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
Animal Spirits are too high and volatile or too much in Quantity they raise this Fermentation so high that the Blood is presently put into a Preter-natural Heat from whence proceeds that Preter-natural Heat in Fevers And the way that Physitians either do or can take in such Cases is either to take down the Animal Spirits by withdrawing Part of their Pabulum and by Acids given internally to harden the Texture of the Blood and make it less subject to grow too Hot by Fermentation or otherwise by cooling and fixing those predominant Spirits and evacuating other accessory Causes by proper Excretories and Emuctories of the Body Lastly That the more any rarified Sulphureous Body is expanded betwixt the more gross and solid Parts of Matter those gross ones are put into a stronger Motion is evident from a Musket charged with Shot which with a small quantity of expanded Matter will scarce be moved but by a greater quantity of exploded Matter are put into so swift a Motion that they fly forcibly a considerable way Having thus far proved what I proposed to be reasonable and likely and nothing but what is consonant to the Practice of most Rational Physitians I proceed to shew that the sharper the Particles of the Blood are they corrode and grind the Spirits into small and minute Particles with a great deal more Violence and by that means cause them to expand more vigorously and by putting them into a strong Motion cause a higher Degree of Heat This is sufficiently proved by the Preter-natural Effects that Scorbutick Salts cause in some People for when the Mass of Blood is impregnated with Acid Acrid Humors these meeting with the Spirits cause Preter natural flushing Heats which appear in several Parts of the Body and sometimes in the whole which are so violent that those that are affected with them complain that they feel themselves as Hot as if they were in a Stew or a Bagnio That this Preter-natural Heat proceeds from Corrosive Salt Humours fermenting with the Spirits is very manifest since these Symptoms are only curred by such Medicines as correct the Acidity and Acrimony of the Blood viz. When it most partakes of Acrimony by sweet diaphoretick Decoctions or some sort of Acids which dull and take off their corroding Edges or when they are more Acid by volatile Salts that carry them off by Sweat or Urine or by Acid Absorbers which by correcting the Acidities of the Pancreatick Juice leave the Ferment of the Liver more predominant and the bitter Choler being by that means bred a great deal more plentifully digests and carries off those crude Humors which by the aforesaid means being made thin enough to go off by Urin and insensible Transpiration are dispersed and carry'd off those ways and the Mass of Blood being cleansed of those sharp Humors is reduced to a healthful State If then by considering the Nature of those Medicines that correct vitious Humors we may learn to know what is the Nature of those Humors we must conclude that whatever is corrected by Medicines directly contrary to Acrimony the nature of that Humor is Acrid and when by the Use of volatile Salts the distempered Humors of our Bodies are attenuated and disposed to Evacuation and at the same time we know that volatile Salts by volatizing and preparing the superfluous fixed Acid Acrid Humors of the Mass of Blood dispose them to be carried off we have all the Reason imaginable to conclude that when we find those Medicines carry off such Symptoms that they are caused by such Humors And that these flushing Heats in the Scurvey proceed from Acrid Acid Humors is plain because all Salt Meat that abounds with Acids and all sharp Acrid Bear that hath an Acrid Fluid Salt predominant in it as also Vinegar and such like make those Symptoms more violent If then both from the Method of Cure and the Cause it self augmented by such Sorts of Juices we gather they proceed from sharp Acrid Acid Humors we may be certain that those Symptoms are caused by such Humors grinding and corroding the Animal Spirits and that by putting them into a Preter-natural Motion they are the Causes of such Sensations And that those Sensations only proceed from thence we may easily conceive for since as long as those Humors circulate with the Mass of Blood and forcibly meet with the Animal Spirits they can only affect them by moving amongst them they must needs put them into a more swift Motion and an unusual Expansion by corroding and grinding them more powerfully betwixt their Particles which is evident from the cause of those flushing Heats I just now mentioned and from