March 28. 1683.  
ORdered, that the Three Anatomic Lectures read on the 19, 20, and 21 days of this present Month, in the Theatre of His Majesty's Royal College of Physicians in London, by Dr. Walter Charleton, Fellow of the same College, be forthwith Printed, and Published.  
Tho. Cox, President.   

THREE Anatomic Lectures, CONCERNING 

1. The Motion of the Blood through the Veins and Arteries;  
2. The Organic Structure of the Heart;  
3. The Efficient Causes of the Heart's Pulsation:    
READ On the 19, 20, and 21 days of March 1682/3  
IN THE Anatomic Theatre of His Majesty's Royal College of Physicians in London.  
BY WALTER CHARLETON, M. D. And Fellow of the same College.  
Published by Command of the most Learned Precedent.  
LONDON, Printed for Walter Kettilby, at the Sign of the Bishops-head in St. Paul's Churchyard, 1683.   

PRAELOQUIUM.  
CUM non ita pridem, Clarissime, Ornatissiméque PRAESES, mandatum tuum, ut ad Saxum hoc anatomicum hîc denuò volvendum me accingerem, ad obsequium paratus accepissem; mox apud me ultrò citróque agitare coepi, quodnam argumenti genus prae caeteris mihi seligerem, quo & Excellentiae tuae expectationi aliquatenus satisfacere possem, simul & caeterorum è Doctissimis meis Collegis (quorum hîc florem video tota urbe delibatum) auscultationi prolixiùs gratificari. Plurima quidem tunc temporis anxiae ac in diversa distractae sese offerebant menti, nec ad gratiam vulgi conciliandam fortassis incommoda: Sed Principum virorum, quos in celeberrimo hocce Theatro placidè considentes venerabundus aspicio, erudita curiositate prorsus indigna judicabam omnia. Tandem verò animo se meo ingessit summum illud, necdum etiam Medicorum vulgo satis intellectum Naturae mysterium, Sanguinis, nempe, motus Circularis: quo de quidem plerique omnes passim gestiunt garrire; paucos tamen reperias, qui de causis ejusdem, de conditionibus atque circumstantiis, & (quod caput est rei) de ratione Mechanica cogitarunt unquam; & (quod seriò dolendum) adhuc pauciores existunt, qui malè se habentibus consilium daturi, respicere soliti sint ad fidissimam illam morbis sive acutis, sive chronicis medentium Cynosuram. His ego igitur adeò pudendam, adeò etiam valetudine adversa languentibus periculosam nunc demum ut excutiam incuriam; utque aliquod remedium illorum inscitiae adhibeam: mecum statui, arreptâ hâc nuper demandatae mihi provinciae occasione, de veris, hoc est, Mechanicis causis, quibus in orbem perpetuò sanguis movetur, pro ingenioli mei tenuitate, inquirere. Affulsit quippe animo spei scintillula quaedam, ex iis, quae ist â de quaestione apud vos dicenda habeo, lucis nonnihil afferri posse ad eam penitùs explicandam. Quamobrem, ne spem alnisse videar inanem, permissu vestro primùm agam de Sanguinis per venas ad Cor recurrentis motu rapidissimo, itemque de causis istius tantae velocitatis: deinde Cordis ipsius conformationem Organicam perscrutabor: & postremò conabor causas cordis Pulsationem efficientes, quae hactenus omnium elusisse videntur Anatomicorum solertiam, explorare. Haec autem dum viritìm enucleare molior, clarioris doctrinae gratiâ, demonstrationes aliquot Mechanicas, ad institutum meum apprimè facientes, ex Alphonsi Borelli, omnium quotquot hoc saeculo nostro floruêre, Mathematicorum facilè solertissimi, scriptis mutuabor: omittendo interea caeterorum ferè omnium, qui post Harveum nostrum de Circuitione Sanguinis conscripserunt, opiniones; idque ne aut tempus frustrà conterere, aut memoriae vestrae fidelitati diffidere censear. Habetis itaque, Auditores Aequissimi, praesentis mei summam consilii, eorumque quae dicere aggredior, seriem. Quam dum ingenii toto impetu persequi contendam, nolo existimetis, me mihi veritatis arbitrium arrogare. Semper equidem verum quaero; quinetiam, Senecae illustri exemplo animatus, quaero sine inveniendi spe: tantum abest ut credam, esse me aliis docendis parem. Neque etiam adeò sum mihi Suffenus, ut cujusquam expectem conatibus meis applausum. Novi enim, quam difficile sit, & diligentiae laudem, simul & gratiam celeritatis mereri. Caeterùm unum illud me solatur, quòd fermè rebus suâ naturâ difficillimis venia sit prolixior apud prudentes viros, quibus non ignotum, quam sit arduum, novis autoritatem, obscuris lucem, dubiis fidem afferre.   

PRAELECTIO I. Of the Circular Motion of the Blood, and the admirable Effects thereof.  
SO plausible and favourable hath the Hypothesis of various Ferments, congenial to and perpetually resident in the various parts, principally in the Viscera of Sanguineous and more perfect Animals, seemed to many of the Virtuosos of this our inquisitive age; that they have not doubted to ascribe to them a powerful energy and necessary influence in all the divers Motions, all the Mutations, all the Concoctions, all the Secretions, and other operations instituted by Nature in such Animals, either for the conservation of them in their single beings, or for the propagation of their respective Species. Nor is it easy for us to name any particular function, any action, though really and manifestly Organical, which the Sectators of this Hypothesis will not presently attribute to some peculiar Ferment lurking and operating in the part, by which that action is done, and conferring (forsooth) somewhat of efficacy toward the doing of it: as if the organical constitution of that part were insufficient to the function and uses for which it was designed, without the help and cooperation of a Specific Ferment; or as if the whole Animal Oeconomy depended upon no other Harmony but that of numerose Fermentations. In a word, they make them only not Omnipotent. As Heraclitus the Ephesian dreamt [〈◊〉 〈◊〉 〈◊〉 〈◊〉 〈◊〉] that all places are full of Spirits and Daemons, 
Diogen. Laert. in vita Heracliti.  that presided over human actions: So these Gentlemen imagine all the parts of Animals to be full of I know not what Spiritual Ferments, that by occult influence regulate and diversify their functions. And this Comment many have endeavoured to assert by their Writings, with as much confidence, as if the verity of it were evident, either from cogent reasons, or by Autopsy: when in truth they are no more able to prove by solid Arguments, or by sensible demonstration, the existence of many of their imaginary Fermentative liquors or Spirits in the dissected parts, to which they are pleased to consign them; than Heraclitus was able to exhibit to men's sight any one of his Daemons. I say, many of their imaginary Ferments; I do not say, any. Because the Acid Phlegm found in the Stomaches of various Animals, may perhaps so far emulate the nature of a Ferment, as to deserve the same name. For being endowed with an incisive, penetrating, and dissolving faculty; 'tis not improbable but it may conduce to the dissolution and liquation of solid meats, and together with the drink, serve, as a fit Menstruum, to extract the laudable and alimentary parts of them, ad modum tincturae. But this liquation of solid meats in the Stomach, seems to be effected by motions placid, gentle, and imperceptible in the state of health; not by those violent commotions and irrequiet agitations that always proceed from, and accompany Ferments properly so called, during their working as all men that enjoy good health, feed soberly, and keep a regular course of diet, may easily observe in themselves. And therefore this Acid Phlegm cannot properly, and in Philosophical strictness, be referred to the family of Ferments. The same may with equal reason be said also of the Bile and Pancreatic juice commixed in the Duodenum. They may perhaps conduce somewhat to the farther attenuation and exaltation of the Chyle; they may also promote both the separation of the Nutritive from the Excrementitious parts of the same Chyle, and the insinuation and permeation of the former through the coats or membranes of the Guts into the milky veins: all this they may do, and yet not by way of Fermentation, whereof there is neither necessity, nor sense in statu sanitatis; and to argue from a preternatural state to a natural, is a Paralogism. Now if neither of these two so much celebrated Ferments, hath any more right to that denomination, than what is precariously derived from some remote and slender analogy or semblance imagined to be betwixt their nature, qualities, and effects, and those observed in genuine and true Ferments; as certainly neither of them yet appears to have: What ought we to think of all the rest of invisible Ferments supposed to reside in places, where hitherto they have never been found? Why may we not, till they shall be by Anatomical and other convincing experiments shown to us, believe that they have existence no where, but in the brains of fanciful men? For my part, I blush not, even in this venerable Assembly of most Learned men, where I have as many Judges as Auditors, openly to profess myself to be of this belief: because the non apparentibus, & de non existentibus eadem ratio est; and because I have heard an eminent Member of this first and more ancient Royal Society, a man renowned over all Europe for his Philosophical and Anatomical Writings, deliver this judgement of the multiplicity of Natural Ferments fancied to be in the body of an Animal, that they were a newfound asylum ignorantiae. I say, of Natural Ferments; lest what I have said should be detorted to the exclusion of Preternatural Fermentations, which I do not deny to be incident sometimes to the blood and other humours of the body, more signally in Fevers, and some other acute diseases: though perhaps not so often as vulgar Physicians imagine.  
What I have hitherto said, may perchance seem to some of my Auditors to be a digression; and they may be apt to think, that I have made my first step in a wrong path. I am therefore obliged, in my own defence, to advertise them, that having proposed to myself to inquire strictly into the natural necessity or Mechanical reasons of the Motions of the Blood; and finding the aforesaid Comment of Ferments lying, like a block, in my way: I thought it concerned me rather to remove than to leap over it, and leave it for others to stumble at. For, some there are, and those too, men whose names are deservedly celebrated for their profound knowledge both in Anatomy and the Mathematics, 
joan. Alphons▪ Borellus de Motu Animal. part. 2. pag. 76. Willisius, de Ferment.  who in their books have professedly taught, that even the blood itself, the seat of life, also undergoes a certain natural Fermentation in the heart, lungs, and greater arteries, as necessary to its perfection and vitality. A doctrine, which to me (I profess) seems very improbable, and inconsistent with the wisdom of Nature.  
Improbable; First, Because of all the various liquors found in the body of an Animal, in statu Naturae, the blood seems of itself least prone to Fermentation; which is incident chiefly, if not solely, to new and musty liquors: whereas the greatest part by much of the blood is old, and by repeated Circulations well defaecated in its proper Emunctories, and by insensible transpiration; and by consequence needs no Fermentation. True it is indeed, that new Chyle is ever now and then brought into the rivulet of the blood, out of the common cistern thereof, by the ductus thoracicus and the Subclavian vein, for a recruit: but in a quantity so small (a few drops perhaps at once; for more will not be found to bear a just proportion, either to the capacity of the common Receptacle of the Chyle, which is but little, or to the narrowness of the Pipe leading from thence to the Subclavian vein) as cannot in reason be thought sufficient to perturb and excite a fermentation in the blood, with which it is mixed. If a greater quantity of Chyle were mixed with the blood at one time; certainly the blood would soon lose its native purple, and put on the white livery of the Chyle, especially in the descending part of the Vena cava, where the commixture is first made: which yet no Anatomist (for aught I know) hath ever observed. Secondly, When Ferments are commixed with liquors consisting of heterogeneous particles, they are generally slow in exerting their power, and by degrees insinuate and diffuse their active particles through the whole mass, before they can so far prevail, as to raise an universal commotion and tumult in them; as common experience testifies: but the newly commixed Chyle and blood are in a moment, at most in the space of a few pulses of the heart, rapt out of the Vena cava, first into the right Ear, and then into the right Ventricle of the heart; so that here is no morula, no competent space of time given, to excite an actual fermentation. Thirdly, Here is wanting also convenient place. To all Fermentations is required fit room, wherein the liquors may have liberty to undergo an impetuose commotion and agitation of all their dissimilar and contrasting particles; nor will the Must of Wine itself ever ferment, if it be kept in close and strong casks, as appears from the making of Stum: but the Vena cava, the Heart, and Arteries are filled with blood even to distension, till by their Systole they squirt it forth, and then in the next moment they are replenished. What room then is left for the blood to ferment in? Seeing therefore that the blood is by its own constitution unapt to ferment, as bearing a greater analogy to the nature of Milk, than to that of Wine, whatever the Willisians have said to the contrary; and seeing that neither the small supplies of Chyle which it daily receives, are sufficient to induce, nor the shortness of the time in which it passes through the praecordia, nor the want of convenient room, permit a fermentation: what reason have we to assent to their opinion, who teach, that a fermentation of the blood is necessary to its perfection and vitality? especially if we farther consider, that the same opinion is also  
Inconsistent with the Wisdom of Nature. Whose custom always is, to institute the most direct and compendious methods, for the attainment of her ends; nor ever to use many instruments, where one may suffice, to effect what she hath designed: abhorring to multiply things, without inevitable necessity. To this her admirable Wisdom than it is injurious, to imagine, that when she had ordained in the blood a certain placid, regular, and benign motion, by which all the heterogeneous ingredients or constituent parts of it, should be so agitated among themselves, as by their mutual conflict to produce an alternate expansion and contraction, from whence a vital heat results, and upon which original life continually depends: she should notwithstanding institute a second intestine motion, to be at the same time, in the same subject performed, viz. a Fermentation; which seems unnecessary at best, and which probably might not only hinder, and impugn, but also destroy the former. A Fermentation would indeed raise a tumultuous agitation of the same dissimilar elements of the blood: but such as would be violent, irregular, and of a far different manner from the Vital Mication. But not to insist now upon the manifest disparity of these Two Motions, which may more opportunely be collected from what I shall soon say of the genuine and true one; let it be supposed at present, that both may operate in the same manner, and produce the same effects in the blood, as to the attenuation and comminution of the grosser, viscid, and unagile parts; and the facilitation of the expansive efforts of the Spiritual, volatile or elastic: yet still it will remain to be inquired, why Nature should institute Two Motions, where either of the two might singly do her work as well, if not better. If therefore any defendant of this opinion, which I have here, en passant, impugned, shall vouchsafe so far to illuminate my gloomy understanding, as to solve this Problem: I shall acknowledge the favour, and recant my opposition of it. Mean while, I will suspend the farther consideration thereof, and now address myself to the more important part of my present province, the true and undoubted Motions of the Blood, viz. the Mication, and the Circulation: by both which, though divers in their origines and kinds, yet mutually helping each other, and conducing the one to the accension as it were of original life, the other to the distribution of influent life, the blood is perpetually moved in the vessels that contain it.  
By the FORMER of these, the vital spirits, or if you please the elastic particles of the blood, now passing through the Ventricles of the heart, from their own natural force or expansive energy, endeavour to expand or unbend themselves; while the grosser and viscid parts resist that endeavour to expansion▪ by compressing them. Hence instantly, and by natural necessity, arises a certain Colluctation or mutual striving betwixt the expansive motion or endeavour of the Vital Spirits, on one part, and the renitency of the grosser parts of the blood, on the other. And from this Colluctation, an actual heat is quickly excited or kindled in the blood: actual heat being nothing else but an expansive luctation of the particles of the body or subject in which it is, as I professedly laboured to evince from various instances, and a strong chain of propositions, when I first had the honour to sit in this Chair. Moreover, because this expansive luctation is not violent, nor unequal, nor irregular, nor consequently noxious or hostile to the nature of the blood; but on the contrary always (in statu Naturae) moderate, equal, regular, amicable, and tending not only to the conservation of the blood, but also to the exaltation of all its faculties and operations: and because it proceeds from an internal principle, from the energy of the vital spirit contained in and ruling the blood, or (if this be more intelligible) from the Elasticity of the aereal particles commixed with the blood: therefore the brisk motion or heat thence resulting, is also vital. For in that very expansive motion of the blood, doth the formal reason of life originally consist: which Theorem also I have formerly, in this place, endeavoured to explicate and establish. This admirable motion, from the various notions or conceptions which Learned men have form of it in their minds, hath acquired various names. By some it is called motus sanguinis intestinus sive spontaneus, because it arises from an internal principle, the expansive endeavour of the spirituose, or elastic parts of the blood, and to ●●●tinguish it from the circular motion, which is impressed by an external Movent, viz. the Heart. By others, Motus fermentationis vitalis, from the similitude they fancied between it and common fermentations: but improperly, for the reasons by me just now alleged. By others again 
* Alphons. Berellus de mot. animal. , motus oscillatorius, from the resemblance it hath of the Oscillation or swinging of a Pendulum, whose motion describes a Cycloid 
| Christianus Hugenius, de Motu horologii oscillatorii, part. 1. , and by others 
* Glisson. lib. de ventriculo & intestine. & Charleton, Oeconomiae Animalis exercitat. 6. , Micatio sanguinis, the panting, or reciprocal expansion and compression of the parts of the blood. Of these denominations, the two last seem to me more fully and emphatically than the rest to signify the nature and manner of the thing denominated; as equally comprehending the double motion in a single appellation. Wherefore I intent hereafter to use these promiscuously, when there shall occur to me any occasion of mentioning the same motion. Mean while, I proceed to  
The LATER motion, the CIRCULATION of the Blood; the most noble and most useful of all modern inventions, first obscurely hinted (as some think) by Cesalpinus, but afterward with prodigious sagacity, 
In Exercitat. Peripatet.  most exact judgement, and happy diligence investigated, and with such convincing evidence demonstrated by our immortal Dr. Harvey, that now the verity thereof is no longer doubted of in the world. I wish the same were as well understood, as it is generally acknowledged: and lest I be thought only to wish this excellent knowledge, and of so great importance to Physicians, I will now again do my best devoir to explain so much of the mystery, as I myself have formerly left not sufficiently explicated: omitting to reoire what is vulgarly taught in the Schools and Books of Anatomists, and touching only those things, which have been either pretermitted, or not rightly explicated by others, concerning the Causes, Mechanical modes, and circumstances of this life-conserving motion.  
There intervenes (ye know) a double pause or respite, which by Anatomists is called perisystole cordis, between the two contrary motions of the heart; one betwixt the diastole and the systole, another betwixt the systole and the diastole: and this of absolute necessity, because it is impossible, that the same body should perform two contrary motions, without a morula or space of time, how short soever, be interposed betwixt them. Ye know also, that the force impelling the blood, which is the Compression of the heart, doth not act continually, but interruptedly or per vices, short and almost isochronic or equal quiets interposed: So that the blood expressed by the heart, doth not flow thence in a continued course, as rivers and fountains do, that are without intermission carried on by the weight of their waters; but gush forth and stop alternately, though this vicissitude be exactly regular, and proceeds in a constant order. Now these things considered, it may seem consentaneous to conclude, that the motion of the blood cannot be continuus, since two pauses or quiets are interposed betwixt every two pulsations or Systoles of the heart, during each of which the motion ceases: but on the contrary aught to be esteemed and called an interrupted and mixed motion. And yet notwithstanding the verisimilitude of this conclusion, I doubt not to lay down and expose to your examination this  

