First PROPOSITION, That the bloud is carried in a round through the body of an Animal, in a truly continued, and never interrupted mo­tion▪

[Page 11]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 Bloud into the Arteries, yet it is not true, that the bloud contain'd 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 bloud from the heart being wholly inter­cepted, either by a Ligature applied to the aorta at its original, or by cutting out the heart it self, as is com­monly done in Frogs and Vipers; we see, that ne­vertheless the bloud wherewith the Arteries were fill'd, is by degrees squeez'd 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 bloud into the habit of the parts: and are at the same time compress'd also by the contraction and tension, or the peristaltick 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 bloud, but only Vital Spirits are con­tein'd in the Arteries. Secondly, this appears also in the Veins. For, that the bloud doth continually flow on in them likewise, not only when it is urged forward by the Arterial Bloud pursuing it, but even in [Page 12] the time of the hearts pauses; is evinced from this, that then the bloud runs on through the trunk of the Vena cava to replenish the right Ventricle of the heart. But why do I mis-spend time in alledging reasons to prove a truth that is manifest to sense in Phlebotomy? no sooner is a Vein open'd, than the Bloud flows forth with a swift stream, and while the wound is open, con­tinues to flow without pauses or interruption, which is a demonstration of the thing proposed, viz. of the continual motion of the Bloud 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 Bloud 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 imagin that the Bloud 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 bloud 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 Bloud into the Arteries, is by degrees weakned, and at length languid in those streights of the extreme [Page 13] 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 bloud newly arrived. Thirdly, Because here we can have no recourse to the compression of the Viscera, and the Muscles, whereby the bloud should be squeez'd into the Orifices of the Capillary veins; for we see, that the bloud is suckt 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 confirm'd from hence, that in the Brain, in the Medullary substance of the bones, where no compression can be admitted, the Capillary veins receive the bloud as freely as in the softer flesh it self. Seeing then that the effect cannot be denied, viz. that all the bloud effused out of the Arteries is after absorpt 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 compell'd to assert, that the Bloud is imbibed by the Capillary Veins for the same reason, and by the same Mechanick action, by which Syphons, Sponges, Filtres, Chords, and all Porose bodies are penetrated by water with which they are moistned: which power is no other than the gravity of the fluid it self, 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 bloud can want no more [Page 14] than water can, when it finds the small chanels 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 resist­ence of the streights in all Filtres and Porose bodies: and consequently the bloud 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 bloud, is now at length solved.

The bloud having in this manner passed the afore­said streights, and entred 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 bloud following behind; as we see water suckt 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 bloud 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 stretch'd, as all Nervose and other tensile bodies are observ'd to do: Secondly, The Compression of the Veins by the weight of the Circumambient air or Atmosphear, and the Elastic virtue of the air in­spired: Thirdly, The Tonic motion of the Muscles, [Page 15] 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 bloud 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 Bloud toward the heart with a moti­on doubly swifter; not indeed in a continual flux, but with little pauses interpos'd, 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 expos'd to sight.Figure II. These Valves (ye see) are nothing but half pockets of a membranose substance, or little bladders affixt 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 Bloud be pro­truded toward the heart. Imagine then, that the same portion of the Vein HMQL is replete with bloud; and because by the circular Fibres of the Vein itself, and by the ambient Muscles, and perhaps also by [Page 16] the gravity of the Atmosphear, 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 turn'd into two little funnels, HVL, MVQ; which are less capacious than the former Cylinder, and therefore the bloud which was contained in the spaces VHS, and VLT, will be expell'd out of the Orifice HL; but the remaining quantity of bloud contained in the spaces VSM, and VQT, will be squeez'd without the Orifice MQ, toward IK. It appears then, that from the above-mentioned compression of the sides or walls of the Vein, the bloud is express'd 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 fastned two Valves; it is necessary, that the bloud impuls'd by a compressi­on made in ST, be forced through the narrow chink NO; because the yielding fluid contain'd in the cavi­ties of the Valves, and urged by the advenient bloud, 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 bloud coming on from MSTQ, may be insinuated, and pass forward be­yond AB. Again, after the bloud hath passed the confines of the Valves PO, RO, there necessarily follows a restriction of the little chink NO. For, the bloud it self must, by reason of its heavy bulk, and fluidity, fill the little baggs 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; [Page 17] therefore after the bloud is transferr'd 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 bloud, that was contain'd in the spaces EAG, FBG, cannot flow back toward AB, finding the obstacle AOB fill'd with bloud, and retain'd by the Valves; it is compell'd 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 Bloud that was contain'd in the spaces EDG, FCG, is protruded beyond DC: therefore a double quantity of bloud 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 bloud, though but half so much as the double. Wherefore Natures 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 it self into a greater: in both which cases the necessity of this demonstrated acceleration of the mo­tion of the Bloud, 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 compress'd, and consequently the Bloud flowing through it, proportionately promo­ted. In the Iugular veins also none have yet been ob­served; [Page 18] probably because in them the bloud 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 bloud, 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 bloud, 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 bloud 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 bloud into the aorta. ¶ ⸪