the Reason I have before given of Heat But that the sharper the Mass of Blood is the more the Animal Spirits are ground and expanded betwixt the Particles of it is evident from Reason it self for it being proved before that the Heat of the Blood proceeds from a swift intestin Motion of the Particles of the Blood and Spirits caused by Attrition nothing is more Reasonable than that the more solid the Mass of Blood is the stronger the Attrition is and consequently the Motion of Particles which upon our sensory cause heat must be more violent and as in striking of a Flint with a peice of Steel the more firm and hard the Steel is the more powerfully it loosneth the Texture of the Flint and strongly expanding it's Sulphureous Particles puts them into that Motion which constitutes Flame so by Parity of Reason we may expect that the Particles of Blood will cause the Sulphureous volatile Parts of the Spirits to expand more powerfully the more solid and compact they are And that the Texture and Constitution of Saline Humors is more Solid and their Parts more Corroding than of a sweet Balsamick Liquor I think none can deny who compares Vinegar and Spirit of Vitriol with Tincture of Sulphur and although in Fevers where the Blood abounds with too much exalted Sulphur Spirit of Vitriol and other Acids cool the Blood by fixing the Spirits and Coagulating the Sulphur yet when the Blood is impregnated with Scorbutick Salts Acidity joyning with Acrimony causes Heat by corroding the Spirits when they want a Mixture of crude Sulphur to dull their Edges of which it would be no difficulty to convince those that are considerably troubled with scorbutic Symptoms But furthermore I shall prove that the Mass of Blood the more it abounds with volatile Salts and Sulphurs is more easily put into a violent Heat and that it's Particles being more easily put into Motion readily joyn with the Animal Spirits and encrease theirs and that on the contrary the more dull and phlegmatic any Body is the less apt are it's Particles to be put in Motion And as it is commonly taken notice of in all Bodies so it is not less observable in the Mass of Blood for we always find that the least quantity of any volatile Liquor
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
A TREATISE Concerning the HEAT OF THE BLOOD And also of the USE OF THE LUNGS By RICHARD BOULTON of Brazen-Nose College in OXFORD LONDON Printed for A. and J. Churchill at the Black Swan in Pater-Noster-Row 1698. IMPRIMATUR JO. MEARE Vice-Can Oxon. Jan. 24. 1697. HUNC Librum cui Titulus A Treatise of the Heat of the Blood c. dignum Censemus quî Imprimatur Thomas Millington PRAESES Samuel Collins Edward Hulse Richard Morton Charles Goodall CENSORS Martij 5. 1697 8. TO THE Reverend Dr. JO. MEARE PRINCIPAL OF Brazen-Nose College AND VICE-CHANCELLOR OF THE University of Oxford SIR IT is not any great Opinion I have of my present Performance though there are some who would perswade me that it is not altogether despicable that makes me presume to prefix your Name before it Indeed amongst Men of Sense and Learning Truth for the most Part brings it's own Recommendation along with it and finds that Candid and ready Reception which it deserves But the Generality of Mankind will not relish any thing that bears not in the Front some great and eminent Name And for this Reason it is that I have made bold to make this Dedication Your real Worth which hath deservedly placed you in two Eminent Stations to both which you do more Honour than you receive from them And the Encouragement and Favour you shew to all Persons of Industry Vertue and good Learning under your Government soon determined me in the Choice of such a Patron though my small Share of each of the latter could merit neither of the former And here according to the usual Mode of Dedications I might easily enlarge upon so fair a Character But as it is your peculiar Delight to oblige do good with all the ease and sweetness imaginable so with as little Noise and Ostentation possible And I should sooner hope for your Pardon for this Presumption and the Faults of my Book than for such an Attempt upon your Modesty I shall therefore only add that you would be pleased to accept this as a Testimony of my Duty and Gratitude and that I shall always remain Reverend SIR Your Ever Obedient and Obliged Servant R. BOULTON To the very LEARNED AND JUDICIOUS Dr. R. ANGELL Resident in the CITY of CHESTER Learned Sir SIXTEEN Years Education in a University and a great many more improved in succesful and judicious Practice hath sufficiently qualified You for a Judge and Patron when I consider the