First PROPOSITION, That the blood is carried in a round through the body of an Animal, in a truly continued, and never interrupted motion▪  
This perhaps may sound like a Paradox: but that shall not a-whit discourage me from asserting it, while I remember that remarkable sentence of Minutius Felix (in Octavio) Inest & in incredibili verum, & in verisimili mendacium.  
Though it be true and evident, that the heart doth not, in the time of its pauses, express any Blood into the Arteries, yet it is not true, that the blood contained in the Arteries, in the Viscera, in the habit of the body, and in the Veins, doth at the same time stagnate, and stop its course; but on the contrary is always carried on in its journey, though with unequal velocity. First, the Verity of this appears in the Arteries. For the afflux of blood from the heart being wholly intercepted, either by a Ligature applied to the aorta at its original, or by cutting out the heart itself, as is commonly done in Frogs and Vipers; we see, that nevertheless the blood wherewith the Arteries were filled, is by degrees squeezed out, so that they are soon after left altogether empty. And doubtless this exinanition of the Arteries happens, because they by their own spontaneous motion constringe themselves, and contracting their Circular Fibres, express the blood into the habit of the parts: and are at the same time compressed also by the contraction and tension, or the peristaltic motion of all the Muscles of the Body. From the observation of this vulgar Phaenomenon, viz. the emptiness of the Arteries in dead bodies; the Ancients perhaps took occasion to believe and teach, that not blood, but only Vital Spirits are contained in the Arteries. Secondly, this appears also in the Veins. For, that the blood doth continually flow on in them likewise, not only when it is urged forward by the Arterial Blood pursuing it, but even in the time of the hearts pauses; is evinced from this, that then the blood runs on through the trunk of the Vena cava to replenish the right Ventricle of the heart. But why do I misspend time in alleging reasons to prove a truth that is manifest to sense in Phlebotomy? no sooner is a Vein opened, than the Blood flows forth with a swift stream, and while the wound is open, continueth to flow without pauses or interruption, which is a demonstration of the thing proposed, viz. of the continual motion of the Blood in the Veins.  
Being thus assured of the effect, let us proceed to investigate the Causes; which are not equally evident, nor can we hope certainly to solve this Problem, without enquiring the Mechanical reason of the continual motion of the Blood through the Veins. This therefore I will now attempt to do. That Nature hath instituted no immediate Communication betwixt the Capillary Arteries and the Capillary Veins, per anastomôsin, is manifest to sense, and now acknowledged by all Learned Anatomists: and therefore it cannot stand with reason to imagine that the Blood in its Circular course is emitted immediately out of the Arteries into the Veins, these vessels being separate. And though we opine, that there is some secret communication betwixt the extreme Orifices of the Arteries and those of the Capillary veins, by the intermediate Spongy substance of the flesh, Viscera, and glandules, or by the Cribrose substance of the Bones, as by the Pores of a Pumice stone: yet we are still to seek, by what motive force the blood may be carried on from those intermediate Porosities, and insinuated into the veins. First, because 'tis consentaneous, that the impulsive force, whereby the Systole of the heart squirts the Blood into the Arteries, is by degrees weakened, and at length languid in those straits of the extreme vessels, and of the intermediate Porosities. Secondly, Because the Orifices of the Capillary veins cannot continue always open and dilated; their consistence being not hard and bony, but membranose, soft and slippery; so that they are apt to be closed by conniving, and consequently to hinder the ingress of the blood newly arrived. Thirdly, Because here we can have no recourse to the compression of the Viscera, and the Muscles, whereby the blood should be squeezed into the Orifices of the Capillary veins; for we see, that the blood is sucked up by the Capillary veins, not only when the Muscles are invigorated and upon the stretch, but also when they are quiet and relaxed, and do not exercise their compressive power; as is most evident in sleep, when the Circulation proceeds without intermission. This is confirmed from hence, that in the Brain, in the Medullary substance of the bones, where no compression can be admitted, the Capillary veins receive the blood as freely as in the softer flesh itself. Seeing then that the effect cannot be denied, viz. that all the blood effused out of the Arteries is after absorbed and carried off by the Veins, to be brought back again into the heart; and seeing also that this is not effected by way of Attraction, there being no such thing as attraction in Nature, as I have more than once elsewhere proved: we are compelled to assert, that the Blood is imbibed by the Capillary Veins for the same reason, and by the same Mechanic action, by which Syphons, Sponges, Filtres, Chords, and all Porose bodies are penetrated by water with which they are moistened: which power is no other than the gravity of the fluid itself, which is augmented by the impetus of its proper motion, and by the impulse communicated to it from external force. So the motive force of Gravity, which the blood can want no more than water can, when it finds the small channels of the Capillary veins open (for they can never be so closely constringed by the flagging and connivency of their thin membranes, as to leave no entrance for a fluid; as appears in the Pores of Ropes how hard soever twisted) must of necessity overcome the weak resistance of the straits in all Filtres and Porose bodies: and consequently the blood may be insinuated into the Capillary veins by a Mechanic action like that of Filtration. If this proposition be true, the greatest difficulty occurring in the whole mystery of the Circulation of the blood, is now at length solved.  
The blood having in this manner passed the aforesaid straits, and entered into the Canales of the small veins, by the same motive force, whereby it was insinuated (for such an ingress is not possible without motion) may be advanced a little farther in its way by its proper force, and by external force, and also by the impulse of the new blood following behind; as we see water sucked up by a Filtre, to be carried on to the end of the list. Afterward, because many small veins meeting together, make one wider ductus or pipe; and because in this larger pipe the former impulsive force of necessity grows more and more languid and faint by degrees, and by consequence the motion of the blood is retarded: therefore it stands in need of some auxiliary forces, to be carried on the rest of its journey. These are, First, the force by which the Circular Fibres of the Veins, that naturally have a peristaltic virtue, contract themselves always after they have been stretched, as all Nervose and other tensile bodies are observed to do: Secondly, The Compression of the Veins by the weight of the Circumambient air or Atmosphere, and the Elastic virtue of the air inspired: Thirdly, The Tonic motion of the Muscles, when they act; together with the various motions of the Viscera, and of humours discurrent through the body; all which more or less compress the veins. Now, that the manner how this compression promotes the continual decurse of the blood in the Veins, may be the more fully and clearly understood; I will take liberty to lay down this   

Second PROPOSITION. That by the artifice of the Valves, the Compressions of the Veins protrude the Blood toward the heart with a motion doubly swifter; not indeed in a continual flux, but with little pauses interposed, and with unequal velocities.  
We here behold in the Crural vein slit open from end to end, 
Figure I.  certain Valves placed at unequal distances in the inside of the Vein: which for demonstration sake are accurately represented in this Figure exposed to sight. 
Figure II.  These Valves (ye see) are nothing but half pockets of a membranose substance, or little bladders affixed to the sides or walls of the Vein, and resembled by AONMP. and BONQR. They are found sometimes single, sometimes in pairs placed one opposite to the other, and laterally touching each other; as at NO. the convex tops of which pair respect the Capillary beginnings of the Veins beyond HL; but the Orifices of their cavities PO, RO, open toward the heart, have respect to the parts IK. Now I am to demonstrate, that from this structure and situation of the Valves, it is necessary that the Blood be protruded toward the heart. Imagine then, that the same portion of the Vein HMQL is replete with blood; and because by the circular Fibres of the Vein itself, and by the ambient Muscles, and perhaps also by the gravity of the Atmosphere, one part of the Vein is constringed after another all along; it must be, that the lateral walls ST come nearer to each other toward V: and then the Vein so girded will lose its Cylindrical form, and be turned into two little funnels, HUL, MUQ; which are less capacious than the former Cylinder, and therefore the blood which was contained in the spaces VHS, and VLT, will be expelled out of the Orifice HL; but the remaining quantity of blood contained in the spaces VSM, and VQT, will be squeezed without the Orifice MQ, toward IK. It appears then, that from the abovementioned compression of the sides or walls of the Vein, the blood is expressed in equal quantity to the opposite parts; and this would certainly happen, if the Valves were removed. But because to the walls of the Vein within, MP, QR, are fastened two Valves; it is necessary, that the blood impulsed by a compression made in ST, be forced through the narrow chink NO; because the yielding fluid contained in the cavities of the Valves, and urged by the advenient blood, is constringed, and thrust out of them; and then instantly the sides of the Valves, that before touched each other, NO, receding one from another, leave an open way, by which the flux of blood coming on from MSTQ, may be insinuated, and pass forward beyond AB. Again, after the blood hath passed the confines of the Valves PO, RO, there necessarily follows a restriction of the little chink NO. For, the blood itself must, by reason of its heavy bulk, and fluidity, fill the little bags of the Valves, and so their soft and pliable sides being dilated till they mutually touch, ought closely to shut the rimula NO.  
Moreover, because the Vein is not constringed in all its parts at the same time, but part after part successively; therefore after the blood is transferred beyond the Valves within the little funnel ABCD, there follows a constriction of the walls AD, BC, in the same time, in which ST is not constringed. And because by reason of the close shutting of the rimula NO, half the blood, that was contained in the spaces EAG, FBG, cannot flow back toward AB, finding the obstacle AOB filled with blood, and retained by the Valves; it is compelled with a reflex motion, like that of a Tennis-ball rebounding from the wall, to flow toward DC: and since by the same compression, the Blood that was contained in the spaces EDGE, FCG, is protruded beyond DC: therefore a double quantity of blood is in the same time, in which the compression is made, expelled through that same aperture DC: but when a double quantity of a fluid is in the same time emitted at the same Orifice, it must run out with a double Velocity. Thus is our Proposition verified. And as to single Valves; from what hath been said of the use of double, it may easily and genuinely be inferred, that they also help to promote the course of the blood, though but half so much as the double. Wherefore Nature's wisdom is admirable in placing single Valves both at less distance one above another, and for the most part where the Cavity of the Vein is a little narrower, or where a less Vein laterally exonerates itself into a greater: in both which cases the necessity of this demonstrated acceleration of the motion of the Blood, seems to be less. In the trunk of the Vena cava no valves are found; as well because of its ample Cavity, as because of its contiguity to the trunk of the great Artery, by whose pulsations it cannot but be somewhat compressed, and consequently the Blood flowing through it, proportionately promoted. In the jugular veins also none have yet been observed; probably because in them the blood descends swiftly enough, from its own weight and fluidity. In small veins they are not placed; unless in the Coronary veins of the heart, just at the place where they empty themselves into the right Ventricle of the heart: and of these too the use is, not to promote the course of blood, of which there is no need in so small a circuit; but only to prevent the reflux of it out of that Ventricle, in the systole of the heart, as appears from their situation, and from their conformation. Nor are any found in the Arteries, in which the blood, with mighty force impulst by the constriction of the heart, and of the Arteries, needs no additional machine to accelerate its motion: except those that are placed in the inlet and outlet of the left Ventricle, to obviate the regurgitation of the blood into the arteria venosa, and out of the aorta into the left Ventricle; and the two very little Valves sited in the two Coronary Arteries, at their origine from the aorta, to prohibit the regress of the blood into the aorta. ¶ ⸪  
If this Artifice of the Valves affixed within the veins be so necessary to promote the reflux of the blood toward the heart; certainly he that first discovered them, deserves to be remembered with honour. But who was that fortunate man?  

Tractatu 4. the venar. Ostiolis.  Fabricius ab Aquapendente put in his claim to the glory of the invention, as wholly due to himself; in these very words. De his itaque [ostiolis nempe venarum] locuturus, subit primùm mirari, quomodo ostiola haec, ad hanc usque aetatem, tam priscos, quam recentiores Anatomicos adeo latuerint; ut non solùm nulla mentio de ipsis facta sit, sed neque aliquis prius haec viderit, quam Anno Domini Septuagesimo quarto supra millesimum & quingentesimum, quo à me summa cum laetitia inter dissecandum observata fuere.  
But Padre Fulgentio professly ascribes the invention to that prodigy of Wisdom, Learning, and Virtue, Padre Paolo the Venetian: at the same time openly accusing Aquapendens of disingenuous arrogance and theft, for challenging to himself the honour of having first discovered the Valves, to which he had no right; and for stealing the glory due only to Father Paul. 
In vita Patris Pauli.  The sense of his impeachment is this. The whole Tractate concerning the Eye, which passeth under the name of Aquapendens, or at least so much of it as contains new and rare Speculations and Experiments, is the work of Padre Paolo; whereof I have had speech with some, that were eye-witnesses, and knew that a due part of the praise was not attributed to him that deserved it all. But much more in another matter of more moment, which was the finding out of those Valvulae, those inward shuts or folds that are within the Veins. Of which argument I do not find, that any, either ancient or Modern, hath made mention; because it was a thing unthought of till these times, when Aquapendens moved the question in a public Anatomy. But there are still living many eminent and Learned Physicians, among whom are Santorio, and Pietro Asselineo a Frenchman, who certainly know, that it was no Speculation, nor invention of Aquapendens, but of Padre Paolo. Who considering the weight of the blood, grew into an opinion, that it could not stay in the Veins, except there were some bunch to hold it in, some folds or shutting, at the opening and closing of which there was given a passage and necessary Aequilibrium to life. And upon his own natural judgement he set himself to cutting with more accurate observation, and so found out those Valves, etc.  
Having thus faithfully recited the Pleas of these two great men, I leave it to you to decide the controversy, and to fix the Laurel on the head of which of the Competitors you please. For my part, if my judgement were considerable, I should declare myself on Padre Paolo's side, as to the invention; and allow to Aquapendens the honour of being the first that by writing made the thing known to the world. Understand me, I beseech you, only of the Valves themselves, not of the true use of them, which neither Aquapendens, nor the Father had the happiness to discover.  
Not Aquapendens; because of the two uses by him assigned to these Valves (which he most improperly named Ostiola) namely the corroboration of the Veins, which might otherwise be by the blood every where distended and broken into varices; and the retardation of the blood in the Veins, that so all parts of the body might have time to take in their due shares of blood, for their nourishment, and not have their meat (forsooth) snatched away before they have filled their bellies: of these two mighty uses, I say, neither is true, and both are raised upon this Supposition, that the course of the blood is out of the greater and superior Veins into the smaller and inferior; which is most evidently false even by the testimony of the sight. But lest I be thought, either not well to understand, or to misrepresent his meaning; I am obliged to recite his own words. 
Aquapend. Tract. 4. the Venar. Ostiolis.  Nam cum in varicibus, in quibus aut laxari, aut rumpi Ostiola par est, plus minusve dilatatas semper venas conspiciamus; dicere proculdubiò tutò possumus, ad prohibendam quoque venarum distensionem fuisse Ostiola à Summo Opifice fabrefacta, etc. Thus far then I have done him no wrong. He proceeds. Erat profectò necessaria Ostiolorum constructio in artuum venis, quae non exiguae, sed vel magnae, vel moderatae sunt magnitudinis; ut scilicet sanguis ubique eatenus retardetur, quatenus cuique particulae alimento fruendi congruum tempus detur, quod alioqui propter artuum declivem situm confertim ac rapidi fluminis instar in artuum extremitates universus conflueret, ac colligeretur, idque tum harum partium tumore, tum super positarum marcore. Here also I have faithfully interpreted his words, and ye see that he thought the contrivement of the Valves necessary to retard the motion of the blood, because he took it for granted, that the blood descended through the greater Veins into the less: grossly erring in both opinions. For, that the former is false, we have seen demonstrated from the construction and situation of the Valves themselves: and that the latter also is false and absurd, is known to all who understand any thing of the Circulation of the Blood. To these errors he hath in the same Page added a third much more extravagant; which is, that the blood is by a flux and reflux perpetually carried forward and backward in the Arteries. For, attempting to give the reason, why Nature hath framed no Valves in the Cavities of the Arteries, he saith; Arteriis autem ostiola non fuêre necessaria, neque ad distensionem prohibendam, propter tunicae crassitiem, ac robur; neque ad sanguinem remorandum, quòd sanguinis fluxus refluxusque in Arteriis perpetuò fiat. It appears then, that this famous Anatomist, who in many other things deserved well of the Commonwealth of Physicians, had no just title to the honour of having first invented the true and genuine use of the Valves: nay, that he understood no more the Mechanic reason of their conformation, than if he had never heard of or seen them.  
Nor in truth did Father Paul (whom yet I never can mention without secret veneration) if the afore-recited account, and what follows immediately after, given by his most intimate friend during his life, and after his Historian, Fulgentio, be true and full. For in Fulgentio's narration of the manner how the Father came first to find out the Valves, there is this passage. And upon his own natural judgement he set himself to cutting with more exquisite observation, whereupon he found out those Valvulae, and the right use of them; which do not only stop and hinder the blood from dilating itself by its weight into the Veins (as we observe in some crooked and swelled knots) but also that blood running up and down with so much liberty, and in so great quantity, it might easily suffocate the natural heat of those parts, which ought to receive their nourishment from it. Whence it is plainly apparent, that the Father also attributed a double use to the Valves: one, the very same with the former dreamt of by Aquapendens, who probably borrowed it of the Father; viz. to prevent the dilatation of the blood into Varices, by stopping its impetuous motion up and down in the Veins: the other, quite contrary to Aquapendens' second use, viz. to prevent a surfeit of the parts upon too much blood, and an extinction or suffocation of their natural heat by that excess; whereas Aquapendens feared they would be famished, if the Valves did not detain their food, as Tantalus is feigned to be. Now if these were truly the Father's Sentiments concerning the Valves, certainly he had no right conception of Nature's design in making them; as may be collected from the precedent demonstration of their true use.  
To come then to a conclusion, and draw all the lines of this scrutiny to a point; since it is evident, that neither Father Paul himself, nor his disciple Aquapendens had a right notion of the proper use of the Valves; and that both believed the blood to flow out of the greater Veins into the less, which the Fabric and situation of the Valves plainly contradict: it necessarily follows, that neither of them could be Author of that much more noble and more difficult invention of the CIRCULATION or the blood, which it was morally impossible for any man to deduce from their absurd opinions concerning the use of the Valves, and the glory of which is wholly due to that incomparable man Dr. HARVY. Who by admirable Sagacity of Spirit, by numerose Experiments and Observations Anatomical, and by assiduous Meditation, perhaps also by the secret Manuduction of Fate, that had reserved the secret for his knowledge, attained at length to the invidiose felicity of finding it out, and revealing it to the world. I wonder therefore that some men of not obscure names in the Catalogue of Anatomists, have shown themselves so ungrateful and envious toward this immortal man, as to ascribe this divine invention to Padre Paolo: I mean, 
Joh. Walaeus epist. 1. de motu Chyli & Sanguinis.  joh. Walaeus and Tho. Bartholinus. The former of whom doubted not to write thus. Vir incomparabilis Paulus Servita Venetus Valvularum in venis fabricam observavit accuratiùs, quam magnus Anatomicus Fabricius ab Aquapendente postea edidit, & ex ea Valvularum constitutione aliisque experimentis hunc sanguinis motum [puta Circularem] deduxit, egregioque scripto asseruit, quod etiamnum intelligo apud Venetos asservari. Ab hoc Servita edoctus vir doctissimus Gulielmus Harveius sanguinis hunc motum accuratiùs indagavit, inventis auxit, probavit firmiùs, & suo divulgavit nomine. The other had the confidence to affirm, 
Thom. Bartholin, epist. Medicinal. venture 1 epist. 26.  that Veslingius had communicated to him, as a secret never to be revealed (forsooth) to any third person, that the Circulation of the blood was the invention of Father Paul the Servite, who had written a book of it, which was in the custody of Fulgentio at Venice. To refute this palpable fiction, to what I have already said of Father Paul's ignorance of the right use of the Valves, I need add only this, that if Fulgentio had had in his hands any such Manuscript of the Fathers, as these Detractors have imagined; 'tis wonderful strange he should never so much as mention either that or the Circulation in his whole History of the Father's life; when of all the subtle Speculations and discoveries of natural secrets by him attributed to the Father, nothing would have so much conduced to the propagation of his glory, as that. Here therefore I put an end to this long digression, to which the necessary contemplation of the Valves gave an inviting occasion, and which, being intended only to do right to the venerable memory of Dr. Harvy, all lovers of truth, as well as all Members of this Noble Society will (I presume) easily pardon. ¶ ⸫  
Having inquired into the velocity of the motion of the blood in the Veins, and the mechanic causes thereof; let us next consider the velocity of the motion of the same blood in the Arteries. For the clearer understanding of which I lay down this Third Proposition,   

