sensum nobis ipsi adimamus neque dubitationis â—muli aut fatui aut aliud ejusmodi quidvis simus sed quod tum rectum est tum modestis Hominibus convenit quod quidâ—m evidens est promptè accipiamus quod autem dubium est per ocium quaeramus ¶ Errors of the Presse Correct thus PAge 1. line 20. read Plostique page 5. line 1 read Aristoteleans pagâ— 8. line 2 read Void and line 20. read 〈◊〉 〈◊〉 〈◊〉 〈◊〉 〈◊〉 page 10. line 7. read Homaeomerian p. 13. l. 10. read ructus acidus and l. 25 one and the same c. page 15. line 9. read difficultly page 17. line 13 read Pecquet page 26 line 29. read Pecquet page 31. line ult read other branches page 40. line 4 read it s own nature c. page 61. line 13. read apposition page 64. line 4. read Venous p. 72. l. 1. r. Slegelius and the same line 12. page 77. line penult read only thus much pag. 83. line 18. read draw themselves c. page 86. line 12. read Fracastorius page 89. line 29. read lax page 95. line 17. read voided page 114. line 7. read Capsula page 116. line 10. read Nerve page 157. line 19. read Nerve page 190. line 8. read veins page 192. line ult read covered page 193. line 17. read Taylors Mascle OF NVTRITION Exercitation the First Of Nutrition THe Platonist Article though He holds the Deity and the world to be coeternal Nutrition and Generation one and the same Act of the soul or Formative virtue doth yet allow the World to have been created by God and to solve the seeming contradiction saith that Priority was not 〈◊〉 〈◊〉 〈◊〉 〈◊〉 〈◊〉 in respect of time but 〈◊〉 〈◊〉 〈◊〉 〈◊〉 〈◊〉 in respect of Nature as the Sun and light are coaevous though the one be the Cause the other the Effect This certainly might be more justly said of the Generative Nutritive Faculties if at least they be not one and the same by one of which an Animal is produced and by the other conserved For though the Formative Virtue may seem to precede in its operation yet are the Stamina or rudiments of the Embryo scarce delineated or adumbrated when the Nutritive begins to augment and perfect them So as that it may rather be said to go hand in hand with the Plastick's faculty than to follow after it and what priority there seems to be in their operations is rather in respect of Nature than of time To forme and nourish are not only acts of one and the same soul but so alike that it is no easie matter to distinguish betwixt them For Generation and Accretion are not performed without Nutrition nor Nutrition or Augmentation without Generation To nourish is to substitute such and so much of matter as was decay'd in the parts namely flesh nerves veins arteries c. And what is that in reality but to generate flesh nerves veins arteries c In like manner Accretion is not effected without Generation for all natural bodies upon the accession of new parts are augmented and those nevv parts are such of which these bodies were first composed and this is done according to all the dimensions so that to speak properly the parts of an Animal are encreased distinguished and organized all at once Farther this is necessary both in respect of the Efficient cause and of the Matter The Former because idem esse principium efficiens As well in respect of the Matter as of the Efficient nutriens conservans in singulis animalibus necesse est nisi aliam formam in puero aliam in adolescente et in sene aliam constituamus The Latter because all Animals such as are produced per Epigenesin of which is our discourse not of such Insects as are produced per Metamorphosin are corporated of one part of the matter prepared by the Formative Spirit and nourished and augmented by the rest For Nature doth nourish and amplify all parts of an Animal with the same matter or humour not with a diverse out of which she constituted or framed them at the first Because whatsoever is superadded to the parts during their growth ought to be of the same substance with what was prae existent and so must consist ex congenere materiâ their Renovation as well as first Corporation being effected by Epigenesis Aggeneration or superstruction So that we may well conclude that Nutrition is nothing else but continual Generation and as necessary to the Conservation of every individual nature as Generation it self is to the conservation of the Universe To make this Necessity the more evident we are to consider The necessity of Nutrition two-fold viz. Augmentation Conservation 1 That forasmuch as an Animal cannot performe all the functions of which its nature is capable whilst it remains in the minute parts and rude beginnings in which it is first formed therefore there must succeed a Nutrition that may dilate and amplify those slender stamina by interweaving and assimilating so many other congenerous parts as serve to advance and augment the Animal to a convenient magnitude 2 That since the chief principle of life in every Animal is a certain indigenary Heat analogous to pure flame such as the most rectified Spirit of Wine yeelds upon accension which by continuall motion and activity agitating the minute and exsoluble particles of the body doth dissolve and consume or disperse them of necessity the whole Fabrick would soon be destroy'd unlesse there were a continuall renovation or reparation of those decayes by a substitution and assimilation of equivalent particles in the room of those dispersed and absumed So that we see the Necessity of Nutrition is Two-fold one in respect of Augmentation the other in respect of Conservation As to the continuall Decay or Depredation of the substance of our bodies wherein the latter necessity of Nutrition doth consist that we may the better understand the manner how it is effected we are to enquire into the Causes thereof viz. the Agent or Depredator and the Matter or substance depredated The Agent or Efficient Cause with all Philosophers The Efficient cause of the consumption of the parts is the Vital Flame we hold to be the Naturall Heat or Vital Flame at first kindled by the vegetative soul or Plastick spirit in the blood constantly burning in the Heart as in its fountain or primary Focus and thence by diffusion of it selfe through the arteries warming cherishing and enlivening all parts of the body This Lar familiaris is called 〈◊〉 〈◊〉 〈◊〉 〈◊〉 〈◊〉 ingenitus ignis by Hippocrates 〈◊〉 〈◊〉 〈◊〉 〈◊〉 〈◊〉 Accensio animae in corde the Kindling of the soul in the heart by Aristotle and generally known by the name of Calidum innatum the innate Heat The principle of life therefore being a certain Fire certain it is that the same cannot subsist or endure one moment of time unless it be perpetually maintained or fed with some
have undergone severall Circulations and as many fresh Accensions in the Heart For in every Circulation they grow more and more subtile and agile and so must at length be brought to the requisite height of volatility To which having once attained in the very next Circulation though they are restrained and kept in by the sides of the heart and coats of the arteries while they remain therein being diffused upon the outward parts of the body as they warm and vivify those parts so do they soon flye away and disperse themselves into air And while these thus flye away other Spirits lesse volatile are by the colder temperament of the parts by which they pass somewhat repressed so that the force of their expansive motion is much abated the Mication or panting of the bloud interrupted and the bloud wherein they are of Arterial or vital bloud is made venouse or Natural and such it continueth untill the next circulation bring it again to the heart there to be kindled afresh and exalted to the due heat of vitality Which once acquired it recovers its intermitted motion of Mication or rising and falling alternately and yeeldeth a fresh supply of spirits vital which being transmitted to the habit of the body are soon dispersed like the former And thus is the vital Flame kept alive at no lesse expence The Reason of the Mication or panting motion of the Blood in the arteries than a continual dissipation of the most votatile spirits of the blood For that vital Heat ariseth from within and the most subtile spirits are the first Movers to the excitement thereof the motion by which they do it being their indeavour to expand themselves and to dilate their bounds while the other grosser elements or ingredients of the bloud oppose them