or provocative, do often exert an incredible force. It behoves us then to inquire from which of these ways it comes to pass, that the mo∣tive force doth in the Muscles so far exceed the force transmitted from the Brain through the Nerves, or whether the action of the Musculary Motion be merely con∣tractive, or rather elastick, or in some measure explosive?

Concerning these things it manifestly appears, that the Muscles do draw, to wit, being abbreviated, do bring the Tendon with the hanging part towards it self. Fur∣ther, for as much as there is need for the offices of traction to be sometimes more strongly, sometimes more weakly performed by them, so to have the Centers of Gravity now nigher, now farther off planted from the beginning of the motion; hence the Muscles which extend or bend the Thigh, especially the Psoae and Glutaei (great Muscles beginning in the Breast, and reaching into the Thigh) do hide their fleshy moving fibres deeply within the Trunk of the Body: but those which turn about the Thigh are constituted either near the hole or the rising of the Bone of the Thigh, or somewhere thereabout; in like manner it is observed in all the rest of the mem∣bers, that the belly of the Muscle gets a more remote or nearer site from the article or hinge of motion, as it designed for performing either a stronger or weaker motion: But truly this doth not hold as to the other moving parts, to wit, the Brain and Nerves, which cooperate with the Muscles in the motive Act; because, although the motive force is carried by a long passage through all these Organs, yet it seems im∣possible, that a contraction so strongly performed by a Muscle, should be begun by the tender and immoveable Brain, and continued through the small and fragil Nerves, but that it must necessarily be supposed some motive Particles are hid in the Muscle, which, as occasion is given, are stirred up according to the Instinct, delivered by the Nerves from the Brain, into motion, as it were with a certain explosion. But what these Particles may be, by what means they are instigated into motion, and how they induce the contraction of a Muscle, seems most difficult to be unfolded.

Truly it may be lawfully concluded from the effect, that elastick Particles, and fit to move themselves, are contained in the Muscles, and hid every where within the fibres, because the Anatomy of living Creatures discovers often a motion in a separated Muscle, yea in its fibres divided one from another. The Hearts of some Animals beat a long while being pulled out of the Body, the Muscles cut off, some∣times perform the motions of contraction. In great labouring Beasts slain or dying, although the Heart and the Brain be taken out, the fleshy Pannicle performs for some time very many turns of contractions and relaxations. From these it is manifestly clear, that there are among the Particles of the Muscles some agil and self forcers, or carried by their own force heaped together, which, although the animal oeconomy be very much disturbed or overthrown, do enter into motion of their own accord, yet in a tranquil estate they perform no actions, unless commanded by the Brain or Cerebel, and delivered by the Nerves.

Whilst a Muscle is contracted, the cutting up of a live Creature shews only the fleshy fibres to run into motion by themselves, to wit, being made more tumid, sharper, and shorter at the same time, to amplifie or enlarge the belly of the Muscle, and in the interim, the Tendons, as if immoveable of themselves, to wit, not altered either as to their thickness or length, only pulled as it were by the fleshy fibres, to be moved, and to draw with them the moved part; whence it seems to be manifest, that the animal Spirits or elastick Particles, which soever they are, whilst they perform the Musculary Motion, are only or chiefly agitated among the fleshy fibres. Fur∣ther, hence any one may strongly think, that such Particles are not at all contained, or are wholly idle in the tendinous fibres; for as we have noted, that the Tendon is not changed in the act, we may lawfully suspect, that it is only instead of a Crook, by which means the fleshy fibres being contracted, may draw the member to be mo∣ved at a distance from them towards themselves.

But indeed it sufficiently appears by evident signs, that the animal Spirits or elastick Particles do lodge within the tendinous fibres, and truly much more plentifully than in the fleshy: First, the sense shews this, to wit, the touch, which is much sharper and far more sensible in the Tendon than in the flesh: yea any irritation or breach of the unity happening in that part, brings not only a most troublesom sense, to wit, a very cruel pain, but besides, is wont to excite in the neighbouring flesh a Tumor or Swelling, and frequently most grievous Convulsions; whence we necessarily con∣clude, that the animal Spirits do inhabit the tendinous fibres in great abundance: but what they do there, and by what means they serve to the motive function, we will next inquire.