PROPOSITION III. That the Arteries of an Animal, their constriction or pulsation being complete, do not remain wholly empty of Blood.  
Evident it is even to sense, that all the veins of a Sanguineous Animal taken together, are larger or more capacious, perhaps in a quadruple proportion, than all the Arteries put together: and the whole mass of blood runs through all both Veins and Arteries, which mass in fullgrown men commonly exceeds not 18, or 20 pints: and though the Veins, by reason of their transparent coats, always appear full of blood, yet a man may doubt, whether the Arteries also be always full; that is, whether they only give passage to the blood in the time of the pulsation, and then in the time of their quiet remain wholly empty, or not. To resolve this doubt therefore, I say, that the Arteries, if they were wholly empty in the intervals of their pulsations, then being laid naked to the sight, they would appear constringed and lank, like chords extended: but our eyes assure us, that on the contrary they retain their round and plump figure, and being pressed by the finger resist the pressure; neither of which can possibly consist with a total exinanition. Again, the Veins being laid naked, if, after the pulsation of the heart, the Arteries remained empty; then certainly would the pipes of the Veins by the quantity of 5 pints of blood crowded into them more than what they are proportioned to contain, be distended at least a third part more than they ought: but this is sensibly false, for their coats are not distended beyond their usual rate. Ergo, the Arteries are at no time wholly empty.  
Moreover, in Animals whose Arteries are transparent, as in Snakes, Vipers, Eels, Frogs, etc. we may from their Purple or bluish colour perceive the Arteries to be full of blood. Which is alone sufficient to evince, that the Arteries do not remain empty after the pulsation of the heart, but contain at least a 4 th' part of the whole mass of blood, which in a man is about 5 pints.  
Yet farther, the Arteries, in the moment of their pulsation, are highly turgid, when yet not above 3 ounces. of blood is emitted into them by the Systole of the heart. Therefore, if before the Systole the Arteries were wholly empty, a space 20 times greater than their bulk is, would inevitably be filled by the 3 ounces of blood emitted by the heart: but this certainly is impossible without such a rarefaction of the blood, which no man of common sense will admit. Therefore to replenish so great a vacuity in the Arteries, there must come into them five pints of blood, either from the heart, or back, out of the Veins: but neither of these is possible in nature.  
Let us add, that 3 ounces of blood emitted by the Systole of the heart, cannot fill a space greater than half a foot of the next Arteries to the heart. Therefore, if the Arteries were empty before the Systole; truly all the rest of the Arteries would remain empty also in the following Systole; and consequently could not beat at the same time with the heart, and the Circulation of the blood through them would be interrupted or discontinued, contrary to the mechanic necessity thereof.  
In fine, we are convinced by common experience, when an Artery, whether it be great or small, is cut, the blood is in every pulsation squirted out with mighty violence. Now it is impossible this should happen, unless all the Arteries were full of blood all along from their beginning to their end; because the violence of the stream of blood gushing from the incision, hath no other efficient cause, but the protrusion of the blood coming on behind and urging the antecedent. But in the following pulsation there is an accession of no more than 3 ounces of blood; which cannot by its quantity replenish half the capacity of the Arteries. Therefore unless there remain, after every pulsation, 5 pints of blood in the Arteries, they cannot be made turgid again in the following pulsation. So that nothing is more certain or more evident than this, that in a living Animal the Arteries are never empty. Quod erat ostendendum.  
From the praecedent Theorem naturally arises this Consectary:  
That after the pulsation of the heart, there remains in the Arteries the 4 th' part of the whole mass of blood contained in the body of an Animal; and in a man commonly about 5 pints: and that the proportion of blood expressed by the Systole of the heart into the Arteries, is about one twentieth part of the blood contained in them. As also that 3 ounces of blood ejected out of the heart into the Arteries, fill a space in the Arteries next to the heart no greater than half a foot, namely so much as is triple, or quadruple to the latitude of the Ventricles of the heart.   

PROPOSITION. That the motion of the Blood in the Arteries, is threefold swifter than the motion of the Heart, that impells the Blood;  
Because in the same time are absolved all these motions, viz. the dilatation of the Pores of the heart, the restriction of its Cavities by the swelling inward of the walls of the Ventricles, the expulsion of the blood. contained in the Ventricles, the motion of the expulsed blood in the Arteries, and the promotion of the mass of blood preaexistent in them, caused by the urgency of the new blood coming on out of the heart: all these actions, I say, are performed in the same time.  
And it appears, that the three former operations are performed with the same velocity in the heart, because the Fibres of the heart, by reason of their abbreviation, are with the same motion moved through the same space of the amplitude of the Ventricles, through which they are moved by restringing the same Ventricles, and squirting out the blood that was contained in them. And the two last operations likewise are performed with the same velocity. For look how much space the blood expelled out of the heart runs through in the Arteries, just so much space must the mass of blood preaexistent in them be driven through, in the same time; because one part of the blood must give way to another urging it forward, as fast as that comes on behind.  
But if the motion of the constriction of the heart be compared with the progressive motion of the blood in the Arteries; then doubtless they will not be found to be of equal velocity: because the former motion, viz. of the constriction of the heart, is made through a space equal to the latitude of the Ventricles of the heart, which at most exceeds not 3 inches breadth: but the space through which the 3 ounces of blood expressed out of the heart, run in the Arteries, is equal to the length of half a foot. Therefore the space will be triple at least to the space of the former motion: and yet both these motions are performed in the same time. Ergo, the motion of the blood in the Arteries is threefold swifter than the motion of the heart, that causes it. Quod erat propositum.  
I add this remark, that the motion of the blood in the Arteries is always the same, whether the three ounces of blood emitted into them out of the heart, exactly fill the space dilated in them; or whether any portion of it be after their repletion expelled out of them. For in both cases, the blood preaexistent in the Arteries, is just so much promoved in its course, as 3 ounces newly emitted take up of space, which run through more of length than half a foot. ¶ ⸪  
Here I cannot fairly decline to encounter a vulgar error, that stands in my way. Which is, That the blood is expelled out of the Orifices of the Arteries into the substance of the Parts, by no other cause but the constriction of the Heart. To refute which I will assert this   

PROPOSITION, That the cause expelling the Blood out of the Arteries, is not the Systole of the Heart alone, but the constrictive or peristaltic motion of the Arteries themselves naturally and necessarily succeeding their expansion.  
To the pulsation of the heart two effects are subsequent, viz. the repletion of the Arteries by the blood emitted into them, and the expulsion of the same blood out of them into the habit of the parts. Now certainly these two operations cannot be performed together or at the same time; because the former is done by dilatation, and the other by constriction of the same Arteries, which two contrary motions cannot be coincident. Wherefore it is of absolute necessity, that the repletion of the Arteries be precedent, and the evacuation be subsequent.  
But the repletion cannot be made without a violent distension of the transverse or circular Fibres of the Arteries, and we all know, that all the Fibres of vessels, no less than those of the Muscles, of the Guts, Stomach, Tendons, Membranes, and the like Fibrose parts, naturally resist distraction, and have a power of contracting themselves after extension. Yea more, we see that all Fibres even in their natural posture are somewhat upon the stretch: for when they are cut, they instantly shorten themselves toward both ends: which would not happen, if they had been constituted in a middle state betwixt laxity and extension, as a Bow unbent is quiet, suffering neither contraction nor distraction of its parts.  
Now if all Fibres even in their natural state suffer some degree of stretching; certainly when the Arteries are replenished with blood, their cavity must be dilated; and in the dilatation of their cavity, their transverse or circular Fibres must suffer much more stretching, than they did before. And because to this dilatation of the Arteries a constriction immediately succeeds, which is not possible to be effected without an abbreviation of the circular Fibres of the Arteries; and because that abbreviation or contraction is connatural to the Fibres themselves: therefore it is impossible, that the Arteries, after that violent stretching caused by their repletion and turgency, should not exercise, by natural necessity, that mechanic power they have of contracting themselves, by virtue of their circular Fibres girding them inward: and equally impossible, that the Arteries should so contract themselves, without expelling at the same time out of their Orifices, the blood that dilated them. Whence it appears beyond dispute, that the spontaneous constriction of the distended Arteries is the cause of the expulsion of the blood out of them into the substance of the parts; contrary to their opinion, who ascribe this expulsion only to the Systole of the heart. ¶ ⸪  
The natural method of acquiring Science, ye know, is to begin from things more known, and then to advance to things less known; to proceed from effects to their causes. Seeing therefore that we are now certain that the blood in Animals is carried by a perpetual circular motion through all parts of the body; our next business is to inquire, what are the Causes of this admirable motion, as well the final as the efficient.  
I begin from the final; it being a question worthy our consideration, why or to what end Nature, all whose counsels and actions are ordained by an infinite wisdom, hath instituted this rapid Circulation of the blood.  
Constant it is even from common experience, that whenever the blood is quiet or ceases from motion, whether within or without the body of an Animal, the red and grumose part of it soon curdles, and is separated from the serose or albumen: and so the constitution or contexture of it is dissolved and corrupted: whereas on the contrary, while the blood continues in perpetual motion within its vessels in the body of a living Animal, so long the ordinate mixture of its elements, due temper, and vital constitution of it is conserved; for mechanical reasons in our ensuing discourse to be explained.  
It seems then, that such a mixture of the constituent parts of the blood, upon which the vitality of it doth necessarily depend, cannot be otherwise conserved, than by a continual agitation and concussion made in the vessels, first by the heart, with strong force impelling the blood through the Arteries; then, that impulsive force languishing by filtration in the spaces intermediate betwixt the Arteries and Veins; next in the Veins, by the constriction of their circular Fibres, by the compression of the Muscles, and the Viscera, and the inspired air. All which compressions would not suffice, were not Valves placed commodiously within the Veins, by which the motion of the blood is accelerated, and a farther conquassation of it made.  
And here we meet with a fair occasion to reflect upon the mutual Anastomôses of the Capillary Veins, and the infrequent distribution of Valves in one and the same Vein: for both these contribute also their proportions toward the end now under our disquisition. For, the texture of the Veins being indeed lax and soft, yet such as may by virtue of their circular Fibres be constringed and contracted: hence it is, that by the blood regurgitating in those tracts of the Veins, that have no Valves, by the great quantity and force of its regurgitation or recoiling, the lowest part of the Vein is much dilated; and on the contrary the highest part is contracted: So that the blood being by this reflux, though inobservable, agitated and conquassated, may revive its due commistion, and conserve its vital constitution. It appears then, the defect of Valves also hath its use. Within the cavities of the Arteries (as I said before) no Valves are placed, because the grand force, by which the blood is impelled through them, is more than sufficient to conquassate and commix it, by wedging in as it were the more fluid albugineous particles among the red grumose particles, that from both sorts commixed per minimas moleculas (as they say) and yet mutually reluctant, the Vital Mication, or Oscillatory intestine motion of the blood may be continued. So then here is neither need of, nor place for a Fermentation. Now from the consideration of these things premised, I conclude, that the Circulation of the Blood was instituted for the conservation of its requisite temper and vital constitution: Which was to be inquired, and which leads us to  

The admirable effects and benefits arising to the Animal Oeconomy from the same Velocity of the Circulation of the Blood;  
Which being certainly so great, that the whole mass of blood runs its circular race in the twentieth part of an hour, or thereabouts, even in a sedentary and sedate man; as hath by many been demonstrated from the quantity of blood commonly contained in the body, from the number of Pulses made in an hour, and from the quantity of blood expressed by every pulse of the heart: and we having already seen what advantage redounds to the blood itself from this velocity: our curiosity spurs us on to inquire also, what other scopes or ends Nature may probably be conceived to have proposed to herself, when she instituted this so rapid motion; or what emoluments and benefits from thence redound to the Oeconomy of the whole body.  
Of these the first seems to be this, that in every pulsation of the heart, a great quantity of blood is effused and protruded out of the Capillary Arteries into the habit of the parts, for their refocillation by influent life (of which I have formerly discoursed copiosely in this place.) For, by how much swifter the motion of any liquor or other fluid through a pipe or canal is, so much a greater quantity of it is, in equal time, effused at the Orifice thereof; as hath been ingeniously demonstrated by B. Castellus: 
Lib. de aquae fluxu.  and therefore the blood is, like a full and rapid torrent, impelled into the Pores of the flesh and Viscera.  
The second is the energy of the stroke, with which the blood projected by the heart, dashes against the same extreme parts: which energy is composed of the degree of velocity, and of the quantity of blood impulsed, 
Tract. de vi percussion. Cord. prop. 28.  as that excellent Mathematician Io. Alphonsus Borellus hath fully demonstrated. By this stroke it is, that the newly emptied and conniving porosities of the Muscles and Viscera are forced open and replenished with the impulsed blood, that communicates to them vital heat and fresh vigour: and that the torpid, useless, and excrementitious particles there remaining, are protruded and expelled, partly through the pores of the skin, partly through vessels destined to their transportation and expulsion. So that by this rapid rushing in of the blood, nature attains to not only a reviving of the solid parts of the body, but also to the expurgation of the blood itself from its unprofitable and excrementitious parts, in the Emunctories ordained for that office.  
A third advantage is, that by the same rapid velocity of the blood, and its vehement intrusion into the narrow meatus of the parts; the current thereof dislodges, rinses away, and carries with it many other amoveable particles of various kinds, Saline, Sulphureous, etc. principally the relics of the nutritive and nervose juices brought thither from the brain; which though unprofitable now to the refection and invigoration of the parts in which they were left, may yet be of some use to recruit and conserve the Crasis of the blood, and to expedite the secretion of its excrements. This artifice of nature we may more easily comprehend, by observing, that the foreign particles now mentioned are extricated and rinsed away by the blood, not in ample vessels, but after the egress of the blood out of the Capillary Arteries, in the intermediate spaces betwixt them and the Capillary Veins, where end innumerable small Canales, some of which bring in the nutritive and nervose liquors, others export the superfluous and less profitable particles of them; which small pipes are, like the Capillary roots of plants, almost every where disseminated into the fleshy parts, into the Viscera, and (most frequently) into the glandules. And this seems to be done, to the end that so many particles of these spiritual and noble juices, being rinsed away by and commixed with the the blood, may advance and conserve the due consistence and constitution of it.  
Now of these three considerable benefits, no one seems to me possible to be attained otherwise than by the perpetual and rapid motion of the blood. Wherefore I am not destitute of a rational ground to support my conjecture, that for these ends Nature thought fit to institute the swift motion of the blood in its Circulation. ¶ ⸪   

But what may we conceive to be the reason that induced Her to institute also so multiplied a repetition of this course of the blood through the same ways?  
A River, we know, though the water be in a continual flux, is yet still the same river, because the elapsed parts are continually succeeded by new waters coming on with the same degree of speed to supply it. But to maintain this perpetual succession and supply, upon which the identity of the river necessarily depends, there is required, either an immense quantity of waters from a spring to feed the current, or the same elapsed water must be brought back again to the fountain whence it flowed, that so by perpetually reiterated circuitions the course of the river may be conserved, which otherwise would soon fail and cease.  
We are then no longer to admire that Nature, having designed to bring the river of blood with a most rapid course through the whole body of an Animal, for the various ends above explained; and resolved to make that course perpetual, during the life of the Animal: made use of the same expedient, viz. to repete the circuition of the same blood without intermission. For the whole mass of blood commonly found in the body of a man, not exceeding 20 pints; and that quantity not sufficing to maintain the course above 5 or 6 first minutes of an hour: lest the current might cease, and so life also fail, it was necessary that the circulation of the same mass of blood should be continually reiterated, for the conservation of life.  
Besides this necessity, there are many admirable uses and advantages which Nature brings to an Animal, by often repeating the period of the circuition of the blood through the same ways. For if the Circulation were not in this manner reiterated, the blood could not be defaecated from its biliose excrement in the Liver, nor (according to the vulgar opinion) from the matter of Urine in the Kidneys; nor could either the Chyle be commixed with the blood in the heart, or the Lympha be brought to temper and dilute it in the Veins: nor could various other operations necessary to the Animal oeconomy be performed. All which it were not difficult for me to deduce from this repeated circuition of the Blood, if the shortness of the time appointed to me for the administration of my present province, did not oblige me to pass by all collateral disquisitions, and to peruse my principal Theme, the Motion of the Blood. From the final causes of which I will therefore in a direct order proceed to the Efficient. ¶ ⸪     

PRAELECTIO II. Of the Heart, and its Pulsation.  
TO measure the Divine Wisdom elucent in every Organ of an Animal, by the short line of human Reason, is indeed extreme folly: and yet I doubt not to applaud and follow the counsel of Erasistratus, who (as Galen relates) advised Physicians to solve all the actions naturally done in the body of an Animal, by Mechanic Principles; so far at least, as the dim light of my limited understanding may serve to guide me in my researches. For not to depend upon the authority of Plato, who said, 〈◊〉 〈◊〉 〈◊〉 〈◊〉 〈◊〉, that God always works by Geometry; or of his greatest disciple Aristotle, who from thence called God, 〈◊〉 〈◊〉 〈◊〉 〈◊〉 〈◊〉, the Mechanic of the world: we have the greater authority of the Sacred Scripture itself, that God hath framed all things in number, weight, and measure. Whoever therefore intends with due care to study any part of his works, must therein chiefly consider number, weight, and measure, i. e. the Mechanism of it: otherwise, in the end he will find his mind rather swelled with opinion, than filled with knowledge. Why then may not we, who are Christians as well as Natural Philosophers, take those parts of an Animal to be Machine's or Engines, which evident reason, and chiefly sense show to be such? or who hath prohibited us to investigate the formal reason and manner of their operations? It is not more certain, that no mortal can know enough of God's works; than it is, that the more we are able to discover of his wisdom, power, and goodness discernible in the mirror of his Creatures, the more we shall find ourselves obliged to admire, love, and adore him. Equally certain it is also, that no kind of devotion is more acceptable to him, than that which proceeds from knowledge of his infinite Perfections: and that the Sacrifice of Praises offered up to Heaven from the mouth of one, who has well studied what he commends, are more suitable to the Divine Nature, than the blind applauses of the ignorant. Wherefore, since we are now come to the Efficient cause of the before described motion of the blood, which our senses plainly show, and all learned Anatomists acknowledge to be the Pulsation of the heart; and since it is equally manifest, that this Pulsation is an action entirely Mechanic: let us attentively contemplate and consider the Mechanism of the heart, from whence that action necessarily proceeds. For the true reason and manner of the Pulsation being known; our disquisition of the motion of the Blood will be complete, and we shall so much the more admire and laud the skill of the Divine Engineer, who contrived and made the Machine of the heart of so small a bulk, and yet of so stupendous power and force. Nor ought we to despair of finding what we search for: because though the Heart of man be to us inscrutable, as to its 〈◊〉 thoughts and reserves; it seems not to be inscrutable, as to its Fabric and Conformation. I will therefore endeavour to explain the structure of it.  
That the Heart is a Muscle of the same nature with the Muscles of the Limbs, is apparent to the sight, and will be more apparent, if the Carnose Fibres of it be plumped up by boiling. For than we may plainly perceive, that it is composed of robust fleshy Fibres of the same Prismatical Figure, of the same colour, and consistence, and tenacity, as the Fibres of other Muscles have: and therefore the Fibres of it are in like manner inelongable, and resist distraction; they, as those of other Muscles, spontaneously contract themselves after extension, may be swelled, and acquire hardness, when they act in the Pulsation of the heart. So far the resemblance holds.  
But yet the Fibrose constitution of the heart differs from that of all other Muscles, in this, that the flesh of the heart is firm, hard, uniform, of a deep ruddy colour; nor are the prismatic columns separated from the little membranes and innumerable Tendinose Fibres, as the Fibres of the other Muscles are. Besides, the disposition and configuration of the Fibres of the heart is extremely divers from that observed in all others. For here the Fibres are neither direct, nor parallel among themselves; but curve and spiral, and in wonderful manner variously interwoven and implicated, not by a Texture like that by which Wicker Baskets are made, as Vesalius imagined them to be, but disposed with a more admirable artifice. For, immediately under the outward membrane investing the heart, from the Basis of the heart, and from the Circular Tendinose Orifices of it, in which the Vena Cava and the Vena Arteriosa are terminated; as also from the beginnings of the aorta and arteria venosa, is propagated a stratum or Layer of Carnose Fibres, which are almost aequidistant among themselves, and tending directly from the Basis toward the Cone of the heart; where variously inflected and contexed, they are reflected toward the Cavities or Ventricles within the ●● volutions and mutual intersections, seem to give to the heart its circular and Conical Figure, in which it is not resembled by any other Muscle whatsoever; are disseminated in great multitude sprigs of Nerves, derived from the interior branch of the Eighth pair, properly named par vagum: all which passing betwixt the arteria pulmonaris and the aorta, first bestow many smaller surcles upon the Auriculae on each side, and then implant themselves into the Fibrose substance of the heart in divers places. The manner of which their implantation is plainly visible in the heart of a Calf, Lamb, or other new born Animal, while it is yet warm.  
But because in things Anatomic, the Eye is a better instructor than the Ear; I have caused to be accurately represented in this Figure, the whole System of Nerves pertaining to the Heart and its Ears; to help both the understanding and memory of younger Students, for whose sake chiefly Lectures were at first instituted in this College.  