therein And this strife or Counter-activity of the spirits on one part and of the grosser ingredients of the blood on the other doth exhibite the general Essence of Heat To which may be added this short observation that in this Contention one while the spirits prevailing do lift up or swell the mass of bloud another while the grosser elements the contraction of the Heart and arteries assisting them prevailing countermand and interrupt that expansive motion and that by this alternate conquest of these Antagonists is made the Mication or Rising and Falling of the blood the one in the Dilatation the other in the Contraction of the Heart and arteries Forasmuch therefore as the vital Heat doth consist in the rarefactive motion of the spirits and the renitence of the grosser parts of the bloud and that the spirits for the most part at least alternately obtain the victory and dominion over their opponents it seems most consentaneous to truth that this vital Heat cannot be preserved without a perpetual expence of the most pure i.e. the most volatile spirits of the blood and consequently necessary that during life fresh spirits must be perpetually minted out of the blood to defray that vast and continual expence And this we conceive to be the true progress of Nature from the first reception of the spirits contained in the Aliment to their education into the Chyle their sublimation in the heart their gradual exaltation to the highest degree of volatility and lastly their dissipation through the skin into aer upon which depends the Conservation of the vital Heat and the continual Generation of the vital Spirits OF THE MOTION OF THE BLOOD ITS CONDITIONS AND CAVSES Exercitation the Sixth Of the Motion of the Blood its Conditions and Causes NAture which in all her works hath the End The Method of the Chapter and Means conducing to that End alwayes closely connected in one idea having ordained the perpetual generation of this vital Nectar the Blood in Animals for the Uses in the precedent Chapter recited that she might not be deficient in the means requisite to fulfill those Uses hath also ordained that the blood should be carried from the Fountain to all the parts in living streams by a certain admirable Motion necessary to its distribution through the whole body Now that we may fully understand the nature of this Motion we are to consider 1 the Manner 2 the Conditions 3 the Causes of it Concerning the FIRST we observe That the Motion of the blood is Circular that the blood is continually carried or rather driven from its fountain the Heart in the centre of the body by the Arteries to the circumference and back again from the circumference to the centre by the veins irrigating cherishing and vivifying all the parts as it passeth along and that therefore this Motion was by the glorious Inventer of it Dr. Harvey called the Circulation of the blood quòd Ejus enim semper redeat labor actus in orbem For in the first place From the Vena Cava into the right Ventricle of the heart the blood is effused out of the vena Cava into the right ventricle of the Heart as may be evidently seen in living Animals dissected especially in Coneys For if the trunck of the vena Cava be bound with a ligature both above and below the heart you may perceive all the blood contained in the space betwixt the ligatures to be speedily discharged into the right ventricle of the heart to which the vena Cava is conjoyned From the right ventricle of the heart it is the heart contracting it self expelled into the vena arteriosa From the right Ventricle by the Vena arteriosa into the Lungs and so into the Lungs but not through the septum transversum or middle partition of the heart as some have imagined conceiving the same to have some certain obscure passages from the right into the left ventricle only because they could without much violence thrust a style or probe through it when indeed those passages are not made by Nature but by the point of the probe the flesh of the heart being so tender as that it is easily penetrated by any hard and pointed instrument though but gently intruded Passing through the vena arteriosa into the very substance of the Lungs the bloud is immediately returned into the venosa arteria From the Lungs through the Arteria Venosa into the left Ventricle and through that into the Left ventricle of the Heart This is demonstrable thus Having made a ligature upon the great branch of the Arteria venosa neer the pericardium in the lungs of an Animal yet living you may observe that branch to be soon filled and much distended with bloud in that part which is toward the lungs and that emptied and flaccid that is next the heart and upon remove of the ligature the bloud will flow amain from the lungs to the left ventricle Now there being no other way by which this bloud can flow to the left ventricle but from the lungs it must of necessity descend thence by the Arteria venosa The left ventricle having thus taken in a quantity of bloud
Nerves are framed for the performance of some one Common Office it is not unreasonable to conceive that all of them are perforated more or less so as to be capable of conveying the Succus Nutritius This may be in good part inferred even from hence that the Apoplexy often ends in a Palsy in which case all Physicians grant that the Humor oppressing and obstructing the Brain is discharged thence upon the Spinal Marrow and Nerves affected which could not be unless the Nerves were capable of being obstructed by the Humor protruded or impelled into them You will reply perhaps that they are capable indeed of the influx of Animal Spirits unless their originals chance to be obstructed as in the case of the Palsey but as for any Liquor or Humor of far lesse subtility than those Spirits it is impossible they should admit it into them And we may return that the supposed Animal Spirits nor intruth the Vital ones are any where to be found in the whole body pure or sincere and without mixture and therefore if the Nerves were framed for the reception of any matter pure and distinct from all others certainly that matter must be of a grosser substance than simple and abstracted Spirits Furthermore that there are small Channels in the Nerves may be perceived by their Compression in our limbs as when we have long fate upon a hard seat or otherwise streightned our sinews for in that case we feel a certain stupor or Numbness the vulgar say their limbs are asleep in that part to which the compressed Nerves are prolonged a certain document that the free passage of some matter through them is at that time intercepted and the compression being removed there instantly ensues a kind or troublesome Tingling or Pricking as if the part were pierced with needls and this only because what was arrested and intercepted there begins again its former liberty of motion These things duely weighed we may lawfully conclude that it is not sufficiently 〈◊〉 that the Nerves are impenetrable by the Succus Nutritius only because they have no manifest cavity Second that in the dissection of an Animal alive Solution of the Second yeelding the reason why no swelling aâ—iseth in a Nerv when bound with a Ligature in a living Animal it generally happens that by reason of the extream striving and agony of the poor tortured Creature before the dissector can come either to apply a ligature unto or to cut a Nerve all the Liquor contained therein is squeezed forth into the part wherein the Nerve is terminated so that no wonder if there appears neither swelling on either side of the ligature nor any exstillation of liquor from the ends of the Nerve cut off And this Violent streyning of the Nerves in dying Animals and the squeezing of the Liquor contained in them into the parts to which they are inserted seems to be the Cause why that Lympheduct which corresponds to the Nerve bound or cut is found more full and distended than ordinary as hath been of late frequently observed And yet we have been assured by judicious and credible persons that they have seen no small quantity of the Nutritive juice exstilling out of the Nervous Chord of the Thigh in a man and presâ—ed some of it out of the Axillary Chord in Dogs Third as to the Second adding withall that besides what hath been said Solution of the Third shewing the reason why the Succus Nutritius is not