As often as the motion of a living Muscle was beheld by me, I considered and weighed in my mind by what means all the fleshy fibres were contracted and released by turns, I could conceive or collect no other thing than that in every contraction, the Spirits or certain elastick Particles did rush into the fleshy fibres from either Ten∣don, and did intumifie and force them nearer towards themselves or together; then the same Particles presently coming back from the flesh into the Tendons, the relaxa∣tion of the Muscles happened. In a bare or naked Muscle, when I had separated every fleshy fibre or a company of them apart from the rest in the whole passage by help of a Microscope, I most plainly perceived the Tumor, begun at either end of the flesh, to be carried towards the middle, as it were by the Spirits, entred here and there at once. Further (which I mentioned before) each fibre being tyed about the middle, being as it were as yet free and compacted with the others, was contracted or drawn together; but a Ligature being put to both ends, it remained flaggy con∣stantly above or beyond the bound place. But that I might no longer doubt concern∣ing this, I applied two Ligatures, at equal distances from the middle and the ends, about the same bundle of fleshy fibres, which being done, a contraction and swelling up arising presently from either fleshy extreme to the places bound, went no farther; the middle part between in the mean time being unmoved, remained flaccid; whence it may be well concluded, that in every musculary contraction the animal Spirits or elastick Particles do leap out from the tendinous fibres into the fleshy, and vicissively in the relaxation, recede or run back from these into those.

However this being proved and granted, there yet remain very many difficulties concerning Musculary Motion; for first, it may be asked how the animal Spirits, which enter silently, or without any incitation, or Tumor, the tendinous fibres do so blow up the fleshy fibres, that they are able to force them altogether into shorter spaces.

For the producing this effect, plenty of Spirits leaping from the tendinous fibres, do not seem alone sufficient; but besides, we may suppose some other kind of Parti∣cles, implanted in the fleshy fibres, meeting with the others flowing from the Ten∣dons, do forthwith strive, whence a mutual rarefaction, and turgescency or swelling up of them, or an inflation or sudden blowing up of the containing bodies, together with an abbreviation or shortning of them, doth arise; not much unlike, as when the Corpuscles or little bodies of fire entring into a piece of leather, or any thing, and forcing variously here and there its implanted Particles (whereby they are presently insnared) make it so to be stuffed and wrinkled; in like manner also the animal Spi∣rits, although they pass through the Tendons, where they are solitary or by them∣selves, without moving them (as the Effluvia's of heat in Metals or more dry bodies) yet being dilated in the flesh, for that there joyning with elastick Particles of another

kind, they are expanded or stretched out, they cause the sudden inflations and cor∣rugations of the containing fibres. But we have elsewhere shewn, that such Particles divers and wholly heterogene to the nature of the Spirits, may be copiously and easily carried to the Muscles. For indeed it is plain by ocular demonstration, that the blood doth every where wash and water outwardly all the fleshy fibres, which besides, it is thought not only to nourish, but also to be busied about the offices of the animal Fun∣ction: and what can be less suspected, than that it doth instil into their Pipes a cer∣tain subtil liquor, whose Particles being agitated, and also rarified by the Spirits flow∣ing therein, stuff up the fibres, (as we but now hinted) and compel them intumified, by reason of the assault on either side made, into shorter spaces?

But that the fleshy belly of the Muscle, whilst it is contracted, doth swell up, is not at all to be doubted, because this is evidently beheld by the sight and touch in the dif∣fection of living Creatures: to wit, all the fleshy fibres being wrinkled together, are made more tumid and sharper, and so shorten the Muscle, and make it also thicker and broader: For the more certain belief of this, when I had bound some of the fleshy fibres, separated from the knitting of the rest, and had left others near them loose, there appeared a notable difference between those flaccid or not swelled, and these in∣tumified or swelled up in every contraction of the Muscle.

But if it be demanded, of what nature, to wit, whether spirituous saline, as may be believed, or of any other disposition, the animal Spirits, derived from the Brain into the Muscles, may be; and then whether the other Latex, immediately carried to them from the blood, is sulphureous or nitrous. Concerning these, because it ap∣pears not to the sense, we shall pronounce nothing rashly or positively. But even as in other natural things, the active Particles of a various kind, which being unlike among themselves, are found apt mutually to grow hot, or to be struck off from one another, or otherwise to be rarified or expanded; and as the intestine motions of Bodies, and especially the elastick, such as are the contractions of the Muscles, can only proceed from the congressions of such like, certainly it may be lawful to pre∣sume, that these do wholly depend upon such a cause.

Therefore as to the Musculary Motion in general, we shall conclude after this man∣ner, with a sufficiently probable conjecture, viz. that the animal Spirits being brought from the Head by the passage of the Nerves to every Muscle, and (as it is very likely) received from the membranaceous fibrils, are carried by their passage into the tendi∣nous fibres, and there they are plentifully laid up as in fit Store-houses; which Spirits, as they are naturally nimble and elastick, where ever they may, and are permitted, expanding themselves, leap into the fleshy fibers; then the force being finished, pre∣sently sinking down, they slide back into the Tendons, and so vicissively. But whilst the same animal Spirits, at the instinct given for the performing of motion, do leap out of the tendinous fibers into the fleshy, they meet there with active Particles of another nature, supplied from the blood, and presently they grow mutually hot; so that by the strife and agitation of both, the fleshy fibres, for that they are lax and porous, are stuff∣ed up and driven into wrinklings, from all which being at once wrinkled or shrivell'd up, the contraction of the whole Muscle proceeds; the contraction being finished, the sincere or clear Spirits, which reside or are asswaged, go back for the most part into the tendinous fibres, the other Particles being left within the flesh; the loss or wasting of these the blood supplies, as the Nerves do those. By what instinct the musculary contraction begins and ends, shall be inquired into presently.