FIGURE III.  
In this Figure, AA, AA, represent the Nerves of the Eighth pair cut off: which though derived from the same origine, are yet, in a man after they have passed out of the Skull, divided into two Trunks; of which the exterior, denoted by BB, is called the Intercostal branch, because in its descent toward the parts of the lower belly, it receives many Spriggs of other Nerves shooting forth between the ribs from the Spinal marrow, as auxiliaries; and the interior, named par vagum, from its various windings and turnings, first distributes divers surcles in its passage downwards to the heart; then subdividing itself into more threads, is disseminated into the Viscera contained in the abdomen.  
DD, The plexus of the former or intercostal branch, called ramus Cervicalis, because in man it is sited on each side in the middle of the neck.  
EE, The plexus of the Nerves of the later branch or par vagum.  
F, The Cardiac plexus, in which are terminated smaller Nervose tendrels, GGG, arising on each side from the plexus cervicalis of the intercostal nerve.  
HH, Surcles of a conspicuous nerve shooting forth from the plexus of the par vagum, and terminating itself in the plexus Cardiacus.  
TWO, Many nervose productions from the plexus of the par vagum, distributed to the Pericardium, to the vessels conjoined to the heart, and to the ears of it.  
K, Remarkable surcles of nerves from the plexus Cardiacus, which passing betwixt the arteria pulmonaria, M, and the aorta N, are terminated in the substance of the heart.  
LL, Two considerable Nerves sent from the par vagum to the heart; which are variously combined, as it were by mutual inosculation, both among themselves, and with Nervose branches issuing from the plexus Cardiacus; to the end, doubtless, that both might be strengthened by that union. These seem to be the principal of all Nerves pertaining to the heart, and most likely to convey influence from the brain to the heart (whatever that influence be) to invigorate it, and maintain it in perpetual motion; probably by supplying the heart with succus nutritius in great plenty.  
OOOO, The Musculose substance of the heart, into which the said Nerves are inserted.  
In this manner hath Nature furnished the heart of man with store of Nerves; thereby providing for its strength and continual motion. Nor hath she much diversified her work in the hearts of Brutes. For all the difference that hitherto hath been observed in them, as to the Nerves, is only this; that beside the productions that come from the Nerves of the Eighth pair, in a place somewhat higher, and are distributed to the heart; in most Brute Animals there are moreover very many sprigs shooting from the same Nerves, where they pass above the heart, and receive as auxiliary supplies, nervose surcles passing betwixt the ribs from the Spinal marrow; which are sent down directly into the substance of the heart, as if the more easily to convey some influence into it. No great difference this: and yet the cause that induced Nature to make it, may be great. What it is, is difficult to find out. It may probably have some respect to the prone posture of Brutes, which being horizontal, must cause the ponderose machine of the heart to swagg, and the cone to point, not toward the midrif as in erect man, but toward the Sternum: and therefore in them there might be need of more auxiliary Nerves to assist the heart's motion in that position. But whatever may be the true reason, I do not assent to their conjecture, 
Lowerus de Cord pag. 14. noviss. edition. & Willis de Cerebro, in Neurologia.  who say, that because the heads of beasts look downward, therefore the providence of Nature hath furnished their hearts with more Nerves, lest Animal Spirits should not in sufficient swarms be sent every moment from the prone head into the heart of a Brute, that position of the brain (forsooth) rendering the transmission of these Spirits more difficult and slow. And the reason why I do not assent to this witty conjecture, is because neither the Authors of it, nor any other man whose writings I have read, have sufficiently proved, that there are such things as Animal Spirits in rerum naturâ. In some books indeed whole Commonwealths of them are found, so that ye can hardly pass along without meeting crowds of them. But till I see their Existence otherwise than precariously asserted; I am justly excusable if I doubt thereof.  
The Heart being thus composed of many myriads of strong Fibres of various orders, by most dense contexture compact; and of various Nerves intersperst: it required to be continually cherished with due heat as well without as within. Wherefore the Heart having no heat but what it receives from the blood, in which only the true Calidum innatum, the lar familiaris resides; Nature hath furnished it with two Arteries, for its own peculiar use, divided almost from their origine into two trunks; the Orifices of which open themselves near to the beginning of the aorta, immediately without the Valvulae Semilunares. They are fitly called Coronary Arteries, because their trunks do not presently enter into the parenchymas or substance of the heart, but first make their tour or circuit, the more commodiously to disperse their branches, round the basis of it, in manner of a crown, or rather a Diadem: and though from their very original they divide, and recede the one from the other to the opposite regions of the heart; yet they meet again in their extreme branches, and by mutual Anastomóses or inosculations communicate betwixt themselves, so that if any liquor be injected into either of them, it will in a moment appear to diffuse itself also through the other. And this mutual Communication seems to be designed to a good end. For since the necessity of influent heat or life is equal in all parts of the heart, that necessity could not be more commodiously satisfied any way, than by this Artifice of mutual inosculation betwixt the extremities of these two Arteries.  
No sooner hath the blood thus imported, communicated its vital heat to the substance of the heart, than it is thence exported by the two Coronary Veins, which in like manner encompassing the heart, and by their numerose emissary surcles imbibing the blood effused out of the Arteries, reduce it into the right Ventricle, thence to be brought through the Lungs back again into the left. So that here is a private circulation in a small circuit, instituted for the peculiar benefit of the Heart. As the extreme surcles of the Coronary Arteries are mutually inosculated, so also are those of the Coronary Veins, as is apparent from ocular inspection. For, if you take the heart of a Calf or any other very young Animal (for in such these vessels are most easily discernible) and with the back of a penknife gently impel the blood from one side of the heart toward the other, you shall see it flow out of the Vein of one side into that of the other, and vice versâ. Nor is it to be doubted, but that in all other parts of the body there is the like mutual communication per anastomôsin betwixt Capillary vessels of the same kind.  
Besides the proper vessels of the heart now described, there are annexed to its basis also two Subsidiary Muscles, hollow and round, from thence called Auriculae cordis, framed with no less art than the Heart itself, though of less bulk. For they are composed of robust Fibres too, and disposed in the same order; and as their motion precedes that of the Heart, so have they Nerves from surcles of the Eighth pair before they reach to the heart itself. Besides, their intermediate fleshy Fibres, which form little musculose columns, are elonged to opposite Tendons. For the Tendon at the basis of the Heart is common also to the ears of it, and serves them for a fulcrum or prop; and on the other part of the right Ear, where it respects the Vena Cava, it is firmed by a harder and Tendinose circle: betwixt which two Tendons the Fibres tending to each are terminated; as appears in the right Ear of a human heart inverted. Of these Ears, the right is always greater than the left. Perhaps because the flux of the blood being less rapid out of the Vena Cava into the right Ventricle of the heart, than out of the Arteria Venosa into the left, whither it is impelled by the compression of the Lungs, and by the coincident elasticity of the inspired air: it was therefore requisite, the capacity of the right Ear should be proportionately larger, to receive and transfund into the right Ventricle a quantity of blood sufficient to fill it. For evident it is, that the office of these Ears is, like that of funnels, to transmit the blood into the Ventricles of the heart.  
For the same reason, the trunk of the Vena Cava, when it approaches to the heart, participates somewhat of the nature of a Muscle. For there it is furnished with fleshy circular Fibres, by which it is constringed, and consequently the blood running through the canal thereof is urged the faster into the right Ear: in the same manner as when a gut or bladder is outwardly constringed by the hand, the liquor therein contained is expressed, and its regress hindered.  
We have now surveyed the Structure of this admirable Machine the Heart, at least so much thereof as may serve to render more plain and intelligible what I am about to say concerning the Action thereof. To which I now pass. ¶ ⸫  
Evident it is both to the sight and to the touch, that in the act of Pulsation, the whole fleshy substance of the heart is stretched, and hardened with very great force, as all other Muscles are, when they act: and certainly this tension and induration arises from the very Structure of the heart. For the Fibres of the columns of it, and their cylindrical fasciculi or combinations, have not their ends fastened to Bony or Tendinose props, as most other Muscles have; but relying only upon, and having both their beginning and end in the pendulous heart itself, are retained by an instable foundation or hypomochlium, yet with tenacious firmness. Hence it comes, that the turgency of the Fibres of the heart seems not to have been ordained by Nature for the traction and approximation of their extreme terms; but on the contrary, that there might be made a decurtation or shortening of the Fibres, that by their swelling they might restringe and lessen the hollow perimeter, and so, like a Press, squeeze out the blood therein contained, just as boys Spirit the stones of plums by compressing them strongly betwixt their thumb and forefinger. This is evinced from hence, that in every Pulsation or Tension of the heart, the blood contained in the Ventricles is with very great violence Squirted out into the Arteries, as water is Squirted to great distance out of a Syringe by the embolus or rammer. But more evidently by putting your finger into a hole made by incision in the heart of a living Animal. For in every Systole of the heart, you shall feel your finger pinched all round about, as by a pair of pincers, by the swollen and indurated flesh of the Heart. Though therefore the external superficies of the heart be not in the Pulsation augmented; yet certainly the whole fleshy substance of it is at that time truly swelled up, and increased, and indurated.  
Here I have affirmed two things difficult to be conceived, more difficult to be proved. The one is, that the decurtation of the Fibres of the heart, which always is effected in its act of Pulsation, doth by lessening the cavities of its Ventricles, express the blood contained in them. The other is, that though in the same Pulsation, the outward superfice of the heart be not augmented, yet the whole fleshy substance of it is so enlarged, as to fill a greater space than before. Wherefore, since this action of the heart cannot be clearly understood, unless the Mechanic reasons of both these Propositions be first explained; and since that work hath been done to our hands, with great labour of mind and profound judgement, by that excellent Mathematician Io. Alphonsus Borellus, in his second Volumn de motu Animalium; not long since published: I choose rather, in so obscure a way, to lead my Auditors of the Younger sort by his brighter Torch, than by the Glow-worm light of my own understanding. Omitting then the Lemmata or introductory propositions by him premised to his demonstrations of the Mechanic reason of the Action of the Heart: I will venture to make myself an Interpreter of so much of his Theory concerning that abstruse subject, as seems to me requisite to the explication thereof: referring those, who shall not be satisfied with my Epitome, to the book itself, in which the argument is treated at large, and more Mathematico. I begin from his 47 th' Proposition.  
Let us represent to our imagination a glome or bottom of small twine or thread, ABR hollow within, composed not of one thread, but many, and those too tied to a ring, or the semidiameter of the glome AETR, fixed, and to the superfice of the cavity; and wound about Concentrically, or Spirally. Now if the cavity be filled by swelling of the threads by their humectation, the internal threads MOQ, must be corrugated or shriveled up unequally, always the more increasing their wrinkles or folds, by how much the nearer they come to the Centre; and the external Figure of the glome will remain unaltered.  
Because in a Rope of Hemp, whether the Rope be made of a single twine, or composed of many twines twisted together Spirally, the external Spires do in the same order strictly embrace and bind down the internal Spires, so that they cannot be removed out of their places; we see that ropes are equally by humectation swelled, contracted, and suspend equal weights. Therefore in like manner glomes of thread, composed of one or more threads, ABR, aught in the same manner to be swelled, and their cavities MOQ, to be filled by that swelling. For the beginnings and ends of their Spires are with equal firmness retained in the same places, whether they be mutually knit by continuation, or whether they be tied or fastened to the rings or other firm places of the glome, as in the 4 th' Figure. For, in both cases the threads are the same, of the same form, disposition and thickness; and the external threads by their Tension spirally gird in and embrace the internal; therefore they must become, in the same manner, thicker by a few drops of water, and consequently in the same proportion corrugated; always so much the more shrinking into little wrinkles, by how much the nearer they approach to the Centre; and their external Figures will remain of the same bulk and magnitude.  
To accommodate this to our present Theme; I say, that when the Porosities of the Fibres of the Muscle of the Heart are by internal humectation dilated, the cavities of it ought of necessity to be filled by the fleshy substance of it, without variation of the external Figure thereof. For, because the Heart is a glome hollow within, composed of innumerable Fibres, Spongy, very strong, and not extendible in length; which Fibres are fastened to the Tendinose rings of the four orifices of the heart, and spirally involved and contexed: and because all these Fibres are by internal humectation swelled no otherwise than the twines of a rope, and the threads of a glome are made to swell, and become turgid by a few drops of water insinuated into their pores: Therefore by the same necessity, by which a glome contexed of threads is transformed inwardly, must the cavities of the heart be filled, the internal Fibres of it being corrugated, and shortened unequally, always augmenting their swollen wrinkles, by how much nearer they approach to the Centre of the heart; the external Figure of the heart being the while neither augmented, nor diminished. And thus is the difficulty of the latter of our two Propositions solved.  
Let us therefore in the next place resume the consideration of the former, viz. That the constriction of the Ventricles of the Heart cannot be made by the force of the contraction of its Fibres.  
If, according to the common doctrine of Anatomists, the proper action of all Muscles be a Contraction of their Fibres; than it may seem consentaneous, that the proper action of the Muscle of the heart should also be a contraction of its Fibres: and because the heart is not tied or bound to any joints, as most other Muscles are, for the bending of them, but ought only to constringe its own Ventricles; let us see, whether the Ventricles of it may be constringed by a simple contraction of its Fibres, or not. And First, if the Heart be like to a glome composed of threads spirally involute; it is manifest from what hath been said, that Fibres, when they act, cannot possibly exercise their force by their contraction, and by drawing their extreme terms towards the middle; because by a corrugation or shrinking up into wrinkles of their length, they must rather be relaxed. Therefore as a weight hung on to a lax cord cannot be raised thereby, while the cord continues lax: So by Fibres lax and corrugate cannot the opposite walls of the Ventricles of the heart be violently drawn together, and conjoined.  
Secondly, but if we suppose, that the Fibrose Spires of the heart are not wound about tortuosè, with turnings and windings quite home to the Ventricles, but extended in a direct course into the Ventricles, and there bound together into those fasciculi or sheafs, which compose many little Cylinders or cords: then indeed a man may think, that by simple contraction of the Fibres those little Cylinders may be totally shortened, and so the opposite walls of the heart be brought to meet together. But this is evidently impossible; because in such a position there must necessarily be admitted a corrugation of the whole concave superficies of the heart intercepted betwixt the bases of those little columns or cords; and therefore innumerable Fibres there contexed must be crowded up together, and in like manner corrugated, i. e. relaxed; and by consequence could not act by their tense contraction; which is repugnant to the supposition.  
Besides, in the right Ventricle of the heart are found but very few of those little Cylinders or columns: and therefore this subterfuge can have no place there.  
Yet farther, a total decurtation of those same columns or cords could not be made, unless the lengths of the Spires ending in the columns themselves, ran out betwixt other Fibres, as into sheaths, or about pulleys; neither of which contrivances is to be found in the heart. For the Fibres of the heart are with decussated directions contexed, and so closely and firmly bound among themselves; that they cannot by various and contrary motions start out of their places, and run out among other Fibres embracing them.  
In fine, that the Tension of the heart cannot be solved by a simple contraction of its Fibres, as heretofore hath been commonly imagined, may be sufficiently evinced even from this, that the bulk of the Muscles of the Limbs, which when they act, are truly contracted, is sensibly diminished rather than augmented; but the bulk of the heart, while it acts, is augmented, since the Cavities or Ventricles of it are filled up by the fleshy substance, the outward figure of the whole heart being at the same time unchanged and undiminished. Wherefore the proper action of the heart is not performed by contraction of its Fibres. Quod erat probandum.  
Hence arises this Corollary; That the cavities of the Heart are constringed, not because the lengths of the Ventricles are shortened, but because their side-walls are brought nearer each to the other, so as almost to touch.  
This appears from the very position and configuration of the Ventricles of the Heart, and from its operation. For, the left Ventricle, dissected from the bottom to the top, is (ye see) extended through the whole length of the heart, from the Basis down to the Cone, which ends into a sharp pointed and slender wall: and since the external figure of the heart, while it beats, is not shortened; therefore neither is the length of this cavity diminished, that is to say, the Basis of the Cavity is not brought nearer to the Cone of it. Besides, the Base and Cone of the heart cannot at all be inflated and incrassated; because the Base wants Fibres, and is entirely destitute of flesh, as being wholly occupied by the four ample Orifices of the Veins and Arteries: and the wall of the Cone is very thin and slender. Therefore the Cavity cannot be filled by inflation of the Fibres of the Basis and Cone of the heart. It remains then of absolute necessity, that the Cavity be filled by inflation of the side-walls of the heart, which are very thick, full of Fibres, and therefore easily capable of inflation. Lastly, as was said before, if a man put his finger into a hole made by incision in either of the Ventricles of the heart of any Animal yet living, he shall perceive a strong constriction of the side-walls, but none of the Basis and Cone tending to their approximation one toward the other. By this Consectary thus verified, we are led to understand.  