former and withal my own Weakness I confess I have less Reason to desire the latter But sinoe it usually happens that those that are least subject to Faults are commonly candid Criticks and most ready to forgive others I am bolder to beg your Patronage yet not for it's Faults since that is below your Judgment but whatever Truth is contained in it which will scarce be deny'd by One that is so much an Encourager of Learning But perhaps I ought to make an Apology to You as well as the World for deviating from the Opinions of some Learned Men especiatly of that never too much Honoured Dr. Willis who was One of the Greatest Physitians of his and preceding Ages And truly all that I can say for my self is That as it would be below the Character of so Great a Man to write any Thing upon any other Consideration than an Improvement of Knowledg and Truth so undoubtedly he would not desire any Thing he writ should be believed except it seemed so That then which I hope will be an Apology for such an Attempt is That I have considered his Opinion with no other Design than an Endeavour after Truth and have offered nothing against his Opinion but plain and unprejudiced Reasons and though I have given Reason enough to prove he was mistaken in this Point yet I must ever have the greatest Veneration and Esteem for all such Men of unparallelled Worth and Learning and so candidly Ingenuous But whether this little BOOK may pretend to any Reason for what it offers or not I am more encouraged to ask Your Patronage it being approved by Men of noted Learning and eminently Judicious the President and Censors of the College of Physitians of which Number that your Self is not a Member no other Reason can be given but that Your own Choice of a more retired Life hath fixed you in that CITY where you are now resident to the Satisfaction and Good of those that commit themselves to your Care But Learned Sir That I may not press too much upon your Patience That Patronage which you were pleased to Give my Last when I was a Stranger to You both encourages me to hope for it now You have been pleased to take me into Your Favour and also that You 'll Pardon me for taking this Liberty since it is only designed to testify my Gratitude for those Favours You have already been pleased to Confer on Your very Humble and Obliged Servant R. BOULTON THE CONTENTS THE Introduction Page 1 Our Knowledg is very short ibid. And Imperfect p. 3 The Pursuit of Knowledg very desirable p. 4 Where most easily attained p. 5 The Heat of the Blood not obscure in respect of it's Cause p. 6 The Opinion of the Antients very Superficial p. 9 Dr. Willis's Opinion answered p. 11 But one Way by which Bodies grow hot p. 13 Fire is rarified Matter in Motion p. 16 Heat not actually in the Body that causes it p. 19 Heat only a Sensation p. 20 Heat only produced one Way proved further in Answer to Dr. Willis p. 23 An Objection answered p. 27 His comparison of the Blood 's Accension with Flame answered p. 28 Several Degrees of Heat without Flame p. 29 Nitre makes no Part of the Flame p. 32 How Nitre promotes Flame p. 33 Why a Candle in a Glass-Globe is extinguished by extracting Air. p. 36 Whether Nitre promotes the Heat of the Blood p. 39 Liquids fetter up Heat without Nitre p. 41 Blood may grow hot without a Sulphureous Pabulum p. 42 His Comparison of the Recrements of Flame and Blood answered p. 43 A Digression why Flame usually ascends p. 50 Why it sometimes descends p. 60 Diemerbroek's Opinion answered p. 62 Dr. Henshaw's Opinion answered p. 65 Of the true Reason of the Heat of the Blood p. 67 Animal Spirits Demonstrated p. 80 That they are in Motion through the Nerves p. 89 The Nature of them p. 91 The Reason of the Heat of the Blood explained p. 94 That Reason of it's Heat prov'd p. 100 By Attrition p. 103 How the Animal Spirits rarify the Blood p. 111 Why the Heat varies p. 112 How Sp. of C. C. raises the Pulse p. 116 The Reason of flushing Heats p. 120 How far the Blood and Spirits are Active and Passive p. 131 How the Heat of the Blood is continued p. 132 Some Objections answered p. 134 Why it's Heat declines p. 139 Of the Use of the Lungs p. 159 In Respect of the Soul p. 162 Why they