That the animal Spirits, flowing from the tendinous Fibres, may enter equally all the fleshy, there are two Tendons in every simple Muscle, which are so constituted, according to opposite Angles, that the Spirits running to them from a twofold starting place or bound, might presently fill the whole belly of the Muscle, and that motion being finished, might immediately swiftly retire. If the contraction ought to be performed indifferently towards the middle of the flesh, the Tendons for the most part are equal; but if the motion inclines more towards one region of the flesh, one Tendon (to wit, which may supply a greater company of Spirits) exceeds the other in magnitude. If the Muscle, whereby it may be the stronger, is big and en∣dued with an ample bulk or substance, it is divided as it were into many Lobes or Bel∣lies, and two Tendons are ordained to each of them; to wit, to the end that the animal Spirits might be carried through short passages from the Tendons into the fleshy fibres, and might leap back again: because the compounded Muscle doth not always contain more series of moving fibres, that it might perform many and divers motions,

but that it might make the same motion often with the greater strength. For, as we hinted before, as a simple Muscle was as a single leaver or bar, the compound seems as if it were many leavers or bars serving for the removing the same body con∣junctly.

Further, hence we may observe in some Muscles, which are simple and regular, that all the fleshy fibres are equal, and so all the tendinous of one extreme being put together, are equal to all of the other end being put together; yet they single, where they are shorter in one Tendon, are longer in the other, and so disposed, that the tendi∣nous fibres on either part, the top and bottom, have their excesses inverse, and at once equal; to wit, that here a long is laid upon a short, or the longest upon the shortest, and there quite contrary; the shortest upon the longest, to the end, that the motion might be so made every where in this or that side of the Muscle, or at the end more strong, more plentiful Spirits flow together into those parts from the longer ten∣dinous fibres, and on the contrary: wherefore in some Muscles less necessary, where the part of the flesh growing to the bone, either becomes immoveable, or only serves for the filling up of empty spaces, one Tendon is shorter or lesser, and oftentimes degenerates into a bony or cartilaginous hardness. Further it is observed, as to other strong and greatly moving Muscles, that their Tendons are not so disposed, as if they were only stays, props, handles, or hanging crooks of the fleshy fibres; for so they are only constituted in their extreme ends; yet the tendinous fibres, that they may be made more apt promptuaries of the animal Spirits, being stretched out almost into all parts of the Muscle, receive every where both ends of the fleshy; which indeed yet more manifestly appears in the compound Muscles, for that one Tendon being compounded, embraces the extreme flesh, and the other enters into the middle of the flesh, as hath been already shewn.

But truly the animal Spirits, whilst they leap out of the tendinous into the fleshy fibres, are not sufficient of themselves for the wrinkling of them, but require another elastick Copula from the blood; this may be argued from many reasons. First, it seems to appear from this, that the same Spirits being solitary or by themselves, though most thickly planted within the Tendons, stir up no Tumor or Contraction whilst they are moved in them; wherefore being dilated within the fleshy fibres in a lesser quantity, and having got a larger space, they would be stretched out, unless they met or strove with other Particles, much less would they obtain a contractive force. Besides, when any wound or grievous trouble happens to a Tendon, the belly of the Muscle or fleshy part is chiefly troubled with a Tumor or Spasm; for the Spirits being irritated, not so much within themselves, but where they are violently driven among heterogene Particles, stir up the greatest tumults and inordinations. But fur∣ther, when the fleshy fibres are watered with the sanguineous humor beyond other parts, and more than may suffice for their nourishment, for what other use should it be assigned, unless that it may contribute to the motive function? Especially we take notice in lean Bodies, which are more sparingly nourished, that the Muscles being fused or drenched with more plentiful blood, do perform the strongest endeavours of mo∣tions: moreover, it doth not appear by what way besides, the expence of the Spirits in a Muscle, consumed with continual hard motions or labours, should be made up or renewed, unless, besides the small supplements by the Nerves, others sufficiently plentiful should be supplied from the bloody mass. Add to these, that members destitute of the wonted afflux of blood, easily fall into weakness or a Palsie; and that from the observation of Doctor Steno, in a live Dog the trunk of the descending Ar∣tery being tyed, all the lower or posterior members were suddenly deprived of motion. And though it doth not yet appear plainly to me, whether the exclusion of the blood from the spinal Marrow, or from the Muscles themselves, or from both together, be the cause; yet however it comes almost to the same thing, for as much as the animal Spirits being procreated within the Head, and stretched out by the medullary and nervous Appendices into every member, without the concourse of the blood, they should not be able to perform the loco-motive power.

