is necessary to its perfection and vitality especially if we farther consider that the same opinion is also Inconsistent with the Wisdom of Nature Whose custom always is to institute the most direct and compendious methods for the attainment of her ends nor ever to use many instruments where one may suffice to effect what she hath design'd abhorring to multiply things without inevitable necessity To this her admirable Wisdom then it is injurious to imagine that when she had ordained in the bloud a certain placid regular and benign motion by which all the heterogeneous ingredients or constituent parts of it should be so agitated among themselves as by their mutual conflict to produce an alternate expansion and contraction from whence a vital heat results and upon which original life continually depends she should notwithstanding institute a second intestine motion to be at the same time in the same subject performed viz. a Fermentation which seems unnecessary at best and which probably might not only hinder and impugn but also destroy the former A Fermentation would indeed raise a tumultuous agitation of the same dissimilar elements of the bloud but such as would be violent irregular and of a far different manner from the Vital Mication But not to insist now upon the manifest disparity of these Two Motions which may more opportunely be collected from what I shall soon say of the genuine and true one let it be supposed at present that both may operate in the same manner and produce the same effects in the bloud as to the attenuation and comminution of the grosser viscid and unagile parts and the facilitation of the expansive efforts of the Spiritual volatile or elastic yet still it will remain to be inquired why Nature should institute Two Motions where either of the two might singly do her work as well if not better If therefore any defendent of this opinion which I have here en passant impugned shall vouchsafe so far to illuminate my gloomy understanding as to solve this Problem I shall acknowledge the favour and recant my opposition of it Mean while I will suspend the farther consideration thereof and now address my self to the more important part of my present province the true and undoubted Motions of the Bloud viz. the Mication and the Circulation by both which though divers in their origines and kinds yet mutually helping each other and conducing the one to the accension as it were of original life the other to the distribution of influent life the bloud is perpetually moved in the vessels that contain it By the FORMER of these the vital spirits or if you please the elastick particles of the bloud now passing through the Ventricles of the heart from their own natural force or expansive energy endeavour to expand or unbend themselves while the grosser and viscid parts resist that endeavour to expansion by compressing them Hence instantly and by natural necessity arises a certain Colluctation or mutual striving betwixt the expansive motion or endeavour of the Vital Spirits on one part and the renitency of the grosser parts of the bloud on the other And from this Colluctation an actual heat is quickly excited or kindled in the bloud actual heat being nothing else but an expansive luctation of the particles of the body or subject in which it is as I professedly labour'd to evince from various instances and a strong chain of propositions when I first had the honour to sit in this Chair Moreover because this expansive luctation is not violent nor unequal nor irregular nor consequently noxious or hostile to the nature of the bloud but on the contrary always in statu Naturae moderate equal regular amicable and tending not only to the conservation of the bloud but also to the exaltation of all its faculties and operations and because it proceeds from an internal principle from the energy of the vital spirit contain'd in and ruling the bloud or if this be more intelligible from the Elasticity of the aereal particles commixt with the bloud therefore the brisk motion or heat thence resulting is also vital For in that very expansive motion of the bloud doth the formal reason of life originally consist which Theorem also I have formerly in this place endeavour'd to explicate and establish This admirable motion from the various notions or conceptions which Learned men have formed of it in their minds hath acquir'd various names By some it is call'd motus sanguinis intestinus sive spontaneus because it arises from an internal principle the expansive endeavour of the spirituose or elastic parts of the bloud and to â—â—â—tinguish it from the circular motion which is impress'd by an external Movent viz. the Heart By others Motus fermentationis vitalis from the similitude they fancyed between it and common fermentations but improperly for the reasons by me just now alledged By others again motus oscillatorius from the resemblance it hath of the Oscillation or swinging of a Pendulum whose motion describes a Cycloid and by others Micatio sanguinis the panting or reciprocal expansion and compression of the parts of the bloud Of these denominations the two last seem to me more fully and emphatically than the rest to signifie the nature and manner of the thing denominated as equally comprehending the double motion in a single appellation Wherefore I intend hereafter to use these promiscuously when there shall occur to me any occasion of mentioning the same motion Mean while I proceed to The LATER motion the CIRCULATION of the Bloud the most noble and most useful of all modern inventions first obscurely hinted as some think by Cesalpinus but afterward with prodigious sagacity most exact judgment and happy diligence investigated and with such convincing evidence demonstrated by our immortal Dr. Harvey that now the verity thereof is no longer doubted of in the world I wish the same were as well understood as it is generally acknowledged and lest I be thought only to wish this excellent knowledge and of so great importance to Physicians I will now again do my best devoir to explain so much of the mystery as I my self have formerly left not sufficiently explicated omitting to reoire what is vulgarly taught in the Schools and Books of Anatomists and touching only those things which have been either pretermitted or not rightly explicated by others concerning the Causes Mechanical modes and circumstances of this life-conserving motion There intervenes ye know a double pause or respite which by Anatomists is call'd perisystole cordis between the two contrary motions of the heart one betwixt the diastole and the systole another betwixt the systole and the diastole and this of absolute necessity because it is impossible that the same body should perform two contrary motions without a morula or space of time how short soever be interposed betwixt them Ye know also that the force impelling the bloud which is the Compression of the heart doth not