If this Artifice of the Valves affixt within the veins be so necessary to promote the reflux of the bloud to­ward the heart; certainly he that first discovered them, deserves to be remembred with honour. But who was that fortunate man?

Tractatu 4. de 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, quàm recentiores Anatomicos adeo latuerint; ut non solùm nulla mentio de ipsis facta sit, sed neque aliquis prius haec viderit, quàm Anno Domini Septuagesimo quarto supra millesimum & quingentesimum, quo à me summa cum laetitia inter disse­candum observata fuere.

[Page 19]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 sence 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 deserv'd 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 publick 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 bloud, grew into an opinion, that it could not stay in the Veins, except there were some bunch to hold it in, some folds or shuttings, at the opening and closing of which there was given a passage and necessary Aequilibrium to life. And upon his own natural judgment he set himself to cutting with more accurate observati­on, and so found out those Valves, &c.’

[Page 20]Having thus faithfully recited the Pleas of these two great men, I leave it to you to decide the controver­sie, and to fix the Laurel on the head of which of the Competitors you please. For my part, if my judg­ment were considerable, I should declare my self 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 assign'd to these Valves (which he most improperly named Ostiola) namely the corroboration of the Veins, which might otherwise be by the bloud every where distended and broken into varices; and the retardation of the bloud in the Veins, that so all parts of the body might have time to take in their due shares of bloud, for their nourishment, and not have their meat (for­sooth) snatcht away before they have fill'd their bel­lies: of these two mighty uses, I say, neither is true, and both are raised upon this Supposition, that the course of the bloud is out of the greater and superiour Veins into the smaller and inferiour; 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. de Ve­nar. Ostiolis. Nam cùm 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, &c. Thus far then I have done him no wrong. He proceeds. Erat profectò necessaria Ostiolorum constructio in artuum venis, quae non exiguae, [Page 21] 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 bloud, because he took it for granted, that the bloud 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 Bloud. To these errors he hath in the same Page added a third much more extravagant; which is, that the bloud 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 afore­recited [Page 22] 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 judgment 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 bloud from dilating it self by its weight into the Veins (as we observe in some crooked and swell'd knots) but also that bloud 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 bloud into Varices, by stopping its impe­tuous motion up and down in the Veins: the other, quite contrary to Aquapendens's second use, viz. to pre­vent a surfeit of the parts upon too much bloud, and an extinction or suffocation of their natural heat by that excess; whereas Aquapendens fear'd they would be fa­misht, if the Valves did not detain their food, as Tan­talus is feign'd to be. Now if these were truly the Fa­ther's Sentiments concerning the Valves, certainly he had no right conception of Natures 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; [Page 23] and that both believed the bloud 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 bloud, 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 shewn 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. Ioh. 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, egregio (que) 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. [...]en­tur. 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 bloud was the invention of Father Paul the Servite, who had written a book of it, [Page 24] 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 bloud in the Veins, and the mechanic causes there­of; let us next consider the velocity of the motion of the same bloud 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 Bloud.

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 [Page 25] of bloud runs through all both Veins and Arteries, which mass in full-grown men commonly exceeds not 18, or 20 pints: and though the Veins, by reason of their transparent coats, always appear full of bloud, yet a man may doubt, whether the Arteries also be always full; that is, whether they only give passage to the bloud 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 press'd 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 remain'd empty; then certainly would the pipes of the Veins by the quantity of 5 pints of bloud crouded into them more than what they are proportion'd 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, Froggs, &c. we may from their Purple or bluish colour perceive the Arteries to be full of bloud. Which is alone sufficient to evince, that the Arteries do not remain empty after the pulsation of the heart, but contain at least a 4th part of the whole mass of bloud, 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. [Page 24] [...] [Page 25] [...] [Page 26] of bloud 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 bloud emitted by the heart: but this certainly is im­possible without such a rarefaction of the bloud, 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 bloud, 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 bloud 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 bloud 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 bloud is in every pulsation squirted out with mighty violence. Now it is impossible this should happen, unless all the Arteries were full of bloud all along from their beginning to their end; because the violence of the stream of bloud gushing from the in­cision, hath no other efficient cause, but the protru­sion of the bloud coming on behind and urging the antecedent. But in the following pulsation there is an accession of no more than 3 ounces of bloud; which cannot by its quantity replenish half the capa­city of the Arteries. Therefore unless there remain, after every pulsation, 5 pints of bloud in the Arteries, [Page 27] 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 4th part of the whole mass of bloud conteined in the body of an Animal; and in a man commonly about 5 pints: and that the proportion of bloud expressed by the Systole of the heart into the Ar­teries, is about one twentieth part of the bloud con­tain'd in them. As also that 3 ounces of bloud 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 Bloud in the Arteries, is threefold swifter than the motion of the Heart, that impells the Bloud;