found in the nerves of dead bodies dissected of the cutting of the Nervous Fibres in divers plants without effusion of the least drop of their Alimentary juice the Motion of the Succus Nutritius through the Nervs is neither Continual nor impetuous but by intervalls and gentle so as not to be perceived and that all of it being forced into the parts by reason of the strong Contention or streyning of the Nervs in the very agony of death and all impulsion of humors in the body ceasing after death it cannot seem strange that none of the Succus Nutritius can be found in the Nervs of bodies dissected after death These Grand Objections thus solved it remains that we enquire 1 What is the Principium Elaboratioms of the Succus Nutritius or where it is praepared 2 What is the Principium Dispensationis of it or whence it is immediately infused into the Nervs which convey it to the parts 3 By what vessells it is imported into that principium Dispensationis 4 What kind of Motion it hath in the distributing Nervs and 5 What is the Cause of that Motion Concerning the First What is the Principium Elaborationis of the Nutritive juice viz. the Glandules of the Mesentery of the Loins and the Thymus viz. the Parts wherein the Succus Nutritius is prepared immediately before it is imbibed by the Nervs there is good reason for us to believe that this work is effected in the Glandules of the Mâ—sentery in the Three Glandules of the Loins and in the Thymus or Glandule in the Thorax Which opinion that we may the better explain it is requisite we make a short Digression concerning the Differences and Vses of the Glandules according to the observations and consequent Conjectures of Dr. Glisson and Dr. Wharton Of the Glandules in the body there seem to be 3 sorts respectively to the Nervs whereof some are inservient to Excretion some to Reduction and some to Nutrition For though it be most true that the Common office of all the Glandules is Secernere to make some separation yet is it no less true that that separation is various as tending to Excretion in some in others to Reduction and in others to Nutrition and the Matter it self which is separated by those divers wayes of Secretion being likewise various the first sort being a meer Excrement the Second an Excrement only in relation to some parts but profitable in relation to others and therefore not to be excluded but retained and the last the true Succus Nutritius Under the First Classis of those Glandules are comprehended the Testicles the Prostates the Vesiculae Seminales the Paps in women and the Glandulae Maxillares or spitting Glandules under the Tongue all which are furnished with a peculiar Excretory vessell by which they discharge and avoid some superfluous matter brought into them by the Nervs To the Second inservient to the secretion of a humor and the reduction of it into the veins afterward belong the Glandulae Renales or Deputy Kidneys the Glandules neer the Fundâ—ment those adjacent to the Oesophagus the Parotides Axillary Inguinal c. Glandules All which receive from the Nervs a certain humor more rough and acrimonious and approaching to the nature of the blood than is agreeable with the Succus Nutritius and therefore the Nervs by the help of these Glandules discharge themselves of it and retain only the more sweet mild and profitable juice But because the Humor thus rejected by the Nervs hath some affinity to the
conjoyned net-work of its Nerves becomes more tense and firme than in sleep which seems to render it moist and lax and since that Tension cannot but in a manner ex-press or squeez forth the liquor contained in the original of the Nerves it is reasonable to conceive that the motion of the Succus Nutritius from the brain to the parts is to be imputed thereunto especially it being by us observed that the diffusion of the nourishment is chiefly soon after we awake and rise from sleep And lastly as for the Motion of the Nerves themselves nothing is more manifest than that while the Nerves and Muscles are distended in Voluntary motion the juice contained in the Nerves must be impelled or ex-pressed to the parts into which they are inserted the extension of any nervous body necessitating the flux of any liquor contained betwixt its filaments from one extream to the other But this we deliver not as doctrine but meer Conjecture Nor should we have adventur'd to deliver it but that we hope that as the singular obscurity of the Argument may incite some other more able brain to labour in the same scrutiny so it may excuse us if we have not been so happy as to light upon the knowledge of the true Causes we sought after there being among Candid Spirits not only pardon but even commendation due to ingenious Errors especially in things of Difficulty and where the discovery of Truth is to be hoped rather from Time and multiplied Observations than from the single felicity of Witt. OF VOLUNTARY MOTION Exercitation the Eleventh Of Voluntary Motion or the Use of the Muscles FRom one Use of the Nerves Article viz. the conveying of the nourishment to all parts requiring it The Inference and Method of this discourse we now transfer our contemplation to the other viz. the transmission of the Animal Spirits from the Brain the principal throne of the Soul where she judgeth of the good or evill of objects and from whence she dispenseth her commands to the Muscles the immediate and proper instruments of Motion Voluntary and here for the more perspicuity we shall take the liberty of permitting our Curiosity to exspatiate it self a while in that delightfull and ample field the admirable Art of Nature shewn in the Structure of those organs in their Variety and in the Reason of their Motions The things required to Voluntary Motion Requisites to Voluntary motion are 1 the object communicated by the sense to the judicatory Faculty or Soul 2 the Soul perceiving that object judging it to be good or evill and accordingly pursuing or avoiding it 3 the Instrumentum Mediatum by which the Soul impresseth a motive-Faculty upon the Muscles and immediately acteth toward the attainment of her end and 4 the Instrumentum Immediatum by which immediately the motion intended is executed or effected Concerning the Exciting Cause That the Animal Spirits are the Mediate Instruments by which the Soul moves the Muscles argued from or object and the primary Agent there is nor can be no dispute it being most evident that the Soul is the principle of Motion and that it is excited thereunto by the good or evill appearing in the object But concerning the Instrumentum Mediatum or that by which the Soul doth cause the Muscles to move either the whole body or some member of it in order to her embracing or avoiding the object many especially of late yeers have seemed very much to doubt To satisfie them therefore in this particular we with all the Ancients conceive that the Animal Spirits sent from the brain by the Nerves into the Muscles are the Immediate instrument of the Soul whereby she doth impress an actuall motion upon the Muscles and to evince the probability of this opinion we offer these few yet in our judgment weighty Reasons 1 Voluntary Motion being nothing the Mutation of Figure both in the Muscle and Member moved but the willing translation of the body of an Animal or some part of it out of one place into another it is necessary the member moved should measure the determinate space betwixt the Terminus à quo and the terminus ad quem and consequently that the proportion of the member moved be answerable to the proportion of that intermediate space now from that necessary proportion there ariseth a change of Figure as well in the member moved as in the Muscle moving as we shall ere long demonstrate by Principles Mathematical in explanation and confirmation of the doctrine of our Master Galen in 1. de motu Musculor cap. 8. but that Mutation of Figure in the external instrument cannot arise immediately from the Soul it self which being Immaterial can of her self produce no such effect and therefore it must arise from something more proportionate to the immediate energy of the Soul than either the grossness of the member or muscles ordained to move it will admit them to be which Something can be no other than the Animal Spirits whose subtility makes them to approach neerer to the nature of the