marrow which are sent down directly into the substance of the heart as if the more easily to convey some influence into it No great difference this and yet the cause that induced Nature to make it may be great What it is is difficult to find out It may probably have some respect to the prone posture of Brutes which being horizontal must cause the ponderose machine of the heart to swagg and the cone to point not toward the midrif as in erect man but toward the Sternum and therefore in them there might be need of more auxiliary Nerves to assist the hearts motion in that position But whatever may be the true reason I do not assent to their conjecture who say that because the heads of beasts look downward therefore the providence of Nature hath furnished their hearts with more Nerves lest Animal Spirits should not in sufficient swarms be sent every moment from the prone head into the heart of a Brute that position of the brain forsooth rendring the transmission of these Spirits more difficult and slow And the reason why I do not assent to this witty conjecture is because neither the Authors of it nor any other man whose writings I have read have sufficiently proved that there are such things as Animal Spirits in rerum naturâ In some books indeed whole Common-wealths of them are found so that ye can hardly pass along without meeting crouds of them But till I see their Existence otherwise than precariously asserted I am justly excusable if I doubt thereof The Heart being thus composed of many myriads of strong Fibres of various orders by most dense contexture compact and of various Nerves intersperst it required to be continually cherished with due heat as well without as within Wherefore the Heart having no heat but what it receives from the bloud in which only the true Calidum innatum the lar familiaris resides Nature hath furnished it with two Arteries for its own peculiar use divided almost from their origine into two trunks the Orifices of which open themselves near to the beginning of the aorta immediately without the Valvulae Semilunares They are fitly called Coronary Arteries because their trunks do not presently enter into the parenchyma or substance of the heart but first make their tour or circuit the more commodiously to disperse their branches round the basis of it in manner of a crown or rather a Diadem and though from their very original they divide and recede the one from the other to the opposite regions of the heart yet they meet again in their extream branches and by mutual Anastomóses or inosculations communicate betwixt themselves so that if any liquor be injected into either of them it will in a moment appear to diffuse it self also through the other And this mutual Communication seems to be design'd to a good end For since the necessity of influent heat or life is equal in all parts of the heart that necessity could not be more commodiously satisfied any way than by this Artifice of mutual inosculation betwixt the extremities of these two Arteries No sooner hath the bloud thus imported communicated its vital heat to the substance of the heart than it is thence exported by the two Coronary Veins which in like manner encompassing the heart and by their numerose emissary surcles imbibing the bloud effused out of the Arteries reduce it into the right Ventricle thence to be brought through the Lungs back again into the left So that here is a private circulation in a small circuit instituted for the peculiar benefit of the Heart As the extreme surcles of the Coronary Arteries are mutually inosculated so also are those of the Coronary Veins as is apparent from ocular inspection For if you take the heart of a Calf or any other very young Animal for in such these vessels are most easily discernable and with the back of a pen-knife gently impel the bloud from one side of the heart toward the other you shall see it flow out of the Vein of one side into that of the other and vice versâ Nor is it to be doubted but that in all other parts of the body there is the like mutual communication per anastomôsin betwixt Capillary vessels of the same kind Besides the proper vessels of the heart now described there are annext to its basis also two Subsidiary Muscles hollow and round from thence call'd Auriculae cordis framed with no less art than the Heart it self though of less bulk For they are composed of robust Fibres too and disposed in the same order and as their motion precedes that of the Heart so have they Nerves from surcles of the Eighth pair before they reach to the heart it self Besides their intermediate fleshy Fibres which form little musculose columns are elonged to opposite Tendons For the Tendon at the basis of the Heart is common also to the ears of it and serves them for a fulcrum or prop and on the other part of the right Ear where it respects the Vena Cava it is firmed by a harder and Tendinose circle betwixt which two Tendons the Fibres tending to each are terminated as appears in the right Ear of a human heart inverted Of these Ears the right is always greater than the left Perhaps because the flux of the bloud being less rapid out of the Vena Cava into the right Ventricle of the heart than out of the Arteria Venosa into the left whither it is impell'd by the compression of the Lungs and by the coincident elasticity of the inspired air it was therefore requisite the capacity of the right Ear should be proportionately larger to receive and transfund into the right Ventricle a quantity of bloud sufficient to fill it For evident it is that the office of these Ears is like that of funnels to transmit the bloud into the Ventricles of the heart For the same reason the trunk of the Vena Cava when it approaches to the heart participates somewhat of the nature of a Muscle For there it is furnished with fleshy circular Fibres by which it is constringed and consequently the bloud running through the canale thereof is urged the faster into the right Ear in the same manner as when a gut or bladder is outwardly constringed by the hand the liquor therein contained is expressed and its regress hinder'd We have now survey'd the Structure of this admirable Machine the Heart at least so much thereof as may serve to render more plain and intelligible what I am about to say concerning the Action thereof To which I now pass ¶ ⸫ Evident it is both to the sight and to the touch that in the act of Pulsation the whole fleshy substance of the heart is stretcht and hardned with very great force as all other Muscles are when they act and certainly this tension and induration arises from the very Structure of the heart For the Fibres of the columns of it and their