ought to be in Motion p. 164 The Use of the Lungs in respect of the Body p. 169 To dilate the Ventricles of the Heart p. 174 How obstructing Respiration kills an Animal p. 178 Whether Air be mixed with the Mass of Blood p. 191 Whether Nitre be p. 192 And how p. 193 What Effects it hath upon the Mass of Humors in the Lungs p. 196 How Nitre depresses the Heat of the Blood p. 198 Pag. L. Read 41. 5. Occasion for Accension 53. 18. Motion for Notion 60. 2. Exploded 84. 8. Blood for Body OF THE HEAT OF THE BLOOD EVEN Philosophy in General is so Mysterious and so infinitely out of the reach of our short and weak Capacities that the best of Philosophers may truly be said to have but a slight and superficial Knowledg of it For if that small Part we know be compared with what we know not all our Knowledg is but as an invisible Speck those things to which it extends being inconsiderable if compared with that vast and endless Mass of the Universe But although that Part of the Universe which in some Measure lyes within the Cope of our Senses be small and inconsiderable when compared with the vast Extent of the whole Creation yet when we reflect on the vast Variety of Objects contained within those narrow Dimensions we find and must needs acknowledg it very considerable and superabundantly furnish'd with Matter for our Senses to work upon For the Extension of our Knowledg as to those Objects is bounded by Limits not very spatious notwithstanding the Diligence and Industry of Learned Men and the great Improvements made in most Parts of Knowledg The wisest Men and the most profound Philosophers must of necessity own that of those Things they know most their Knowledg is very imperfect We know but in Part and indeed so small a Part that it chiefly seems to inform us more sensibly of our Ignorance But so pleasant and desirable is Knowledg and we find so much uneasiness in Ignorance when once we have tasted of it that it 's impossible to abstain from a further Pursuit after it at least notwithstanding the vast disproportion betwixt our Knowledg and Ignorance which continually lyes in our way to discourage us And as we thirst after Knowledg with a desire to attain to a more adequate and compleat Apprehension of it so we most eagerly pursue those Parts of it which we hope to understand most clearly and which we expect to make a Progress in with the most considerable Advantage Since then the Microcosm which is as if it were a Type and Epitomy of the Macrocosm lyes much more within the narrow Cope of our Senses since we can dive and search into all and the inmost Recesses of it and come nearer to those Springs and Fountains upon which all the Effects we perceive in it depend we have much more solid and firm Foundations to proceed upon than in any other Parts of Philosophy whatsoever and may much more reasonably hope for Certainty and Truth besides the Pursuit of it must needs be not only more Pleasant but Advantagious And although in a Man's Body some Things are much more apparent clear than others yet the most obscure may easily be so far explained and understood as is necessary and subservient to shew the Use of them and to what Ends they were designed Amongst those that are accounted most obscure the Heat of the Blood is unfortunately one but the Reason why it is so is not that it is less apparent in it self but rather the Inadvertency of those that searched into it If possible such great Men as have writ concerning it may be guilty of so great a Fault which although otherwise no small one is much more excusable in those whose more weighty Concerns take 'em of a deeper Enquiry Since then so many learned Men and those to whom Physick is not least obliged for considerable Improvements have writ on this Subject I think it not only Justice but also Reasonable I should shew upon what Grounds and for what Reasons I have rejected their Opinions before I take leave to propose my own It would be needless to spend time in Informing my Reader that both Antient and Modern Writers have endeavoured to account for it and it would be Information to but a few since none that have made any considerable Progress in Physick can be ignorant of it I shall only as briefly as I can mention the Opinions of the Antients that it may better appear to the more unlearned wherein they are deficient and then I shall consider the most remarkable Opinions of the Moderns that less competent Judges and young Students in Physick may spend less time in convincing themselves how far they come short of explaining the Reason of the Heat of the Blood Amongst the Ancients who wanted those Improvements in Anatomy that have been made of late to direct them in their Judgments some fancied that it proceeded from a Calidum innatum or innate Heat which was fixed and rooted in all the Parts of a Man's Body before his Birth and that This continued Heat by communicating it self successively to the Nourishment of the Parts as soon as it was received by them Which indeed was so weak and superficial an Account of it that it rather served