Having thus far explained by what means a Muscle being contracted in the fleshy part, as to all the fibres at once, performs the motive function; we shall next inquire, what is the reason of the Instinct whereby every motion, both regular and irregular, is wont to be obeyed or is performed. Concerning this in general, it first appears, that the motions of every regular motion, yea and the impulses of some irregular mo∣tions being conceived within the Brain or Cerebel, are transmitted from thence by

the Nerves to every Muscle. This (as we have elsewhere shewn) is most evidently declared by the effects and consequences: yet here great difficulties remain, to wit, how by the same passages fresh forces of animal Spirits are conveyed from the Head to every Muscle, and at the same time the old ones exercising the Empire of the Soul; besides, with what difference and divers carriage of the inflowing Spirits, the Nerves perform either of these tasks, or both these offices.

Of these, as I conjecture, it seems that the animal Spirits, which flowing conti∣nually from the Head to refresh the forces of the implanted Spirits, are carried to the Muscle by the Nerves, do move to it quietly and easily, and being there presently received by the membranaceous Fibres, they go apart into the Tendons: which kind of relief, although it should be but little in bulk, yet because it is carried night and day by a constant course, it easily arises to a sufficient provision for the continual fil∣ling up of the Tendons. But that we suppose, the Spirits so brought perpetually to the Muscle to be transferred by the membranaceous Fibres, and not by the fleshy, to the Tendons, the reason is, because if they should first enter into these, straight run∣ning into an elastick Copula, they would stir up the Muscle into continual motions: more over, for that in the Heart and Muscles of Respiration the fleshy Fibres are ex∣ercised with a perpetual motion, they wait not for the passage of fresh Spirits to the Tendons.

But as to what respects the Instincts delivered through the Nerves from the Head for the performing, or staying, or any ways altering of the musculary motion, of these we ought first to consider, that the moving animal Spirits, whose companies or throngs constitute the Hypostasis of the bodily Soul, have these two properties as it were implanted in their nature; to wit, that whilst they are lively, numerous, and free, they exert or expand themselves, then that force being finished, they being a little diminished, retire themselves and grow quiet; but afterwards being refresh∣ed, they leap out again, and so vicissively. Waking and sleep, and the alterations of work and idleness or rest, inbred in all living Creatures, sufficiently declare this. Wherefore to the impulse or instincts of some Muscles, (which are wont to be per∣petually contracted and released) scarce any thing more is required, but that their Tendons may be supplied by the Nerves with a constant influx of animal Spirits; but the Spirits themselves, because they are numerous and expeditious of their own na∣ture, do willingly leap out into the moving Fibres, then the charge being performed, after a small loss or expence, they immediately withdraw, and being again presently recruited, they are again expanded, and so vicissively. Further, their actions (which chiefly are Pulse and Breathing) are variously changed according to the degrees of heat or of the affections, for as much as the Spirits being brought by the Nerves, are sent from the Cerebel, sometimes more remisly, sometimes more plentifully, or more nimbly.

Further, in some other Muscles subject to the Empire of the Appetite, as the ani∣mal Spirits naturally affect turns of expansion and recess, there is only need of a sign to be given, either for the performing or stopping of the commanded motion; either of which, the inflowing Spirits by their various knocking against the Muscle, easily perform, in ordering the implanted Spirits into various aspects or tendencies. When the Muscle is contracted, the implanted Spirits, whilst they are loosned from either end towards the middle, look and tend with a changed front from the middle towards either end. And so, whilst the inflowing Spirits carry the Symbol of performing Contraction, they being incited by heaps within the Nerve, more fully blow up its end, inserted to the Muscle, (where they are more thickly crowded together) and so cause it there to be contracted and abbreviated; whereby it comes to pass, that the same inflowing Spirits, about to enter into the Muscle, are at that time stopped by a mere heap, or rather are called back towards the intumified Nerve; wherefore by and by the whole series of the implanted Spirits (hence their inclination being chan∣ged) also looks that way, and so the inhabitants of the Tendons, leaping out from their little Cells into the fleshy Fibres, cause motive contraction: then the motion is broken off or ceases assoon as the Spirits being before called back towards the Nerve, do tend again into the Muscle, and so the front of the Army being again changed, bands of the implanted Spirits are presently compelled into the Tendons. That the thing is in a manner thus, I am perswaded, not out of a mere agreeableness or con∣cinnity of our Hypothesis, but from Anatomical observation. Because once dissect∣ing a Whelp alive, when by chance I beheld some Muscles of the hinder part of the

Head and Neck divided and separated at the same instant, wherein the fleshy Fibres, as also the Nerves inserted into them, were seen at once to be contracted, and being intumified, to be abbreviated.