Soul and whose sudden influx through the Nerves into the body of the Muscle causeth a swelling or distention and so a contraction thereof and consequently a change of Figure in the member 2 Since every Instrument ought to be accommodate the Quickness of voluntary motion as well to the nature of the Agent which is to use it as to the effect to be produced by the use of it and that Voluntary Motion is performed as it were in an instant and by a most swift and speedy Impulse from the soul it followeth that betwixt the incorporeal Agent the soul and those corporeal instruments the Muscles there must be some Intermediate instrument such as is capable of being so transmitted from the Brain into the Muscles with the greatest velocity imaginable and of setting them instantly a-work according to the determination and direction of the soul. Now no part of an Animal can be thought capable of such easie and expedite Mobility but the spirits which flow through the body in less than the twinckling of an eye and therefore we conclude that They are the Immediate instrument of the soul in voluntary motion according to the assertion of Galen in 4. de locis affect cap. 6. in these words Est in cerebri ventriculis Spiritus Animae primum instrumentum quo sensum motum per universas corporis partes Anima transmittit c. 3 As the Power or Faculty of Seeing doth not reside in the Eye the conquest of the acting Muscle over its Antagonist nor that of Hearing in the Eare but is imparted to the organs of sight and hearing from the soul by the mediation of Nervs and Spirits so likewise is not the Virtue Motive inhaerent in the Muscles but communicated to them upon occasion from the same soul and seems to consist wholly in the quick afflux of spirits as that by which alone they are moved Which
of plain concernment in the explication of it such as without which our disquisition into the nature of Voluntary Motion vvould be obscure and unsatisfactory Fundaments Geometrical Principles Geometrical of necessary importance toward the understanding thereof Proposition 1. What are equal to the same are equal also among themselves è contra Proposition 2. All right lines drawn from the Center to the Circumference are equal Proposition 3. Two right lines whatsoever mutually cutting each other make at the vertex Angles equal among themselves Proposition 4. The squares of equal lines are equal Proposition 5. A right line falling upon two right lines aequidistant or parallels makes equal Angles Proposition 6. In Triangles where the Angles are equal the sides also are equal and proportional proposition 7. In a Triangle where any one Angle is greater there the side subtending that Angle is also greater proposition 8. In every Parallelogram the Complements of those Parallelograms that are about the Diameter are equal among themselves Demonstration Suppose A B C D the Parallelogram A D the Diameter or Dimetient and the supplements H B and H C. We say the supplement H B. is equal to the Supplement H C. because the Parallelogram hath for its Diameter A D and therefore the Triangle A B D. is equal to the Triangle A. C D. Again because AEGH hath its diameter A H. therefore the Triangle A G H. is equal to the Triangle A E H. By the same it is demonstrated that the Triangle H F D. is equal to the Triangle H I D. Now since the Triangle A G H. is equal to I D and E H G. equal to F D I it followes that the supplement H B. is equal to H C. Which was to be demonstrated proposition 9. If a streight Line be divided into parts equal and unequal the Parallelogram that is contained in the unequal segments of the whole Line given together with the square of that which is between the segments will be equal to the square described by the half Line Demonstration Let the right line be A B divided into equal parts at the point C and into unequal at the point E. Let from the point A to the proportion of the equal segment be made a square A C G H and from the point E on the unequal segment be drawn a parallel line E F and from the point A the Diameter or Dimetient A H and a parallelogram E F B D. We say the Parallelogram E D. with the square F H. is equal to the square A H which is proved from the Antecedents proposition 10. To make a Square equal to a Parallelogram given Let the Parallelogram be A B C D. To which to find a square equal draw a line from C to E to the proportion of G D and divide A E into equal parts into the point F. from whence make a circle A G E and continue the line C D to the point H. We say the Line C H. is the roote of the square I K C H. which is in equal proportion to the Parallelogram A B C D. Demonstration Because the Line AE is divided into equal parts at the point F. and into unequal parts at the point C and the Parallelogram contained in the unequal segments together with the square FC is equal to the square FH or FE the equal segment according to the ninth proposition precedent it followes that the Parallelogram ABCD. is equal to the square IKHC according to the 47. proposition 1. lib. of Euclid Which was intended Fundaments Architectonical out of Vitruvius Principles Architectonical of the same Concernment lib. 10. cap. 8. Proposition 1. In the Center all Gravity ceaseth so that therein nothing is either Heavy or Light 2. The power of all Motion is varied according to the ration of the Center to the Circumference 3. By how much the more remote or elonged from the Center any thing is by so much the swifter is it moved 4. By how much greater the Circumference of the Circle so much greater the Diameter and so much swifter the Motion Demonstration Let the Center be E. from which under the Diameter E F. let the weight be placed at F. We say this weight at F. doth not rest there but moveth to its Center towards C. Again if the same weight be elonged or removed to A then by reason of its greater distance from E and of the greater Circle it will be moved towards its Centre C with the greater velocity accordingly 5. Bodies equal and under the same Diameter equally distant from the Center do cutt a perpendicular Line at right Angles Demonstration In the former Scheme let one body be at B and another at A. upon the Diameter of the Circle whose Center is E. and neither of them shall move because their Gravity is equall in that proportion of the Diameter and so hasten to the Center C. with equal swiftness but because they make equal Angles with the perpendicular DE. 6. If to one of two equal bodies placed under the same Diameter and equally distant from the Center any weight be superadded that whose weight is increased shall move more strongly and make an acute Angle with the perpendicular or wholly obtain the place of the Center as in the last Scheme the weight A is encreased to the magnitude G and therefore it must move the more strongly as is evidently concluded And let these suffice for the Fundamentals To come to their Concernment in the Motion of the Muscles we observe that every Muscle hath a twofold Motion viz. one Natural wherein the Fibers of the muscle spontaneously recontract themselves after they have been extended or restore themselves to their native tenour That every Muscle hath a Twofold Contraction viz. Natural and Animal by Philosopher named the motion of Restitution common to all Tensile bodies and this is alwayes from the end towards the beginning of the Muscle according to the position of its Fibers another Animal wherein the same Fibers are further Contracted by the forcible and copious influx of Animal spirits at the command of the soul in order to the performance of some action intended That the Natural Contraction of a Muscle is not sufficient to voluntary Motion That the Natural Contraction is not the cause of Voluntary Motion but only the Animal though we allow every muscle to be made upon the stretch i.e. in an extended position is manifest from hence that betwixt each Muscle and its Antagonist there is an equal power of naturally-moving themselves toward their originals so that betwixt two Contrary forces the one drawing one way the other the clean contrary the member must be held immoveable as appears in the 5th proposit Architectonical Necessary it is therefore to voluntary Motion that one Muscle over-power the other not by reason of its spontaneous or Natural Contraction but of its impressed or Animal which depends upon the supply of spirits transmitted from the