to please the Unlearned then to satisfie the Curious and more Inquisitive Others thought that there was a sort of Flame lodged in the Heart which kindled the Blood as it passed through it But Moderns having learnt by a further and a deeper Insight into Mens Bodies that the former of those was rather the Effect than the Cause and by frequent Dissections that the Heart was altogether incapable of containing such a Flame and also that that which they supposed to be the Pabulum of it to be clotted Blood they have with sufficient Reason rejected them both Wherefore passing by these I shall proceed to consider those Modern Opinions which are thought most worthy our Consideration The first that I shall take Notice of is the Opinion of the most Ingenious Dr. Willis who although in some things he hath had the Fortune to be mistaken with other Learned Men the best being not exempt yet for the most part hath made the greatest Improvements of any of his Predecessors in Theory This Learned Author in the eight Paragraph or thereabouts of his Exercitation concerning the Heat of the Blood takes Notice that there are three Modes or Sorts of Causes by which Liquids grow Hot. First à culido ad moto or by applying them to something that is Hot as when Water boyls over the Fire Secondly when Saline Corrosives mutually act upon one another or on sulphureous Bodies mixed with them by an intense and powerful Agitation Thirdly when a Liquor abounding with much Spirit or Sulphur takes Flame from some other Body And in the next Paragraph
sometimes so high a degree of it as actual Flame as when Spirit of Wine and Oyl of Turpentine are mixed together And that Heat proceeds from an Attrition of sulphureous Particles and their violent Motion I have not only brought Instances enough to make it appear but have sufficiently proved it before in my Answer to Dr. Willis's Opinion And now since not only Solid but also Liquid Bodies grow hot by an Attrition of their more volatile and sulphureous Particles betwixt the more gross ones and since there appears from what I have before said but one way by which all Bodies grow hot we must needs conclude that the volatile salino-sulphureous Particles of the Spirits grow hot by being ground betwixt the grosser Particles of Arterial Blood and that those by putting the whole Mass into a more violent Agitation cause the Heat of the Blood But some will perhaps say that in all those Phaenomena I have mentioned these grosser Parts of Matter which grind upon the sulphureous Particles are put into Motion by something else But they do not perceive how the grosser Parts of the Blood are put into Motion first To which I answer that the Particles of the Mass of Blood are put into Motion by that force which is always inseparably joyn'd with Circulation so that in a Man's Body as there is a continual Circulation of Humours so there is of Causes for the Fermentation in the musculous Glands is raised by the Mass of Blood grinding the Animal Spirits betwixt the Parts of it in which Fermentation a subtile Liquor is prepared which being forced into the Fibres of the Heart cause it to contract which Contraction forces the Blood and consequently the Nervous Juice through their distinct Vessels and so causes them again to meet and ferment a second time in the Glandules and as Circulation is preserved and carried on by the subtile Liquor which is continually prepared in this Fermentation so the Particles of the Blood are mixed with the Spirits and preserved in Motion by Circulation Having thus shew'd that the Heat of the Blood may as probably proceed from Attrition as Heat in any other Bodies since Heat is nothing else in respect of that which causes the Sensation than a quick intestin Motion of Parts and since those can be put into Motion no other way but by Attrition I should in the next Place prove that the Particles of refined and rarified Matter always expand and endeavour to fly away but being reverberated by the Opposition of those gross ones with which they swim their Motion is inverted and by that means much increased But it is so evidently True that it needs not for we always observe that where any two Bodies meet together and strike against one another that which is less yields to that which is most solid and makes the strongest Opposition this is manifest in Flame it self as also in the Expansion of Gunpowder for if a Gun be shot against a Wall the Flame of the expanded Gun-powder striking against it presently flyes back again and by mixing with that which immediately follows it encreaseth the force of it and for this Reason a Gun which is charged