For the promoting the recess of the Spirits out of the fleshy Fibres into the Tendons, whilst the Muscle is contracted, the membranaceous Fibrils, which every where cut cross-wise the fleshy, and thickly stick between, seem to help. The texture of these never to be enough admired, is better perceived in a Muscle endued with large Fi∣bres, viz. an Oxes being boiled to a tenderness. For in such a one, if gently opening the fleshy Fibres, you shall draw them one from another through the whole series, you shall see little Fibrils, like hairs, most thickly extended upon every one of those Tubes, which little Fibrils not only close and knit together the fleshy Fibres, but also lying upon every one of their series, and cutting them in oblique Angles, they also are all carried parallel, from Tendon to Tendon, in an opposite site to the fleshy: therefore whilst the Muscle being contracted, the fleshy Fibres do swell up, the Fi∣brils embracing them, that they may give place, are somewhat distended; then as soon as the swelling up remits, these returning to their wonted straitness, press to∣gether every where the flesh, and the Spirits being expulsed on either side, they re∣duce them to their pristine length. It makes for this, that whilst the Muscle is con∣tracted, the Spirits inflowing through the Nerves, depart from their membranaceous Fibrils; wherefore these being empty and lax, are able more easily to be distended; but whilst the Muscle is relaxed, the Spirits again entring the Fibrils, fill them, and that they may the better bind the fleshy Fibres, they make them shorter.

The Instincts of Motions, to be obeyed by the Muscles, so delivered by the Nerves, are, being sent either from the Brain, performed at the command, and with the know∣ledge of the Appetite; or from the Cerebel, according to the Laws of Nature, for the most part unknown to us. But besides, sometimes the Muscles are carried be∣yond, or contrary to the pleasure of the Appetite or Nature, into irregular motions, viz. violent and convulsive, and that happens after various manners and for divers causes. Concerning these, some time since discoursing more largely, we have shewn, that from thence do arise many kinds and differences of convulsive motions; as the Spasmodick matter being somewhere fixed, doth subsist either about the beginnings, middle, or ends of the Nerves; or because the same thing being wandring and loose, runs about here and there through the whole passages of the Nerves, and so variously transfers from place to place convulsive distempers. But besides these divers kinds of Convulsions, which are excited by reason of some evil or vice sticking somewhere to the Nerves themselves, this our Myology or Doctrine of the Muscles, hath discovered some Convulsions of another kind arising from the Muscles being chiefly affected.

For indeed we must advertise you, that the animal Spirits, disposed among the Muscles themselves, by reason of a taint or evil derived from the Brain, or from the Blood, or perhaps oftentimes from both together, are infected with certain hetero∣gene Particles, by reason of which they cannot rest or lye quiet in their Cells; but being always unquiet and restless, leap out of their own accord from the tendinous Fibres into the fleshy, and so oftentimes produce frequent and cruel Convulsions. But this we have observed to be done after a twofold manner, viz. first, for that the Spirits being burdened with an elastick Copula, remain not long within the Tendons, but leaping out from thence into the fleshy Fibres, induce frequent Convulsions of a Muscle, but short, and as it were by leaps; or secondly, because the animal Spirits, although they sometimes lye quietly within the Tendons, yet being inordinately snatched into the flesh, and there cruelly exploded, they cannot be presently repres∣sed, brought into order, or reduced into the Tendons, but whether we will or not, they persist a long while expanded, and so bring forth a long and very painful con∣traction of the Muscle. Which kind of Spasm, sufficiently known, we vulgarly term the Cramp.

The former distemper (called the Convulsive Leaping) is familiar both to malignant Feavers, and to the Scurvy. As to those, we have ordinarily known, when either no Crisis, or an evil one is obtained, that heterogene Particles from the blood and nervous juyce very much vitiated, are not only laid up in the Bowels, (whose dispositions and functions they pervert) but almost every where in the Muscles; and there growing to the Spirits, do affect them with a certain madness, so as they cannot continue peaceably together, or rest within the Tendons, but being divided and distracted one from another, leap out from thence by bands into the flesh, and there stir up the

lesser and most frequent Spasms or Convulsions. In like manner, by reason of the Spirits inhabiting the Muscles, being burdened with an elastick Copula there growing to them, some labouring with an inveterate Scurvy, cannot contain their limbs in the same site or position, but are necessitated sometimes to extend the hands or feet, sometimes to fling them about here and there, to transfer them variously, and some∣times to subdue their madness by running, leaping, or other hard labours.

Treating some time since of Convulsive Motions, we did almost wholly omit the Aetiology of the continuing Spasm or Tetanism, as a thing which depended upon the Doctrine of the Muscles, to be treated of afterwards: Then we only hinted, that the contraction of that kind did arise in one Muscle, because its other Antagonist was resolved or loosned, which indeed oftentimes happens in the face and some members; in which, whilst the parts upon one side are troubled with the Palsie, those opposite on the other, as it were loosned in the Reins, are too much contracted. Notwith∣standing this kind of Spasm for the most part is without pain; besides, this is not easily or presently passed over or cured no more than the Palsie, which is the cause of it.