which the parts are made is not blood but a certain liquid juice very like the White of an Egg. 60 13. Nevertheless blood may be the nourishment of such parts whose substance is mostly Sanguineous and what those are 61 14. The Manner how the Vital Heat is conserved and the vital spirits continually recruited ex Sanguine 62 15. The Reason of the Mication or panting Motion of the blood in the Arteries 64 Exercitation the Sixth Of the Motion of the Blood its Conditions and Causes Art 1. The Method of the whole Chapter 66 2. That the Motion of the Blood is Circular ibid. 3. From the vena Cava into the right ventricle of the Heart 67 4. From the right ventricle by the vena arteriosa into the Lungs ibid. 5. From the Lungs through the Arteria venosa into the Left ventricle ibid. 6. From the Left ventricle into the Great Artery and thence into the smaller arteries 68 7. From the smallest Arteries through the substance of the Flesh into the smallest veins ibid. 8. How the New-made blood is circulated with the old 69 9. That more blood passeth through the Heart in an hour than can be supplied from the Chyle in several dayes ibid. 10. The Necessity of this Circulation inferred from three Considerations viz. 70 11 The Quantity of blood contained in the Heart in its Diastole 71 12 The Quantity expelled out of it in its Systole ibid. 13 The Number of Pulses in an hour 72 11. That the Circulation is Universal in all the Arteries and veins of the body 73 12. But after a peculiar manner in an Infant unborn 75 13. That this Motion of the blood is Continual 76 14. Vehement 77 15. Swift ibid. 16. Of equal velocity in the Arteries and Veins 78 17. The blood not the Cause of its own Motion in respect of any Motive Faculty inhaerent in it 80 18. Nor in respect of its Ebullition ibid. 19. Nor of its Rarefaction 81 20. But of its Quantity distending the ventricles of the Heart 83 21. The blood not moved by Attraction 84 22. Nor by Vection ibid. 23. But by Impulsion of the Heart endowed with a Pulsifick Faculty if any such may be admitted ibid. 24. The Fabrique of the Heart a remote Cause of the Motion of the blood 87 25. The Motion of the Heart described as consisting of two contrary motions and a Respite betwixt them ibid. 26. And the Figure of it in each 88 Exercitation the Seventh Of the Depuration of the Blood Art 1. The Genealogy of the Excrements in the blood 91 2. Exemplified in the Destillation of Wine 93 3. The several sorts of those Excrements and their Definitions 94 4. The Reason why each particular Excrement is determinately imported into the part particularly comparated for its separation 97 5. Not that it is so directed by any Intelligence or Distinguishing Faculty 99 6. Nor that it is Attracted by the like Excrement contained in that part ibid. 7. But that there is a certain peculiar Conformity of the Magnitude and Figure betwixt the minute particles of this or that Excrement and the pores of this or that part peculiarly constituted for the reception of it 100 8. Which is also the Cause of the Separation of particular Excrements in particular parts 101 9. The Differences of Colatures used by Nature in the separation of Humors in the body 102 10. The Reason and Manner of the separation of the Serum from the blood in the Kidneys 104 11. Of the Phlegmatique Excrement in the stomach and Guts 105 12. Of the Bilious Excrement's accompanying the Phlegmatique so far 106 13. Why the blood is not carried immediately out of the trunk of the Vena portae into that of the Vena Cava but through the various meanders in the Liver 109 14. And why it is transmitted through the Parenchyma of the Liver ibid. 15. That the Parenchyma is the Principal part of the whole Liver 110 16. And a kind of Streyner 111. 17. Whose particles are contexed after a peculiar manner and pores of â—ivers sorts in respect whereof the Bile is therein separated from the blood Mechanically ibid. 18. The same inferred from Four Considerables viz. 112 The equal distribution of the capillary branches of all the vessels of the Liver ibid. The Pulsation of the vena portae within the Liver 113 The assistance of that pulsation by the Hepatique Nerve 114 The Resuscitation of vitality in the blood in the branches of the vena Portae within the Liver and a new Fermentation thereof previous to the separation of the Bile ibid. 19. The various Manner of the Excretion of Excrements after they are separated and collected 116 20. The particular Manner of the Excretion of the Bile and 117 21. The Cause thereof 118 22. Paradox that we have a certain Natural Feeling wholly distinct from the Animal and independent upon the Brain 119 Exercitation the Eighth Of Respiration Art 1. The Connexion of this discourse to the precedent 126 2. The Disparity betwixt Respirà tion and Pulsation both as to their Times or Periods and as to their Uses ibid. 3. Respiration described 130 4. The Efficient Cause of Inspiration is the Dilatation of the Breast impelling the ambient Aer into the Lungs ibid. 5. And the Cause of Exspiration is only the spontaneous Contraction of the breast 132 6. The Disatation of the Chest and Lungs not from any Motive Faculty congenial to the Lungs 133 7. Nor from the impulse of the blood out of the Heart into the Lungs 134 8. Nor from the motion of the Muscles of the Thorax 135 9. But from the Diaphragme moved by a congenite Faculty ibid. 10. Yet the Intercostal and Pectoral Muscles are allowed to conspire with the Diaphragme in respiration violent and arbitrary 137 11. The Final Cause of Respiration not the Refrigeration of the Heart or Vital Flame but the subtiliation of the blood which by the admistion of Aer is made the more convenient fewel of the vital Lamp and matter of the spirits 138 12. The same exemplified in the accension of flame in wood by Aer blown out of Bellows and 139 13. inferred from the structure of the Lungs 140 14. The Use of Expiration 141 15. A Problem of the respiration of the Foetus in the mother's womb 142 16. The motion of the Brain not dependent upon Respiration but upon the Pulsarion of the Arteries 145 17. The Secondary Uses of Respiration 147 Exercitation the Ninth Of the Lympheducts Art 1. The Lympheducts a new and excellent invention 149 2. To whom the honour of their discovery is to be ascribed ibid. 3. Their Description 150 4. Differences 151 5. Origination ibid. 6. Insertion ibid. 7. Situation and Progress 152 8. Liquor deduced partly from the Arteries and 153 9. paâ—tly fâ—â—m the Nerves 154 10. The Uses of that Liquor 155 Exercitation the Tenth Of the Distribution of the Nourishment through the Nerves Art 1. That the Nerves are vessells carrying the Nutritive juice
either of its Ventricles or Ears 3 It hath been observed in Doggs that after the point of the heart hath been cut off and the remainder turn'd upside down though the ventricles could not be halfe full the blood hath yet been squirted forth at the top even to the distance of three or four feet which were impossible in case the rarefaction of the blood were the cause of its motion 4 The musculous flesh of the heart is more firme and strong than to be subject to inflation and detumescence meerly from the rarefaction of the blood It must be a more forceible Agent that moves that great and weighty machine of the heart 5 If the blood were so much rarefied in the Ventricles then certainly ought the orifices of the Vena Arteriosa and Aorta to have been much larger because the blood would have required more room for its egress than for its ingress 6 The motion of the heart and of its valves would be confused for the Diastole of this and opening of them would happen at the same time and consequently the valves would become useless both which are repugnant to experience Besides the opening and shutting of the valves would be co-incident with the Systole of the Great Artery 7 That the blood should be rarefied in the heart and in a moment again refrigerated in the arteries is contrary both to sense and reason and if the rarefaction should so soon cease why is it at all It remains therefore that if the blood be the efficient of its own motion it must be so only ratione Quantitatis But of its Quantity distending the Ventricles of the heart by reason of its quantity filling and distending the Ventricles of the