Title does not at all diversify the Action But if any one would rather signify the Heat of the Blood by any of these different Words I shall be equally pleas'd with them or any of them provided they all meet in the Matter signified by them and do not deny that which seems to be true That the Heat proceeds from a swift intestin Motion of it's Particles Which Motion is the Reason why it affects our Sensory so as to cause a Sensation of Heat But as the Reason why it affects our Sensory so is not sufficiently satisfactory to explain what is the Cause and how it comes by that Power of causing such a Sensation In making an Enquiry into the Cause of that I shall beg leave to make Use of that Word which I think to be most expressive viz. Fermentation For since in every mechanical Action there is an Agent and a Patient and the Agent operates upon the Patient by moving powerfully against the Parts of it And in that Motion the Parts of the one strike against and rub upon the other so far it may be called Attrition And if by the force of the Agent the Motion and consequently Attrition be more violent and the consequence of that Attrition be a Production of a Power to cause a Sensation of Heat so far it may be called Fermentation If then in causing the Heat of the Blood there be such a Motion and Attrition and the consequence of it be Heat we may properly say the Blood grows hot by Attrition and Fermentation But because to signify the Heat of the Blood by Attrition and Fermentation would be needless I would signify all that Action by Fermentation And when I say the Blood grows hot by Fermentation I would be understood to mean and signify both that Attrition of Parts which is the Cause of Fermentation and also Fermentation which is the consequence of Attrition yet if any one would rather say it grows hot by Accension they have my assent provided they mean thereby not so high a degree of Heat as is usually signified by that Word but since it sounds rather too harsh and implies too high a degree of Attrition and Fermentation than that which is commonly in the Blood I more willingly make choice of the former viz. Fermentation And since I have said thus much of the Use of Words applyed to signify the Heat of the Blood I shall here take Notice of what was by way of Discourse told me by one to whom I communicated in some Measure my Notion concerning the Heat of the Blood which was this He said he thought he could prove that it was done by Mixture and Pressure and that he could explain the Heat of the Blood by that Notion I shall here conceal the Authors Name because he hath not made it public upon this account though upon some others to very little purpose and because he told me he intended to publish it I shall for his satisfaction and also the satisfaction of those to whom he hath communicated it say that as I have shewn that in mechanical Actions there is a Motion and by that Motion there must be implyed a Mixture to any one that doth but understand the Circulation of the Humors in a Man's Body and it will consequently follow that where there is a Mixture and a Motion of Humors there must needs be also an Attrition of Parts so moved which Attrition implies a Pressure For there can be no Attrition without a Pressure tho' Pressure does not imply Attrition This is all he told me and consequently all that I can Answer but for as much as I cou'd gather from the remaining Part of his Discourse the most Essential Part of his Notion but from what he said it appearing not what Pressure he meant that is a Pressure of what whether of the Particles of Blood with one another or not and it being plain that he did not believe that Animal Spirits circulated through the Nerves I not only concluded that his Pressure was only of the Particles of Blood because there are none other except Serum to mix with it but also that what he had to say for it was rather about the Use of Words then any thing else and therefore I have shew'd him how far his Words are significant in my Hypothesis But Words whereby we signifie the Heat of the Blood being nothing at all to the Cause of it and to dispute whether it may be called Accension or Fermentation not at all informing what are the Principal or Accessory Causes of it I shall proceed to shew how it is begun and carryed on and by what That is what Humors are Active and what Passive in producing Heat or a Power to Heat and how they are so and after what manner as also where they chiefly operate And that it may appear we are to consider that the material and corruptible Part of a Man in which the immaterial and immortal is lodged is made up of Solid and Liquid Parts the Solid Parts are all those Vessels that make the Body a curious contrived Vascular Engin which are filled with and actuated by Liquids and in which they all circulate And as those Vessels carry different sorts of Liquids so they are called by different Names Veins Arteries Nerves c. Through the Arteries and Veins the Mass of Blood continually circulates and Animal Spirits through the Nerves The Veins and Arteries being as if it were both rooted and springing from the Heart are branched up and down the Body both through the External as well as Internal Parts except those that the Vena Porta supplyes and the Nerves taking their Original from the Brain and spinal Marrow are dispersed through the whole and meeting with the capillary Terminations of the Veins and Arteries they being interwoven one with another terminate all together and as I Metaphorically expressed it in my Treatise of Muscular Motion all terminate in small Glands in the Cavities of which both through the substance of the Muscles as well as the Internal Parts the Arteries lay down Blood and the Nerves either mediately or immediately Animal Spirits and having there also proved that a subtile Liquor made and prepared in these Glands by Formentation was according to the different degrees of Spirits sent there by our Appetite not only subtilized but thrust out by a succession of Matter into the Fibers and circulating through them distends 'em and by that means contracts the Muscles and there also having shewn that the Fermentation was caused by a mutual Conflict of the Blood and Spirits I shall now in this Treatise endeavour to explain from that mutual Conflict the Heat of the Blood And because some as yet doubt whether Animal Spirits circulate through the Nerves or not and others though they are willing and find it necessary to grant that Spirits do really run through them yet profess that they cannot be demonstrated