with a greater weight of Shot more forcibly recoils the Powder not finding free Liberty to expand but flying backward with a greater Force It is also further evident from the Reason which I have given why Nitre is beneficial-in continuing Flame and making it more vigorous The gross Parts of the Blood having thus put the Animal Spirits into a swift Motion and by inverting them in their Motion having caused them to encrease one anothers Motion the Spirits at last set upon the Mass of Blood and by breaking and dissolving the Particles of it rarifie them and cause them to expand also so the Rays of the Sun being in a swift Motion and gathered into a Point by a burning Glass grow more vigorous so as to dissolve and burn even solid Bodies and after the like manner Flame by the force of it subtilizeth and attenuates the Sulphureous Parts of it's Fuel neither does it only rarifie and expand the Sulphureous Matter of it's Fuel but also carries violently the Ashes of the calcined Matter along with it where it may be observed that as the Particles of Animal Spirits are not in so strong a Motion as those of Fire so the Particles of the Blood are moved with a more easie force then Ashes which are far more Solid But for a further Proof that the Mass of Blood grows hot in a Natural state by the Methods and Ways which I have endeavoured to explain I shall in the next place prove that the Animal Spirits being put into Motion according to their different Quantities differently expand themselves and exagitate the Mass of Blood and put it's Parts in a more violent or weaker Motion and consequently encrease or diminish the Heat of it And this is easily manifest if we do but observe that young healthful People whose Nerves as well as the Fountains from whence they spring are full of and abound with Spirits are always of a more brisk and vigorous Heat then People of a declining Age whose Nerves are less plentifully stocked with them But it is not only observable in People of different Ages but also in different Constitutions that as the Pabulum of the Animal Spirits is more plentiful and yields a more constant and large Supply so the Heat of the Blood is more powerful and intense as in cold and Phlegmatick Constitutions where the Mass of Blood abounds with dull Phlegmatick Humours or Acid and Austere Juices of too close and compact Texture and a large Supply of Spirits is denyed the Blood is not of so hot a Temper as in Cholerick Constitutions whence it evidently appears that the Heat of the Blood depends on the Vigour of the Animal Spirits for if when the Vessels are filled with Spirits and plentifully supply the Glands that Fermentation is raised higher and by that means the Heat of the Blood is accordingly encreased it is a most certain Conclusion that the Heat of the Blood depends upon the Effects that the Animal Spirits have in that Fermentation Which is further confirmed by the common and constant Practice of all Physitians for when the Natural Heat as some call it is languid and weak and almost extinguished they give such Medicines as increase the Heat of the Blood by renuing the Vigour of the Spirits whence to People that are almost a dying their Spirits being dulled or exhausted nothing is more usual then to give them Spirits of Harts-horn or of Armonick-salt or some other Saline or Sulphureous Spirits which presently joyning with those in the Nerves encrease the Fermentation in the Glands and by that means put the Mass of Blood into a more swift Exagitation and by raising the Fermentation not only renue Circulation but the Heat of the Blood On the contrary when the
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
except by hindring the fierce volatile Parts which ought to be dissipated from flying away through the Pores of the Skin which being increased thereby to too great a Quantity exagitate the Mass of Blood too much From hence it breifly yet plainly appears that the Nitre of the Air alters the Colour of the Blood and also serves to temper the Heat of it I shall now consider what Effects it hath upon the serous Lympha and if we may but compare it to Milk which differs only from Chyle by being less impregnated with Oyl it will be manifest that it precipitates the Watry Parts of the Serum which joyning with the fixed Salts of the Blood dispose them to be separated and carryed off by the Urinary Passages This is so strongly proved both by Non-Naturals and Medicine that to deny it would be to contradict Reason and plead Ignorance of those Things it is almost impossible for us not to take notice of for if we sit by a Fire in a close warm Room and drink