which they far exceed therefore it is necessary they should exactly shut those Orifices before the Systole of the heart is complete Wherefore it is also necessary that the bloud contein'd in the cavities of the Ventricles should by the process and continuation of the constriction of the heart until a total union of their walls be effected be all expressed thence through the Arteriose Orifices which are then open to give it free egress Fifthly If the clausure of the Ears did not precede those little and thin Valves would not be able to resist that mighty violence with which the bloud comprest by the heart invades them and otherwise would certainly break them therefore to secure them provident Nature hath put a fleshy fornix or Vault viz. the constringed Ear that she might with a double door shut the ample Orifice of the heart Hence naturally arises this remarkable Corollary that the action of the Ear is longer in time than the Systole of the heart For the constriction of the Ear begins while the heart doth not act and ends in the same moment in which the Systole of the heart is completed Finally It is worthy observation that in the Arterial Orifices or outlets of the heart there is no need of the like apparatus to prevent the regress of the expulsed bloud into the Ventricles For after the exit of the bloud and after the greatest part of it is expulsed without the Capillary Arteries it cannot be impell'd back again as well because it is not urged by the force of an Antagonist Muscle of equal strength with the heart as because it is already expell'd out of the extreme Arteries Wherefore Valves of little strength are sufficient here such as is proportionate to the force which the not-intire fulness of the Arteries can make which is very inconsiderable And therefore the Semilunar Valves are far weaker than those Triangular but yet strong enough to hinder the regurgitation of the bloud expulsed by the heart Thus have we run through all the proper actions and offices or uses of all the parts of this incomparable Machine of the Heart in their natural order and found them all to be plainly Mechanic i. e. necessarily consequent from the structure conformation situation disposition and motions of the parts by which they are respectively performed If the Mechanism hath been by us rightly explicated as I am perswaded it hath in the precedent discourse no man has reason longer to believe that the manner of the motion of the heart is a thing to human wit wholly impervestigable Probable it is therefore that when that excellent Anatomist and our worthily honour'd Collegue Dr. Lower said Cùm nimis arduum sit de ratione quâ Cordis motus perficiatur quicquam ritè concipere atque Dei solius qui secreta ejus rimatur motum quoque cognoscere praerogativa sit in eo ulteriùs perscrutando operam non perdam he was out of modesty willing to limit his own curiosity in that particular but not to set bounds to the future disquisitions of other men ¶ ⸫ PRAELECTIO III. Of the Efficient Causes of the Pulsation of the Heart DElighted with the Contemplation of the Structure of this Master-piece of Nature the Heart I have sometimes revolved the Books of the most Celebrated Authors who have professedly written of Architecture and of Hydraulic Engines in search of some example of a Machine that might be at least in a few respects compared with it Of many that occurred that which seemed to me to come nearest in similitude to this inimitable Prototype of Nature was the Hydraulic Mint at Segovia mentioned rather than described by that every way Noble Gent. Sir Kenelme Digby in these words This Engine or rather multitude of several Engines to perform different Operations all conducing to one work is so artificially made that one part of it distendeth an Ingot of Silver or Gold into that bredth and thickness as is requisite to make Coin of which being done it delivereth the Plate it hath wrought unto another that prints the Figure of the Coin upon it and from thence it is turned over to another that cuts it according to the print into due shape and weight And lastly the several pieces fall into a reserve in another room where the Officer whose charge it is findeth treasure ready Coined c. For betwixt this Engine and the Heart I fancied something of Similitude at least in the few particulars following First As the design or end of the former was to Coin mony which is the bloud of all States as well Monarchies as Republicks for the support of the Government so the office and work of the latter is to stamp the character of Vitality upon the mass of bloud for the maintenance of life in all parts of the body and regulation of the whole Animal oeconomy Secondly As the one is moved by a stream of Water so is the other by a current of bloud as to its diastole at least Thirdly As the Artificial Engine was composed of many less Machines each of which performed its proper office by a distinct operation yet all conspired to one common end So the Natural being also complex consisteth of various smaller Machines viz. the Ears Valves Ventricles Musculose flesh Fibres of different orders Chords Columns Papillae c. all which have their peculiar functions and motions yet so combined that they all co-operate to the Vital motion or heat of the bloud and diffusion of the same Fourthly By the Segovian Engine Ingots of Silver were distended to a bredth and thinness requisite to make mony by the heart and its Ears vehemently constringing themselves and repeting their strokes the Silver Chyle or publick revenue of the Animal is attenuated its viscid and grumose parts dissolved the cruder parts concocted and all by conquassation and compression so perfectly commixt with the bloud as to be fit to make good and current bloud Fifthly From the Mint-engine the new stampt Coin was quickly transferred into a receptacle in another room thence to be distributed by orders of the Mint-master From the Heart is the new Coined bloud instantly transmitted into the Arteries to be distributed according to the ordinance of Nature Sixthly As the various parts of the greater Engine were so situate disposed and connected as that if any one of them were by chance displaced broken or hindred in its motion and action presently all the rest must fail to procede in their respective operations and the work of making Coin cease So in the much more subtile and mysterious Machine of the heart if any the least part though but the chord of a Valve be broken or arrested in its motions all the rest will soon be at a stand and the grand work of making the bloud vital be at an end Thus far methought the Parallel held fairly enough and I was not ill pleased with the ramble of my imagination but when I had attempted to