any thing as one that 's in a Fit of the Epilepsie but our Bodies being accustomed to it and it being made agreeable and consistent with Circulation of the Blood becomes less troublesome when we have occasion for Extraordinary Respirations For these Reasons it is plain why the Lungs ought to be in a continual Reciprocal Motion the first of which is self-evident and needs no further Proof and the second is sufficiently evinced by the Consequences that follow when this Lympha is not evacuated When it is too thick or too much in Quantity or on the other side the Air which we breath is too thick and moist and it is not duly carried off there follow Obstructions of the Ducts of the Trachea from whence proceed Symptoms of an Asthma Orthopnaea and Duspnaea some sorts of Phthisicks and a great many more dangerous Symptoms For when it is too thick it sticks fast to the Coats of the Lungs and not being easily enough mixed and incorporated with the Air the Quantity of it encreases till it stuffs up the Cavity of the Lungs and when it is too much in Quantity though it be thin enough yet the Air being not able to carry it off fast enough it runs down the sides of those tender Vessels and by a gentle Irritation raises a tickling Cough Lastly when the Humor that moistens the Lungs is almost Natural as to Quality and Quantity yet if the Air be thick and moist it being so much impregnated with it's own Moisture is incapable of carrying off the Moisture supplyed by the Serum of the Blood whence People that are inclined to Obstructions of their Lungs in foggy and moist Air find them more oppressed that Moisture which ought to be carried off being left behind But if we consider further the Use of the Lungs with respect to the Body we shall find other Reasons not only why it should be in a constant Motion but also we may understand why we cannot live without a continual and free Circulation For in respect of the Body the Lungs seem in some Measure to perform the Office of another Heart and as the left Ventricle of the Heart contracting sends out the Blood into all the Parts of the Body by the Ramifications of the Sanguiferous Vessels so the Lungs contracting force the Blood contained in the Sanguiferous Vessels which are distributed through their Lobes into the left Ventricle of the Heart and the left Ventricle being by that means more vigorously dilated and more plentifully filled with Blood a larger Quantity of it is forced out into the Aorta and consequently the Blood in the Branches of the Aorta is more copiously pressed by subsequent Matter into the Roots of the Vena Cava and so forwards into the right Ventricle of the Heart so that by the help of the Lungs the Dilation of the left Ventricle of the Heart is immediately and the Dilation of the right mediately promoted That the Lungs thus promote the Dilation of the Ventricles of the Heart it is very reasonable to believe not only because it is self-evident but because otherwise it will be very hard to conceive since the Motion of the Heart is only Contraction and the Dilation of it's Ventricles only a Cessation from that Motion how the Blood is forced into them with Vigour enough to distend their Cavities For there is so little Reason to expect that they should dilate of their own Accord that we should rather believe they would be continually contracted since all the Weight of Blood contained in the whole Sanguiferous Vessels of the Lungs could not possibly dilate them without some other force to help it for the Substance of the Heart being contracted and the Cavity of the left Ventricle so considerably diminished so small a Portion of blood as hath Liberty to press against it's Orifice would make but a weak Pressure and much too small to dilate the Ventricle in so little time as intervenes the successive Contraction besides the Heart having no Tendency at all to dilate it self since that would make it unapt to yield to Contractions we must suppose that a Part of such Substance cannot easily be dilated but would require some Force greater then can be supplyed by an inconsiderable Pressure of Blood faintly intruded by almost nothing at all But the Lungs being almost in a continual Contraction in respect of the Sanguiferous Vessels and consequently squeezing out the Blood contained in them help to dilate and extend the Left Cavity of the Heart and consequently the Right That the Dilation of the Ventricles of the Heart is only a Resolution or Cessation from Contraction is allowed and agreed upon to prove then that the Venal Blood cannot return with Force sufficient to dilate the Right Ventricle of the Heart nor is sufficiently able duly to extend the Left in order to the next Contraction by that force it received from and was put into by the former Contraction but is assisted by the Lungs we may easily perceive For not only the Blood in it's Vessels but even any Liquor being forced through Pipes whose Cavities encrease the further they run from their narrow and small Original always moves with less force the farther it goes So that although in every Systole the Blood should be forced forwards from the left Ventricle by a successive Pressure of subsequent Matter and the Motion should be strong enough to make it circulate briskly through the narrow and capillary Twigs of the Arteries yet when it came into the Veins it would move much more slow and by that time it came to the Heart again would want Force sufficient to dilate the right Ventricle and the right Ventricle being not duly dilated so little Blood would be squeezed into the Lungs that the Left would want a Supply of Blood to dilate it and consequently the Pressure of Blood through the Aorta and Vena Cava would be so weak that the next Dilation of the Right Ventricle would be weaker than the former and so Circulation would gradually decrease But that weak Motion of the Blood into the Right Ventricle being encreased by the Force of subsequent Matter from the Left the Motion of the Blood into the Lungs is consequently more plentiful and as it passes through them is violently forced into the Left and so on and by that means as I said before the Lungs distend the Left immediately and consequently the Right mediately That the Motion of the Blood is thus weakned by so long a Course in the Veins is further evinced if a Vein and Artery be open'd at once for the Blood runs out of the Artery much more forcibly and indeed it would be reasonable to think it so though it were not manifest by so plain an Experiment for if Water in a Cistern be put into a violent Motion at one end the further it runs along the less violent is the Force of it And it is further evident that the Motion of