a good Quantity of Beer which is not very strong it presently if we go into the cold Air runs off by Urin besides nothing in Medicine is a more known and common Diuretick than Sal. Prunel which is purified Nitre concentered and condensed and it is no less observable in an Experimental Observation of the Famous Dr. Lower's who in his Book de Corde takes notice that as much Serum is precipitated in a short time after we rise from Bed as in the whole night when we are less affected with the ambient Air. How Beneficial Nitre is in Precipitating the Serum of the Blood and what Advantages the Animal Oeconomy receives thereby I shall not now enquire yet how inconsiderable a Part of it's Office soever it may seem yet if it be duly weighed it will appear very useful From what I have said concerning the Alterations made on the Blood and it 's Serum I should now proceed to consider how they influence each other but since as much as is sufficient for our present Purpose may be gathered from what hath gone before it being plain that the cool Serum will help to temper the Heat of the Blood and vice versa I shall wave a further Notice of it here and should rather shew That The Lungs perform many more and considerable Offices in respect of each Part But to explain them would not only be to treat of the Lungs but the whole Body and the Use of all the Parts which being not my present Design I shall omit giving an imperfect Account of them because they are so interwoven mutually with one another that they cannot truly be understood without an Account of the whole FINIS Our Knowledg in Philosophy is limited to a small Part of the Creation Which is furnished with Objects too copious for our Senses Of which at the best we have but an imperfect Knowledg The Pursuit of Knowledg very desirable Especially of that which is most Advantagious There is more Reason to expect Truth and Certainty in the Microcosm than the Macrocosm Where it is easily attained The Heat of the Blood not obscure in respect of it's Cause Both Antients and Moderns have differed as to the Cause of it The Opinions of the Antients very Superficial and Insatisfactory Dr. Willis ' s Opinion considered Who asserts that there are three ways by which Liquids grow hot And that the Blood grows Hot by Accension To which it is answered that there is but one way in Philosophy by which all things grow hot Several degrees of Heat differ only in Degrees of a peculiar Power to cause Heat And Fire which is the highest is rarified Matter in a swift Motion which Masked in different Subjects affects not our Sight Heat is not actually in the Body that causes it but potentially because that Body hath a power to cause such a Sensation Heat is only a Sensation which is actually where there is Sense to perceive it That Heat is only produced one way further proved Viz. by putting the Parts of Matter into Motion A seeming Objection answered His Comparison of the Bloods Accension with Flame considered There are several degrees of Heat produced without visible Flame Nitre makes up no part of the Flame The Nitrous parts of the Air promote Flame by keeping i'ts Matter from dispersing too soon Wherefore Fire burns better in the Winter than in the Summer Why a Candle in a Glass Globe is extinguished by extracting the Air. His Comparison of extinguished Flame compared with the Death of an Animal considered Nitre does not promote the Heat of the Blood but rather depresses For in Liquids the volatile Parts are sufficiently opposed by the Parts of the Blood and kept from flying away Blood may grow hot without a Sulphureous Pabulum His Comparison of the Recrements of Flame and of Blood considered Which appears widely inconsistent First because that Juice that sweats through the Coats of the Trachea and the Skin is not Recrementitious And the Fuliginous Effluviums of Fire are Recrements Secondly because the former if not carried of encrease it But Smoak extinguishes Fire Smoak is not altogether an Effluvium of Flame Smoak thus compounded A Digression in which is given the Reason why Flame Ascends rather then Descends Which is because it hath less Opposition in it's Motion that way Because the Air the nearer to the Center makes stronger Opposition than that above Which is proved by these Experiments It is also proved by the Expansion of Gunpowder The Motion of Flame downwards is a natural Motion in Philosophy Diemerbroek's Opinion examined Dr. Henshaw ' s Opinion considered Antient and Modern Writers have rather disputed about the Vse of Words than much difference observable in their Opinions The Reason why Heat affects our Sensory