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 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 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 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 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 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 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
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 4 th 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 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 they cannot be made turgid again in the following pulsation So that nothing is more certain or more evident than this that in a living Animal the Arteries are never empty Quod erat ostendendum From the praecedent Theorem naturally arises this Consectary That after the pulsation of the heart there remains in the Arteries the 4 th part of the whole mass of 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 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 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 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 ¶ ⸪ 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 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 the Bloud was instituted for the conservation of its requisite temper and vital constitution Which was to be inquired and which leads us to The admirable effects and benefits arising to the Animal Oeconomy from the same Velocity of the Circulation of the Bloud Which being certainly so great that the whole mass of bloud runs its circular race in the twentieth part of an hour or thereabouts even in a sedentary and sedate man as hath by many been demonstrated from the quantity of bloud commonly contein'd in the body from the number of Pulses made in an hour and from the quantity of bloud exprest by every pulse of the heart and we having already seen what advantage redounds to the bloud it self from this velocity our curiosity spurs us on to enquire also what other scopes or ends Nature may probably be conceived to have proposed to herself when she instituted this so rapid motion or what emoluments and benefits from thence redound to the Oeconomy of the whole body Of these the first seems to be this that in every pulsation of the heart a great quantity of bloud is effused and protruded out of the Capillary Arteries into the habit of the parts for their refocillation by influent life of which I have formerly discoursed copiosely in this place For by how much swifter the motion of any liquor or other fluid through a pipe or canale is so much a greater quantity of it is in equal time effused at the Orifice thereof as hath been ingeniously demonstrated by B. Castellus and therefore the bloud is like a full and rapid torrent impelled into the Pores of the flesh and Viscera The second is the energy of the stroke with which the bloud projected by the heart dashes against the same extreme parts which energy is
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
said that Fibres when they act cannot possibly exercise their force by their contraction and by drawing their extreme terms towards the middle because by a corrugation or shrinking up into wrinkles of their length they must rather be relaxed Therefore as a weight hung on to a lax cord cannot be raised thereby while the cord continues lax So by Fibres lax and corrugate cannot the opposite walls of the Ventricles of the heart be violently drawn together and conjoyned Secondly but if we suppose that the Fibrose Spires of the heart are not wound about tortuosè with turnings and windings quite home to the Ventricles but extended in a direct course into the Ventricles and there bound together into those fasciculi or sheafs which compose many little Cylinders or cords then indeed a man may think that by simple contraction of the Fibres those little Cylinders may be totally shortned and so the opposite walls of the heart be brought to meet together But this is evidently impossible because in such a position there must necessarily be admitted a corrugation of the whole concave superficies of the heart intercepted betwixt the bases of those little columns or cords and therefore innumerable Fibres there contexed must be crouded up together and in like manner corrugated i. e. relaxed and by consequence could not act by their tense contraction which is repugnant to the supposition Besides in the right Ventricle of the heart are found but very few of those little Cylinders or columns and therefore this subterfuge can have no place there Yet farther a total decurtation of those same columns or cords could not be made unless the lengths of the Spires ending in the columns themselves ran out betwixt other Fibres as into sheaths or about pullies neither of which contrivances is to be found in the heart For the Fibres of the heart are with decussated directions contexed and so closely and firmly bound among themselves that they cannot by various and contrary motions start out of their places and run out among other Fibres embracing them In fine that the Tension of the heart cannot be solved by a simple contraction of its Fibres as heretofore hath been commonly imagined may be sufficiently evinced even from this that the bulk of the Muscles of the Limbs which when they act are truly contracted is sensibly diminished rather than augmented but the bulk of the heart while it acts is augmented since the Cavities or Ventricles of it are filled up by the fleshy substance the