inflames the Blood of those that are of a tender and open Constitution much sooner then phlegmatic and melancholly Peoples and as the former is evident in those that are subject to Fevers so the latter is not less remarkable in those of cold Constitutions for to encrease the natural Heat of their Blood when it is too much depressed it is not only necessary to take away some of those crude Humors which stuff up the Vessels and too much depress the Spirits but also by volatile and spirituous Medicins to encrease the Spirits and at the same time to exalt and spiritualize the Blood by absorbing Acids and exalting the volitile and subtile Parts to render them predominant Moreover that the Animal Spirits do not only according to their different Quantities and the different State of the Blood variously exagitate and encrease the Heat of it but also according to their different Degrees of Activity and Strength is put beyond Dispute by the different Effects that Spirit of Wine or Aqua-mirabilis hath upon us from Sack which any one that does but taste must soon acknowledg It remains in the next Place that I should shew how far the Animal Spirits are Active and how far Passive in causing these Effects as well as the Blood which evidently appears from what I have already said For when the Spirits and Blood are forcibly driven together then they seem to be mutually Active and Passive the Spirits being forced betwixt the Particles of the Blood and vice versâ but the Animal Spirits being ground and rarified betwixt the Particles of the Blood are so far Passive but being by that means expanded by a powerful expansive and elastic Motion exagitate the Mass of Blood and by that means are active so that throughout the whole Process it appears that neither of them singly are altogether Active or Passive but both mutually and by turns From what I have said it appearing how the Heat of the Blood is caused I shall in the next Place proceed to shew how it is continued which will be sufficiently evident if we do but consider that the Animal Humors are in a constant and continual Circulation for since all the Blood in a Man's Body is allowed to circulate through the Heart several times in an hour and that the Blood from thence is continually forced and dispersed through the Parts of the Body and so great a Quantity of Blood is at one Pulsation laid down in the whole Habit of the Body and ferments at the same time with the Animal Spirits there must needs be raised in the Blood a considerable Heat or in other Words the Parts of the Blood and Spirits must of necessity be put into so swift and intense a Degree of Motion as to enable them to produce an extraordinary Heat when they strike upon our Sensory The whole Mass then circulating thus through the Extremities of the Vessels there is not only a great deal of Blood fermented every Pulsation but also by a continual Succession of Pulsations the Blood being forced into a Fermentation by the expansive Motion of the Spirits is by that Means preserved in a constant and continual Heat But I know here will some Difficulties offer themselves and perhaps some may doubt whether the Blood only ferments in the Extremities of the Vessels and not in the Vessels themselves and since it is hot in the Arteries before it be laid down in the Glands as well as in the Veins after Fermentation they may think it reasonable to conclude that where-ever it ferments there it 's Fermentation is caused and because there is a great deal of Blood betwixt their Extremities and the larger Vessels they may think that the Fermentation in the Extremities cannot be the Cause of the Heat of the Blood in the larger Vessels it being an old Maxim that tolle Causam tollitur Effectus which is as much as to say the Cause immediateley goes before the Effect Another Doubt which perhaps may arise will be that since I affirm that there is such a mutual Action and Passion in the Attrition of these Humors in order to a Fermentation whether Fermentation can be carried on in such a manner in so short a Time as the quick Circulation and consequently Protrusion of the Blood from the Extremities of the Vessels admits As to the First To wit whether the Fermentation of the Blood be caused in the Extremities of the Vessels or the large ones I affirm that it is chiefly and originally caused in the Extremities of the Vessels just where the Nerves and Arteries meet and where their contents are first mixed together and that the Fermentation in the larger Vessels is but a Continuation of the Effects of the same Original Cause and as when Water is heated over a Fire that Part of the Water which is at the top of the Vessel that contains it is as truly said to receive it's Heat from the Fire as that in the Bottom so that Blood which is in the Body of the Vena Cava is as really put into a Fermentation by a Mixture of Spirits as that in the Extremities for the Animal Spirits being mixed with the Arterial Blood in the Glands and ground betwixt their Particles and being by that means put into an elastick and expansive Motion they powerfully ferment and exagitate the whole Mass This Blood then so fermented is thrust out of the Glands by a Succession of Matter forced in the next Pulsation and so forwards by the next successively till it be driven into the Vena Cava Now as soon as it is thrust out of the Glands those Spirits which did so powerfully expand before and the remaining Part of them which are not mixed with that subtile Liquor that circulates through the Fibres being yet further corroded and exagitated by Pulsation still continue to expand themselves and by that means keep the Blood in a continual Heat And the Animal Spirits being yet more expanded do not only continue but in a great Measure encrease the Heat of it But these Spirits being frequently opposed in their Expansion by striking against the Blood loose in a short time a great deal of their Vigor the Particles that before grund the Animal Spirits betwixt them obstructing their Motion and the Animal Spirits not being able any longer to keep them in a just Motion sufficient to continue the Heat which is Natural to human Blood they are as if it were linked and fettered up betwixt those grosser Parts are incorporated into one Substance with them which is the Reason that the Blood by frequent Circulations is ripened and digested and for this Reason the flesh of a Hare grows tenderer by being coursed along time The Blood being thus impregnated with Animal Spirits and by that means wanting Spirits in a free and strong Motion would by degrees grow cold but the Intervals of time while the Blood moves from the Extremities of the Vessels to