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 bloud. contein'd in the Ventricles, the motion of the expulsed bloud in the Arteries, and the promotion of the mass of bloud praeexistent in them, caused by the urgency of the new bloud coming on out of the heart: all these actions, I say, are performed in the same time.

[Page 28]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 bloud that was conteined in them. And the two last operations likewise are per­formed with the same velocity. For look how much space the bloud expelled out of the heart runs through in the Arteries, just so much space must the mass of bloud praeexistent in them be driven through, in the same time; because one part of the bloud 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 bloud 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 excedes not 3 inches breadth: but the space through which the 3 ounces of bloud 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 bloud 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 bloud in the Arteries is always the same, whether the three ounces of bloud emitted into them out of the heart, exactly fill the space dilated in them; or whether any portion of it be after their repletion expell'd out of [Page 29] them. For in both cases, the bloud praeexistent 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 bloud 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 Bloud 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 bloud emitted into them, and the expulsion of the same bloud 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 distention 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 [Page 30] 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 replenisht with bloud, 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 vertue 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 bloud that dilated them. Whence it ap­pears beyond dispute, that the spontaneous constricti­on of the distended Arteries is the cause of the expul­sion of the bloud out of them into the substance of the parts; contrary to their opinion, who ascribe this expulsion only to the Systole of the heart. ¶ ⸪

[Page 31]The natural method of acquiring Science, ye know, is to begin from things more known, and then to ad­vance to things less known; to procede from effects to their causes. Seeing therefore that we are now certain that the bloud in Animals is carried by a per­petual circular motion through all parts of the body; our next business is to enquire, 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 bloud.

Constant it is even from common experience, that whenever the bloud 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 bloud 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 bloud, 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 bloud through the Arteries; then, that im­pulsive force languishing by filtration in the spaces intermediate betwixt the Arteries and Veins; next [Page 32] 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 bloud 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 bloud 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 bloud 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 bloud is impell'd 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 comixt per minimas moleculas (as they say) and yet mutually reluctant, the Vital Mication, or Oscillatory intestine motion of the bloud 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 [Page 33] the Bloud was instituted for the conservation of its requi­site temper and vital constitution: Which was to be inquired, and which leads us to

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, fastned to Tendons, and enlivened by bloud 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 diversifie 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 [Page 78] 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 bloud alone however violently rushing into it, or by the same bloud 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 enquire. In the mean time, I will lay down this other

PROPOSITION, That the Mediate Cause of the Hearts 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 [Page 79] 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 exhibite 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 formed. 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 hearts 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 [Page 80] 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 Can­dor 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 procede.

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 destroy'd; as common experience witnesseth: So if the Nerves of the Eighth conjugation be either strictly compress'd 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 de Corde, 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 alledge, if it were not universally acknowledged by Anatomists, that the [Page 81] 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 Corde, 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 & constante 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 humor 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 publickly 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 [Page 82] 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 my self into the same period with such ex­cellent men) my self. 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. [Page 83] 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 threds of Filtres, and when they at length arrive at the end, fall down in equal drops, with equal pauses betwixt the precedent and the succeding 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 succedes 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 alway plenty to maintain a perpetual succession of drops; and the li­quor it self 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 hindred 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 vitious 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 [Page 84] in the Small Pox, the matter of which seems to be, not the bloud, 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 repeted, 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 [Page 85] 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 Romantick Giants, in my way, to deterr 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 annext to the heart may remain still full of, and turgid with the roscid Succus Nervosus, which being hindred 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, [Page 86] or some sharp and pungent liquor, may be able, by its peristaltic constriction to squeez out the few re­maining drops of the roscid liquor. Which being done, the Pulsation ceaseth for ever. To the bloud, this effect ought not to be ascribed; for after all re­liques of it have been, with warm water and a Sy­ringe, washed out of the Ventricles, and squeez'd 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 bloud 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 exprest 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 perteining 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 [Page 87] 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 Goliah 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 swell'd 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 compells me to hunt after. Should I imagine Valves affixt 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, [Page 88] 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 formed, 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 vigor; 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 rendred 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 Optick 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 [Page 89] 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 excells 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 [Page 90] 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 disintangle 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, [Page 91] 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 alledged, 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 conjoyn 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 hast, or want of due circumspection, run my self into the Bryers 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 [Page 92] 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 Bryers. ¶ ⸫

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 easie.

