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 my self more inclined to applaud the judgment of that prodigy of Mathematical knowledge Archimedes of Syracuse for never attempting to counterfeit the motions of the heart than to admire his wit shewn in making a Sphear of Glass Athan. Kircher denies that any part of it was Glass but only the out-side 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 bloud 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 enquire 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 Mans body namely by weights suspended by them and since therefore in this disquisition we cannot from the effect procede 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 Machines 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 contein 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 intire Fibre 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 Fibre we may imagine more than twenty little Machines 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 conteined in that space therefore in the length of every one of the Fibres that compose the said two Muscles there will be conteined more than twenty of those most minute Machines And since the weight of 150 pounds may be suspended by one single Stratum or Layer of these small Machines 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 ought 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 Fibre 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 contein'd in those two Muscles be equal to the multitude of most minute Fibres contein'd 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 swell'd 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 hearts Motive Power we are not to expect to learn either what it is or whence it procedes 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 assign'd 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
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 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 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 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 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
act continually but interruptedly or per vices short and almost isochronic or equal quiets interposed So that the bloud express'd 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 bloud 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 ought to be esteem'd and call'd an interrupted and mixt 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 bloud 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 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 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 't is 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 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 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
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 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 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 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 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 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 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 't is 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 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
Perfections and that the Sacrifice of Praises offer'd up to Heaven from the mouth of one who has well studied what he commends are more sutable 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 bloud which our senses plainly shew and all learned Anatomists acknowledge to be the Pulsation of the heart and since it is equally manifest that this Pulsation is an action intirely Mechanick 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 Bloud 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 inscruâ—â—â—â—e 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 plumpt up by boyling For then 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 extention may be swell'd 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 â—â— 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 spriggs 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 call'd 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 contein'd in the abdomen DD The plexus of the former or intercostal branch call'd 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 II Many nervose productions from the plexus of the par vagum distributed to the Pericardium to the vessels conjoin'd 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 strengthned 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 spriggs 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
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 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 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 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 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
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 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 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 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 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 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 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