then it will follow that the Heart being a Part in constant Motion and that Motion proceeding from a successive Supply of Spirits the Blood must needs acquire the most considerable Degree of Heat in the Substance of it But although I say that the Blood for these Reasons acquires a greater Heat in the Heart then in any other Part I would not be thought to mean that it grows hot so in the Ventricles of the Heart For the Use of the Heart being only to force the Blood out of it and by dilating to receive it in again for another Expulsion and so to keep it in Circulation it can get no great Heat there since it wants Spirits to ferment with it but I only mean that considering the Substance and Dimensions of the Muscular Part of the Heart and that small Portion of Blood contained in the Arteries dispersed through it that that Blood acquires a greater Heat than that Quantity of Blood does in another Part that is not in Motion But there being besides Muscular Parts many considerable Internal Parts in a Man's Body in which a great Number of Blood Vessels are distributed it perhaps will be asked whether Fermentation be carried on in these too To which I answer that Animal Spirits and Arterial Blood being either mediately or immediately laid down in them all there must needs be a Fermentation which being proved upon such Premises by what I have already said there is no need I should repeat it again But since Anatomists have not as yet discovered Nerves to be distributed through the Liver although Blood be communicated to it by the Vena Porta which supplies the Office of an Artery to the Liver it perhaps may be doubted whether Fermentation is carried on after the same Manner there and consequently whether the Office of the Liver be performed by Fermentation or not that it is I shall shew hereafter and also how the Glands in that Part are supply'd with Spirits From what I have hitherto said it appears what are necessary to continue the Heat of the Blood and also what is the Cause of it For First It is necessary that the Animal Spirits and Blood should be in a continual Circulation that being forcibly driven together their Particles might be intimarely mixed one with another And Secondly That the Animal Spirits should be grund betwixt the Parts of the Mass of Blood that they may be thereby rarified and expanded and their Particles put into a swift Motion And Thirdly It is requisite that the Animal Spirits should be of an oyly Sulphureous volatile Temper that being more easily rarified and expanded they may be presently put into Motion and cause the whole Mass to ferment Having then explained the Heat of the Blood and proved it agreeable to these Circumstances I am for the Reasons before mentioned perswaded to believe that the Heat of the Blood thus proceeds from Fermentation OF THE USE OF THE LUNGS FOR as much as appears from the Books of several Learned Men the Use of the Lungs hath not been hitherto indisputable no more than the Use of other Parts For as there are several Opinions concerning others so there are no less Disputes about this whilst some would have it to be only a sort of Fan to cool and air the Blood And others that it was designed to kindle and put the Blood into a Flame by continually supplying it with Nitre Whether of these is most probable may easily be gathered by considering the Effects that Air hath upon us For since the Air is continually drawn in and thrust out again in Respiration any one that does but know what Effects it hath upon himself cannot be ignorant of the Use of the Lungs in respect of the Heat of the Blood evidently finding himself cooled by it and if any one that by daily Experience finds that it cools him can conclude thence that it kindles and promotes the Heat of the Blood he may be pleased with his Notion but no Body else will with such as contradict self-evident Truth But that it may appear how far the Lungs may be said to be a Fan or Ventilabrum to the Blood and whether the Air promotes the Heat of it or not I shall take this Method First consider the Use of the Lungs with respect to the Rational Soul and Secondly with respect to the Body The Use of the Lungs with a more immediate Respect to the Soul appears to be nothing else but as a large capacious Vessel endued with a Cavity to contain a great Quantity of Air so that it performs the same Office in the Body as a Pair of Bellows to Organs For as in Organs the Bellows supply Pipes of different sizes with Air and that being driven through them produces different Sounds so the Lungs dilated and extended by the Motion of the Thorax and being full of Air contract and accordingly as the Pharinx and it's Parts are differently modulated so the Air forcibly driven through them causes different Voices In which Action the Lungs seem chiefly to be an Organ made on purpose to be serviceable to the rational Soul to express all it's Conceptions and Reasons and to form Voices or Articulate Sounds to signifie those Notions contained in and apprehended by it that those Things which must otherwise remain in silence might be communicated to promote a mutual Commerce and Conversation amongst Men. But here some may ask if it be chiefly designed to form articulate Sounds as it really seems to be why do we take our Breath continually Or why are our Spirits constantly consumed by keeping the Part in a perpetual Motion Since sometimes we use it very little for a long time to express any Thing by one half of our Lives and the larger too being passed away in Silence To which it may be answered that it is necessary the Lungs should be in a constant and continual Motion that they might be kept in readiness to express what and whenever we have a Mind Another Reason is that since the Cavities of the Lungs are constantly supplyed with a serous Lympha to moisten their Coats and to moderate the Acrimony of the Air it is necessary there should be a constant and continual Respiration to carry that serous Lympha off which would otherwise stuff up the Bladders of the Lungs that they would be incapable of receiving Air but every Inspiration that superfluous Moisture being mixed and incorporated with the Air is by every Expiration carried off which prevents those ill Consequences which would otherwise follow Another Reason why the Lungs ought to be always in Motion is least they should Preter-naturally affect and disturb the Constitution of our Bodies when put in Motion as we have a mind to express our selves for if the Lungs were at other times quiet and still our Bodies would be put into such Disorder by violent and sudden Motions that we should be as unfit to discourse of