The Mechanic reason of this Operation.  
That by Mechanic necessity the Cavity of the heart cannot be shortened, may be farther proved thus. Because a Contraction of the heart cannot be made, but by a Contraction of its Fibres; therefore those parts of it, that want Fibres, will not be capable of Contraction: but of that immense multitude of Fibres descending from the Basis of the heart, not so much as the thousandth part attains to the Cone (because if they should be there connected, they would, being accumulated stratum super strato, make the acuminate and thin wall of huge depth or thickness: whereas now that wall is very slender, in such a situation) and all the rest of the Fibres, that are spiral, are woven together, and reflected into the heart with a transversal Circuit before they reach to the Cone. Ergo they will not be able to draw up the Cone of the heart toward the Basis; and by consequence, the length of the cavity of the heart will not be shortened.  
But the Cause by which the side-walls of the Ventricles are brought to meet, is this. Because almost all the innumerable Fibres of the heart are wound obliquely and transversly about the sides of it, and of them are composed very many Layers one above another, like Membranes. But when the Fibres of any Layer are inflated or huffed up, they, touching each the other laterally, and lying in one Superfice, will of necessity crowd and press each the other laterally; and so thrust each the other out of their places, and urge them farther, viz. sideways toward the Basis, and toward the Cone. Wherefore the interval betwixt the Basis and the Cone ought to be rather augmented. But because the other external Fibres obliquely encompassing and closely girding the transverse, and intersecting them decussatim, hinder their elongation and protuberance; it comes to pass, that of necessity the inflation of the Fibres ought to cause them to swell inwardly toward the cavities; and so the insides of the walls being puffed up, must be brought nearer together.  
Moreover, the septum cordis, or partition-wall of the Ventricles, consisting for the most part of transverse Fibres, will not be shortened by their inflation, but the thickness of it is much augmented: and the outward walls ought likewise to be inflated inwards towards the internal cavities; therefore the insides of the opposite walls ought to meet, the Basis remaining always at the same distance from the Cone. Quod erat ostendendum.  
Hence we may deduce this genuine Consectary, That the meeting of the opposite insides of the walls of the Ventricles of the heart, is the sole and immediate cause of the expression of the blood, that was contained in them, into the Arteries. For, the swelling or incrassation of these opposite walls being all inward toward the Centre of the heart, and withal so great, as to fill up the cavities of the Ventricles; it is necessary that the blood contained in the cavities, being on all sides vehemently compressed, give way and flow forth through the apertures or Orifices by Nature provided for its efflux: the resistance of the fluid blood holding very little proportion to the mighty force of the solid compressing it.  
But so grand an intumescence of the fleshy substance of the heart could not otherwise be made, than by a great swelling and turgency of its Fibres: and therefore we may infer, that the thickness of the Fibres of the heart is, in the act of Pulsation, doubly greater than in the diastole. This being granted, I consider, that the external Fibres of the heart exercise very great force, not by shortening themselves, but by resisting distraction; (as the iron hoops of a hogshead) that the perimeter of the heart be not augmented; and at the same time they are inflated in their Concave part or under side, as we have said, the threads of a glome are: and in like manner the internal Fibres, when they are swelled and incrassated, exercise very great force by making folds and turgid wrinkles, so tense and rigid, that they do the office of wedges, by which not only the cavity of the heart is filled up, but the blood therein contained is by vehement compression squirted out, by a motion very much resembling that, by which we spirit Plum-stones, with our Thumb and forefinger compressing them behind.  
But the slender fleshy Columns holding in the opposite walls of the Ventricles of the heart, are at the same time also incrassated, and withal shortened (their Fibres being swelled and corrugated) to help fill up the cavity. Yet they exercise greatest force, to perform the office of wedges. They exercise none towards the drawing together the opposite walls of the Ventricles, because themselves are lax, by reason of the corrugation and shrinking of the length of their Fibres: and besides this, they could never exactly conjoin the opposite walls, because being of a musculose constitution, they cannot be totally shortened, the nature of the Muscles being such, as suffers not contraction greater than the third part of their length. Yet it cannot be denied, but these musculose Columns serve, as cords, to retain and conserve the due disposition of the internal parts of the heart, and to prevent the immoderate distension and distraction of the Ventricles, which too great a quantity of blood rushing into them out of the Veins, might otherwise cause.  
Finally, the Papillae, or little fleshy teats standing up within the Ventricles, and to which the membranose filaments of the triangular valves of the heart are fastened, do also act their part in this Scene: not only by admitting the like inflation of their Fibres, but also by firmly erecting themselves, ad instar penis.  
All these things are verified in the left Ventricle, and in the Ears of the heart; but in the right Ventricle, where is not found an equal number of Columns, the constriction is made by incrassation of the external wall, namely by inflation and decurtation of the Fibres thereof, so that the hollow crookedness of it, by swelling inward, comes near to a Plane, and the Arch within becomes straight. Also the inflation and swelling of the Septum cordis, or middle wall of the heart, of great thickness naturally, contributes not a little to the repletion of the right Ventricle. For hence it is, that the Convex superfice thereof doth become more prominent and stretched out, whence that space resembling the figure of a concave Lens, is filled up, and the walls mutually touch, the circuit of the Lenticular cavity remaining still the same.  
Now this whole operation is exactly conform to the institute of Nature, which primarily fills and amplifies the Pores of the Spongy Fibres by the humectation above explained; from which she attains to a double effect. For, in the Muscles of the Limbs that swelling of the Pores of the Fibres, produces a secundary effect, which is the decurtation of the Muscle, and the strong traction of the joint: but in the heart, from the very inflation of the Fibres, and consequent incrassation of the walls, she effects the repletion of the Ventricles. But the Machine is the same in both, namely, the force of a wedge dilating the Pores of the Fibres.  
But that this expression of the Blood out of the heart is not made by a Spiral contorsion or twisting of the heart, such as that by which water is commonly squeezed out of a wet napkin, as some late Writers 
* Lower de. Cord.  have thought, is easily to be proved. I acknowledge it to be most true, that the expression of the blood out of the heart, no less than the wring of water out of a wet cloth, is made by constriction of the Cavities and Pores, which were filled by the fluid: but at the same time I deny, that such a constriction is made in the heart, and such an expression of the blood thence, by the same cause, the same Organs, and the same Mechanic action, by which water is squeezed out of wreathed Linen. For, in a Linen cloth, before its Contorsion, the threads were all lax, and therefore they admitted many Interstices, that might be filled with little drops of water. Afterward, the cloth being strongly twisted, the threads are forced to make many circuits about the twist, of almost the same altitude, and so they must not only be much elonged in those prolix Gires, but also extenuated and stretched; and consequently their sides being made smooth by extension of their folds and wrinkles, will mutually touch, and their interstices vanish, whence the little drops of water that were in them before, will presently be squeezed out. But in the heart, the repletion of the Ventricles is performed in a manner far different from this. For, in the act of Pulsation, the bulk of the heart is not extenuated or diminished, but rather augmented in a double proportion, nor are the Fibres of the heart elonged, but rather contracted as the nature of all Muscles requires. The same Fibres do not mutually touch, nor are their interstices filled up by reason of violent traction and extension, but of their inflation.  
Notwithstanding this, we are not to think, that the Spiral disposition of the Fibres of the heart is of no use. For, they serve to the firm binding or hooping as it were of the walls thereof, that the face and configuration of the heart may continue still the same: which Nature hath provided for also by Girths of other Fibres wound round about from the external Tendinose Orifices of the Vessels of the heart, to the Columns within, and with admirable Artifice decussated and woven together. And thus we have made good our Proposition. That the proper Action of the heart is the Constriction of its Ventricles, and the consequent compression and expression of the blood contained in them; not by a Contorsion of its Spiral Fibres, but by an inflation and corrugation of them.  
Here some perhaps may be willing to propose to me this question. If it be true, that in the Systole or act of Pulsation, neither the exterior Superfice of the heart is augmented, nor the Cone of it drawn up toward the Basis; both which we have asserted: how then comes it, that in every Systole, the Cone of the heart knocks against the left side of the breast?  
Which may be thus Answered. Because the heart is hung in the middle of the Breast by strong Ligaments, and yet in every Systole is brought to touch and strike the inside of the Breast; therefore it is necessary that this be done, either by a dilatation of the heart, or by local motion and translation of it, or by erection of the whole, or by flexion and incurvation of the Cone thereof. And as our observation and experience rejects the three former causes of this Phaenomenon, so it obliges us to embrace and acquiesce in the last. Wherefore it remains only that we investigate the Mechanic reason of this effect. Which seems to depend first upon the disposition of the Fibres of the heart. For, we see that a crooked gut tied about with a thread, and not wholly filled with water, is by the weight of the water extended directly or in a straight line: but if the water be impelled toward either end by compression, than the gut becomes crooked again, as the nature of it exacts, and the other pendulous extremity will be erected, and strike against your hand held a little over it. This plainly follows from the curve figure of the membrane of the gut, which is longer in the convex part, and shorter in the concave. So in the left part of the Ventricle of the heart, the left wall is shorter, less fleshy, and less crooked, than the two walls that make the right Ventricle. Wherefore in the Systole of the heart, the Cone of it ought to be erected toward the left side of the breast, and to strike against it, more or less strongly, according to the degree of violence with which it is erected. This may be somewhat helped also partly by the erection of the heart lying obliquely, partly by the situation and disposition of the Fibres, which are wound about obliquely and spirally from the right side of the Basis of the heart toward the left side of the Cone; whence in the act of Pulsation, when the Fibres are shortened, the Cone may be a little distorted and erected by the fasciculus or combination of Fibres, forwards toward the left side, and so the Percussion may be made.  
Seneca (as ye may remember) in epist. 57 most elegantly describes, first the inevitable horror that invaded him while he was passing through the dust and darkness (a darkness so thick, as even to be seen) of the Crypta Neapolitana, now named the Grot of Pausilype, in the way between Naples and Putzole: and then the cheerfulness (he calls it alacritatem incogitatam & injussam) that returned to his mind upon the first sight of the restored light. The same surprising alacrity, methink, I now feel within myself, after my passage through the no less darkness, in which Nature had, through a long Series of ages, involved her great secret of the Motion of the Heart, made more obscure by the dust of men's various opinions; and my arriving at the light of knowledge, both what is the proper Action of the Heart, and by what Mechanic necessity that Action is performed.  
In the ardour of this alacrity, I proceed to the use, and action of the Ears of the Heart, and of its Valves.  
The end of the Vena Cava, which is conjoined to the heart, is (as hath been said before) in greater Animals, Musculose round about, that the trunk of it may be constringed as Sphincters are closed by virtue of their circular Fibres. But the end of the Vena Pulmonaris wants the like fulciment, and therefore cannot constringe itself. Then both these Veins end into the Musculose Ears, which are hollow, like little bags affixed to the sides of the heart; and whose structure much resembles that by which the left Ventricle of the heart is contexed in the hollow part of it. For the Ears also consist of fleshy Fibres intersecting each other like a St. Andrews Cross, which within are bound together into many little Cylindrical Columns, and trenches connecting the sides of the bags. To these Ears succeed three membranes in the right Ventricle, and two in the left; which are of a very strong contexture, of a triangular figure; the bases of which are closely affixed to the whole Circuit of the Tendon of the Orifice of the heart. Then the areae or middle spaces of these little membranes are branched within the Ventricles of the heart into many little Tendinose Strings or cords, which are fastened to the tops of the papillae or teats that stand pointing upwards, placed on the opposite side. Now this admirable structure being known, let us inquire the design or use of it.  
First the extreme part of the Vena Cava seems not to be made Musculose for strength, lest it should be broken by the current of the blood rushing in; but rather by its constriction to protrude the blood into the oblique Sinus of the right Ear, and to render the same turgid. Which action is helped by the peristaltic constriction of the whole trunk of the Vena Cava, and by the compression of the Muscles and Viscera of the whole body, as was yesterday demonstrated, when we considered the motion of the Blood. Hence it comes, that the blood impelled through the open aperture of the Ear, fills the cavity of it, and then runs into the right Ventricle: and by the like necessity the blood flows out of the Vena pulmonaris into the left Ear, and thence into the left Ventricle of the Heart.  
No sooner are the Ears filled and distended with blood, but they both at the same time constringe themselves, by a contractive and compressive action common to all Muscles, resembling that of a Press; in this order, that first by shutting their apertures they hinder the regress of the blood into the same Veins out of which it came in: then by the great force of compression they squeeze it into the Ventricles of the heart, until they be filled and made turgid. To this action of the Ears immediately succeeds the compression of the press of the Heart itself, by which the blood itself, by reason of its abundance, inflating and distending the triangular and mitral valves, exactly shuts the Orifices or mouths of the Veins, and so prevents its own recoiling into them. Whence it is of absolute necessity, that the same blood be expressed into the Pulmonary Artery or Vena Arterialis, and into the aorta. These are the Actions and Uses of the Ears and Valves of the heart, first discovered by our immortal Dr. Harvey, and since confirmed by various experiments of other excellent Anatomists. Being then certain of the Phaenomena, it remains only that we endeavour to explore the Mechanic causes of them.  
In the first place, because the Ears of the heart are Muscles, round, hollow, and composed of fleshy Fibres wound about Spirally, and intersecting each the other decussatim; and because they end into little columns and trenches, in the same manner as the left Ventricle is framed: therefore must they operate by the same Mechanic necessity, and Artifice, by which the heart operates, viz. by the force of a Press, and by wedges insinuated into the Pores of their Fibres, they must be swelled, and so constringed, and consequently express the blood contained in them.  
Secondly, That the constriction of these Ears, aught to precede the contraction of the Ventricles of the heart, though both motions seem to be performed at one time; may be thus demonstrated. For, if this be not true, then either the Ears, and Ventricles of the heart are constringed in one and the same moment of time, or the heart is first constringed and then the Ears. If the first, because the triangular valves have no use before the heart is constringed, nor after the constriction of it is complete, because the shutting of the Valves would be in vain, when the blood cannot flow back; and slow back it cannot before the heart is constringed, because then the blood is not yet in the Ventricles, and so cannot be impelled by the Systole of the heart; and after the constriction of the heart, the expulsate blood can much less flow back: therefore it is necessary, that at what time the Ventricles are constringed, at the same time the Venose orifices ought to be exactly shut by the Triangular Valves, that the blood may be impelled, not backwards but forwards into the Arteries. But if at that same time the Ears were constringed, they would inevitably vomit out the blood contained in them into the Ventricles, and so open the clausure made by the triangular Valves, because they are so disposed, as to be opened and dilated by the very coming of the blood. Wherefore at the same time the blood would be impelled by the Ear into the heart, and repelled by the heart: and so these two contrary motions would mutually destroy each the other, and both be in vain. Besides, when two outlets are at the same time open in one Ventricle of the heart, the whole compressive force of the heart is divided into two equal parts, which impel the two halfs of the blood, one backward, the other forward into the Arteries: and therefore Nature would foolishly by a double endeavour attain but half her end. We may add, that the triangular Valves would be wholly useless, since they would then (urgente necessitate) be open, when they ought to be shut: Wherefore it seems impossible, that the Ears of the heart, and its Ventricles should be constringed at the same time.  
But if we suppose the natural order to be inverted, i. e. that first the Ventricles of the heart are constringed, and then the Ears compressed; this would be much more absurd: for half of the blood contained in the Ventricle would flow back into the Ear on both sides open, and thence into the Vein.  
It must therefore be confessed, that the constriction of the Ear ought to precede, and then immediately ought the constriction of the Ventricle to succeed; and then all the operations proceed regularly and compendiously. For the Ear being compressed, first the regress of the blood into the Vein is hindered, next the blood is expressed out of the Ear into the cavity of the heart; Thirdly, the Orifice of the heart is shut by the constringed Ear; Fourthly, the Ventricle of the heart being filled with blood, and distended, the Membranes of the triangular Valves are expanded. These actions being in this order of succession done, then in the fifth place follows the swelling of the heart, by which all the blood in the Ventricles, which cannot, by reason of the double clausure, slow back, is forced to run forth by the open door of the Artery.  
Thirdly, it is observable, that the action of the right Ear differs from that of the left; because the blood ought to flow out of the Arteria Venosa or (as some call it) the Vena Pulmonaria, which is very ample, into the left Ventricle of the heart, with a swift current, by reason of its gravity, and of the compression of the Lungs. For this reason, a little Ear is sufficient to transmit the blood so swiftly running into the left Ventricle: and, with the help of the mitral Valves, also exactly to shut the aperture of the heart.  
On the contrary, in the right Ear, the slowness of the blood's influx ought to be compensated by the amplitude of the Canale. And moreover, because the right Ear ought not only to close the Orifice of the heart, but also to impel rapidly the slow paced blood into the right Ventricle: therefore Nature hath made the Muscle and cavity of the right Ear stronger and larger, than that of the left.  
Fourthly, We may farther gratify our curiosity, by considering the manner how the triangular Valves exactly shut the Orifices of the heart; which seems to be this. Because these Membranose Valves have their bases fastened to one part of the circular Tendon of the Orifice of the heart, as flags are fastened to their staves; and their other sides are by many Tendinose Filaments or strings fastened to the fleshy teats in the opposite part of the cavity of the Ventricle, as Webs of Linen exposed to the Sun are kept upon the stretch by many small cords tied on each side: Hence it comes, that by the stream of blood rushing in, the cavities of the Ventricles are dilated; and so these Membranose Valves, which before were lax, and flagged, are drawn and expanded transversly, so as to spread themselves through the whole space of the Orifice. Necessary it is therefore, that the points and sides of these Triangular Valves, thus drawn by the little cords decussated, should be conjoined, and being conjoined make one Conical superfice, greater than the plane of the Orifice, or of the circle of the basis of the same Cone. After this, follows the Systole of the heart, when the insides of the Walls of the Ventricles are united, and therefore those little cords of the Valves are at the same time relaxed, and united also: and so the faces of the Triangular Valves themselves must be united, and acquire a Sinuose or embowed figure, their Superfice not diminished, because their membranes are not contracted. Whence it comes, that the blood filling the Ventricle, doth by repelling the membranes, and inflating them, bow them, as the Sails of Ships swelled by the wind, are bowed into a hollowness. Again, since those membranes thus embowed are transferred toward the Tendinose Orifices of the heart, the round area of which they far exceed: therefore it is necessary, they should exactly shut those Orifices, before the Systole of the heart is complete. Wherefore it is also necessary, that the blood contained in the cavities of the Ventricles, should by the process and continuation of the constriction of the heart, until a total union of their walls be effected, be all expressed thence through the Arteriose Orifices, which are then open to give it free egress.  
Fifthly, If the clausure of the Ears did not precede, those little and thin Valves would not be able to resist that mighty violence, with which the blood compressed by the heart invades them, and otherwise would certainly break them: therefore to secure them, provident Nature hath put a fleshy fornix or Vault, viz. the constringed Ear; that she might with a double door shut the ample Orifice of the heart.  
Hence naturally arises this remarkable Corollary; that the action of the Ear is longer in time, than the Systole of the heart. For, the constriction of the Ear begins, while the heart doth not act; and ends in the same moment, in which the Systole of the heart is completed.  
Finally, It is worthy observation, that in the Arterial Orifices or outlets of the heart, there is no need of the like apparatus, to prevent the regress of the expulsed blood into the Ventricles. For after the exit of the blood, and after the greatest part of it is expulsed without the Capillary Arteries, it cannot be impelled back again; as well because it is not urged by the force of an Antagonist Muscle of equal strength with the heart, as because it is already expelled out of the extreme Arteries. Wherefore Valves of little strength are sufficient here, such as is proportionate to the force, which the not-intire fullness of the Arteries can make, which is very inconsiderable. And therefore the Semilunar Valves are far weaker, than those Triangular; but yet strong enough to hinder the regurgitation of the blood expulsed by the heart.  
Thus have we run through all the proper actions and offices or uses of all the parts of this incomparable Machine of the Heart, in their natural order; and found them all to be plainly Mechanic, i. e. necessarily consequent from the structure, conformation, situation, disposition, and motions of the parts, by which they are respectively performed.  
If the Mechanism hath been by us rightly explicated (as I am persuaded it hath) in the precedent discourse, no man has reason longer to believe, that the manner of the motion of the heart is a thing to human wit wholly impervestigable. Probable it is therefore, that when that excellent Anatomist, and our worthily honoured Colleague Dr. Lower said, 
Lib. de Cord cap. 2.  cum nimis arduum sit de ratione, quâ Cordis motus perficiatur, quicquam ritè concipere; atque Dei solius, qui secreta ejus rimatur, motum quoque cognoscere, praerogativa sit; in eo ulteriùs perscrutando operam non perdam: he was out of modesty willing to limit his own curiosity in that particular, but not to set bounds to the future disquisitions of other men. ¶ ⸫     