heart and irritating them to discharge it by contracting or shurting themselves For the heart being as it were burdened with the blood distending its cavities doth contract its Fibers and so its Ventricles to vindicate it self from that oppression no otherwise than the stomach guts bladder womb c. which being extended by meat chyle wind urine and the infant drive themselves together by the help of their Fibers and so exclude that was burdensome to them And thus is it probable that the Heart is continually moved by the blood like a Mill perpetually agitated by a stream of water which stream being cut off the motion instantly ceaseth This may be credited upon the force of this one experiment if the Vena Cava be intercepted by a ligature so soon as the heart hath disburdened it self of what blood it hath received from thence it instantly remitteth its motion and upon letting in the stream again by removing the ligature it as suddenly recovers it Than which there cannot be a more convincing argument that the quantity of the blood flowing into the ventricles is a cause of the motion of the heart and so of its own motion We say A Cause not the only cause for we shall soon find another efficient as necessary and immediate Thâ— blood not moved by Attraction to the motion as the blood in the respect mentioned That nothing doth Attract the blood either to or from the heart is evident from hence that in Nature there is no such thing as the motion of a body by attraction as hath been by solid and irrefutable arguments proved by that heroical wit Apolog pro circulat sang advers Parisan â—pag 27. ad 49. and most accomplish't Scholar Dr. Ent and also by our selves in the beginning of our discourse of Occult Qualities whither for expedition sake we referr the unsatisfied Nor is it moved per modum Vectionis by way of Carriage Nor by Vection For nothing can be imagined to carry along the blood in its course but the spirits and those would in respect of their Levity carry it only upward but we see that the blood is moved also downward and ad latera It remains therefore that the blood is moved in round But by Impulsion of the heart endowed with a Pulsifick Faculty per modum Pulsionis by impulsion or protrusion and the Impellent can be no other but the Heart contracting it self and so expelling the blood contained in its ventricles into the Great Artery from whence it is urged or pressed forwards into the smaller arteries by the succeeding current We conceive therefore that the Heart is endowed with a certain Motive-virtue inhaerent and essentiall called the Pulsifick Faculty which is conjoyned as a concomitant cause with the blood it self in giving it a due motion whether it be that this Faculty doth regulate the influx and efflux of the blood which would otherwise be irregular or that of it self it produceth the motion which cannot be afterward continued in case the flux of the blood be once interrupted That this Faculty is necessary may be inferred from these Reasons 1 As the Pulse so the influx of the bloud would be alwayes unequall unless it were regulated by a Faculty 2 When the bloud is moved vehemently in Fevers by the intense heat agitating and urging it and in men at the point of death propter extremos naturae conatus by reason of Natures agony and last efforts yet is the pulse more weak and low than at other times because the Pulsifick Faculty is either much opprest or much weakned On the other side though the Faculty continue strong yet is the influx of the bloud much diminished after large haemorrhages or upon great obstructions of the capillary arteries and veins in the habit of the body Which consideration seems to us sufficient to import the necessity of conjoyning a Pulsifick Faculty with the quantity of the blood distending and so molesting the Heart as a double proxime cause of the bloods motion 3 Though the heart be cut in pieces yet will each piece have a kind of weak pulsation as long as it continues warme which in all probability is to be ascribed to the Faculty implanted in all its Fibres and not yet utterly destroyed 4 It would be derogatory to the majesty of that Prince of all the parts the Heart to be moved by the violent impulse of an external principle and it self conduce nothing thereunto Notwithstanding these reasons alleaged we dare not set up our rest in this doctrine of the Ancients concerning a Pulsifick Faculty implanted in the heart only we have recited it as the most probable Conjecture of all others touching this abstruse Argument the proxime Cause of the Motion of the blood Nor shall we adhere to it longer than untill we shall be so happy as to meet with a more satisfactory solution of that admirable Phaenomenon In the mean time Modesty commands us to declare that we find this Knot to be too hard and intricate for the teeth of our weak understanding And well may we make this acknowledgment when the subtle Frucastorius after a long scrutiny into the same subject was at length forced to desist with Motum cordis soli Deo cognitum
humors which passeth through the habit of the body but that it should be discharged in thick clouds of exhalations in every systole of the arteries this is plainly impossible because at that time the coats of the arteries are constringed and compressed and there might be an easier egress for them in the Diastoles when the cavities of the arteries are dilated So that among these many Arguments there is not one but doth clearly detect and throughly refute the Error of those Men who have confounded the Uses of the Arteries and Lungs of Pulsation and Respiration This capital Error eschewed we may the more safely progress to explicate the nature of Respiration as a thing in sundry particulars distinct from Pulsation though perchance instituted by Nature as in some sort subservient to the vital Faculty And that we may proceed methodically it is requisite we consider 1 the Manner of Respiration 2 the Efficient Cause and 3 the Final Cause or Use of it Concerning the First Respiration 〈◊〉 〈◊〉 〈◊〉 〈◊〉 〈◊〉 is an Action of the Breast and Lungs consisting of two contrary motions alternately successive or of two parts Respiration described viz. 1 Inspiration 〈◊〉 〈◊〉 〈◊〉 〈◊〉 〈◊〉 in which the ambient aer is impelled into the Lungs and chest at that time dilated 2 Exspiration 〈◊〉 〈◊〉 〈◊〉 〈◊〉 〈◊〉 wherein the same aer is again expelled out of the Lungs and Chest those parts spontaneously contracting or compressing themselves Concerning the Inspiration the grand Question is Whether the Breast and Lungs are dilated because they are filled and distended with the aer as a bladder is distended by aer blown into it or Whether they receive in the aer because they are dilated as a pair of Bellowes is filled with aer only because it is dilated or opened by external force To solve this difficulty in a word we say the Breast is first dilated The Efficient Cause of Inspiration is the Dilatation of the Breast impellinâ— the ambient 〈◊〉 into the Lungs before it can be filled with aer and that Dilatation or heaving up of the brest is the cause of the airs rushing in at the mouth and nostrills down the Aspera Arteria or wind-pipe into the Lungs For since there is no vacuity at least no Coacervate one in the world no body can be moved out of its place but the next body must give way and the next to that likewise give back till such a part of space as is adequate to the dimensions of the body first moved be made to receive it and the space which it abandoned be again fully possessed by another body succeeding into it we say since this is necessary it is manifest that the aer next incumbent on or contiguous unto the Breast and Abdomen being urged and impelled by the breast while that is dilated or expanded is forced to give back and press the aer next to it which likewise drives back the next aer untill at length the compressed aer wanting room to retreat into and endeavouring to avoid further compression its own Elater ingaging it thereto rusheth into the breast and there possesseth that room or part of space which was left by the breast when it began its motion So that so much aer is impelled into the breast as is driven out of its place by the superfice or outside of the breast during its expansion or dilatation As for the Attraction of Aer into the Lungs ad fugam vacui it is a meer