which we find in the Body of the Heart on its right side This Cavity is called the right Ventricle of the Heart As soon as the Ventricle is full of Blood it contracts its self and empties its self by this contraction It is here to be remarked that at the opening of the right Auricle into the right Ventricle of the Heart there are certain small Skins which they call Valves They are three in number almost of a triangular Figure whose sides are notched Their Base adheres to the opening of the Auricle and their point is plac'd within the Ventricle Their point is upheld only by small Tendinous Fibres strong and of a good Length which without being stretch'd are strongly fastned to small carneous pillars plac'd upon the concave surface of the Ventricle This disposition shews to the Eye that these Valves are so many small doors which the Blood opens of its self when it runs from the Auricle into the Ventricle and which it shuts after it is entered there Indeed as soon as the Ventricle is full of Blood it contracts its self and the Blood is prest equally on all sides by this contraction For this cause it gets under these Valves lifts up their point towards the opening of the Auricle which is thereby so exactly shut that no drop of Blood can pass that way So the Blood shuts up to its self this passage and cannot get out the way by which it has entered Nevertheless it does not stay in the right Ventricle of the Heart it goes out by another door to which the beginning of an Artery is strongly fastned This Artery is divided into many branches which distribute themselves into the Lobes of the Lungs At its passing from the right Ventricle it has in its Cavity three Valves made like Crescents and ranked each at the side of the other Their Convexity adheres to the Artery and turns towards the Ventricle and their Concavity is disengag'd and turned towards the Artery This situation shews us that they do not oppose the motion of the Blood when it comes from the Ventricle to the Artery but by rising up they stop its course if it presse from the Artery into the Ventricle After that the Blood has past from the right Ventricle into the Lungs by the Pulmonary Artery it returns from them by a Vein which is called the Pulmonary Vein This Pulmonary Vein discharges its self into a little bag fastned to the left side of the Heart which is called the left Auricle As soon as this Auricle is full it contracts its self thrusts by its Contraction the Blood into a Cavity in the substance of the Heart plac'd on its left side which is called the left Ventricle As soon as this Cavity is full of Blood it contracts its self and by this contraction throws out all the Blood which it contains That we may learn where the Blood goes when it passes from the left Ventricle of the Heart we are to take notice that at the opening of the left Auricle there are Valves situated after the same manner as at the opening of the right Ventricle Their use also is the same They permit indeed the Blood to run from the Auricle into the Ventricle but they hinder it from coming out of the Ventricle into the Auricle when the Heart contracts its self The Blood therefore takes another way Indeed it gets out of the left Ventricle by another passage which makes the beginning of the great Artery which they call the Aorta We find in the Cavity of this Artery next to the Heart three Valves made Crescent wayes disposed after the same manner as those of the Pulmonary Artery They permit the Blood to get out of the left Ventricle and to run into the Aorta but they hinder the Blood from flowing back from the Aorta into the left Ventricle There is yet an important remark to be made upon the motion of the Auricles and Ventricles of the Heart It is that the two Auricles do contract and dilate themselves at the same time and the two Ventricles in like manner With this Circumstance that at the time the Auricles contract themselves the Ventricles are dilated and when the Ventricles contract themselves the Auricles are dilated in course Which makes us conjecture that the Heart is a Muscle whose Auricles may well be reputed the Antagonist Muscles Before we enquire if this conjecture be a truth it will not be impertinent to observe that since the Auricles contract themselves at the same time they do also at the same time shed the Blood into the Ventricles of the Heart By the same reason the Ventricles of the Heart do at one time press the Blood into the Pulmonary Artery and into the Aorta When we consider the Heart narrowly we perceive that it is composed of Carneous Fibres which have all of them communication with a Membrane made of Tendinous Fibres This Membrane is plac'd at the Base of the Heart and keeps the Auricles fixt to it Which makes us judge that the Heart is a Muscle In the Heart we observe three orders of Fibres the first is of those which go in a straight line from the Basis of the Heart just to its point and they lye in a small number over the right Ventricle The second is of those which go from the Base and after they have extended themselves to the middle of the Heart ascend again and return to the Base from whence they came The third is of those which goe from the Base and come to the point describing about the Heart a spiral Line There they re-enter within the Heart and re-ascend