the Lungs does assist the Dilation of the Heart as I have shewed by stopping the Breath of any Animal which for want of free Circulation presently dies and not because the Flame of the Blood is by that means extinguished for as long as the Lungs duly perform Respiration and the Heart violently contracts and drives the Blood contained in it's Ventricles forcibly out that Motion of the Blood being by a continued waving Pressure decreased is enabled by the Assistance of the Motion of the Lungs to dilate the Ventricles of the Heart with a sufficient Quantity of Blood to be forced out the next Contraction but as soon as the Lungs cease to assist the languid Motion of the Blood in dilating the Ventricles it is not only less plentifully forced successively thus into the Ventricles of the Heart but by a weaker Pressure of the Contents of them thrust out each succeeding Pulsation the Arterial Blood is less plentifully driven forwards so that the whole Mass circulates flower by degrees and also the Animal Spirits being driven less violently into the Muscles that Supply of Spirits separated in the cortical Part of the Brain being not so powerfully thurst after by an equal Succession of Matter the Fermentation in the Glands is weaker and consequently the following Contractions gradually decline both in Number and Vigour till at the last they cease But if before the Circulation of the Blood be quite stopped that Animal be again permitted to breath the contractive Force of the Lungs drive Blood more forcibly into the left Cavity of the Heart so that the next Pulsation a greater Quantity of Blood is forced into the Arteries which makes a more considerable Protrusion of Blood into the Muscular Glands and also of Spirits through the Nerves by which means the Thorax contracting more violently forces the Blood in greater Quantities into the left Ventricle of the Heart and the Motion of the Heart at the same time increasing raises Circulation to it's natural Force by squeezing Blood forwards into the Right and so successively From hence it appears that the Blood is forced into the Ventricles of the Heart by the help of the Lungs for if when the Motion of the Lungs is obstructed the Systole and Diastole of the Heart ceaseth in a short time it must needs follow that it is in some measure preserved in that Motion by them and it is further proved because the Motion of the Heart does not only sooner stop when Respiration ceases but also because it is increased by a renued Respiration and any one that would be further satisfied of the Truth of it let him hold his Breath a considerable time and he will find his Pulse gradually decay which is again renued by reiterated Breathing But though from hence it may appear that the Motion of the Heart is promoted by the Assistance of the Lungs yet it perhaps may be a Question how this Defect is supply'd in unborn Infants and how their Blood circulates since then their Lungs do not perform the Office of Respiration To which I answer that in an Infant before Birth the Placenta supplys that Defect for that additional Force which the Infants Blood receives from the Motion of Nourishment violently forced into the Umbilical Vessels by the Pulsation of those Arteries that separate it from the Mother's Blood in the Womb do prove equivalent and supply the Office of the other but as soon as the Circulation of the Blood ceases to be promoted by a Sepaparation and Protrusion of that Juice it immediately if unborn dies and after it is born hath a continual Necessity of Breathing as long as it lives Where it is to be noted that as in one that breaths the Lungs more immediately assist the left Ventricle so in one unborn the Placenta more immediately promotes the Dilation of the right Now although it from hence appears that the Motion of the Heart is promoted by the reciprocal Motion of the Lungs yet it does not wholly depend upon it for if it did the Motion of the Heart would as suddenly stop as that of the Lungs but since it does but partly depend upon it Circulation declines by degrees upon the stopping of it But that it may be better understood how the Lungs promote Circulation I shall next shew that the sanguiferous Vessels in the Lungs are not only contracted by the Contraction of the Thorax but also in every Inspiration And since it is known that the Bladders of the Lungs are encompassed about with the small Twigs and minute Ramifications of sanguiferous Vessels every Systole of the right Ventricle of the Heart these must needs be filled and distended with Blood and if so consequently that Blood must needs be forced by the Contraction of the Thorax through the Vena Arteriosa with a considerable Force and so be driven into the left Ventricle of the Heart with more case where we may by the way take Notice that the Blood in the Arteria Venosa from the Orifice of the right Ventricle is not only by that means thrust into the minute Vessels of the Lungs more easily but also the Blood that is to be forced forwards by the next Pulsation is more readily received by the Vena Arteriosa and the Ventricle more easily contracting when the Vessels of the Lungs are thus emptied by a Contraction of the Thorax than if they were distended that subsequent Matter in the depending Parts is received and driven after it with less difficulty the resistance that distended Vessels would make to the Egress of it being thus prevented by the help of the Lungs That the Blood is thus forced out of the Lungs into the Ventricle of the Heart is not only evident from Reason but also Experience for in violent Coughing where the Lungs are almost in a continual Contraction the Blood is more violently driven into the Habit of the Body that it is forced into the Face visibly appears and that it also flows into the Habit of the Body is evident in People that are let Blood which by coughing much is plentifully forced out of the Orifice and that the Contraction of the Lungs in coughing can no otherwise force the Blood into the Habit of the Body but through the left Ventricle is very plain and Lastly that not only the left Ventricle is by that means further dilated but consequently the right by the Assistance of the Lungs is manifest because Circulation is presently quickned by coughing so that this one Phaenomenon proves all that I have asserted concerning the Use of the Lungs with respect to the Heart But it may here also be questioned how the Lungs supply the Heart in Inspiration when the Cavities of the Lungs are dilated To which I answer that though the Cavities of the Lungs are dilated in Inspiration yet the Bladders which are swelled and dilated with Air even then make a moderate Pressure upon and consequently a Contraction of the Blood Vessels that are