PRAELECTIO III. Of the Efficient Causes of the Pulsation of the Heart.  
DElighted with the Contemplation of the Structure of this Masterpiece of Nature the Heart, I have sometimes revolved the Books of the most Celebrated Authors, who have professedly written of Architecture, and of Hydraulic Engines; in search of some example of a Machine, that might be, at least in a few respects, compared with it. Of many that occurred, that which seemed to me to come nearest in similitude to this inimitable Prototype of Nature, was the Hydraulic Mint at Segovia, mentioned rather than described by that every way Noble Gent. Sir Kenelm Digby, in these words. This Engine, or rather multitude of several Engines, 
Treatise of Bodies, chap. 23.  to perform different Operations, all conducing to one work, is so artificially made, that one part of it distendeth an Ingot of Silver or Gold into that breadth and thickness, as is requisite to make Coin of: which being done, it delivereth the Plate it hath wrought, unto another, that prints the Figure of the Coin upon it, and from thence it is turned over to another, that cuts it according to the print, into due shape and weight. And lastly, the several pieces fall into a reserve, in another room, where the Officer, whose charge it is, finds treasure ready Coined, etc.  
For betwixt this Engine and the Heart, I fancied something of Similitude, at least in the few particulars following.  
First, As the design or end of the former, was to Coin money, which is the blood of all States, as well Monarchies as Republics, for the support of the Government: so the office and work of the latter is to stamp the character of Vitality upon the mass of blood, for the maintenance of life in all parts of the body, and regulation of the whole Animal oeconomy.  
Secondly, As the one is moved by a stream of Water, so is the other by a current of blood, as to its diastole at least.  
Thirdly, As the Artificial Engine was composed of many less Machine's, each of which performed its proper office by a distinct operation; yet all conspired to one common end: So the Natural, being also complex, consisteth of various smaller Machine's, viz. the Ears, Valves, Ventricles, Musculose flesh, Fibres of different orders, Chords, Columns, Papillae, etc. all which have their peculiar functions and motions; yet so combined, that they all cooperate to the Vital motion or heat of the blood, and diffusion of the same.  
Fourthly, By the Segovian Engine Ingots of Silver were distended to a breadth and thinness requisite to make money: by the heart and its Ears vehemently constringing themselves, and repeating their strokes, the Silver Chyle, or public revenue of the Animal, is attenuated, its viscid and grumose parts dissolved, the cruder parts concocted, and all by conquassation and compression so perfectly commixed with the blood, as to be fit to make good and current blood.  
Fifthly, From the Mint-engine the new stamped Coin was quickly transferred into a receptacle in another room, thence to be distributed, by orders of the Mintmaster: From the Heart is the new Coined blood instantly transmitted into the Arteries, to be distributed, according to the ordinance of Nature.  
Sixthly, As the various parts of the greater Engine were so situate, disposed, and connected, as that if any one of them were by chance displaced, broken, or hindered in its motion and action, presently all the rest must fail to proceed in their respective operations, and the work of making Coin cease: So in the much more subtle and mysterious Machine of the heart, if any the least part, though but the chord of a Valve, be broken, or arrested in its motions, all the rest will soon be at a stand, and the grand work of making the blood vital be at an end.  
Thus far, methought, the Parallel held fairly enough, and I was not ill pleased with the ramble of my imagination: but when I had attempted to carry on the resemblance a little farther, I soon discovered the disparities to be so many, and so great, that it was impossible to reconcile them into a just Analogy. Whereupon, condemning the extravagance of my fancy, I soberly concluded, that the Heart of an Animal is an Engine never to be imitated by human art: and I found myself more inclined to applaud the judgement of that prodigy of Mathematical knowledge, Archimedes of Syracuse, for never attempting to counterfeit the motions of the heart, than to admire his wit shown in making a Sphere of Glass (Athan. 
De Magn●te lib. 1.  Kircher denies that any part of it was Glass, but only the outside, that men might discern the wheels and motions within) which represented the perfect order and motions of the Celestial Bodies; and which Claudian describes in one of his Epigrams.  
Now if we desire clearly to understand this inimitable Excellency of the Machine of the Heart, and in what Proprieties of it the same doth chiefly consist; we shall be obliged well to consider two things, neither of which hath yet been explicated by us, and without a due explication of both which, all that we have hitherto said concerning the motion of the Heart, will be maimed and unsatisfactory. These are, the Mighty and incredible Motive force of the Heart, by which it expresseth the blood out of the Ventricles: and the Efficient Causes of its Motion. Things so worthy to be known, that I need not deprecate your impatience, most Candid and accomplished Auditors, if I detain you a few minutes longer, while I inquire into them.  
As to the FIRST therefore, viz.  

The admirable Motive force of the Heart.  
Since the round and Conical Figure of the Heart doth not permit us to attempt the measuring of its Motive power by the same way, by which the most Learned Alphonsus Borellus hath with singular sagacity measured the forces of very many other Muscles of Man's body, namely by weights suspended by them; and since therefore in this disquisition, we cannot from the effect proceed to the knowledge of the cause: we are compelled, from some other Sign to raise a probable conjecture, whence we may investigate the greatness of the effect. And this Sign shall be the Similitude and Analogy, which the Muscule of the heart seems to hold to other Muscles of the same Animal. Let us then with the same excellent Mathematician Borellus (in whose footsteps I now again tread) suppose, that all, even the least Fibres, or little Machine's of the same, or divers Muscules, in the same Animal, are equally strong, and exercise an equal motive force, in the same time, in the state of health. And because equal bulks of two Muscles contain equal multitudes of the least Fibres, it follows, that if we have foreknown the total motive power of one of the two equal Muscles, we shall be able thence to conjecture, what is the total power motive also of the other. Therefore the fleshy bulk of the heart being of almost equal magnitude to the bulks of one of the Temporal muscles, and of one of the Masseters; and Borellus having demonstrated to us the total motive force of those two muscles: we may probably infer, that the motive force of the heart is equal to that, which those two muscles shutting the mandible exercise.  
Now because no entire Fiber of these two muscles, is less than two inches long (taking all the Fibres one with another, that the excesses of the longer may compensate the defects of the shorter) and because in an inches space of every single Fiber, we may imagine more than twenty little Machine's, or Rhomboid Pores contained, like the links of a chain in a Watch, or the Meshes of a Net in a row one above another; let us notwithstanding suppose no more than ten smallest Fibres to be contained in that space: therefore in the length of every one of the Fibres that compose the said two Muscles, there will be contained more than twenty of those most minute Machine's. And since the weight of 150 pounds may be suspended by one single Stratum or Layer of these small Machine's of the same Muscles: therefore, that we may have the whole force that Nature exerciseth in those Muscles, the force of that one Layer, viz. that which is able to sustain 150 pounds, aught to be twenty times multiplied. Wherefore the whole force that Nature exercises, to dilate all the Rhomboid meshes or pores of the said two Muscles, when they act, is greater than the force of 3000 pound weight, and would, if applied to the opposite end of the beam of a balance, preponderate.  
If then every most minute Fiber of the Heart exerciseth, in the Systole of it, a force equal to that, which every Rhomboidal Machine of the Temporal, or Masseter muscle makes, when they act, as most certainly it doth, the motive power of all Fibres of the Muscles, in the same Animal, in the state of health, being equal; and if the multitude of least Fibres contained in those two Muscles, be equal to the multitude of most minute Fibres contained in the Muscle of the Heart, as the visible equality of their magnitudes warrants us to suppose it to be: we may thence deduce this conclusion, that the force, which all the most minute Fibres of the heart, when they are swelled, exercise to constringe the Ventricles, i. e. when they act all together, exceeds the force of 3000 pound weight, and would preponderate, if it were applied to the contrary end of the beam of a just balance. Quod erat demonstrandum. And thus have I given you a summary of what Borellus hath from a long chain of most ingeniose Propositions and Theorems in fine inferred. I come therefore to the.  
SECOND and last considerable proposed to be inquired, viz. the Efficient Causes of this so wonderful Motive force of the Heart. These seem to be no more than two: of which one is immediate, the other mediate.  
As to the the former, viz. the immediate cause of the heart's Motive Power; we are not to expect to learn, either what it is, or whence it proceeds, from the doctrine of the Ancients. For, they having observed, that the heart was not, as all the other Muscles of the body are, moved ad arbitrium voluntatis, at the command of the Will; not only named the motion of those Voluntary, and the motion of this Natural, as they had good reason to do; but also conceived and taught, the cause of the motion of the heart to be divers from the cause of the motion of the rest of the Muscles, and accordingly constituted and assigned to the heart a certain blind and unintelligible Pulsifick Faculty, whereto alone they ascribed as well the diastole, as the Systole thereof; which they had no just reason to do. To evince this their palpable error, I will assert this   

PROPOSITION, That the immediate Motive cause of the heart, is the very same with that, by which the Muscles of the Limbs are moved Voluntarily.  
First, it is most evident to sense, that the Muscle of the heart is composed of the same constituent parts with all other Muscles, viz. of bundles of carnose Fibres of the same Tendinose and Contrahible substance, of the same prismatic Figure, in the same manner disposed, Layer upon Layer, bound down by mutual contexture, in the same manner interspersed with branches of Nerves, fastened to Tendons, and enlivened by blood irrigating them out of the Arteries. In a word, there is no sensible difference or disparity, the Figure of the whole heart excepted; which yet doth not diversify the Organic nature of it, no more than the diversity of Figures among other Muscles, doth make them of a different nature. Then if we consider the action of both the Heart and all other Muscles, we shall find, that as well the Fibres of the heart, as those of all other Muscles act by contraction of themselves. If we descend to the immediate motive cause, and the Mechanic mode of their operating; from what we have already said, it is manifest, that it is as impossible for the heart to be inflated and moved by an incorporeal Faculty, or by Spirits, or by the blood alone however violently rushing into it, or by the same blood to what degree soever rarified in its Ventricles, or by a Fermentation, conflict, and displosion of Acid and Saline juices met together in the heart: as it is for the Muscles of the Limbs to be regularly moved by the same causes. It remains therefore, that as all other Muscles are moved by contraction of their Fibres, the Pores of them being filled and distended; so also it is most probable, that the proxime or immediate cause of the motion (I mean only the Constriction) of the Heart, is the dilatation or distension of the Pores of its Fibres, which causes their abbreviation or contraction, i. e. the Systole of the heart. But what the Mediate 'Cause is, by which the Pores of the Fibres are dilated to the abbreviation of the Fibres themselves, we shall after a few minutes inquire. In the mean time, I will lay down this other   