outward figure of the whole heart being at the same time unchanged and undiminished Wherefore the proper action of the heart is not performed by contraction of its Fibres Quod erat probandum Hence arises this Corollary That the cavities of the Heart are constringed not because the lengths of the Ventricles are shortned but because their side-walls are brought nearer each to the other so as almost to touch This appears from the very position and configuration of the Ventricles of the Heart and from its operation For the left Ventricle dissected from the bottom to the top is ye see extended through the whole length of the heart from the Basis down to the Cone which ends into a sharp pointed and slender wall and since the external figure of the heart while it beats is not shortned therefore neither is the length of this cavity diminished that is to say the Basis of the Cavity is not brought nearer to the Cone of it Besides the Base and Cone of the heart cannot at all be inflated and incrassated because the Base wants Fibres and is intirely destitute of flesh as being wholly occupied by the four ample Orifices of the Veins and Arteries and the wall of the Cone is very thin and slender Therefore the Cavity cannot be filled by inflation of the Fibres of the Basis and Cone of the heart It remains then of absolute necessity that the Cavity be filled by inflation of the side-walls of the heart which are very thick full of Fibres and therefore easily capable of inflation Lastly as was said before if a man put his finger into a hole made by incision in either of the Ventricles of the heart of any Animal yet living he shall perceive a strong constriction of the side-walls but none of the Basis and Cone tending to their approximation one toward the other By this Consectary thus verified we are led to understand The Mechanic reason of this Operation That by Mechanic necessity the Cavity of the heart cannot be shortned may be farther proved thus Because a Contraction of the heart cannot be made but by a Contraction of its Fibres therefore those parts of it that want Fibres will not be capable of Contraction but of that immense multitude of Fibres descending from the Basis of the heart not so much as the thousandth part attains to the Cone because if they should be there connected they would being accumulated stratum super strato make the acuminate and thin wall of huge depth or thickness whereas now that wall is very slender in such a situation and all the rest of the Fibres that are spiral are woven together and reflected into the heart with a transversal Circuit before they reach to the Cone Ergo they will not be able to draw up the Cone of the heart toward the Basis and by consequence the length of the cavity of the heart will not be shortned But the Cause by which the side-walls of the Ventricles are brought to meet is this Because almost all the innumerable Fibres of the heart are wound obliquely and transversly about the sides of it and of them are composed very many Layers one above another like Membranes But when the Fibres of any Layer are inflated or huffed up they touching each the other laterally and lying in one Superfice will of necessity croud and press each the other laterally and so thrust each the other out of their places and urge them farther viz. sideways toward the Basis and toward the Cone Wherefore the interval betwixt the Basis and the Cone ought to be rather augmented But because the other external Fibres obliquely encompassing and closely girding the transverse and intersecting them decussatim hinder their elongation and protuberance it comes to pass that of necessity the inflation of the Fibres ought to cause them to swell inwardly toward the cavities and so the insides of the walls being puft up must be brought nearer together Moreover the septum cordis or partition-wall of the Ventricles consisting for the most part of transverse Fibres will not be shortned by their inflation but the thickness of it is much augmented and the outward walls ought likewise to be inflated inwards towards the internal cavities therefore the insides of the opposite walls ought to meet the Basis remaining always at the same distance from the Cone Quod erat ostendendum Hence we may deduce this genuine Consectary That the meeting of the opposite insides of the walls
of the Ventricles of the heart is the sole and immediate cause of the expression of the bloud that was conteined in them into the Arteries For the swelling or incrassation of these opposite walls being all inward toward the Centre of the heart and withal so great as to fill up the cavities of the Ventricles it is necessary that the bloud contained in the cavities being on all sides vehemently compressed give way and flow forth through the apertures or Orifices by Nature provided for its efflux the resistence of the fluid bloud holding very little proportion to the mighty force of the solid compressing it But so grand an intumescence of the fleshy substance of the heart could not otherwise be made than by a great swelling and turgency of its Fibres and therefore we may infer that the thickness of the Fibres of the heart is in the act of Pulsation doubly greater than in the diastole This being granted I consider that the external Fibres of the heart exercise very great force not by shortning themselves but by resisting distraction as the iron hoops of a hogshead that the perimeter of the heart be not augmented and at the same time they are inflated in their Concave part or under side as we have said the threads of a glome are and in like manner the internal Fibres when they are swell'd and incrassated exercise very great force by making folds and turgid wrinkles so tense and rigid that they do the office of wedges by which not only the cavity of the heart is filled up but the bloud therein conteined is by vehement compression squirted out by a motion very much resembling that by which we spirt Plum-stones with our Thumb and fore-finger compressing them behind But the slender fleshy Columns holding in the opposite walls of the Ventricles of the heart are at the same time also incrassated and withal shortned their Fibres being swell'd and corrugated to help fill up the cavity Yet they exercise greatest force to perform the office of wedges They exercise none towards the drawing together the opposite walls of the Ventricles because themselves are lax by reason of the corrugation and shrinking of the