about them But though there were no such Contraction upon Inspiration yet the Dilation of the Thorax is not so long continued but that the Lungs renue the vigorous Contractions of the Heart before they are sensibly decreased as I have before explained it From what I have said of the Use of the Lungs with respect to the Rational Soul as well as the Motion of the Heart it appears that the Lungs perform a Sort of a mixed Action partly voluntary and partly involuntary with respect to the Body it is involuntary being carry'd on whether we will or not and when we are able to take no notice of it and with respect to the Soul voluntary it being in our Power to quicken or remit the Motion of them differently to modulate our Voices as occasion and necessity require or our own Will inclines us But besides these extraordinary Offices it performs in promoting both a Circulation of Humors and of Discourse since there is such a great Quantity of Air drawn in by every Inspiration it must needs produce some Effects in the Mass of Blood and those Humors that circulate along with it and since it is so minutely mixed with it by the small and circular Windings of the Blood Vessels about the Bladders of the Trachea the Blood must needs be sufficiently impregnated with Nitrous Particles But it being a Question how the Nitre of the Air comes to be mixed with the Blood and whether the Air it self be mixed with it also before I proceed to shew how the Mass of Blood is affected by it I shall endeavour to solve these two Questions And First That the Air it self is no otherwise mixed with the Mass of Blood but as I have shew'd viz. by the Mediation of the distinct Vessels in which each run is plain because we don't perceive the Effects of it in that Mass and also we may probably guess so because Air would hinder Circulation and much disturb it Air being always unapt to mix with Liquids and to fly from their Embraces there being therefore these Reasons why it ought not to be mixed with the Blood and none that it shou'd nor any Sign of it being so we have Reason to conclude that it is not But Secondly That those Nitrous Particles which swim in the Air are mixed with it we see manifestly by the Effects which are caused by them there being the same Alterations in some Measure made in the Blood as it passes through th Lungs as when exposed to the open Air. But the Question then will be how the Nitre of the Air is mixed with the Mass of Blood and by what means To which it may be answered that if we consider what fine and subtile Bodies those Particles of Nitre are which we draw in by Inspiration and through what minute and small Pores they are capable of passing so that they penetrate the most solid Bodies in Nature well may we suppose that they can find Pores fine enough to pass through the Coats of the Vessels That they pass through the most compact and solid Bodies Bodies that are much more close and less Porous than the Vessels of the Lungs are is certain for otherwise hot Water contained in a brazen Vessel would never grow cold and that the substance of Brass is less porous than the Substance of the Lungs no thing is less dubious Moreover since that the Nitrous Particles of the Air are conveighed into the Blood is so plain from the Effects that are there caused by them they must needs be conveighed through those Pores there being no other ways at all for them to pass by But Another Question which may perhaps be asked will be how the Nitrous Particles of the Air are forced through those Pores which will be easily understood by taking notice that when the Thorax is violently contracted the Air contained in the Bronchia being violently pressed together in order to an Expulsion of it a considerable Number of those Particles of Nitre must needs be pressed through those Pores that are wide enough to receive them and that there are Pores wide enough is visible from what I have said It appearing hence how the Nitre of the Air is mixed with the Blood I shall next consider how it affects it and what Effects it produces in respect of Heat To understand then the Effects that it hath upon all that Mass of Humors that circulates through the Veins and Arteries to wit Blood and serous Lympha we are to consider them both together and apart together that it may appear how they influence each other and a part that we may know for what end each is impregnated with those Nitrous Particles and because when we are acquainted how it alters each singly it will better appear how they influence each other I shall first consider them apart The Effects then which we perceive the Nitre of the Air hath upon our Blood and the Alterations we are sensible it produces are either in respect of it's Colour or Heat That the Air alters the Colour of the Blood and makes it more florid is very plain in extravasated Blood and is so commonly known that I need not take any further Notice of it but shall shew what other Effects it causes in the Blood and how Having therefore explained the Heat of the Blood in the foregoing Treatise and it appearing that it is caused by a swift and violent Agitation of the Particles of the Spirits and Mass of Blood the way to understand how Nitre affects the Heat of the Blood is to consider how it promotes or hinders the Motion of those Parts of Matter which cause Heat which as I conceive and as Reason seems to evince is performed after this Manner The Nitre of the Air consisting of Particles not at all inclined to Motion but on the contrary disposing those Bodies they are mixed with to rest except by accident when they are too powerfully resisted and opposed These I say being mixed with the Mass of Blood inviscate and fetter up the most subtile Spirituous Parts and hinder them from Motion by which means the more gross ones are moved more slow and the Heat of the Blood consequently abated but when the Mass of Blood is so Elastick and the Parts of it move so strong that the Nitre cannot depress them sufficiently and check them the Heat of the Blood is increased the Motion of those Parts being inverted That the Nitre of the Air inclines those Bodies to rest with which it is mixed and consequently the Blood is not evident only by exposing hot Water to a cold freezing Air but even Blood and nothing is less dubious than that excessive Cold extinguishes a moderate Heat But that Nitre when it is not powerful enough to check and extinguish the Heat of the Blood does increase it I have before explained and the manner how it does it and also that it hath never those Accidental Effects upon Liquids