Therefore as to what belongs to the formal reason of the Spasm, called in our Idiom the Cramp; every one labouring with this distemper, perceives in himself one or more Muscles to be most strongly and involuntarily drawn together, and they being for some time so highly distended, remain as it were stiff; and in the mean time, for that the fleshy Fibres being cruelly contracted, do violently haul or pull either Tendon, to wit, that which is fixed to the immoveable part, perhaps no less than the other part to be moved, they cause a most troublesom pain. But sometimes this Spasm being excited, by reason of the animal Spirits carrying themselves out im∣petuously into the fleshy Fibres, doth not cease until the same Spirits being returned into the Tendons, suffer the flesh to be relaxed; therefore its nearest causes will be both the greater impetuosity of the animal Spirits among the fleshy Fibres, with which they leap thither unbid; and also their long continuance or stay, for that they return back more slowly and difficultly into the Tendons. For the secondary causes may be rec∣koned, both the evil disposition of the animal Spirits, and also the evil conformation of the Tendons, viz. sometimes this, sometimes that, and not seldom both together.

As to the former; this distemper, as other Convulsions, seems to arise, for as much as the animal Spirits, being burdened with heterogeneous Particles or an elastick Copula, at length being irritated, they are incited to the striking of it off: which notwithstanding, being thick and viscous, and for that cause more tenacious, is not soon nor easily shaken off, but that the Spirits being still provoked by the same, and shut up within the fleshy Fibres, are longer detained in the expansion: which thing perhaps happens not so much unlike, as when water and air being joyned together, make a bubble; which, if it be made of water, wherein a little Sope is put, is more tenacious, much more large, and continues longer than that made only of mere wa∣ter. So we observe, that they who abound in thick and tartareous humours, are most obnoxious to these kind of Cramps, and besides, that they who presently sleep upon drinking or eating gross meats, after full eating, and especially after a large and plentiful supper, do suffer most cruel assaults of this disease; but sometimes the Ten∣dons themselves are found to be in the fault, for that they being too hard bound to∣gether or obstructed, they do not easily admit the Spirits returning from the fleshy Fibres. The obstruction of the Tendons is the cause, that Gouty and Scorbutick peo∣ple, whose Tendons salt and tartareous humours easily run into and obstruct, are wont to be cruelly tormented with these kind of painful Cramps: But that the constriction of the Tendons doth sometimes bring forth this disease, appears by this, for that some Women with Child, (as I have been often told) about the latter end of their Time, by reason of the Muscles of the Abdomen being too much extended, are wont to be troubled with frequent Cramps, only in the bottom of their Bellies. For the illustrating of this Pathology we will add this following Case.

A Noble Woman, young and fair, some time since obnoxious to Hysterick distem∣pers, and now above two years ago to Convulsive, and in a manner Epileptical; of late, by reason of the frequent and most cruel assaults of the disease, she became also Cachectical and Paralytical, that at length her Abdomen was distempered with an Ascites, and her Legs with a waterish Tumor, and lastly, all her lower parts, below her Hips, were deprived of motion; hence, as often as the Convulsive fits infested her, she was wont, not now to move her body or members here and there, but some∣times

these, sometimes those parts being snatched with the Tetanism, were variously bent and twisted about, that in the mean time, she her self sitting in her Bed or Chair, remained stiff and almost immoveable. It is not long since, that seeing the whole manner of one of these Fits, I observed, not without great admiration, divers sorts of turns and changes of alterations of the Spasms. At the first assault, her eyes being turned about swiftly hither and thither, she was presently taken with insensibility, then by and by her head being turned and contracted of one side, presently her arms and legs at once became stiff, and all her Joynts, sometimes of one side, sometimes of both, were bowed or stretched out: perhaps after four or five minutes these Spasms both in her Head and Limbs remitting, of a sudden others, for the most part oppo∣site, followed; which being often finished in the like space, others far different did arise, and so for two or three hours, longer Spasms almost of every kind and fashion; being excited through her whole Body, followed upon one another; so that her head being convulsed or pulled by turns from the right to the left, and contracted before and behind, yea and all her Limbs being bent inwardly here and there, or distended outwardly in the Course of one Fit, she exhibited all sorts of Convulsive gestures. When at any time the Spasms of one sort continued longer in the Head or Limbs than usual, it was the custom of the Servants about her to blow up strongly into her No∣strils the Fume of Tabaco; which being done, as the Spirits recovered within, the present Spasms immediately remitted, but upon them others of a new kind succeeded. Of late the Legs of this Lady were so debilitated by being loosned, that she could nei∣ther go nor stand, yea her Tendons under either Ham, being made tumid and shorter, were so contracted, that she could not stretch out her Legs straight.