spirally towards the Base Some of them end in the Ventricles where they make a Texture of their Tendinous Fibres which covers them on all sides Some of those also which come into the Ventricles make those little Eminencies which are called Pillars From the point of these Pillars go many Tendinous Strings which are joyned to the Teeth of the Valves that are plac'd in the opening of the Auricles All these Orders of Fibres do serve by the shortning of themselves to contract the Ventricles of the Heart The straight Fibres shorten it the circular ones straiten it and the spiral wring it The Heart cannot be thus shortned straitned and wreathed but the Ventricles must needs be contracted From whence we must conclude that the Heart is a Muscle whose action consists in straitning the Cavities which are amongst its Fibres As for the Auricles they are also composed of Carneous Fibres of which some of them are interwoven with others They are extended for the most part to the length and those of them which are interwoven seem to cross them to become Circular The shortning of the first does diminish the length of the Auricles and the shortning of the other diminisheth their breadth Which shews us that the Auricles are nothing but Cavernous Muscles whose action consists in the contraction of their Cavity
the least resistance It finds none at the entry of the Tracheal Artery and it rencounters every where else There it enters it gets into the Bronchiae from hence it passes into the Vesicles of the Lungs It blows them up as much as is needful for them to occupy as much space as the Walls of the Breast do abandon Even as the motion which is given to the two Boards of a pair of Bellows when they are raised from one another does thrust as much Air into the Bellows as is needful to occupy the space which the Boards of the Bellows have left By this means the Muscles which serve to draw down the Ribs have their Fibres extremely stretcht to the length The Fibres of the Musculous Tunicle of the Tracheal Artery and of the Bronchiae are also greatly stretcht Both the one and the other by their spring do rebound The Nerves send some Spirits into their Cavity They are shortned By this Contraction the Ribs are forc'd downward The Cavity of the Breast is diminisht and the Cartilages of the Bronchiae do re-enter into one another So the Air which the Vesicles of the Lungs did contain is so prest that it goes out It passeth from the Vesicles into the Bronchiae from the Bronchiae into the Tracheal Artery and from thence out of the Body And it is this going out of the Air from the Lungs which is called Exspiration Since Respiration is no other thing but Inspiration immediatly followed by Exspiration and this Exspiration followed as quickly by a new Inspiration and so forward we may very well affirm that Respiration is made by means of the Muscles of the Breast of the Diaphragm of the musculous Tunicle of the Tracheal Artery and of the Bronchiae These Organs act successively And the action of the one hinders the action of the other From whence we conclude that we may in reason consider them as Antagonist Muscles All the Blood which passeth through the right Ventricle of the Heart goeth from thence into the Lungs and the Lungs receive the External Air into their Vesicles So we have ground to think that this Air produceth some change in the Blood which passeth through the Lungs We remark indeed a great difference between the Blood which enters into the Lungs and the Blood which goes out of them That which enters by the Pulmonary Artery is of a Red passably deep whereas that which returns from the Lungs by the Pulmonary Vein is of a bright and fluid Red. Behold a very considerable change which befals the Blood in passing through the Lungs This change cannot be made but by the Air which blows up their Vesicles and by this means presseth the small Arteries and the small Veins which are spread there This pressure doth mingle more exactly the Principles of Blood and does oblige it to run more quickly into the branches of the Pulmonary Vein to go from thence into the left Ventricle of the Heart But because this exact mixture of the Principles of the Blood and this passage from the Arteries into the Veins is not capable of producing the change that we have remarked it must needs be that some Principle of Air extremely subtile mingles with it This Principle may pass through the Pores of the Arteries and insinuate its self among the parts of the Blood That which makes the thing yet more probable is that the Blood which is exposed to the Air acquires a surface extremely Red and of a colour like to that of the Blood which comes from the Lungs by the Pulmonary Vein By which we see that the Air produces in the Blood a bright and florid Red by being mingled with it Since therefore the Air does produce this effect we cannot in reason doubt that the change of colour which befals the Blood in passing through the Lungs comes from the Air which swells its Vesicles All the difference which is between the Blood of the Veins and that of the Arteries is the same with that of the Blood which enters into the Lungs and of that which comes from them So we may truly affirm that this difference is made in the Lungs and not in the Ventricles of the Heart where the Blood does not