I shall before I proceed to shew how the Heat of the Blood is caused endeavour to demonstrate those Spirits and prove that they circulate through the Nerves as plainly as we can by the help of our Reason and the Testimony of our Senses demonstrate any and the most apparent Things whatsoever For any one that does but look into the Substance of the Brain I think needs neither doubt nor be ignorant what the Animal Spirits are nor of their Nature which appear as manifestly as the Humors of a Mans Body But perhaps it will be a hard Task to perswade some that that oily and clammy Moisture in the Brain is Animal Spirits since it seems as some say to be as gross a Substance as any Liquid in the Body To this I answer that if we take Animal Spirits or that Moisture in the Brain and compare it with coagulated Blood it is much more fine and pure and not half so tough and clammy whereas if it were a more gross and sluggish Body it would be a great deal more Viscid and Phlegmatick But if we further compare the Taste of the Brain with the Tast of the Blood it will be evident that that sweet Substance is the Spirit of the Blood and consequently that it is Animal Spirit For as the Blood is a sweet Mass inpregnated with diverse sorts of Salts and Phlegmatick crude Serum so the substance of the Brain is moistened with an oyly sweet Salino-Sulphureous Mass free from those indigested Dregs that swim along with the Blood being separated from those Impurities in the cortical Part of the Brain now if a Spirit partakes of the Nature of that Body it is separated or drawn from this is an Argument strong enough to convince any Rational Man that that Moisture is the Spirit of the Body since we learn by our Taste that it is the purest and most refined Part of the Blood as a Spirit ought to be But some think it too gross a Humour to perform all those Actions which they think the Animal Spirits do yet if they grant that the Mass of Blood is the Pabulum of the Animal Spirits as I think none can deny since any considerable Evacuation of it presently sinks and diminisheth them then it will be very manifest that those Spirits are able to perform all those Actions that we can truly suppose Animal Spirits to do for if by withdrawing that sweet Viscid Pabulum that sweet oyly Mucilaginous Moisture in the Brain be diminished and upon that Diminution the Animal Spirits are presently less vigorous and on the contrary if by enriching the Blood and consequently encreasing the stock of Animal Spirits the Actions of the Body as well as of the Mind be stronger we must consequently believe that they are moderately performed by them when that oyly Substance neither too plentifully abounds nor is too much spent and consumed But some People will not believe That to be Animal Spirit because they say they cannot get so much as one drop of it out of the Vessels To which I answer that if they deny it to be Animal Spirits because they cannot gather it in drops by the same Reason they may deny Blood to be Blood because in small capillary Veins when it is coagulated it cannot be dropped out For not only the capillary sanguiferous Vessels are so small that they cannot be seen by good Microscopes but also the Nervous Fibers are so extreamly diminutive and fine that they have been computed to be fourscore times as Fine as a Hair and consequently the Liquor contained in each must be so little that five or six Hundred Vessels must be joyned together to make one Drop so that being separated and divided into very small Portions by the Intermixture of the Vessels it is no sooner exposed to the Air but is immediately chill'd and coagulated Which we may more easily believe when we take Notice how thin and fluid the Mass of Blood is as long as it is in a swift and constant Circulation that if a capillary Vessel be but pricked with a small Pin Blood immediately spurts out yet how soon when exposed to the Air does it thicken and coagulate though it be exposed in great Quantities so that one would scarce think it fit to move through Veins so small that they cannot be discerned by the best Microscopes much rather then may the Animal Spirits whose Portions are so incomparably diminutive be forthwith chill'd and thicken'd when they immediately as soon as they are expos'd to the Air are almost equalled with Particles of Nitre But be it never so evident that these are the Animal Spirit 's that are in the Brain yet most deny them a constant and free Circulation But since we see that Blood which is much more gross and thick than Animal Spirits when coagulated as long as it is in a quick and brisk Motion can move through the smallest Capillaries we have great Reason to believe that the Animal Spirits would move much more swift when separated and preserved from the Nitre of the Air and although they immediately thicken when exposed to the Air yet are they much more thin and liquid when in Circulation But it is not only evident that these Spirits are in a continual Motion but also highly necessary For either they must be in Motion or stagnate and if they should stagnate they would in a short time corrupt and putrify Besides since there is a continual and constant Supply separated in the Cortical Parts of the Brain there must be a continual Decrease or otherwise there would be no room to receive them which Evacuation we can rationally imagin to be no other way but through the Branches of the Nerves and also because we perceive the Effects of them in the Musculous Parts From hence it appearing that that oyly Substance in the Brain is separated from the Mass of Blood being the sweetest and most spirituous Part of it and that it must needs circulate continually through the Nerves I shall now consider the Nature of it that we thence may gather more clearly the Manner of it's Operation Which presently appears if we do but consult our Taste the Taste of it being oyly sweet and mucilaginous that Substance being made up of the most volatile sulphureous and salt Particles of the Mass of Blood which are incorporated in some of the most digested and ripen'd Serum of the Blood and by that means appear in the Form of a Mucilage That these Spirits are made up of the finest Sulphureous Particles and the most volatile Salts of the Blood is apparently proved by our constant Diet for we always perceive our selves most full of Spirit after Meat that abounds with Sulphur volatile Salts and Oyls whereas all Acids Austeres c. which thicken Oyl and take of the Force of volatile Salt and Sulphur depress our Spirits and keep them too low That these Spirits are full of
