the chief Fibres of all the Muscles which is the Heart that they encompass its Orifices Auricles and Arteries that they spread themselves even in the substance of the Lungs and so by their different motions produce very considerable changes in the Blood For the Nerves which are dispersed through the Fibres of the Heart cause it somerimes to extend and then again to contract with too much force and precipitancy pushing with much violence a great quantity of Blood towards the Head and all the external parts of the Body yet sometimes these Nerves produce an effect directly contrary And the Nerves which encompass the Orifices Auricles and Arteries of the Heart cause very near the same effect with those Spiracles or breathing Holes with which the Chymists moderate the heat of their Furnaces and as the Spouts do which are made use of in Fountains to diminish or encrease the force of the stream For the use of these Nerves is diversly to contract or dilate the Orifices of the Heart and so to hasten or retard the filling and evacuation of the Blood and thereby to augment of diminish its heat Thus the Nerves which are dispersed through the Lungs have also the same use for the Lungs are compos'd only of the branches of the Wind-pipe of the Venous Artery and Arterious Vein interwoven one with another it is visible that the Nerves which are extended throughout the whole substance by contracting of them hinders the Air from passing with so much liberty through the branches of the Wind-pipe and likewise impedes the motion of the Blood through the Venous Artery into the Arterious Vein and so into the Heart Thus these Nerves according to their different agitation still augment and diminish the heat and motion of the Blood In all our Passions we have very sensible Experiments of these different degrees of heat in our Heart Sometimes we feel it manifestly encrease and diminish all of a sudden and as we falsely judge that our Sensations are in the parts of our Bodies and so by that means excite our Soul as it was explained in the first Book so almost all our Philosophers have imagined that the Heart was the principal seat of the Passions of the Soul and this is still the most commonly received Opinion Now because the faculty of Imagining receives great changes by what happens to the Animal Spirits and that the Animal Spirits differ very much according to the different fermentation of the Blood which is made in the Heart it is very easie to discover why passionate Persons imagine things quite after another manner from those who consider them in cold Blood The other Cause which contributes very much either to the augmenting or diminishing these extraordinary fermentations of the Blood in the Heart consists in the action of many other branches of the Nerves which we have already spoke of These branches spread themselves in the Liver II. Of the change of the Spirits caus'd by the Nerves which go to the Liver to the Spleen and the rest of the Bowels which contains the most subtile part of the Blood or what is commonly called the Bile and in the Spleen which contains the more gross or Melancholy in the Pancreas which contains an acid Juice very proper for fermentation In the Stomach Bowels and other parts which contain the Chyle And indeed they are dispersed through every place which can contribute any thing to the varying the fermentation of the Blood in the Heart Also the Arteries and Veins are united to these Nerves as Willis has discovered of the lower Trunk of the great Artery which is ty'd to them near the Heart of the Axillary Artery on the right side the Emulgent Vein and of some others Thus the use of the Nerves being diversly to act those parts to which they are join'd it is easie to conceive how the Nerve which environs the Liver may in contracting it cause a great quantity of Bile to run into the Veins and into the Duct of the Bile which being mingled with the Blood in the Veins and with the Chyle enters into the Heart through the Duct of the Bile and there produces a more violent heat than ordinary Thus when we are mov'd with certain Passions the Blood boils in the Arteries and Veins and this heat spreads it self through the whole Body the Head is inflamed and filled with so great a number of Animal Spirits which being too brisk and too much agitated by their impetuous course hinder the Imagination from representing any other things than those whose Images they form in the Brain that is from thinking of any other Objects besides those of the Passion which Rules It is the same of the little Nerves that go to the Spleen or to other parts which contain a thicker Matter and less susceptible of Heat and Motion it renders the Imagination altogether languishing and dull in causing some gross Matter and such as is difficult to be put in Motion to run into the Blood As for those Nerves which environ the Arteries and Veins their use is to hinder the Blood from passing and by contracting them compel it to run into such