dream as well because all motion is by Impulsion as because Nature doth not abhor vacuity primario or ex se In Physiolog-Epiarro-Gassendo-Charltoniae lâ—b 1. cap. 5 pag. 40. but only ex Accidente or in respect of the confluxibility of the insensible particles of Fluid bodyes as we have elsewhere amply demonstrated And if there were any Cause to be found that might blow the aer into the breast as it is blown into a bladder so as to distend it or at least if the aer could be conceived to enter into the breast spontaneously or of its own accord without impulsion so as to force or heave up the same then indeed would the Comparison betwixt the dilatation of the breast and that of a Bladder by wind blown violently into it hold good and we should not need to seek further But there being no such insufflating cause assignable and it being ridiculous to imagine the aer should spontaneously move it self so as to flow uncompelled into the cavity of the Chest as is manifest not only in dead men into whose breasts though their mouths and nostrils are wide open the aer doth not croud it self but also in living men when they at their pleasure keep their breasts compressed or hold their breath as the vulgar phrase is it seemes much more reasonable to explain the reason of Inspiration by that other similitude of the flux of aer into a pair of Bellows there being no other difference betwixt the repletion of the Chest and the repletion of a pair of Bellows with aer but only this that the Bellowes are opened by an externall force and the Chest is dilated by an internal And as for the Exspiration that is evidently from the compression of the breast and Lungs And the cause of Expiration is only the spontanâ—ous contraction of the Breast which is the naturall motion of Restitution For the Dilatation being an action whereby the parts of the Chest are distended into a position more large than is natural to them the Contraction seemes to be nothing else but a certain falling down or relaxation of the parts distended whereby they spontaneously return to their natural position and such as they hold in a dead body and this not onely in the Lungs but also in the Diaphragme which in dead bodyes is not extended downward to the stomach and guts as in inspiration but riseth upward toward the Lungs and Heart But if it be here demanded whether Inspiration or Exspiration be first we answer that it is necessary that the aer should be first inspired before it can be exspired and every ANIMAL dyes Exspirando in Exspiration Concerning the Second The Enquiry is By what cause the breast and Lungs are so dilated The Dilatation of the Breast and Lungs not from any Motive Faculty congeâ—iall to the Lungs as we have asserted And this indeed is a Difficulty not so soon resolved as proposed for besides the obscurity of the thing it self we find our selves benighted with the various opinions of Authors Some wil have that the Lungs are endowed with a certain Faculty of Dilâ—ting themselves and so elevating the whole breast as the Heart hath a pulsifick faculty by whose virtue the ventricles contract themselves in each Systole And hereupon was it that Aristotle the Author of this opinion doth compare the Lungs to a pair of Bellowes as if they did of themselves first attract the aer and then emit it again But though it be
and transportation of it to the principle of its Dispensation For it seems the Nutritive juice is first imbibed by the small branches of the Nerves of the sixth Conjugation and those though very many being yet too few for the transportation of so large a quantity of that rich Nectar as is required to the nourishment of the whole body Nature hath conjoyned with them a vast number of other Nerves as Auxiliaries in that great work So that it is not dissentaneous to reason to conceive that by these Nerves and their Coadjutors the Succus Nutritius is carried to the brain and Spinal Marrow thence to be afterward derived to all parts for their sustenance Concerning the Fourth What is the Motion of the same in the Nervs viz. not continual nor vehement but by intervalls and slow and gentle to the brain in sleep and from it to the members after sleep viz. the Motion of the Succus Nutritius in the Nerves though it be a problem of great obscurity yet doth the light let in at the postern gate of Conjecture discover thus much that it is not continual as that of the blood in the Arteries and veins but by intervals nor violent but slow and gentle as the defect of any swelling on either side of a Nerve bound about in a living creature doth sufficiently manifest Nor is it unreasonable to conceive that in a short time after each meal immediately upon the distribution of the Chyle through the Venae Lacteae the Succus Nutritius is imbibed by the Nerves of the sixth Conjugation and by them carried to the brain and Spinal Marrow Which perhaps is the reason why alwayes within an hour or two after meat we perceive a certain dulness in our heads together with an indisposition to motion and a propensity to sleep according to that proverb When the belly is full the bones would be at rest and soon after all those vanish again and we perceive our selves more light strong and active than before our refection because then the nourishment begins to be diffused from the principle of Dispensation of outwards into the limbs and other parts of the body And with this opinion agrees that observation of Bartholinus that the Lympheducts are more plainly discernable about five or six hours after meat than at other times as being at that time more filled with the superfluities of the Succus Nutritius Nor is it improbable that the Brain and Spinal Marrow are chiefly nourished in sleep and that then the Nutritive Liquor is usually carried to them relaxing them with its sweet and mild vapours and so both inducing and prolonging sleep From whence perhaps it comes that after long sleeps we perceive our brains to be oppressed and beclouded with vapours our senses dull and the motive-faculty enervated Besides in sleep all motions of humors flowing to the patts by the Nerves seem to be suspended and yet the Circulation of the blood is certainly at that time more free and quick than while we wake So that It cannot be thought the cause of that cessation but the Nerves onely which intermit their office of distributing the Succus Nutritius during sleep And all this will appear more reasonable if we reflect upon the flux of humors in the Nerves immediately after sleep For then the Brain and Spinal Marrow re-contract themselves and become more tense so that the Nutritive liquor is from thence transmitted partly to the members to be nourished and partly to the Glandules as well such as serve for the excretion of its absolute Excrement as those that serve for the reduction of its relative viz. it s acrimonious parts that are returned into the blood for the reason formerly mentioned And concerning the Last And what the Causes of that Motion viz. the motions of the Diaphragme of the Brain and of the Nerves themselves viz. the Causes of this Motion of the Succus Nutritius we may be allowed to conceive at least untill Time shall have dispelled that Obscurity which yet surrounds this abstruse Theoreme and the industry of some more dextrous Anatomist pierced deeper into the mystery of the Nerves a subject not much lesse inscrutable than the Nature of the Soul it self which useth them as her principal instruments we hope we may have the liberty to conceive that the Succus Nutritius is not imported to the brain and Spinal Marrow nor exported from thence to the members by any Attraction similary or Elective against which we have formerly alleadged convincing arguments unnecessary to be here repeated but as the blood and indeed all other humors of the body are moved by meer Impulsion or Protrusion the immediate Cause of all motions in Nature And the Agents in this case impelling we conceive to be the motions of the Diaphragme of the Brain and of the Nerves themselves For since the Depression of the Diaphragme is generally admitted to conduce to the distribution of the Chyle out of the stomach guts Venae Lacteae common Receptacle and Ductus Chyliferi successively into the subclavian Vein by alternately compressing all those parts and so compelling the Liquor contained in them to flow upward