PROPOSITION, That the Mediate Cause of the Heart's Motion seems to differ from that, by which the Muscles of the Limbs are incited to Voluntary Motion.  
Since it is a truth known to all men, that we can move what Muscles we please of any Limb, and continue their Motion as long as we please, and stop it when we please: but the Motion of the Heart is not subject to the Empire of our Will, but, like that of a Mill, perpetual, whether we sleep or wake: and since even without our knowledge or perception, the heart, as agitated by a certain natural necessity, makes most vehement and almost momentany strokes or jerks alternately, short and Isochronical or equally temporaneous pauses interposed betwixt them; nor ever either much varies that constant Rhythm of its pulse, while we are in the state of health, or intermits the same during life: therefore certainly there must be somewhat of difference between the mediate cause of the hearts natural motion, on one part; and the mediate cause of the voluntary motion of all other Muscles, on the other. Besides, in an Egg, from the first days incubation of the hen, the punctum Saliens, and then the Vesicula pulsans exhibit to our sight this dance of life already begun, when we cannot conceive it to be possible, that there should be in that first rudiment of the foetus any sensation of good or evil, any will to pursue the good or avoid the evil; and when nothing of the brain is yet form. Nay more, in the heart of a Viper taken out of the body, and put into warm water, the Pulsation is observed to continue many hours, when by reason of the abscission of the Nerves, all commerce betwixt the Brain and the Heart being extinct, no sensation, or election can be imagined to ordain and command that motion. Wherefore we are obliged to confess, that the first and mediate cause of the heart's Pulsation is in some respect or other, divers from that whereby the other Muscles are incited to motion, at the command of the Will.  
But to explore wherein this nice difference may most probably consist, is a work of so great difficulty, that I wish it were possible for me to revoke the temerarious promise I made to attempt it: nor should I have courage enough to carry me so much as one step farther, if I did not derive it wholly from the well known Candour and benignity of my most Learned Auditors. For, the remaining part of my way, though short, is yet dark, and rocky, with Precipices on both sides: and all the light I can expect, must be from a few Sparks stricken out of my Flinty subject by the force of conjecture. If therefore I chance to stumble, or err; humanity will oblige you, rather to put forth your hands to support, or guide me, than to deride my blindness. In hope of this favour I will venture to proceed.  
Certain it is, that the first and mediate Cause of the Motion of the Heart, as well as that of the motion of the other Muscles, whatsoever it shall at length be found to be, is derived to it by the Nerves from the Brain. For, as if the Nerve inserted into any Muscle be strictly compressed by a Ligature, or cut off, the power of motion in that Muscle is presently intercepted, or totally destroyed; as common experience witnesseth: So if the Nerves of the Eighth conjugation be either strictly compressed by a Ligature round about, or cut off, in the neck of any Animal; there suddenly will ensue a visible change in the Motion of his Heart; witness the memorable experiment made by Dr. Lower, and recorded in his excellent Book the Cord, 
Cap. 2.  where he affirms, that the heart, which before reciprocated its Motions moderately and Rhythmically, presently after the Ligature had been made upon the said Nerves, began to palpitate and tremble, and by degrees grew more and more languid, till the poor creature died, which was within two days. Other experiments confirming the same thing, I might allege, if it were not universally acknowledged by Anatomists, that the Motive force of the heart depends upon some influence from the Brain. And among these, one of the most accurate affirms, that Nature made the Cerebellum as a Storehouse of Animal Spirits chiefly for the use of the Heart, that the Motion of it might be perpetually maintained: saying, Pro motu Cordis praestando tam sedula & sollicita fuit naetura, ut, 
Lowerus de Cord, cap. 2.  praeter Nervorum propagines ubique in illud densè distributas, pro continuo spirituum animalium influxu, Cerebellum insuper, quasi perenne corum promptuarium, ei accommodaverit. A cujus benigna & constant influentia adeò dependet, ut fi spirituum influxus vel minimo temporis momento impediatur, motus ejus illicò deficiat. But why have I recourse to the authority of men, when Nature herself, in her constant process of forming the parts of an Embryon, seems to teach us, that some influence (whatever it be) derived from the Brain to the Heart, is absolutely necessary to the incitement and perpetuation of the Motion of the Heart. For, the Brain is, in a great part, perfected before the heart; though those two Members, ob communem officii necessitudinem, be almost congenite. And I have good cause to believe, that the exordium of the Brain, is that Colliquamentum, which is first seen in an Egg after the first days Incubation of the Hen; and which, by the same warmth continued, doth in a short time concrete, and is condensed into a thicker substance, that is soon invested (as every viscid humour is wont to be) with a thin film or membrane, and shoots forth from itself little Nerves, as branches, every way. From the observation of which that incomparable man Sir George Ent doubted not publicly to declare himself to be of this opinion, 
Antidiatribae, pag. 7.  that not the Heart, but the Brain, is the fountain of life. His words are these, Cor enim▪ (uti arbitror) non est fons vitae (qui cerebro peculiaris est) sed rivulus dunta●at accessorius. Which yet is no new opinion, but ascribed by Galen to Erasistratus, 
Galen de Hippocr. & Platon. decret. lib. 7. cap. 3.  who said: Omnium, quae in corpore sunt, principium esse Cerebrum, apparet: and asserted by Hippon, whom Censorinus introduceth rightly teaching, Caput primò fieri. Now what can we with equal probability conceive to be the reason why Nature finishes the Brain before the Heart, as this I have here given, viz. because the Heart, even from the beginning, hath need of some influence to be transmitted from the Brain to it, for the incitement and continuation of its motion, as well as for the Nutrition of its substance? the latter of which benefits is common to the heart with all other parts of the body.  
Secondly, It is highly probable, that the Brain is, not only the Laboratory, but also the common Promptuary of the true Succus nutritius; and that the Nerves are the Canes, or Filtres through whose long and narrow Pores the same roscid Nutritive liquor is gently distributed to all parts, for their nourishment; both which Propositions have been formerly with many considerable arguments drawn as well from experiments Anatomical, as from reason, asserted by Sir George Ent, Dr. Glisson, and (if it be lawful for me to put myself into the same period with such excellent men) myself. This therefore being supposed, it is not unreasonable to think, that this roscid, balsamic and spirituose liquor, by many called Succus Nervosus, being for the most part in sufficient plenty in the Brain, doth at all times touch, and soak into the open Pores of all the Nerves thence elonged; but more copiously into the Nerves that extend themselves into the Fibrose substance of the Heart; because the Heart is furnished with many more and larger Nerves than any other Muscle of the whole body. And because the extremely narrow cavities of the Nerves are full of a spongy medullary substance, and continually wet with the same roscid liquor creeping through them: therefore the liquor cannot flow out of the lower ends of them, into the Fibres of the heart, otherwise than guttatim, drop after drop; as all liquors, chiefly such as have any thing of viscidity, slowly creep along the threads of Filtres, and when they at length arrive at the end, fall down in equal drops, with equal pauses betwixt the precedent and the succeeding drops. Farther, because the distillation of each drop is almost momentaneous, not persevering; thence it seems to come, that the constriction of the heart is performed and finished in a moment, and a pause succeeds in the next moment, till a second drop comes to cause a second constriction, and so forward. And since in the Brain, or fountain of this roscid liquor, there is always plenty to maintain a perpetual succession of drops; and the liquor itself is (in the state of health) always of the same temper and consistence, and the narrow Canales in the Nerves always equally retard its descent and efflux: therefore it seems necessary, that the times of quiet, or the pauses intervenient betwixt the drops, should be equal, so long as the liquor retains the same degree of fluxility, or is not hindered by greater violence.  
But if it happens, that the liquor is become either more thin and fluxible than is fit (as commonly it doth upon debauches with Wine or other strong drinks) or Saline, Acrimonious, Acid, or of any other vicious and irritating quality (as often it is vitiated in many maladies, chiefly in Scorbuto inveterato) or fall into a Fermentation (which I have reason to conjecture it always doth in Fevers, and more eminently in the Small Pox, the matter of which seems to be, not the blood, but the Succus nutritius in a peculiar manner corrupted, and critically transmitted from the Brain through the Nerves into the habit of the body) or be agitated by any swift motion (as in the more violent passions of the mind, and chiefly in anger, it is) in all these cases the motion and distilling of it into the Fibres of the heart must be accelerated proportionately, and consequently the Systoles of the heart will be more frequently repeated, and the pauses intercedent betwixt them will be, as those intervenient betwixt the drops, shorter. And here a fair occasion offers itself to me of expatiating into the various and numerose differences of Pulses of the heart, and endeavouring to solve them rationally by this Hypothesis, which alone is capable to do it: but the shortness of the time appointed for my sitting in this place, forbids me to make use of the occasion.  
Of this Stillicidium or guttulation of the Succus Nervosus out of the ends of the Cardiac nerves, we have various familiar examples. We see, that Sponges, Filtres, and even Glass tubes of very small bores, though they be continually replete with water or any other liquor; yet the liquor doth not flow out of their lower ends or orifices, in a continued course, as water gushes out of a fountain, or out of the cock of a Cistern; but by drops, with aequitemporaneous stops or pauses betwixt the drops. The true cause of which effect seems to be this; the great narrowness of the Canales, which impedes the free permeation of the liquor, the little particles, or moleculae of the liquor being not exactly smooth, but villose and viscose: and therefore they are forced to creep along with a slow pace through the cavities of the tubes, whose superfices within are equally full of little asperities too; so that they must, as they pass along, be put into a vertiginose motion, and interrupt their course, and consequently fall out of the lower end of the Sponge, Filtre, or Tube guttatim. Now since the Nerves are, like Indian Canes, composed of Filaments running their whole length in direct lines, a medullary and spongy substance, and many little interstices interjacent betwixt the Filaments, with a thin coat investing them; and since the superfices of their little Canales within, must therefore be full of small asperities: it is necessary, that the Succus Nervosus, whose consistence is not much thinner than the white of an Egg well beaten, should pass through them with a slow and interrupted course, and at length fall out of their lower ends in drops, with equal pauses between the drops. Where we find a parility of Causes, we may rightly expect a similitude of effects.  
Here I see two formidable Difficulties standing, like Romantic Giants, in my way, to deter me from proceeding: and I cannot, without shame and infamy, decline to encounter them.  
One is, That after the Cardiac Nerves are cut off, and the heart itself taken out of the body, the Pulsation of it continues for some time. To remove this therefore, I say, that the cavities of the Nerves annexed to the heart may remain still full of, and turgid with the roscid Succus Nervosus, which being hindered from regress by their spontaneous contraction toward the heart, and kept in a state of fluxility by the yet lasting warmth of the heart, may for some time be instilled into the Fibres of it, and by swelling of them cause them to constringe the Ventricles, as before. Then the heart being irritated by the prick of a needle, or some sharp and pungent liquor, may be able, by its peristaltic constriction to squeeze out the few remaining drops of the roscid liquor. Which being done, the Pulsation ceaseth for ever. To the blood, this effect ought not to be ascribed; for after all relics of it have been, with warm water and a Syringe, washed out of the Ventricles, and squeezed out of the Vessels; the Pulsation notwithstanding will continue for sometime: Nor can it be with more reason ascribed to Convulsions of the heart; because all convulsions are disorderly, and unequal both in the times of their girds, and in those of their intermissions: whereas in this case the Pulsations are regular, and isochronical, with equal pauses. Nor to the Heat communicated by the blood to the heart before it was exsected, and not yet quite extinct; because that borrowed heat soon vanishes, and no external heat will revive the languishing Pulsation, after all the roscid juice hath been expressed out of the ends of the Nerves left in the heart. Nothing then remains to solve this Phaenomenon, but the instillation of a few drops of our roscid liquor into the Fibres of the heart, to swell them, and so urge them to constriction of the Ventricles.  
The other Difficulty is this. Why is there not a Pulsation after the same manner also in all the Muscles of the Limbs; since their Fibres are of the same nature in all things, their disposition and direction only excepted; since the Orifices of the Nerves pertaining to them, are in the Brain as open to admit and imbibe the Succus Nervosus there elaborate and provided for them; and since the same Nerves are equally spongy and permeable in their constitution, and so apt to transfer that liquor, as the Orifices of the Cardiac Nerves are to receive, or their Canales to transfer it? If the whole apparatus be the same on both parts, whence comes it, that the same effect is not produced in both?  
At this Goliath I have in my Scrip three Pebbles to throw; and though my arm be weak, I will not despair of hitting him in the forehead. First therefore I say, that it is not yet certainly known to any mortal man, by what mediate cause the Muscles of the Limbs are moved at the command of the Will; whether by simple contraction of the Originals of the Nerves inserted into them, or by the immission of the Succus Nervosus more copiosely and swiftly at the time of their being put into action: though the Mechanism of their Fibres make it more probable, that they are moved by immission of some liquor from the Brain, by which the rhomboid meshes or pores of their Fibres being all at the same time swelled and dilated, a contraction of the whole Muscle must in the same moment be effected; and therefore I prefer this opinion to the former, and have followed it in many places of this rude Discourse. But yet this opinion hath not led me to a discovery of the Cause of the difference, this present difficulty compels me to hunt after. Should I imagine Valves affixed by Nature to the Orifices of the Nerves of the Muscles, as Mons▪ Des Cartes did in the bodies of them; though such an artifice be not impossible, yet, beside that no such Valves have hitherto been found in the Brain, I should still be to seek for a Cause to open and shut them ad arbitrium voluntatis, and so should be put to a stand in my disquisition. Which to avoid, some other Organical contrivement, such as may be not only possible, but probable also, and facile, and fit to untie this Gordian knot, must be excogitated. Let it then be supposed, that in the Brain the Orifices of the Nerves thence elonged to the Muscles of the Limbs, and their Canales are in such a peculiar manner form, as at no time to take in and convey into the Muscles, more of the roscid liquor than what is sufficient to nourish them, and recruit their vigour; unless when, at the command of the Will, under whose jurisdiction they properly are, the Nerves being twitched up or convelled at their Originals, both their Orifices are dilated to receive, and their Canales rendered more pervious to transmit, in a moment, into the Fibres of the Muscles to be used, a greater portion of the same invigorating liquor, viz. so much as is requisite to swell them up, by replenishing their pores, and force them to contraction, which is the common action of all Muscles. On the other part, let it be supposed, that in the Brain Nature hath framed the Originals of the Cardiac Nerves by a different Artifice, namely such, as that not only their Orifices may always be open to imbibe, but also their Canales so easily pervious to transmit the roscid liquor, as that without any Vellication, without any Convulsive motion, the same liquor may, merely by the plenitude of the Canales themselves, be effused guttulatim into the Fibres of the heart, to cause the alternate constriction or Pulsation of it. And it is the more lawful for me to suppose this difference of structure in Nerves ordained for different uses; because it is above all doubt, that the Optic Nerves have a peculiar fabric and contexture, wherein they differ from the Auditory, and all other Nerves inservient to the rest of the external senses; and that the Organ of every sense hath its nerve of a peculiar constitution, accommodate to the nature of its proper object: though those differences consist in such minute and subtle artifices, as have hitherto eluded our most curiose researches, though assisted by the best sort of Microscopes. Why then may it not be thought, that Nature hath given to the Cardiac Nerves also a constitution divers from that of all other nerves: especially when their Function and office is different from that of all other nerves, and no less than the Pulsation of the heart, i. e. the conservation of life itself depends upon that difference? I am not, I confess, so happy, as certainly to know in what singular Artifice the difference doth consist: but am notwithstanding fully convinced, there is some difference. And if so, why may not the difference consist in such an Artifice, as that which I have here supposed and described; since the same is not only possible, but facile also, and sufficient to produce the effect required, viz. the perpetual instillation of the roscid liquor drop after drop into the Fibres of the heart? If this be granted, the mighty Difficulty is solved. If not, I say  
Secondly, That the multitude of Nerves elonged from the Brain to the Heart ought to be considered. What reason can we imagine Nature to have had, when she furnished the Heart with so many nerves more than are inserted into any two, nay three Muscles even of the first rate? Certainly she did it, either for the more exquisite Sense, or for the more copious nourishment, or for the stronger motion of the heart; for no fourth cause can be found. The first is improbable; because it doth not appear, that the Heart excels any other Muscle in the sense of touching or feeling: and because there seems to be no necessity of its being endowed with much of sense, whether we respect the action of it, which is not perception, but Pulsation, and that too with incredible violence, such as is inconsistent with delicate and exquisite sense; or whether we reflect upon the secure Situation of it, which is in the Centre of the cavity of the Thorax, where it hangs free and defended on all sides from harm and offence, either from within, or from without. The Second also is improbable; because the bulk of the heart holds no just proportion to the multitude of nerves inserted into it; and there are many Muscles of far greater magnitude, which yet are plentifully supplied with nourishment by much fewer nerves. The third therefore is true: and by consequence serves to disentangle our Hypothesis from the chords of the Difficulty proposed. For, so great a number of nerves importing into the Heart much more of the nutritive liquor, than can be thought necessary for its nourishment; of what use can the overplus be, unless to maintain the perpetual motion of it? And in this also there is a manifest difference betwixt the Heart and all other Muscles; and such a difference, as may be brought for one reason, why no other Muscle but the Heart hath a Pulsation.  
Thirdly, I say, that the aptitude of the Heart to Pulsation doth consist in its proper Fabric and conformation, in its Conical Figure, in its cavities within, in the disposition and configuration of its Fibres, in a word, in its whole Mechanism, which I have formerly described, and which is far different from the Mechanism of any other Muscle whatsoever. So that if there were no singular Artifice or knack in the structure of the Cardiac Nerves, or if these nerves were fewer in number: yet might the heart be apt for Pulsation, of which all other muscles are incapable, as wanting the like Mechanic conformation. No wonder then, if Pulsation be proper to the heart only, though the Fibres of all other Muscles be of the same nature with the Fibres of the Heart; though the Efficient Causes of the Motion of all other Muscles be the same with those of the Motion of the Heart; and though they, as well as the heart, act by the contraction of their Fibres. Now if no one of the three Reasons here by me alleged, why the motion of Pulsation is not common to all the rest of the Muscles taken single, be thought sufficient: yet if ye please to conjoin and twist them all together into a triple chord, ye may then perhaps find them strong enough to pluck up the proposed Difficulty by the roots.  
But hold, a minute or two. Have I not, through haste, or want of due circumspection, run myself into the Briers of a contradiction? Did I not, in my last Proposition, affirm, that the Mediate Cause of the natural Motion of the Heart differs, in some respect, from that by which all the rest of the Muscles are incited and invigorated to voluntary motion? and have I not, in the Paragraph immediately preceding this, said, that the Mediate cause both of the Motion of the Heart, and of the Motion of all other Muscles, is one and the same, viz. the Succus Nervosus derived from the Brain? Where then is the difference presumed? I answer therefore; that the difference lies not in any change or alteration of the nature and qualities of the Succus Nervosus itself, which I grant to be the same utrobique, on both parts: but only in the divers Modes of its effusion from the Brain. Into the heart, I suppose it to descend through the Cardiac nerves, gently, slowly, and by way of instillation, drop after drop: but into the rest of the Muscles, I suppose the same to be immitted with great force and velocity, swift as Lightning, at the command of the Will. And this seems to be sufficient, to constitute a difference, where the same cause, used by Nature diversimodè, and in Organs of different conformation, produceth so different effects: and consequently to extricate me from the Briers. ¶ ⸫  
From which as well as from the former impediments, being now at length free; I come in the next place, to establish the grand Pillar, upon which the whole weight of this my rude structure relies: that is, to make it appear to be not only possible, but also probable, that a few little drops of liquor instilled into the Fibres of the heart, should only by causing them to swell, or by dilating their Pores, abbreviate them with a force great enough to make a constriction of the heart. This if I shall be able to do, I shall not despair of finishing my Building as I at first designed: for the remaining part of my work will be little and easy.  
As for the Possibility of so great an effect from a cause that seems to be so weak and inconsiderable; that may be without much difficulty proved from the just Analogy or similitude of this effect to many other as great, if not greater effects commonly observed to arise from the like Causes: For, Mechanic Examples of this kind are every where so obvious to sense, and so numerose, that only to enumerate them would be a task hard and tediose. Out of so vast a multitude therefore, I will, for brevity's sake, select only two, such as are not only pertinent and adequate to my subject, but also in themselves eminently remarkable.  
The First is of a new Cable, which upon wetting will very much swell or become thicker, shrink, and shorten itself, beyond the belief of any but a Mariner. And Galilaeus hath well observed this swelling, and the consequent abbreviation of a Cable, to be of so great efficacy, that the violence of a Tempest, the weight and jerks of a loaden ship of 1000 Tuns burden, and the current of the Sea, cannot by their united forces extend the Cable to its former length. This ye will confess to be admirable, that a little water insinuating itself into the Pores of the threads, of which the Cable is composed, should dilate those little and indiscernible Pores with such prodigious force, as not only to swell the close and hard twisted Cable, but to countervail, nay exceed the aggregate of the forces of a furious wind, a strong current of the Sea, and the weight of so great a Ship with its whole Fraight. Yet common experience testifies this to be true.  
The Second Example will perhaps raise your admiration to a higher degree, being of all of this kind that hitherto I have ever read or heard of, the most memorable. It is this: In Rome there stands at this day an Obelisk of one solid stone, a kind of Ophite or spotted Marble, anciently consecrated to the honour of the great julius Caesar, and erected in the Cirque of Nero: but in the Year of Our Lord 1586. removed into a more eminent place, at the vast charge of Pope Sixtus Quintus, and by the admirable skill of Dominicus Fontanus, an excellent Architect and Engineer. This stone is in height 170 feet, above the base; in breadth, at the bottom, 12 feet, and at the top 8, in weight 9586148 pounds: and the weight of the Cables, Chords, Pulleys, and other movable instruments used in raising it, amounted to 1042824 pounds, according to the computation of Georgius Draudius. 
Adnotation. ad. Solini memorabilia, part. 1. fol. 131.  The removing and erection of this Obelisk was thought to be so rare a work of Art, that the Engineer, beside the great mass of treasure he received for a reward from his Holiness, thereby acquired to himself immortal renown; no less than 56 Learned men having since profestly written, to describe his Machine's then used, and to celebrate his praises; as Monantholius relates. 
Comment. in Aristot. Mechanic. cap. 19  But all their praises notwithstanding, he owed no small part of his honour to Fortune, or rather to a Carter, that stood by, an idle Spectator. For the Engineer, a little mistaken in his forecast of the stretching of the Cables and Ropes, found, when he came to set the erected Obelisk upon the Pedestal, that he had not raised it high enough by 2 or 3 inches, and to raise it higher with those Machine's so stretched, was impossible. Confounded with shame and despair by this unforeseen faileur, he begun to meditate flight, to save his life, which he had pawned to the Pope to be forfeited, if he did not accomplish the difficult work he had undertaken: when, as good luck would have it, out of the crowd of vulgar gazers comes a Carter, and advises him to cause all his Cables and Ropes to be wet with water. Which done, the Ropes quickly swelled and shortened themselves so, that they lifted up the Column to a due height: and then the overjoyed Fontanus with ease placed it upon the Pedestal. Now if ye shall be pleased to reflect upon this Example, and to consider, that a little water, only by dilating the Pores of the threads of the Cables and Ropes, swelled and shortened them with force great enough to overcome the immense gravity both of the Obelisk, and of themselves, with the rest of the Mechanic apparatus then used; which gravity hath been computed to your hands: I am confident, you will no longer think it impossible for a few little drops of liquor diffused through the Fibres of the Heart, and like wedges dilating their little Meshes or Pores, so to swell and abbreviate them, as to cause a constriction of the Ventricles, and that too with a force (if Borellus his estimate be right) exceeding the force of 3000 pounds' weight.  
And as for the Probability of this proposition; that cannot be obscure to any man of common sense, who shall consider, first, the near similitude that is between the threads of a chord, and the Fibres of the heart, in Figure, in tenacity and strength, in aptness to swell, and consequently to shorten themselves upon humectation, and in the faculty of restoring themselves to their natural tone after extension: and then the little or no difference betwixt water and the Succus Nervosus, as to the power of insinuating into, and dilating the Pores of bodies naturally apt to swell and shrink. For, since the two Agents, viz. water and the Succus Nervosus, are so alike in their efficacy, as to the dilatation of the Pores of Tensile bodies; and since the two Patients also, viz. the threads of a chord, and the Fibres of the heart, have so full a resemblance in their nature: it is highly probable, if not necessary, that like effects should be produced by them. And this probability is the greater, because of all other Efficient Causes hitherto excogitated by Learned men, to solve the grand Phaenomenon of the Pulsation of the Heart, none can be given, which is either so intelligible, or so congruous to the whole Mechanism of the Heart, as this which I have in this Lecture endeavoured to assert.  
But this Chair doth not make me a Judge. To hear and determine, Most Excellent Precedent, and my most Learned Colleagues, is your right; which I ought not to usurp. I will therefore first (to ease your memory) reduce into few words the heads of what I have delivered, concerning the Efficient Causes of the Motion of the Heart; and then humbly, and without reserve, submit all parts of my Disquisition (for I pretend not to know, but only to inquire truth) to your examen and judgement.  
The sum of the Precedent Hypothesis is this▪ I suppose (First) That the immediate Efficient of the Pulsation or Constriction of the Heart, is the abbreviation of the Fibres of it, arising from the dilatation or expansion of their Pores or little meshes. (Secondly,) That the Mediate Efficient, is the Succus Nervosus, derived from the Brain, through the Cardiac Nerves; which being instilled into, and diffused through the Fibres of the heart, fills and dilates their Pores, and by necessary consequence abbreviates them, with force sufficient to make the Systole or constriction of the Ventricles, and to express the blood contained in them. (Thirdly,) That the short quiets or pauses interceding betwixt the Systoles of the heart, arise from equal pauses or intermissions betwixt the drops of the Succus Nervosus instilled into, and swelling the Fibres of the Heart: and that as the times of the droppings are equal among themselves, so are also the Systoles of the Heart isochronic or aequitemporaneous. (Fourthly,) That the motion and guttulation of the Succus Nervosus into the Fibres of the Heart, being accelerated or retarded, by whatsoever causes; the Systoles of the Heart must be more or less frequent proportionately thereto.  
Which things, if ye now at length shall judge to be consentaneous to right reason, agreeable to the Animal Oeconomy, congruous to the Organical structure of the Heart (to all which I have been careful to adjust them) and in fine consistent among themselves: then I shall with assurance conclude, that the Heart is, as all Automata are, moved by Mechanic necessity. Which is, what I proposed to demonstrate, even without that incredible displosion of Saline and Acid spirits in the Heart, first imagined by Doctor Willis, and since asserted by a man of much greater Erudition, and more solid judgement, namely Alphonsus Borellus; as necessary to be supposed, in order to the Solution of this great Problem of the Pulsation of the Heart, and that of the motion of the rest of the Muscles. Which pretty conceit, I will first revive in your memory, by reciting a few of Borellus' own words faithfully; and then offer to your consideration the reasons that have induced me to reject it. Restat igitur, saith he, quòd sicut omnes musculi contrahuntur, inflatis vesiculis eorum pororum; sic quoque immediata causa tensionis Cordis, erit inflatio vesicularum pororum ejus, facta à fermentativa ebullitione tartarearum partium sanguinis à succo spirituoso ex orificiis nervorum instillato, etc.  
The Reasons that dissuade me from assenting to so great a man, in this matter, are these:  
First, We have the testimony even of our sight (the most certain of all our senses) that in an Egg, after a day or two's incubation of the Hen, the Punctum saliens first, and then the Vesicula pulsans are agitated by a manifest Pulsation, in the Centre of the Colliquamentum or genital humour, which is a pure and homogeneous liquor; even before any the least sign of blood can be discerned. Here therefore the supposed immediate cause of the Heart's motion, viz. an inflation from a Fermentative ebullition of the Tartarous parts of the blood, meeting and conflicting with the spirituose juice instilled out of the Nerves into the Heart, certainly can have no place. For at that time, in the Egg, neither Heart, nor Brain, nor Nerves are yet form, nor is any part of the Colliquamentum converted into blood: & causarum in rerum natura nondum existentium, nulli dantur effectus. Beside, the same Vesicula pulsans is from the beginning of the change of the genital liquor into blood, not only the Conceptacle of it, but also the Engine that gives it motion; and therefore the new made blood can contribute nothing toward the Pulsation thereof.  
Secondly, If not only the natural motion of the Heart, but also the Voluntary motion of the rest of the Muscles, proceed from an explosion of mutually hostile spirits concurring and combating in them, as Borellus affirms: why have not all other Muscles, as well as the heart, a perpetual Pulsation in them; when the same blood, and the same Succus Spirituosus perpetually concur in them, no less than in the heart? And what dominion could the Soul have over the Muscles of the Limbs, to exercise which of them she pleases, and as long as she pleases, and give them rest when she pleases; if they were agitated every moment by Squibbs or Crackers breaking within them? certainly she could never moderate such violent and tumultuose explosions. Besides, it is wonderful strange, if those explosions be made in a Muscle, when it acts, that we should never perceive it to be distended or heaved up outwardly; but that on the contrary, we should plainly perceive, the Muscles, in all voluntary motion, to be strongly constringed inwardly, to be minorated, and become harder; which is a certain indicium, that they are moved in a manner quite contrary to inflation.  
Thirdly, Such an explosion made in the heart, might indeed cause the Diastole of it, by inflating and distending the Ventricles: but would hinder the Systole or constriction of them inwardly, which is requisite to the expression of the blood. For, the supposed explosion consisting, like that of aurum fulminans, or Gunpowder, in a motion expansive; would of necessity dilate the cavities of the heart.  
Fourthly, If an explosion of Acid and Saline liquors meeting, commixed, and warring in the heart, be the immediate efficient of its motion; it is consentaneous to infer, that where the ingredients of this explosive mixture are more copiose, there the explosions ought to be more frequent; & è contra. But in sucking infants, who being nourished only with milk, cannot reasonably be thought to have much, if any thing of Acidity in the nutritive juice, or of saltness in their blood, the Pulse of the heart is notwithstanding, even in the state of health, at least doubly quicker or more frequent, than in full grown men, nay such who delight to feed on salt meats, and drink plentifully French and other subacid Wines. Ergo, 'tis highly improbable, that the Pulse of the heart should be the effect of such explosion.  
These are the reasons that moved me, when I came to this instable bog, to withdraw my judgement from the conduct of Borellus, whom before I had so closely followed; and to divert into a private way, which seemed to promise me smother and firmer sooting; and which notwithstanding I will not commend to others, unless your approbation shall encourage me to pave it. Meanwhile, the hourglass admonishing me to reserve, till I meet with some other opportunity, what may be farther alleged to confirm the precedent explication of the Efficient Causes of the Systole of the Heart; I will now add no more than three short Advertisements, and resign you up to the more profitable, and more pleasant entertainment of your own better thoughts.  
The First is, that is probable, that in every Diastole of the heart, the few and little drops of the Succus Nervosus, which by wedging themselves into the small Rhomboid Pores or meshes of the Fibres of the Heart, and so dilating them, caused the immediately precedent Systole; are by the restitutive motion of the same Fibres, squeezed out of those Pores into the Parenchyma of the Heart, whence they are absorbed and carried off with the blood by the Veins; and so make room for the next succeeding drops, to cause the next Systole, and so the Systoles and Diastoles of the heart come to be alternately repeated, and the Circulation of the blood to be perpetuated. This, I say, is probable; because Nature hath instituted the like absorption of the redundant Succus Nervosus by Veins in many other parts of the body; more eminently in the upper part of the neck, where the jugular Veins imbibe whatever humour distils from the bottom of the Brain, 
Lib. de Cord cap. 6. ubi de Catarrhis agit.  as Doctor Lower expressly affirms, and with good reason; in these words, Humour omnis è cerebro proveniens in venas jugulares resorbetur. I had heretofore, I confess, a thought, that the humour contained in the Pericardium might have no other fountain but the relics of the Succus Nervosus expressed out of the Fibres of the Heart in the Diastoles, when after violent Tension they exercise their natural faculty of restitution: But when I had seen, that the liquor found in the Pericardium is easily capable of coagulation either by heat or cold, so as to become like jelly of hartshorn, or the white of an Egg hardened by boiling, as the Serum of the blood will do; and observed the various little Glands seated about the Basis of the Heart, for which I could find no other equally probable use, as to instil the Serum into the Pericardium, to facilitate the motion of the heart, which most certainly that liquor doth; as the humour instilled out of the glandulae lacrymales upon the outsides of the eyes, serves to moisten and make them more easily movable every way: when I had, I say, observed and considered these things, I rejected that thought, and embraced this, of the absorption of the relics of the Succus Nervosus by the Veins of the heart.  
The Second is, that the Diastole of the Heart, is caused partly by the Relaxation of the Fibres of it spontaneously restoring themselves to their natural posture and length, as all other Tensile bodies are wont to do, after they have been distended: partly by the force of the blood rushing out of the Ears into the Ventricles of the Heart, and replenishing them. Wherefore the Wisdom of Nature is admirable also in this, that she ordained these Two Causes of the diastole, viz. the relaxation of the Fibres, and the influx of the blood into the Ventricles, to be exactly coincident, that with united forces they might cooperate more efficaciously. Whence it appears, that in the diastole, the Heart is not wholly Passive, as all Anatomists hitherto have believed it to be. For, unless the Fibres did restore themselves to their former longitude, which is a natural action, at the same time the influx of the blood happens; certainly there could be no room to receive the blood, because the insides of the Ventricles would continue to touch each the other, and so there could be no diastole.  
The Third and last is, that it appears from the whole Series of this discourse, that the Pulsation or Constriction of the Heart hath its force from that Mechanic power, which is called the Wedge: and that the blood is expressed out of the Heart by virtue of another Mechanic power, which is named the Praelum or Press: and consequently that the Heart itself is, as all Automata are, moved, not by Spirits, nor by a Pulsifick faculty, nor by rarefaction of the blood, nor Ebullition or Fermentation of the blood, nor by explosion of Saline and Acid spirituose liquors, but by Mechanic necessity. Which from the beginning I hoped I should be able fairly to prove.  
If the success of my endeavours hath not been answerable to that hope; I will not go about to extenuate the blame of my faileur, by citing examples of much greater Wits, which have before me in vain attempted to reveal the same secret of Nature: but consolate myself with this, that my judges are men no less beloved for their exemplary candour and humanity, than honoured for their excellency in all kind of Learning; and who need not be put in mind, That Truth is a tree, whose root is in Heaven, and of which even the wisest of us dim-sighted Mortals here upon earth see nothing but the shadow of its branches. I will therefore conclude this inelaborate Disquisition with that memorable saying of the Prince of Roman Orators; 
Cicero in Consolation.  De his statuat unusquisque ut libet. Quid autem verius sit, Deus ipse viderit: hominem quidem scire arbitror neminem. ¶ ⸫  
MY Lectures, such as they are, much Honoured Auditors, Ye have with obliging patience heard. Be pleased, I beseech ye, to hear also, before ye rise, a word which I have to speak in my own defence. Were it not indecent to compare small things with great, I should venture perhaps to advertise you, that the reasons which induced me to attempt a reformation of the Borellian Hypothesis of the Motion of the Heart, which Doctor Harvey himself called the Sun of the Microcosm; 
In epist. dedicat. lib. de mo●u sanguine.  seem to have some kind of Analogy to those, which moved the Prince of Astronomers, Tycho Brahe, to dislike the Ptolemaic System of the Macrocosm or greater World, and to excogitate a new one of more probability and neatness. For, as Tycho animadverting, that the Celestial Orbs had been by Ptolemy distributed unhansomly; that so many, and so great Epicycles were in vain imagined, to explicate the retrogradations of the Planets, and their various respects to the Sun; and that the equality of the Circular motion was measured, not from the Centre of its proper Circle (as it ought) but from the Centre of another Eccentric Circle, against the first principles of Nature and Art: invented a new System exempt from all these incommodities, which is in truth the Copernican inverted. So I conceiving, that in the Borellian Hypothesis, and Explosion of I know not what Saline and Acid materials in the Heart, was not only in itself extremely improbable, and incongruous to the Wisdom of Nature (which always constitutes certain and regular Causes to produce certain and regular Effects) but also unnecessarily supposed to solve the Phaenomenon of the Heart's Pulsation: set my dull Brain on work to reform it, and soon invented another, that seems both free from those inconveniences, and more agreeable to the Organical Structure of the Heart, to which above all things it was requisite I should endeavour to adjust it. This I thought myself obliged to signify, lest any here should believe, either that I have usurped to myself this whole System of the Motion of the Heart, from that most excellent Mathematician Alphonsus Borellus, whose Memory I highly honour; or that I lay claim to more than a Candid attempt to reform it. ¶ ⸫    