places as it finds the freest passage to So that part of the great Artery which supplies all the parts above the Heart with Blood being connected and compressed by these Nerves the Blood must necessarily enter into the Head in great quantities and this way produce a change in the Animal Spirits and by consequence in the Imagination But it must be well observed III. That these Judgments happen without the concurrence of our Will by the order of Providence that all this is performed meerly by Mechanism I mean that all the different Motions of these Nerves in all the different Passions are not produced by the Command of the Will but on the contrary are made without nay even contrary to its Orders So that a Body whose Soul is not so well disposed as that of a healthful Man shall be capable of all the Motions which accompany our Passions Thus even Beasts may have the like altho' they should be only pure Machines And indeed this ought to make us admire the incomprehensible Wisdom of him who hath so well ordered all these Springs that it is sufficient for an Object to move the Optick Nerve after such and such a manner to produce so many different Motions in the Heart the other parts of the Body and even in the Face it self for it hath lately been discovered that the same Nerve which extends some of its branches into the Heart and into the other interior parts also communicates some of its branches to the Eye to the Mouth and to the other parts of the Face So that it cannot raise any Passion within us but it also appears outwardly because there can no motion happen to the branches which go to the Heart but it also communicates it self to some one of those which are dispersed through the Face The
use of our own Wit and so accustom it of it self to discover truth then to suffer it to be spoiled with idleness by only applying it to such things as are already well known and discover'd Besides there are some things to be observed in the difference of Peoples Genii that are so fine and so delicate that althô we may be able to discover and perceive them well our selves yet we cannot represent them to nor make others sensible of them But to explain as much as possible all these differences that are to be observed in Dispositions and that very one may the more easily observe in himself the Cause of all the changes that he feels at different times it seems very proper in general to examine the Cause of these Changes which happen in the Animal Spirits and in the Fibres of the Brain because thereby we shall discover all that are found in the Imagination Man never continues very long in the same Mind every one hath sufficient inward proofs of his own inconstancy he judges of the same Subject sometimes after one manner and sometimes after another In a word the Life of Man consists only in a Circulation of Blood and in another Circulation of Thoughts and Desires and it seems the best way of imploying his time would be in seeking after the Cause of these Changes which happen to us so that way to know our selves CHAP. II. I. Of the Animal Spirits and the Changes to which they are subject in general II. That the Chyle goes to the Heart and thereby produces some change in the Spirits III. That Wine has the same effect 'T IS agreed by every on I. Of the Animal Spirits that the Animal Spirits are only the most subtile and active parts of the Blood which subtilises and agitates it self chiefly by the Fermentation that it receives in the Heart and by the violent Motion of the Muscles whereof this part is composed that the Spirits are conducted with the most of the blood through the Arteries into the Brain and that there they are separated by some parts that are destined to this use which are not yet agreed upon From hence may be concluded that where the Blood is very subtile there are much Animal Spirits but where it is gross there are but a sew that if the Blood is composed of such parts as are easily received into the Heart or very proper for Motion the Spirits which are in the Brain will be extreamly heated or agitated and if on the contrary the Blood ferments not sufficiently in the Heart the Animal Spirits will be languishing without action and without strength so that according to the solidity which shall be found in the parts of the Blood the Animal Spirits shall be more or less solid and consequently have more or less strength in their Motion But these things must be explained more at length by Examples and incontestible Experiments to make the truth evident The Authority of the Antients has not only blinded the Minds of some Men II. That the Chyle goes to the heart and causes some change in the Spirits but we may say it has shut their Eyes also For many Persons have still such a respect for their opinion or it may be so opinionative that they will not see some things which they could no longer contradict if they would only please to open their Eyes We may see every day Persons that are much esteemed for their Learning who