Concerning the case of this sick Noble Lady, it may be demanded, wherefore upon the first coming of the Fit, no throwing about of the Body or Limbs, as is wont in most Convulsive or Epileptical people, but only continued Spasms or Convulsions variously translated from one part to another, and so others, did arise? For the solu∣tion of this, we say, that the Spasmodick matter is not only heaped up in the Brain and Nerves, but also in the Muscles themselves, and grows to the Spirits inhabiting the Tendons: And as that matter is tenacious, and the Spirits weak, and unable for the striking off quickly or easily such a Copula; therefore as often as these being irri∣tated, do leap out of the Tendons into the flesh, the Muscles being first possest, they cause strong and long Contractions; in the mean time, other Muscles, especially their Antagonists or opposites, being hindred and bound up from motion, until the Convulsions of the former are remitted; hence the Members, however convulsed, are not moved out of their place, because the moving or carrying of the Body, or any Members, is not performed but by the help or duty of many Muscles, whilst some of them either rightly cooperate with others, or at least obey them, to wit, so that some respective Muscles, observing due cooperation, are contracted at once, then those being loosned, the contraction of others immediately succeeds. But if they which are unequal and unlike, are at once contracted and strongly convulsed, and so con∣tinue long, so that other Muscles in the mean time cannot be contracted, there will be a necessity for the members bent or extended here and there, to remain as they are wholly stiff. But that the present Convulsions were always remitted by the blowing the smoke of Tabaco up her Nose, the reason is, because the region or some part of the bodily Soul being vehemently affected, if by chance a new passion equally violent be brought upon another part, the first is presently abolished or ceases: For in truth, it appears by constant observation, where-ever the greater or fresher trouble is, that thither greater plenty of Spirits presently flock and make a tumult: wherefore any new irritation being excited in the Brain or its Meninges, whatsoever others were begun outwardly among the Muscles, immediately vanish or are obscured; then as soon as this fresh trouble is passed over, Convulsions outwardly arise forthwith again, but in other parts where more heaps of Spasmodick matter lye not yet consumed. But that long continued Spasms do arise, either by reason of the Spirits being burden∣ed with a more tenacious Copula, or by reason of the Tendons being obstructed with a viscous or tartareous matter from either or both, it appears from hence, because this disease increasing (as in the case of this Noble Lady) the Tendons are at length so shortned by the more plentiful heaping up of the morbifick matter, that they be∣come stiff and shorter, and for that reason they hardly or not at all grant any place to the Spirits for the constant performing of the motive function.

Thus much for the Musculary Motion, both natural and convulsive, and the rea∣sons

of both, which we have proved with what diligence we were able, and by Ana∣tomical Experiments: But if any one shall object, that they are not very firm, be∣cause we have noted in the cutting up of live Creatures, that the Heart and Muscles of Respiration and the fleshy Pannicle, after that the Nerves and Arteries are cut away, do continue for some time their turns of Contraction and Relaxation, whence it is argued, against our Hypothesis, that their motions do not depend upon the con∣stant influx of the blood and animal Spirits; it will be plain to return this Answer, That in those about to dye, it sometimes happens so, because the Soul being then distracted and drawing near to dissolution, all the implanted Spirits at once being cut off from the commerce of those influencing or flowing in, do of their own accord exert themselves, and perform (as long as they are able) their wonted motions; which being continued for a little space only, need not the subsidy or assistance of fresh forces, because the veterane, till they are quite worn out, perform their wonted tasks; yea also the old sanguineous Copula, till it be wholly consumed, receives and lets go their embraces with a constant change: But this more rarely succeeds in other Muscles subject to the Empire of the Appetite, and wont only to be exercised as occasion served.

Moreover, as we have affirmed, that the Instinct for the performing of Motions is brought altogether through the Nerves from the Head to the Muscle, and as every Trunk of the same Nerve, being oftentimes broken into many shoots, variously di∣stributing them, sends it to many destinated Muscles, it may very well be doubted, how the animal Spirits, conveying the Symbol of the motion to be performed with a certain choice, do actuate only these or those branches apart from other branches of the same, and do not indifferently enter all the branches or shoots of the same; to wit, as the blood passes through the Trunk of the Artery, and all its ramifications equally. The most Learned Regius, that he might solve this knot, supposes in the Nerves some little doors, like to those which are found in musical Organs, the aper∣tures whereof admit the Spirits to these or those parts especially, the rest being shut up. But he ought to have shewn, if not the little doors themselves, yet at least by what instinct and by whose direction sometimes these, sometimes those are locked up, and others opened. But in truth, this may rather be said, that all the shoots of the Nerves and lesser branches remain distinct and singular among themselves from the parts to which they are inserted, even to their beginnings; so that a peculiar tract of the Spirits or way of passage lyes open, from the Brain and its medullary Appendix, to every Muscle and nervous part; for in truth, although the Nerves, according to their beginnings, may seem to arise from the greater Trunks; yet it will easily appear, if you shall open the trunk and those branches, that in them many little Nerves, only like hairs, for the sake of a better conduct, are collected together in the same bundle; yea, the coverings being separated, you may follow oftentimes the little Nervulets, and those single to the respective parts and members, to which they are destinated.