 
  

EPILOGUS.  
PRAELECTIONUM quidem vela jam tandem contraxi; nondum tamen dissolutam video concionem. Resistamus igitur hîc parumper, Auditores Ornatissim●, si vobis ita videatur; & ad stupendam illam, cujus rationem Mechanicam hactenus tam anxiè inquisivimus, Cordis fabricam seriò respiciamus. Ind enim, etiamsi alia omnia in universitate rerum deessent Divinae Architecturae documenta, cuivis hominum pronum est inferre, & quam sit immensa illius, caeterorumque omnium in hoc Mundo adspect abilium CONDITORIS solertia; quámque parum ab immedicabili cum animi tum mentis stupiditate olim abfuerit Epicurus. Qui Animalia casu quodam, in prima rerum procreatione, genita fuisse vecorditer censuit: & opinatus est consequenter, totam in iis membrorum varietatem dearticulationemque non aliunde, quam ex Atomorum fortè fortuna, post infinitos inter se in spatio infinito vortices, ita concurrentium, atque commistarum dispositione extitisse. Quamobrem neque ullam fuisse intelligentis Naturae prudentiam, quae ossa, cerebrum, cor, nervos, venas; quae oculos, manus, pedes, viscera; quae caetera omnia conformans, ad fines certos, seu functiones partibus congruas respexerit: sed singulas partes ita delineatas, co-adunatasque fuisse quadam materiae necessitate (talibus nempe, ac tali modo concurrentibus Atomis) ut si nullius deinde usûs futurae participes fuissent. O ridiculum subtilissimi caeteroquin Philosophi stuporem!  
Pudendum profectò, si contemplans palatium, quod sit fundamento securum, tecto concinnum, parietum symmetriâ congruum, exteriore formâ decorum, interiore commodum, fenestrarum constitutione salubre simul, & illustre; cunctis denique partibus absolutum, & elegans; dicere non a●des, Epicure, fortuna exstructum, sed arte, & consilio: intuens verò Hominis corpus, in quo omnia neque exquisitiùs formari, neque congruentiùs collocari, neque utiliùs destinari, neque speciosiùs exornari quacunque tandem arte potuissent; causam illius coecam reputas, expertemque consilii? An non, cum oporteat de causa ratiocinari ex effectu, ejusque conditionibus; colligamus necesse est, ex scitissimo opificio scientissimum Opificem; & ex usibus partium tam appositis, causam ad illos destinantem intelligentissimam inferamus? Ac sunto fortunae suae interdum vices; non tamen, si pictoris spongia in tabulam temerè impacta, equi spumam semel expressit, ideo quotquot vides pictas tabulas, consimili casu sunt elaboratae. Et nisi id sit, quâ fronte id dicis de Naturae operibus, quae tam perfectè, tam constanter, non pinguntur, sed animantur? Nempe Zeuxis, aut Polycletus habetur tibi valdè peritus, cum aliquod Naturae opus imitatus adumbratione, superficieque tenus fuerit: & DEUM, Parentémve Naturam, seu quocunque nomine dicas Architectricem illam causam, ignorasse putas quidnam ageret, cum internam, vivam, veramque ac inimitabilem molita fuerit constructionem? Obstupescis Myrmecidas opusculorum fabricatores, nec potes illum satis mirari, qui pulicis corpusculum scitè repraesentaverit: & te tamen in admirationem non rapit ea causa, quae animalculum tantulum tantâ energiâ donârit; quae innumera organa in tam exigua materia tam distinctè expresserit; quae crus ipsius tantulum articulis distinxerit, pilisque & crustulâ convestierit; quae os proboscide armârit, & intus ventrem, ac intestina, principesque partes disposuerit; quae venas, arterias, nervos, musculos, spiritus, & caetera tam multa ad nutritionem, vitam, sensionem, imaginationem, appetitum, motum necessaria sic concluserit, ut tamen unumquodque horum suam regionem, munusque suum, citra cujusquam alterius interturbationem obtineat? Denique laudas Daedalos, Architas, Heronas, ob solertiam, qua pauca quaedam machinamenta excogitant, parant, componunt, suis includunt automatis: & non commendas Summum Artificem, qui quot Animalia, tot fabricatur automata, non mortua illa, non brevi à motu impresso cessantia; sed omnia viva, atque durabilia; sed suos ex se motus obeuntia, sed innumeris (non unis, pauc●sve) Machinis sic dispositis, ut incomprehensibile sit, quantam in singulis seorsim, quantam in omnibus conjunctim, solertiam, sapientiam adhibuerit? O animum ex atomis verè concretum, & ignorantiae tenebris oppletum; cujus vecordiae mederi, ne Asclepiadi quidem concessum existimo! Quis enim, nisi Margite 
* Quo prodigiosae vecordiae vocabulo Alexandrum magnum appellitavit Demosthenes. Quam vocem insolentem exponens Suidas, deducit à Margite quodam insigni fatuo, qui ultra quinque numerare non posset; & quum Virginem duceret, eam non ausus est attingere, nè illa matri rem indicaret. Videsis Erasmum in Adag. in Margite.  stultior, inspectâ semel cujuslibet Animalis, maximè verò Hominis fabricâ per anatomiam patefactâ, extemplo admiratione raptus, non exclamaret cum Cicerone 
| De nat. Deor. l. secundo. , In universo animalis corpore quid est, in quo non Naturae ratio intelligentis appareat? Omnia enim, quae quidem aut extrà cernuntur, aut intus inclusa sunt, ita nata, atque ita locata sunt, ut nihil eorum supervacaneum sit, nihil ad vitam retinendam non necessarium; & quantum ad hominem spectat, ex ejus natura debet intelligi, nec figuram situmque membrorum, nec ingenii mentisque vim talem effici potuisse fortunâ: aut cum Seneca non diceret, 
De Benef. l. 6.  Scio equidem, scio, non esse hominem tumultuarium & incogitatum opus? Id autem si mero naturae lumine fuit olim Ethnicis cognitum atque perspectum; 
Hâc de re videri meretur Galenus, praesertim quâ parte oculi & manûs usum examinat.  nos profectò, quibus ex Mosaica creationis historia clarior lux affulsit, impii, nedum ingrati Summum erga Numen essemus, nisi summa cum animorum veneratione immens●m ipsius Sapientiam, Benignitatem, Potentiam perpetuò agnosceremus. DEO igitur ter Opt. Max. Creatori nostro sit laus, honor, & gloria, qui tam mirabili nos structura formavit. ¶ ⸫  
FINIS.   

GVALTERI CHARLETONI Scripta jam in Lucem emissa  

Latiné.  
1. DE Lithiasi Diatriba, Lugduni Batavorum, A. D. 1650. in Octau.  
2. Oeconomia Animalis, novis in medicina Hypothesibus superstructa, & Mechanicè explicata: cui accessêre Dissertatio epistolica de Ortu Animae humanae, & Consilium Hygiasticum: Londini, A.D. 1658. in Oct.  
3. Exercitationes Pathologicae, in quibus Morborum penè omnium natura, generatio, & causae ex novis Anatomicorum inventis sedulo investigantur: Londini, 1661. in Quarto.  
4. Inquisitiones II. Anatomico-physicae: prior de Fulmine, altera de Proprietatibus Cerebri humani: Londini, 1665. in Octau.  
5. De Scorbuto, liber singularis: Londini, 1672. in Oct.  
6. Exercitationes de differentiis & nominibus Animalium. Quibus accedunt quaedam de variis Fossilium generibus; déque differentiis & nominibus Colorum; cum Mantissa Anatomica: Oxon. 1677. in Fol.  
7. Oratio Anniversaria, habita in Theatro Anatomico Regalis Collegii Medicorum Londinensium 5 to die Augusti, 1680. in Quarto.  
8. Guilielmi Ducis Novocastrensis vita: Londini, 1678. in Folio.   

Anglicé.  
9 The darkness of Atheism dispelled by the light of Nature, or a Natural Theology, Lond. 1652. in Quar.  
10. Physiologia Epicuro-Gassendo-Charletoniana, or, A fabric of Natural Science upon the Hypothesis of Atoms: Lond. 1654. in Folio.  
11. Epicurus' Morals: Lond. 1656. in Quarto.  
12. The Immortality of the human Soul demonstrated: Lond. 1657. in Quarto.  
13. The Ephesian and Cimmerian Matrons; two remarkable examples of the power of Love and Wit. Lond. 1658. in Octavo.  
14. Character of King Charles II. Lond. 1660. in Quar.  
15. Chorea Gigantum, or Stoneheng restored to the Danes: Lond. 1663. in Quart.  
16. Two Philosophical discourses: 1. of the different Wits of men; 2. of the Mystery of Vintners: Lond. 1672. in Octavo.  
17. A Natural History of the Passions: Lond. 1674. Oct.  
18. Socrates Triumphans, or Plato's Apology for Socrates; and his Phaedo or Dialogue of the Immortality of man's Soul; with useful Reflections: Lond. 1675. in Octavo.  
19 Inquiries into Human Nature, in VI Anatomical Praelections in the new Theatre of the Royal College of Physicians in London: Lond. 1680. in Quart.  
20. The Harmony of Natural and Positive Divine Laws: Lond. 1682. in Octavo.  
21. Three Anatomic Lectures read in the Theatre of the Royal College of Physicians: Lond. 1683. in Quarto.   
FINIS.