write Books and publish Conferences against the visible and sensible Experiences of the Circulation of the Blood against that of Weight the Exastick power of the Air and others of the like Nature The discovery that Mr. Pecquet has made in our time which we make use of here is in the Number of those that are unfortunate only because he discover'd it before he had grey Hairs and a venerable Beard But we shall nevertheless make use of it not fearing but there will be some Judicious Persons who will not find fault with it According to this discovery the Chyle goes not immediately from the Bowels into the Liver by the Mesaraick Veins as the Antients believed but passes from the Bowels into the Lacteal Veins and afterwards into certain receptacles where they meet and from thence it goes by the Thoraick Duct or Canal along the Vertebres of the Back and so mingles it self with the Blood in the Axillary Vein which enters into the upper part of the Vena Cava and thus being mingled with the Blood it meets in the Heart From this Experiment may be concluded that the Blood thas is mingled with the Chyle being very different from the other Blood which has already Circulated many times through the Heart the Animal Spirits which are only the most subtile parts thereof will be also very different in Persons that are Fasting and others who have just Eat Moreover because that amongst Meats and Drinks which are generally used there is great variety and even those Persons that use them have bodies diversly disposed two Persons that have just Dined and at the same Table will feel in their faculties of Imagination so great a variety of changes that it would be impossible to describe It is true that those who are in perfect health digest so quick that the entring of the Chyle into the Heart scarcely augments or diminishes any of its heat and hinders not the Blood from fermenting there almost the same manner as if it entered only by it self so that their Animal Spirits and by consequence their faculty of imagining receives very little if any change But for Old and infirm People they observe in themselves very sensible changes after they have Eat they grow very dull and sleepy or at least their imagination becomes very Languishing and they have neither Vivacity or quickness left they no longer conceive any thing distinctly nor can they apply themselves to any thing whatsoever in a word they are perfectly altered from what they were before But that the most healthful and strongest may also have sensible proofs of what we have already said III. That Wine produces the same effect they need only reflect upon what happens to them when they have drunk more Wine then they are accustomed to or else by observing what would be the effects if they drink Wine one Meal and Water another For 't is certain that if they are not entirely stupid or if their bodies are not composed after a very extraordinary manner they shall soon perceive a gayety of temper some little drowsiness or some other like accident Wine is so Spiritous that it comes near the nature of our Animal Spirits but are these a little too luxurious to submit to the command of the Will because of their Solidity and excessive Agitation Thus even in the strongest and most vigorous Men it produces greater changes in the Imagination and in all the parts of the body Vinum Luctator delosus est then Meat or
any other Liquors do It gives us the Foil to speak with Plautus and produces many effects in the Mind which are not so advantageous as those that Horace describes in these Verses Quid non ebrietas designat Operta recludit Spes jubet esse ratas in praelia tendit inermes Sollicitis animis onus eximit addocet artes Faecundi Calices quem non fecere disertum Contracta quem non in paupertate solutum It would be easie enough to give a reason of the principal effects that the mingling of the Chyle with the Blood produces in the Animal Spirits and afterwards in the Brain and even in the Soul it self As why Wine rejoyces us and gives a certain Vivacity to the Wit when it is taken with Moderation and for sometime besots Men when 't is drank to Excess From whence proceeds the heaviness after Meals and many other such things for which generally very ridiculous reasons has been given But though we shall not here make a Book of Natural Philosophy yet it will be necessary to give some Idea of the Anatomy of the Brain or make some Suppositions as Mr. D'Cartes has done in his Treatise of Man without which 't will be impossible to explain our selves But if one reads this Treatise of Monsieur D'Cartes with attention we may satisfie our selves upon these questions because he explains all these things or at least gives a sufficient light to discover them as he has done by Meditation provided one has some Knowledge of his PRINCIPLES CHAP. III. That the Air one breaths causes likewise some change in the Spirits THE second general Cause of the changes which happens in the Animal Spirits is the Air we