length of their Fibres and besides this they could never exactly conjoyn the opposite walls because being of a musculose constitution they cannot be totally shortned the nature of the Muscles being such as suffers not contraction greater than the third part of their length Yet it cannot be denied but these musculose Columns serve as cords to retain and conserve the due disposition of the internal parts of the heart and to prevent the immoderate distension and distraction of the Ventricles which too great a quantity of bloud rushing into them out of the Veins might otherwise cause Finally the Papillae or little fleshy teats standing up within the Ventricles and to which the membranose filaments of the triangular valves of the heart are fastned do also act their part in this Scene not only by admitting the like inflation of their Fibres but also by firmly erecting themselves ad instar penis All these things are verified in the left Ventricle and in the Ears of the heart but in the right Ventricle where is not found an equal number of Columns the constriction is made by incrassation of the external wall namely by inflation and decurtation of the Fibres thereof so that the hollow crookedness of it by swelling inward comes near to a Plane and the Arch within becomes streight Also the inflation and swelling of the Septum cordis or middle wall of the heart of great thickness naturally contributes not a little to the repletion of the right Ventricle For hence it is that the Convex superfice thereof doth become more prominent and stretched out whence that space resembling the figure of a concave Lens is filled up and the walls mutually touch the circuit of the Lenticular cavity remaining still the same Now this whole operation is exactly conform to the institute of Nature which primarily fills and amplifies the Pores of the Spongy Fibres by the humectation above explained from which she attains to a double effect For in the Muscles of the Limbs that swelling of the Pores of the Fibres produces a secundary effect which is the decurtation of the Muscle and the strong traction of the joynt but in the heart from the very inflation of the Fibres and consequent incrassation of the walls she effects the repletion of the Ventricles But the Machine is the same in both namely the force of a wedge dilating the Pores of the Fibres But that this expression of the Bloud out of the heart is not made by a Spiral contorsion or twisting of the heart such as that by which water is commonly squeez'd out of a wet napkin as some late Writers have thought is easily to be proved I acknowledge it to be most true that the expression of the bloud out of the heart no less than the wringing of water out of a wet cloth is made by constriction of the Cavities and Pores which were filled by the fluid but at the same time I deny that such a constriction is made in the heart and such an expression of the bloud thence by the same cause the same Organs and the same Mechanic action by which water is squeez'd out of wreath'd Linnen For in a Linnen cloth before its Contorsion the threds were all lax and therefore they admitted many Interstices that might be filled with little drops of water Afterward the cloth being strongly twisted the threds are forced to make many circuits about the twist of almost the same altitude and so they must not only be much elonged in those prolix Gyres but also extenuated and stretch'd and consequently their sides being made smooth by extension of their folds and wrinkles will mutually touch and their interstices vanish whence the little drops of water that were in them before will presently be squeez'd out But in the heart the repletion of the Ventricles is performed in a manner far different from this For in the act of Pulsation the bulk of the heart is not extenuated or diminished but rather augmented in a double proportion nor are the Fibres of the heart elonged but rather contracted as the nature of all Muscles requires The same Fibres do not mutually touch nor are their interstices fill'd up by reason of violent traction and extension but of their inflation Notwithstanding this we are not to think that the Spiral disposition of the Fibres of the heart is of no use For they serve to the firm binding or hooping as it were of the walls thereof that the face and configuration of the heart may continue still the same which Nature hath provided for also by Girths of other Fibres wound round about from the external Tendinose Orifices of the Vessels of the heart to the Columns within and with admirable Artifice decussated and woven together And thus we have made good our
Proposition That the proper Action of the heart is the Constriction of its Ventricles and the consequent compression and expression of the bloud contein'd in them not by a Contorsion of its Spiral Fibres but by an inflation and corrugation of them Here some perhaps may be willing to propose to me this question If it be true that in the Systole or act of Pulsation neither the exterior Superfice of the heart is augmented nor the Cone of it drawn up toward the Basis both which we have asserted how then comes it that in every Systole the Cone of the heart knocks against the left side of the breast Which may be thus Answer'd Because the heart is hung in the middle of the Breast by strong Ligaments and yet in every Systole is brought to touch and strike the inside of the Breast therefore it is necessary that this be done either by a dilatation of the heart or by local motion and translation of it or by erection of the whole or by flexion and incurvation of the Cone thereof And as our observation and experience rejects the three former causes of this Phaenomenon so it obliges us to embrace and acquiesce in the last Wherefore it remains only that we investigate the Mechanic reason of this effect Which seems to depend first upon the disposition of the Fibres of the heart For we see that a crooked gut tied about with a thred and not wholly fill'd with water is by the weight of the water extended directly or in a strait line but if the water be impelled toward either end by compression then the gut becomes crooked again as the nature of it exacts and the other pendulous extremity will be erected and strike against your hand held a little over it This plainly follows from the curve figure of the membrane of the gut which is longer in the convex part and shorter in the concave So in the left part of the Ventricle of the heart the left wall is shorter less fleshy and less crooked than the two walls that make the right Ventricle Wherefore in the Systole of the heart the Cone of it ought to be erected toward the left side of the breast and to strike against it more or less strongly according to the degree of violence with which it is erected This may be somewhat helped also partly by the erection of the heart lying obliquely partly by the situation and disposition of the Fibres which are wound about obliquely and spirally from the right side of the Basis of the heart toward the left side of the Cone whence in the act of Pulsation when the Fibres are shortned the Cone may be a little distorted and erected by the fasciculus or combination of Fibres forwards toward the left side and so the Percussion may be made Seneca as ye may remember in epist. 