the Heart and from the Heart to the Extremities of the Vessels again being very short before there can be any sensible or considerable Decay of it the Blood is anew fermented in the Glands and so by a continual Circulation the Heat of the Blood is preserved and because by this time the Animal Spirits mixed in the first Fermentation with the Blood are almost spent being incorporated with it and because Part of it is continually separated in the Brain it meets a second time with new Supplies and also by repeated Fermentations is more impregnated with Spirits as well as digested and ripen'd to a higher Degree of Maturity Thus I have given an Account how the Heat of the Blood is carried on in the Vessels that it might more clearly appear how the Original Cause of Heat is principally in the Glands That the Animal Spirits are put into an elastick Motion in the Glands I have before proved by the grosser Particles of the Blood and that the Blood so fermented is successively cast out into the Veins is plain enough to any one that does but understand Circulation to prove then that the Blood being thrust out of the Glands does by a further Expansion of those Spirits for a while increase the Fermentation and that when the Vigour of the Spirits is spent it will gradually decay we need but take Notice how Fermentation is begun and carried on in other Liquors for when oyl of Vitriol and Spirit of Armoniac Salt are mix'd together the Parts of each being in some measure mixed and put into Motion by dropping the one into the other they presently begin to ferment which fermentation is gradually exalted till by a frequent Collision and Attrition the most Fermentative Parts fly away or their Vigour is lost and then Fermentation gradually decreaseth and in like manner all other Liquors that for a time ferment with a sensible Heat But if possible it will further appear that the Original Principal Cause of Fermentation is in the Glands if we do but consider how Fermentation is carried on in a dying Body For in a Body that is about to die the Vigour as well as Quantity of Animal Spirits being diminished and those too being less vigorously grund betwixt the Parts of the Arterial Blood expand so weakly that they scarce agitate the Mass of Blood sufficiently to preserve it's Heat but as soon as the Blood and Spirits cease to circulate the Heat of the Blood presently grows milder till at last it is quite extinguished Now if when the Fermentation is weak the Heat of the Blood is more remiss and depressed and when Circulation is stoped it consequently ceaseth it must needs follow that the Animal Spirits are the Cause of that Fermentation and that it is promoted by driving those two Liquors forcibly together and that the Fermentation is chiefly caused in the Glands is plain because when the Spirits and Blood cease to be driven together and there fermented the Heat of the Blood decreaseth and that it is not in the Vessels is evident because after Circulation is stoped it presently declines whereas if it were caused in the Vessels it would continue after Death as well as before since it then hath the same Matter though it wants Circulation and a forcible Mixture and what I have shewed to be the Consequences of it I shall only bring one Argument more to prove that the Heat of the Blood depends upon the Attrition and Fermentation in the Glandules which may be inferr'd from this common Observation that the Heat of the Blood is encreased by all violent Motion For upon all violent Motion a larger Quantity of Animal Spirits being sent to the Parts to be moved in order to prepare a greater Quantity of subtile Liquor to distend and dilate the Fibres the Fermentation is not only raised higher in the Glandules but the Motion of the Heart being thus accidentally increased quickens the Circulation of the Blood so much that before the vigorous Motion of it's Parts which was raised in the precedent Fermentation is spent it is again renued But the Circulation of the Blood is not only quickened by the Contractions of the Heart but also by the frequently repeated Contractions of the Muscles For the Heart contracting sends it out into the musculous Parts and again those Muscles drive it sooner and more forcibly back upon the Heart from whence it appears that both the Heat of the Blood is encreased by being often fermented in those Glandules and consequently that it depends on the Mixture and Fermentation of the Animal Spirits and Arterial Blood From hence it is manifest how far Circulation is beneficial in carrying on the Heat of the Blood and if we consider the Reason which I have given of Muscular Motion we shall see that as Fermentation depends on Muscular Motion so Muscular Motion depends on Fermentation so that as I said before there is a continual Chain and Circulation of Causes as well as Humors in a Man's Body To proceed therefore to the second Objection I supposed some might raise viz. Whether this Fermentation can be carried on in so short a time as a continual and quick Circulation will admit This does not only appear Possible from evident Matter of Fact but also if we consider that in much less Time than what is allowed for Fermentation in the Glandules if a Spark of Fire be put to Gun-powder it immediately puts it's Parts into an Explosion and that the Blood not only ferments in so short a time but that it may prepare that subtile Matter which circulates through the Muscular Fibres we may with a great deal of Reason believe if we do but take notice that warm Milk if it be but forcibly milked into Vinegar it presently is separated into two Parts viz. Curd and Whey If then by mixing these two Liquors they cause so great a Change on one another I cannot conceive any Reason why Part of the Animal Spirits fermenting with the Blood may not as soon be mixed with some Part of the rarified Succus Nutritius and forced forward into the Fibres But from what I have said it appearing that the Heat of the Blood Is caused in the Glandules by Fermentation and how it is continued in the Musculous Parts I shall in the next Place consider in what Parts it is most vigorously fermented which will appear only by considering where the Spirits are most plentifully laid down for if Fermentation depends on and is chiefly caused by the Animal Spirits as I have shewn then it must needs follow that the Heat of the Blood is most promoted in those Parts where Animal Spirits are most predominant And having proved that in order to prepare that subtile Liquor which causes Contractions of the Muscles a greater Quantity of Animal Spirits is sent there it will follow that the Blood grows hotest being most vigorously fermented in those Parts that are in Motion and