breath for altho' it does immediately make as sensible impressions as the Chyle nevertheless in some time it produces the same effect as the Juice of our Food does presently This Air enters from Branches of the Wind-pipe into that of the Venous Artery and from thence it mingles it self and ferments with the rest of the Blood in the Heart and according to its particular disposition and that of the Blood it produces great changes in the Animal Spirits and by consequence in the faculty of Imagining I know that there are some Persons who do not believe that the Air mingles it self with the Blood in the Lungs and Heart because by their Eyes they cannot discover in the branches of the Wind-pipe and those of the Venous Artery the passages whereby the Air is communicated But we must not confine the Action of the Mind to that of the Senses it can penetrate what is impenetrable by them and apply it self to such things which they cannot 'T is certain that some parts of the Blood continually pass from the branches of the Venous Artery into those of the Wind-pipe as the smell and moistness of the breath sufficiently proves and yet the passages of this communication are imperceptible why therefore cannot the subtile parts of the Air pass from the branches of the Wind-pipe into the Venous Artery altho' the passages of this communication are not so visible In short more humours are evacuated by transpiration from the imperceptible Pores of the Arteries and Skin than by any other passages of the Body and even the Pores of the most solid Metals are not so small but that there are Bodies in Nature small enough to find a free passage for otherwise these Pores would be clos'd up It is true that the Gross and branchy parts of the Air cannot pass through the ordinary Pores of Bodies and that even Water altho' very gross can glide through those passages where this Air is sometime forced to stop But we are not speaking here of those gross and branchy parts of the Air they are it seems unuseful enough for fermentation 't is only of the smallest parts such as are swift and sharp that we speak of and which have none or very small branches to stop them because they are the most proper for the fermentation of the Blood I might nevertheless affirm upon the Relation of Silvius that even the grossest part of the Air pass from the Wind-pipe into the Heart since he assures us that he hath seen it pass thither by the help of M. de Swamerdam for it is more reasonable to believe a Man who says he has seen it than a thousand others who only speak of it by chance It is then certain that the most subtile parts of the Air which we breath enters into our Heart and with the Blood and Chyle maintains there that fire which gives Life and Motion to our Bodies and that according to their different Qualities they produce great changes in the fermentation of the Blood and in the Animal Spirits The truth of this is every day made evident by the divers Humours and different Characters of Persons dispositions that are of different Countries For Example the Gascons have a more lively Imagination than the Normans those of Roan Diep and Picardy differ very much among themselves and that much more from the Lower Normans Nunquid non ultra est sapientia in Teman Jer. c. 49. v. 7. altho' they be very near together But if we consider Men whose Countries are at a greater distance we shall meet with differences still more strange as an Italian and German or a Dutchman In fine there has in all times been some places that have been renowned for the Wisdom of their Inhabitants as Teman and Athens and others for their Stupidity as Thebes Abdera and some others Athenis tenue coelum ex quo acutiores etiam putantur Attici crassum Thebis Cic. de fato Abderitanae pectora plebis habes Mart. Boeotum in crasso jurares aere natum Hor. CHAP. IV. I. Of the Change wrought in the Animal Spirits by the Nerves that go to the Lungs and Heart II. Of that which is caused by the Nerves that pass from the Liver to the Spleen and so into the Bowels III. That all this is done without the assistance of our Will but cannot be effected without a Providence THE third Cause of those changes that happen to the Animal Spirits is the most general and most active of all because it is that which produces maintains and fortifies all the Passions To apprehend which well it 's necessary that we know that the fifth sixth and eighth pair of the Nerves have most of their branches extended through the Breast and Belly where they are very useful for the preservation of the Body but extreamly dangerous to the Soul because the action of these Nerves do not depend upon the Will as those do which serve to move the Arms Legs and other external parts of the Body I. of the change of the Spirits caus'd by the Nerves which go to the Lungs and Heart for they act much more upon the Soul than that does upon them It must therefore be consider'd that many branches of the eight pair of the Nerves cast themselves amongst