57. most elegantly describes first the inevitable horror that invaded him while he was passing through the dust and darkness a darkness so thick as even to be seen of the Crypta Neapolitana now named the Grot of Pausilype in the way between Naples and Putzole and then the chearfulness he calls it alacritatem incogitatam injussam that returned to his mind upon the first sight of the restored light The same surprising alacrity methink I now feel within my self after my passage through the no less darkness in which Nature had through a long Series of ages involved her great secret of the Motion of the Heart made more obscure by the dust of mens various opinions and my arriving at the light of knowledge both what is the proper Action of the Heart and by what Mechanic necessity that Action is performed In the ardor of this alacrity I proceed to the use and action of the Ears of the Heart and of its Valves The end of the Vena Cava which is conjoyned to the heart is as hath been said before in greater Animals Musculose round about that the trunk of it may be constringed as Sphincters are closed by virtue of their circular Fibres But the end of the Vena Pulmonaris wants the like fulciment and therefore cannot constringe itself Then both these Veins end into the Musculose Ears which are hollow like little bags affixed to the sides of the heart and whose structure much resembles that by which the left Ventricle of the heart is contexed in the hollow part of it For the Ears also consist of fleshy Fibres intersecting each other like a St. Andrews Cross which within are bound together into many little Cylindrical Columns and trenches connecting the sides of the bags To these Ears succede three membranes in the right Ventricle and two in the left which are of a very strong contexture of a triangular figure the bases of which are closely affixed to the whole Circuit of the Tendon of the Orifice of the heart Then the areae or middle spaces of these little membranes are branched within the Ventricles of the heart into many little Tendinose Strings or cords which are fastned to the tops of the papillae or teats that stand pointing upwards placed on the opposite side Now this admirable structure being known let us enquire the design or use of it First the extreme part of the Vena Cava seems not to be made Musculose for strength lest it should be broken by the current of the bloud rushing in but rather by its constriction to protrude the bloud into the oblique Sinus of the right Ear and to render the same turgid Which action is helped by the peristaltic constriction of the whole trunk of the Vena Cava and by the compression of the Muscles and Viscera of the whole body as was yesterday demonstrated when we considered the motion of the Bloud Hence it comes that the bloud impelled through the open aperture of the Ear fills the cavity of it and then runs into the right Ventricle and by the like necessity the bloud flows out of the Vena pulmonaris into the left Ear and thence into the left Ventricle of the Heart No sooner are the Ears filled and distended with bloud but they both at the same time constringe themselves by a contractive and compressive action common to all Muscles resembling that of a Press in this order that first by shutting their apertures they hinder the regress of the bloud into the same Veins out of which it came in then by the great force of compression they squeez it into the Ventricles of the heart until they be filled and made turgid To this action of the Ears immediately succedes the compression of the press of the Heart itself by which the bloud itself by reason of its abundance inflating and distending the triangular and mitral valves exactly shuts the Orifices or mouths of the Veins and so prevents its own recoiling into them Whence it is of absolute necessity that the same bloud be expressed into the Pulmonary Artery or Vena Arterialis and into the aorta These are the
Actions and Uses of the Ears and Valves of the heart first discover'd by our immortal Dr. Harvey and since confirmed by various experiments of other excellent Anatomists Being then certain of the Phaenomena it remains only that we endeavour to explore the Mechanic causes of them In the first place because the Ears of the heart are Muscles round hollow and composed of fleshy Fibres wound about Spirally and intersecting each the other decussatim and because they end into little columns and trenches in the same manner as the left Ventricle is framed therefore must they operate by the same Mechanic necessity and Artifice by which the heart operates viz. by the force of a Press and by wedges insinuated into the Pores of their Fibres they must be swell'd and so constringed and consequently express the bloud contein'd in them Secondly That the constriction of these Ears ought to precede the contraction of the Ventricles of the heart though both motions seem to be performed at one time may be thus demonstrated For if this be not true then either the Ears and Ventricles of the heart are constringed in one and the same moment of time or the heart is first constringed and then the Ears If the first because the triangular valves have no use before the heart is constringed nor after the constriction of it is complete because the shutting of the Valves would be in vain when the bloud cannot flow back and slow back it cannot before the heart is constringed because then the bloud is not yet in the Ventricles and so cannot be impelled by the Systole of the heart and after the constriction of the heart the expulsate bloud can much less flow back therefore it is