receive any alteration For if you take Blood out of the Vena Cava and afterwards out of the Pulmonary Artery you shall find no difference between these two Bloods Nevertheless that which is taken out of the Pulmonary Artery has past through the right Ventricle of the Heart After this if you take of the Blood of the Pulmonary Vein and afterwards of the Aorta you shall see that these two Bloods are alike in all things though the one has been taken at its entrie into the left Ventricle of the Heart and the other at its going out It remains as yet to examine what are the principles of Air which produce the change that the Blood contracts in passing through the Lungs When we consider the Air narrowly We find amongst many principles which compose it a Nitrous Spirit spread through all its Mass There are in Physick and Chymie a prodigious number of Experiments which render the thing certain And because the Spirit of Nitre does produce in the Blood the same change with the Air we have ground to think that the change which the Air makes in the Blood as it passes through the Lungs proceeds from the Nitrous Spirit of the Air its mingling with it The Spirit of Nitre is composed of Acids and Alcalies The Alcalies do rarifie the Sulphurs of the Blood and the Acids ferment with its Volatile Alcalies The Blood becomes thereby more subtile more agitated and more ratified From all this we may conclude that the Respiration serves to make the Blood pass from the Pulmonary Artery into the Pulmonary Vein and to keep up the fermentation of it by means of the Nitrous Spirit which mingles its self with it And since this Spirit heightens the Red colour of the Blood it may be also said that the Respiration serves to maintain it and that by its means the Lympha and Chyle which do mingle with it take by degrees its Colour and Nature The ninteenth Discourse Of the Spleen WHen we follow the Blood which goes out of the left Ventricle of the Heart we find that the first Entrail of those which we have not yet examined to which it goes is the Spleen It is of a red Colour of a considerable bigness plac'd in the lower Belly on the left side and a little lower than the Liver In the Spleen there is an Artery and a Nerve which do enter into it in Company and a Vein which goes out at the same place These Arteries end in little Membranous Cells whose Figure does nearly resemble the Leaf of the Fearn The Vein derives its Origine from the same Cells This appears when we blow into the Artery or the Vein for the Breath passeth into the Cells These Cells are all filled with small Glandules
Lacteal Veins These Excrements do afterwards pass into the Ilium where in divers places they receive again of the Glandulous Juyce which doth produce the same effect as formerly In fine after they are entirely freed of their Chylous parts they pass into the greater Intestines They are then composed of parts which the Ferment of the Stomach could not dissolve and of salts which are formed by the union of Alcalies of the Bile of the pancreatick Juyce and of the Glandulous Juyce with the Acids which were engaged amongst the parts of the Chyle The fourteenth Discourse Of the Mesentery the Lacteal Veins Pecquets Reservatory and the Thoracick Conduit THe Intestines adhere to the Circumference of a Membranous Ruffe which they call the Mesentery The middle of it is so strongly fastned to the Vertebraes of the Loins that it cannot be separated from them unless you tear a part of it or cut it It is composed of two Membranes of which the upper is a continuation of the Peritonaeum and the inferiour a Texture of Tendinous Fibres which come from the Vertebraes of the Loins The Mesenterick Arterie spreads many branches amongst the Membranes of the Mesentery one part of which goes to the Intestines and the other is spread amongst the Fibres of the Membranes which compose it The Veins which come from the Intestines are likewise spread between the Membranes of the Mesentery and many small Veins which come from amongst their Fibres go thither They are called the Mesaraick Veins They go to the Vena Porta Many Nerves which arise from the Vertebraes of the Loins and from the Intercostal are so interwoven one with another upon the Mesentery that they form a Plexus which is called the Mesenterick Plexus Many Nervous Fibres go from it which are spread amongst the Fibres of the Membranes of the Mesentery and a part of which passes even to the Intestines The middle between the Membranes of the Mesentery is replenisht with Far. It appears cheifly about the Mesaraick Veins In the midst of it we find a large Glandule and sometimes two three or four In Oxen and some other Animals there are many more and they are plac'd towards the small Intestines The knowledge of the structure of these Glandules does admirably serve to explain their uses They are a heap of angular Vesicles There is a communication between their Cavites This is found by blowing into them after you have thrust out all that fills them The Air passes from one Vesicle to another and makes them appear such as we have described them In fine we discover between the Membranes of the Mesentery certain small Vessels which come from the Intestines and pass into the Glandules of which we have spoken These Vessels are ordinarly full of Lympha and