and indeed to all other Natural motions why may not the same be thought sufficient also to the Expulsion of the Nutritive juice both out of the Praeparing Glandules into the Nerves of the Sixth conjugation and their Auxiliaries and out of them into the brain and Spinal Marrow their position being such as renders them no lesse subject to compression by the descending Diaphragme than the Venae Lacteae common Receptacle and other Chyliferous parts are If this seem difficult we may have recourse to the reason of the ascention of a liquor from the bottome through all parts of a sponge cloath or other filamentous substance as is experimented in the percolation of Aqua Calcis made by a long piece of woollen cloath whose one end is dipt in the water and the other hung over the brim of the vessel containing it which we have professedly explained in the 356 page of our Physiology and seems to be the same with the reason of the ascention of the nutritive juice of all plants from the roots to the top of the branches And as for the Motion of the Brain though it may seem to be no other but what is impressed upon the brain by the Pulsation of the Arteries ascending from the Plexus Arteriosus mirabilis chiefly to the Dura Mater and copiously disseminating themselves upon it yet since it is credible that the Pulsation of the arteries doth promote the flux of the liquor in the Nerves in other parts especially such where Nerves are either contiguous or neer enough to Arteries to participate of their impulse why may not the motion of the Brain also to which the Nerves are continued serve to ex-press the liquor out of them toward the parts wherein they are terminated Besides it is most certain that immediately after sleep the whole Brain together with the
Galen also doth not obscurely intimate in 1. de mot Musculor cap. 8. where he saith Aequipollens musculorum motus fit quando neuter tonum Animalem habet auxiliarm non aequipollens verò cum alter solus dominatur quare necessum est ut vincat contractio istius musculi qui ab Animali Facultare adjuvatur For what can be understood by this Tonus Animalis or Facultas Animalis unless it be the distention of the conquering muscle by Animal spirits sent from the brain at the pleasure of the Soul 4 What 's the reason the swelling of each Muscle when it moveth that a muscle is never moved but it becomes more hard and swelling in the middle than before as is most evident in both the Masseter and Temporal Muscles when we chew our meat unless because it is then filled and distended with a greater gale of spirits issued out of the store-house of the Brain For it seems more reasonable that this swelling in the body of the Muscle is the Cause of its Contraction than on the contrary that the Contraction should be the cause of the Swelling as those contend who would have the motion to be performed without the afflux of spirits 5 If a Nerve be cut asunder the Muscle into which it was inserted the privation of motion in a Muscle whose Nerve is cut off doth for ever become uncapable of motion and this certainly for no other reason but because the intercourse of the spirits betwixt the brain and that particular Muscle is wholly destroyed So that we may well conclude that the Soul cannot cause voluntary motion but by the distribution of Animal spirits through the Nervs into the Muscles The necessity of Animal spirits as the Immediate Instrument of the soul thus appearing we are next to speculate the Conditions requisite in the Immediate Instrument of the Motion it self that so we may come to a clear understanding both of the structure and diversity of the Muscles and at length of the reason of their moving the members the thing at which our Scrutiny is chiefly levelled As for the requisite Conditions therefore of this last Instrument we observe 1 That in an organ of voluntary Motion is required such a Constitution vvhy a Muscle is composed for the most part of Flesh. as may render it fit to receive the Animal spirits at the pleasure and command of the soul. Which makes it manifest that a hard inflexible and bony substance is most incompetent to an instrument of motion for which reason perhaps Galen adventured to affirme that any part made hard and stiffe by a thick Cicatrice becomes unfit for motion and that it must be such a part as being soft rare spongy and flexible and distinguished with multitudes of Fibers may most easily and readily admit the Gale of spirits flowing into its substance and be by them filled or distended Which is the reason why the substance of the Muscles is for the most part Fleshy than which no part is more soft rare flexible and distendible as Galen hath observed in 1. de usu part cap. 13. 2 Lest the spirits might flow into this flesh of a Nerve indeterminately or at randome and scatteringly there ought to be such peculiar vessells or Conduits which being continued from the brain or spinal marrow quite home to the Flesh into which they are inserted may both carry the spirits thither and preserve them from straying or dispersing by the way and by which the Soul or Regulating Faculty principally residing in the brain the original of the Nervs may rule the members as a Coachman rules his horses by the rains of his bridles that we may use the same comparison with Galen 1. de mot musculor cap. 1. Now the Nervs being the only parts of the whole body thus qualified Nature most wisely inserted one or more of them into each Muscle So that from this constitution of the Nervs it appears that they make the second Essential part of a Muscle Nay according to strict truth we may adventure to say that the Flesh and Nerve are the principal ingredients required to compleat the essence of a Muscle because there are some Muscles viz. those of the Temples of the Forehead of the Eyes of the Bladder of the Fundament c. in whose bodies are neither Tendons nor Ligaments to be found but only Nervs and Flesh distinguished with various Fibres 3 Because in some Members Of a Ligament by reason of their Gravity there is a greater resistence to motion than the Musculous Flesh in respect of its softness and tenderness is able to overcome therefore ought there to be an addition of some stronger and tougher substance which being connected or united to the Flesh of the Muscle may both corroborate the same and firmly conjoyn it to the bones so as to enable it to move the ponderous member to whose bones it is fastned Now this Nature foresaw when she furnished some Muscles with Ligaments especially such as were ordained to bear great stress in moving the greater and more weighty members Which Galen most elegantly expresseth thus Ut enim ossa quae dearticulantur exactè simul ligarentur ac continerentur ne facilè in motibus vehementioribus à sese abrumperentur Ligamentum quoad maximè potuit durum atque ab injuriis remotissimum efficere oportuit ut autem ossibus à Musculis tractis promptè obsequeretur molle rursus esse oportuit atque ob id ipsum imbecillum Atqui forte quidem imbecillo ac durum molli est contrarium Quaenam igitur fuerit in his Naturae solertia quae corpus invenit quod commoditatem utramque haberet idemque ab injuriis tutum esset ex ipsad Anatome discas licet c. 12. de usu part cap. 2. 4 Besides the connexion of the Musculous Flesh to the bone Of a Tendon by the mediation of a Ligament there must be also something to render it prompt easy and agile in its motion so as to answer the celerity of the influx of the Spirits and to fulfill the command of the Soul as it were in an instant Which Nature reflecting upon superadded also a Tendon or Chord which in respect both of its subtility and of its tough and strong Contexture or substance and also of its connexion to the joynt doth make the motion more facile and quick than otherwise it could possibly be as appears in the Muscles of the Hands and Feet c. 5 That these parts named viz. the Flesh of a Membrane investing it Nerve Ligament and Tendon might no be endangered by lying uncovered or confused therefore hath Nature cloathed the whole Muscle with a proper Membrane or Coat which hath these two further Uses that it causeth the Muscles that are contiguous to slip up and down easily and without enterfearing each other and preserves the spirits immitted into the body of the muscle moved from passing quite through or dispersing themselves