But in the mean time, although there be singular passages or chanels of the animal Spirits of most Nerves, distinct among themselves; yet some do variously commu∣nicate with others through the branches and shoots sent on either side; which indeed ought to be so made, that when many Nerves together, are required to some motion of a Muscle equally, all these, by reason of the commerce mutually had between them∣selves, might conspire in the same action; hence, in some motions of the members, as in the striking of a Harp or Lute and other complicated actions, many Muscles co∣operate with admirable celerity; so that, although many be imployed at once, they perform their task severally without any confusion. Besides, there is need for the Nerves to communicate mutually among themselves, because of the Sympathetical motions of the members and of some of the parts, for neither for any other cause is the Nerve of the Diaphragma inserted into the brachial branches, or those belonging to the Arms, than that the exercise of living Creatures, especially in running or fly∣ing, might be proportionate to the tenour of Respiration. Hence it also proceeds, that in any passion, the Praecordia being bound up or dilated, the countenance and aspect of the face, yea and the gestures of the hands and members are pathetically figured. We have proposed sufficient Instances of this sort in our particular History of the Nerves, so that we need not here add any thing more.

What remains for the illustrating our Myology or Tract of the Muscles, we have ta∣ken care to have added, viz. four Figures, which may represent to the life both the exteriour and interiour true and natural faces or appearances both of a simple and compounded Muscle.

[illustration] depiction of muscle

Fig. III.

[illustration] depiction of muscle

Fig. IV.

[illustration] depiction of muscle

Fig. I.

[illustration] depiction of muscle

Fig. II.

The Explication of the Figures.

The First Figure

SHews a simple regular Muscle, described according to its natural appearance, in the Belly of which the fleshy Fibres being opened, are diduced one from another, that the membranaceous Fibrils may be the better beheld.

• A. The right Tendon.
• B. The left opposite Tendon.
• C. The fleshy Belly; all the fleshy Fibres of which lye one by another equal and parallel, but in even and oblique Angles between either Tendon.
• D. The aperture of the fleshy Fibres, which being drawn aside, the membranaceous Fi∣brils, thickly crossing them, appear.

The Second Figure

Shews a simple Muscle cleft in the middle, after the Tendon being cut off, and portions of it pulled away, that the interiour series of the fleshy Fibres, or their commixtures or mingling with the Tendons, may appear.

• A A. The right Tendon being placed above, both portions of which divided, do in some measure appear.
• B B. The left opposite Tendon placed below, either portions of which divided, lye hid for the most part under the Flesh, those towards the edges being only conspicuous.
• C D. Portions of the fleshy Belly divided and separated, which before (this being laid upon that) did cohere, in either of which all the fleshy Fibres proceed equally, and in like manner obliquely from one Tendon to another.
• E. Some membranaceous Fibrils represented, thickly crossing the fleshy Fibres.

The Third Figure

Exhibits a certain Muscle less compounded, to whose two fleshy Bellies two compounded Tendons also (equal to four simple ones) are destinated.

• A. The exteriour compounded Tendon, embracing either side of the fleshy Fibres, which being almost only conspicuous on the edges, lyes hid for the most part under the Flesh.
• B. The interiour compounded Tendon, entring into the middle of the Flesh, which receives on both sides the fleshy Fibres, sent from either side of the exteriour Tendon.
• C. The first Belly of the fleshy Fibres, all whose equal and parallel Fibres lye between the opposite sides of the Tendons in oblique Angles and equal.
• D. The second Belly of the fleshy Fibres, all whose Fibres being in like manner formed, are beheld in the same as in the other Belly.
• E E. Both extremities of the exteriour compounded Tendon.
• F. The extremity or end of the interiour compounded Tendon, the like to the other being opposite, at an equal distance from the end of the Muscle.

The Fourth Figure

Shews a regular compounded Muscle, divided and opened in the middle, so that the inte∣riour face of either Belly may appear.

• A. The exteriour compounded Tendon cleft into four parts.
• B B. Portions of one side of the divided Tendon separated from the other.
• C. Portions near sited, of the other side of the divided Tendon, which for the greatest part lye hid under the flesh.
• D D. The flesh of one Belly also divided, and separated one far from another.
• E E. The flesh of the other Belly also divided, and placed near one another.
• F. The interiour compounded Tendon entring the middle of the Flesh.
• G G. Portions of the same Tendon divided, and with portions of the Bellies, which they receive, separated apart.

Notes

• Exper. Phys. Mec. 50.
• Exper. 1.3.
• Exper. 78.
• Exper. 41.