sometimes we find them full of Liquor like to Milk which is the reason why they call them the Lacteal Veins This Milk is nothing but the pure Chyle which has past from the Cavity of the small Intestines into that of the Lacteal Veins There are four Experiments which confirm us in this Opinion The first is that the Milk which runs into the Lacteal Veins comes from the Intestines this truth appears to the Eye when the Lacteal Veins are prest with the Fingers They empty themselves of the Milk and we see it come afterwards from the side of the Intestines to fill the Vein which has been emptied The second is that Milk is not to be found in the Lacteal Veins but some Hours after the Animal has eaten The third is that we find the Jejunum almost alwayes empty because of the great number of Lacteal Veins which goe from it Moreover the Lacteal Veins have many Valves plac'd very near one another They are so disposed that they permit the Chyle to run easily into the Lacteal Veins in going from the Intestines to the Glandules of the Mesentery but they hinder its return They go from the Intestines in great number and they are Inosculated many of them together accordding as they advance By this means they make up some greater Vessels which empty the Chyle that they carry into the Vesicles of the Glandules of the Mesentery The Chyle goes into the Vesicles of these Glandules to receive there Animal Spirits which come thither in abundance by many Nerves which proceed from the Mesenterick Plexus These Spirits render the Chyle more subtile and fluid by their Volatile Alcalie and if there be any acidity in it they correct it by receiving it into their Alcalies and changing it into Salt After that the Chyle has past through the Vesicles of the Mesaraick Glandules it discharges its self into two or three Conduits which arise from under them They end afterwards in a Membranous bag situated above the Vertebras of the Loins they call it the Reservatory of the Chyle The Reservatory is the same thing with the Cistern of the Lympha of which we have spoken before In this place the Chyle is mingled with much Lympha with which the Reservatory is alwayes full It dilates it and renders it more Liquid that it may run the more easily In fine there goes from the Reservatory of the Chyle a Conduit which is called the Thoracick Conduit for that it goes alongst the Vertebraes of the Thorax Sometimes this Conduit is forked and its branches unite again sometimes it is altogether simple The Thoracick Conduit is inserted into the Subclavian Vein above its Insertion there is a Valve which like a small Vault covers it So that the Blood which runs through the Subclavian Vein runs by without hindring the entry of the Chyle When we blow in the Thoracick Conduit we perceive many Valves in its Cavity They are plac'd at very small distances from one another and are so disposed that they permit the Chyle easily to run towards the Subclavian Vein but they hinder it from descending into Pecquets Reservatory From whence we may conclude that the Chyle runs from its Reservatory by the Thoracick Conduit into the left Subclavian Vein There it mingles with the Blood Whose course it follows and goes into the Vena Cava which carries it into the right Auricle of the Heart The Auricle discharges it into the right Ventricle And whereas the Chyle makes then a part of the Blood it follows its course and circulats with it through all the Body The fifteenth Discourse Of the Heart WHen the Chyle is once entered into the Subclavian Vein it mingles its self with the Blood and follows its course We must therefore follow the Blood if we could know what becomes of the Chyle The circulation of the Blood shews us that it runs from the Subclavian Vein into the Vena Cava and from the Vena Cava it passes into a bag adhering to the right side of the Heart This little bag they call the right Auricle of the Heart When this Auricle is full of Blood it contracts its self and in contracting its self sheds it into a Cavity
There is a communication between the Fibres of the Heart and those of the Auricles by the interposal of the Tendinous Fibres which are gathered altogether pure at the Base of the Heart We may look upon them as a Tendon common to the Heart and the Auricles The animal Spirits therefore which the Nerves distil into this Tendon do easily pass from the Fibres of the Heart into the Fibres of the Auricles and from the Fibres of the Auricles into those of the Heart If we would yet form to our selves an Idaea of the Heart as clear and distinct as may be we may consider it as a Muscle with three Bellies Each Auricle makes one and the Body of the Heart makes the third and the Membrane which is at the Base of the Heart where the Fibres of the Heart and of the Auricles do meet would be the common Tendon The Heart receives Arteries from the Aorta it sends Veins to the Cava it receives Nerves from the plexus Cardiacus and the Par Vagum In fine the Heart is shut up in a Membranous Bag which is called the Pericardium The Pericardium is strong and it is formed of a Texture of the Tendinous Fibres of the Heart of some Veins some Arteries and some Nerves It contains always a little Serosity which the small Glandules that are plac'd amongst the Fat of the Base of the Heart do distill into it From what