necessary that at what time the Ventricles are constringed at the same time the Venose orifices ought to be exactly shut by the Triangular Valves that the bloud may be impelled not backwards but forwards into the Arteries But if at that same time the Ears were constringed they would inevitably vomit out the bloud contein'd in them into the Ventricles and so open the clausure made by the triangular Valves because they are so disposed as to be opened and dilated by the very coming of the bloud Wherefore at the same time the bloud would be impell'd by the Ear into the heart and repell'd by the heart and so these two contrary motions would mutually destroy each the other and both be in vain Besides when two outlets are at the same time open in one Ventricle of the heart the whole compressive force of the heart is divided into two equal parts which impell the two halfs of the bloud one backward the other forward into the Arteries and therefore Nature would foolishly by a double endeavour attain but half her end We may add that the triangular Valves would be wholly useless since they would then urgente necessitate be open when they ought to be shut Wherefore it seems impossible that the Ears of the heart and its Ventricles should be constringed at the same time But if we suppose the natural order to be inverted i. e. that first the Ventricles of the heart are constringed and then the Ears compressed this would be much more absurd for half of the bloud contein'd in the Ventricle would flow back into the Ear on both sides open and thence into the Vein It must therefore be confessed that the constriction of the Ear ought to precede and then immediately ought the constriction of the Ventricle to succede and then all the operations procede regularly and compendiously For the Ear being comprest first the regress of the bloud into the Vein is hindred next the bloud is expressed out of the Ear into the cavity of the heart Thirdly the Orifice of the heart is shut by the constringed Ear Fourthly the Ventricle of the heart being filled with bloud and distended the Membranes of the triangular Valves are expanded These actions being in this order of succession done then in the fifth place follows the swelling of the heart by which all the bloud in the Ventricles which cannot by reason of the double clausure slow back is forced to run forth by the open door of the Artery Thirdly it is observable that the action of the right Ear differs from that of the left because the bloud ought to flow out of the Arteria Venosa or as some call it the Vena Pulmonaria which is very ample into the left Ventricle of the heart with a swift current by reason of its gravity and of the compression of the Lungs For this reason a little Ear is sufficient to transmit the bloud so swiftly running into the left Ventricle and with the help of the mitral Valves also exactly to shut the aperture of the heart On the contrary in the right Ear the slowness of the blouds influx ought to be compensated by the amplitude of the Canale And moreover because the right Ear ought not only to close the Orifice of the heart but also to impel rapidly the slow paced bloud into the right Ventricle therefore Nature hath made the Muscle and cavity of the right Ear stronger and larger than that of the left Fourthly We may farther gratifie our curiosity by considering the manner how the triangular Valves exactly shut the Orifices of the heart which seems to be this Because these Membranose Valves have their bases fastned to one part of the circular Tendon of the Orifice of the heart as flags are fastned to their staves and their other sides are by many Tendinose Filaments or strings fastned to the fleshy teats in the opposite part of the cavity of the Ventricle as Webs of Linnen exposed to the Sun are kept upon the stretch by many small cords tied on each side Hence it comes that by the stream of bloud rushing in the cavities of the Ventricles are dilated and so these Membranose Valves which before were lax and flagged are drawn and expanded transversly so as to spread themselves through the whole space of the Orifice Necessary it is therefore that the points and sides of these Triangular Valves thus drawn by the little cords decussated should be conjoyned and being conjoyned make one Conical superfice greater than the plane of the Orifice or of the circle of the basis of the same Cone After this follows the Systole of the heart when the insides of the Walls of the Ventricles are united and therefore those little cords of the Valves are at the same time relaxed and united also and so the faces of the Triangular Valves themselves must be united and acquire a Sinuose or embowed figure their Superfice not diminish'd because their membranes are not contracted Whence it comes that the bloud filling the Ventricle doth by repelling the membranes and inflating them bow them as the Sails of Ships swell'd by the wind are bowed into a hollowness Again since those membranes thus embowed are transfer'd toward the Tendinose Orifices of the heart the round area of
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 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 duntaâ—at accessorius Which yet is no new opinion but ascribed by Galen to Erasistratus 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 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 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 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
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
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 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 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 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 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 Sucâ—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 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 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 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 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 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 't is 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 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 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 the Diastoles when after violent Tension they exercise their natural faculty of restitution But when I had
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