does not shew how it comes by that Power The Blood grows hot by Attrition the Consequence of which is Fermentation Attrition and the consequence of it both to be signified by the Word Fermentation How far the Heat of the Blood proceeds from Pressure and Mixture To dispute about Words is not material in an Enquity after the causes of Things The whole Body is made up of Vessels and Humors contained in them By what means the Spirits and Blood are mixed in order â—o a Fermentation Animal Spirits demonstrated In the substance of the Brain Viz. that Mucilaginous oily Moisture which we call Brains An Objection Answered That it is the most spirituous Part of the Blood and consequently Animal Spirits proved That oyly Substance is capable of performing all those Actions which we can suppose the Animal Spirits do Another Objection answered That these Spirits are in a constant Motion proved The Nature of the Animal Spirits considered The Reason of the Heat of the Blood explained How it's Heat is promoted The Heat of the Blood varies according to the different Quantities of them It varies also according to the sharpness of those Humors that put the Animal Spirits
into Motion The volatile Salts and Sulphurs in the Mass of Blood make it more apt to be fermented Which is more or less promoted according to the different Degrees of the Activity of the Spirits Neither the Animal Spirits nor Arterial Blood are wholy Active or Passive That the Heat of the Blood proceeds from Fermentation proved That Heat proceeds from Attrition further proved Not only solid Bodies but also Liquids grow hot by an Attrition of their Particles The Particles of 〈◊〉 of these Humours are first put into Motion by Circulation That the Particles of refined and rarified Matter are by an Inversion of their Motion put into a higher degree of it proved How the Animal Spirits rarifie the Blood That the Animal Spirits according to their different quantities differently exagitate the Mass of Blood prov'd By the observation of People of different Ages As also by different Constitutions And the Practical Part of Physick How Spirit of Harts-horn raises the Pulse That the Spirits according to their different Degrees of Activity variously exagitate the Mass of Blood The sharper the Particles of Blood are the more they corrode the Spirits and put them into Motion The Keason of flushing heats in the Scurvy Proved by comparing the Nature of the Medicines that oppose it and correct it That as the Blood as more or less Volatile it's Parts are put more or less easily into Motion proved And that it is differently promoted according to teir different Degrees of Activity of the Spirits How far the Blood and Spirits are Active or Passive How the Heat of the Blood is continued Some Objections considered and answered The first Objection answered viz. whether the Heat of the Blood be chiefly caused in the Extremities of the Vessels The Reason why the Heat of the Blood in time decays And that Reason proved How Fermentation is carried on in a dying Body and the Reason why it ceaseth when it is quite dead Another Argument to prove that the Heat of the Blood depends on and is caused by Attrition Fermentation Circulation mutually depend on one another The second Objection answered viz. That Fermentation may be performed in so short a time as the Circulation of the Blood admits The Blood is more powerfully fermented in the substance of the Heart than in any proportionable Part of the Body besides Fermentation is not only promoted in the Muscular Parts but also in the internal Bowels Three things requisite to continue the Heat of the Blood The Vse of the Lungs in Respect of the Soul Is to express all it's Conceptions and Reasoning Why the Lungs ought to be in a continual Motion is because It carries off that Superfluous Moisture that supplies them And that their voluntary Motion might less Preternaturally affect our Bodies What Effects it causes when too thick and also why thick foggy Air is troublesom to some People The Vse of the Lungs in respect of the Body Seems to be to perform the Office of another Heart By helping the Blood to force violently enough into the Cavities to distend them against the next Contraction How stopping the Breath of an Animal kills it Why by permitting it to breath again the Circulation of the Blood is renued How the Motion of the Heart is promoted in an Infant unborn The Office of the Lungs is partly voluntary partly involuntary What Effects the Air hath upon the Mass of Blood In respect of it's Colour Nitre depresses the Heat of the Blood What effects Nitre hath upon the Serum of the Blood