has been said we may conclude that when the Auricles are full of Blood the Ventricles of the Heart are empty And for that the Auricles how soon they are full of Blood do contract themselves the Blood which they press into the Ventricles of the Heart being aided by the spring of their Fibres does dilate them and constrains the animal Spirits to get out of them and to run into the Auricles to accomplish their contraction But as soon as the Auricles are contracted the Blood which advances on all sides joynn'd with the force of the spring of their Fibres restores them to their former state And the Spirits passing in that moment from the Auricles to the Heart shut it up and cause its contraction It is for this Reason that the Auricles empty themselves when the Ventricles of the Heart are filled and that the Auricles fill themselves when the Ventricles are emptied The heart by its Contraction throws the Blood from its Ventricles into the Arteries But for that the Artery become still narrower the Blood cannot be thrown out impetuously without swelling them When they are thus blown up they restore themselves to their former state by the spring of their Fibres and by this mean make a part of the Blood which they have received run into the Veins of the Heart And since the Heart throws out the Blood into the Arteries by several strokes the Arteries must needs be blown up and fall again by several turns It is this motion of the Arteries which they call the Pulse concerning which it is to be remarked that the dilatation of the Arteries accompanies the contraction of the Heart and the contraction of the Arteries accompanies its dilatation Those who are satisfied with what they conceive clearly will be contented to ascribe to the Heart the office of pressing the Blood into the Arteries and of being the principal Instrument of its Circulation They may leave to those who believe that the Heart is the Organ of sanguification the satisfaction they have to be pleased with a conjecture ill founded as shall be made appear afterwards The Sixteenth Discourse Of the Lungs WE have said in the preceeding Chapter that when the Blood goes from the right Ventricle of the Heart it passes into the Pulmonary Artery This Artery is divided into many great branches which enter into the Body of the Lungs and these branches are again divided into others and these into others till at last the smallest of them are lost into the substance of the Lungs The Pulmonary Artery is not spread alone in the Lungs It is every where accompanied with the Pulmonary Vein a branch of a Nerve which comes from the Par Vagum a small Artery which goes from the Aorta and which they call the Bronchial Artery with a small Vein which is passing into the Vena Cava and which they call the Bronchial Vein and a certain Cartilaginous Conduit which they name the Bronchiae The Bronchiae are nothing but the Ramifications of a great Cartilaginous Pipe which extends its self from the bottom of the Mouth even to the Lungs It lyeth above the Oesophagus and is plac'd in the fore part of the Neck They call it the Arteria Trachaea There is at the top of the Arteria Trachaea a horny part which they name the Larinx It is made up of five Cartilages That which takes up its forepart makes that Eminence which in men they call Adams Bit. Its Figure is almost like unto that of that Buckler which amongst the Latines is called Scutum For this reason they name it the Scutiform Cartilage The second is called the Annular It is made like the Ring which the Turks make use of for drawing the Bow It is strait before and large behind It embraces the whole Larinx and is fastned into the Scutiform The third and fourth are called the Aritenoides They are the productions of the Annular placed on its hinder part and separated from one another by a small slit They make that part of the Larinx which they call the Glottis The fifth is a Cartilage fastned above the upper part of the Scutiform Cartilage They call it the Epiglottis It s Figure is Triangular and its substance softer than that of the others It s Base adheres to the Scutiform Cartilage and the rest of its Body is disengag'd from any other part It is usually lifted up This is that Cartilage which the Aliments put down in passing from the Mouth into the Oesophagus When it is down it shuts the entry of the Trachaeal Artery and thereby hinders the Aliments from going into it The Larinx is reckoned to have thirteen Muscles There are four of them which are common to it with other parts and nine which do properly appertain to it The first pair of the common ones are nam'd the Sternothyoidians They arise from the top of the Sternum lye above the Trachaeal Artery and are fastned to the inferiour part of the Scutiform Cartilage When their Fibres are contracted they draw the Scutiform downwards The second pair is made of the Hyothyroidians They arise from the Base of the os Hyoides and are fastned to the Base of the Scutiform They serve by the contraction of their Fibres to lift up the Larinx The first pair of Muscles proper to the Larinx is made of the anteriour Cricothyroidians They derive their origin from the forepart of the annular Cartilage and they end at the lower part of the same Cartilage By their action they dilate it The second is made of the Posteriour