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 brevitie's sake, se­lect [Page 93] only two, such as are not only pertinent and ad­aequate 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 threds, 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 Iulius 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 [Page 94] 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, Pullies, and other moveable 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 Machines 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 Ma­chines so stretcht, was impossible. Confounded with shame and despair by this unforeseen faileur, he begun to meditate flight, to save his life, which he had pawn'd 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 croud 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 swell'd and shortned [Page 95] themselves so, that they lifted up the Column to a due height: and then the overjoy'd 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 threds of the Cables and Ropes, swell'd and shortned 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 threds 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 Suc [...]us 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 [Page 96] Pores of Tensile bodies; and since the two Pati­ents also, viz. the threds 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 endeavour'd to assert.

But this Chair doth not make me a Judge. To hear and determine, Most Excellent President, and my most Learned Collegues, 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 deliver'd, 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 judgment.

The summ 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 [Page 97] 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 bloud contein'd 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 judgment, namely Alphonsus Borellus; as necessary to be supposed, in order to the Solution of this great Probleme of the Pulsation of the Heart, and [Page 98] 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's 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, &c.

The Reasons that disswade 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 bloud can be discerned. Here there­fore the supposed immediate cause of the Hearts motion, viz. an inflation from a Fermentative ebul­lition of the Tartarous parts of the bloud, 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 formed, nor is any part of the Colliquamentum converted into bloud: & causarum in rerum natura nondum existentium, nulli dantur effectus. Beside, the same Vesicula pulsans is [Page 99] from the beginning of the change of the genital li­quor into bloud, not only the Conceptacle of it, but also the Engine that gives it motion; and there­fore the new made bloud 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, procede 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 bloud, 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 [Page 100] the Systole or constriction of them inwardly, which is requisite to the expression of the bloud. For, the supposed explosion consisting, like that of aurum ful­minans, or Gun-powder, in a motion expansive; would of necessity dilate the cavities of the heart.

Fourthly, If an explosion of Acid and Saline li­quors meeting, commixt, 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 bloud, 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 bogg, to withdraw my judg­ment from the conduct of Borellus, whom before I had so closely followed; and to divert into a pri­vate way, which seem'd to promise me smoother and firmer sooting; and which notwithstanding I will not commend to others, unless your approba­tion shall encourage me to pave it. Meanwhile, the hour-glass admonishing me to reserve, till I meet [Page 101] with some other opportunity, what may be farther alledged 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, squeez'd out of those Pores into the Parenchyma of the Heart, whence they are absorbed and carried off with the bloud 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 repeted, and the Circulation of the bloud 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 Iu­gular Veins imbibe whatever humour distills from the bottom of the Brain,Lib. de Corde cap. 6. ubi de Catarrhis agit. as Doctor Lower expressly affirms, and with good reason; in these words, Hu­mor omnis è cerebro proveniens in venas jugulares resorbetur. I had heretofore, I confess, a thought, that the humour contein'd in the Pericardium might have no other fountain but the reliques of the Succus Nervosus expressed out of the Fibres of the Heart in [Page 102] 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 gelly of harts-horn, or the white of an Egg hardned by boyling, as the Serum of the bloud 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 humor instilled out of the glandulae la­crymales upon the outsides of the eyes, serves to moisten and make them more easily moveable every way: when I had, I say, observed and considered these things, I rejected that thought, and embraced this, of the absorption of the reliques 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 bloud 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 bloud 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 [Page 103] 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 bloud happens; certainly there could be no room to receive the bloud, 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 bloud 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 bloud, nor Ebullition or Fermentation of the bloud, nor by explosion of Saline and Acid spirituose liquors, but by Mechanick 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 my self with this, that my Iudges are men no less beloved for their exemplary candor 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 [Page 104] 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 Con­solatione. 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 Honour'd Auditors, Ye have with obliging patience heard. Be pleas'd, 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 call'd the Sun of the Microcosm;In epist. dedi­cat. lib. de mo [...]u sanguin. 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 [Page 105] 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 Hearts 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 my self obliged to signifie, lest any here should believe, either that I have usurped to my self 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. ¶ ⸫