Part 4

From the description of inanimate Bodies and Plants, I pass'd to that of Animals, and particularly to that of Men. But because I had not yet knowledge enough to speak of them in the same stile as of the others; to wit, in demonstrating effects by their causes, and shewing from what seeds, and in what manner Nature ought to produce them; I contented my self to suppose, That God form'd the body of a Man altogether like one of ours; aswel the exteriour figure of its members, as in the interiour conformity of its organs; without framing it of other matter then of that which I had described; and without putting in it at the beginning any reasonable soul, or any other thing to serve therein for a vegetative or sensitive soul; unless he stirr'd up in his heart one of those fires without light which I had already discovered; and that I conceiv'd of no other nature but that which heats hay when its housed before it be dry, or which causes new Wines to boyl when it works upon the grape: For examining the functions which might be consequently in this body, I exactly found all those which may be in us, without our thinking of them; and to which our soul (that is to say, that distinct part from our bodies, whose nature (as hath been said before) is onely to think) consequently doth not contribute, and which are all the same wherein we may say unreasonable creatures resemble us. Yet could I not finde any, of those which depending from the thought, are the onely ones which belong unto us as Men; whereas I found them all afterwards, having supposed that God created a reasonable soul, and that he joyn'd it to this body, after a certain manner which I describ'd.

But that you might see how I treated this matter, I shall here present you with the explication of the motion of the heart, and of the arteries, which being the first and most general (which is observed in animals) we may thereby easily judge what we ought to think of all the rest. And that we may have the less difficulty to understand what I shall say thereof, I wish those who are not versed in Anatomy, would take the pains, before they read this, to cause the heart of some great animal which hath lungs, to be dissected; for in all of them its very like that of a Man: and that they may have shewn them the two cels or concavities which are there: First that on the right side, whereto two large conduits answer, to wit, the _vena cava_, which is the principal receptacle of bloud, and as the body of a tree, whereof all the other veins of the body are branches; and the arterious vein, which was so mis-call'd, because that in effect its an artery, which taking its _origine_ from the heart, divides it self after being come forth, into divers branches, which every way spred themselves through the lungs. Then the other which is on the left side, whereunto in the same manner two pipes answer, which are as large, or larger then the former; to wit, the veinous artery, which was also il named, forasmuch as its nothing else but a vein which comes from the lungs, where its divided into several branches interlaid with those of the arterious vein, and those of that pipe which is called the Whistle, by which the breath enters. And the great artery, which proceeding from the heart, disperseth its branches thorow all the body. I would also that they would carefully observe the eleven little skins, which, as so many little doors, open and shut the four openings which are in these two concavities; to wit, three at the entry of the _vena cava_, where they are so disposed, that they can no wayes hinder the bloud which it contains from running into the right concavity of the heart; and yet altogether hinder it from coming out. Three at the entry of the arterious vein; which being disposed quite contrary, permit only the bloud which is in that concavity to pass to the lungs; but not that which is in the lungs to return thither. And then two others at the entry of the veinous artery, which permits the bloud to run to the left concavity of the heart, but opposeth its return. And three at the entry of the great artery, which permit it to go from the heart, but hinder its return thither. Neither need we seek any other reason for the number of these skins, save only that the opening of the veinous artery, being oval-wise, by reason of its situation, may be fitly shut with two; whereas the other, being round, may the better be clos'd with three. Besides, I would have them consider, that the great artery and the arterious vein are of a composition much stronger then the veinous artery or the _vena cava_. And that these two later grow larger before they enter into the heart, and make (as it were) two purses, call'd the ears of the heart, which are composed of a flesh like it; and that there is always more heat in the heart then in any other part of the body. And in fine, that if any drop of bloud enter into these concavities, this heat is able to make it presently swell and dilate it self, as generally all liquors do, when drop by drop we let them fall into a very hot vessel.

For after this I need say no more for to unfold the motion of the heart, but that when these concavities are not full of bloud, necessarily there runs some from the _vena cava_ into the right, and from the veinous artery into the left; for that these two vessels are always full of it, and that their openings which are towards the heart cannot then be shut: But that assoon as there is thus but two drops of bloud entred, one in either of these concavities, these drops, which cannot but be very big, by reason that their openings whereby they enter are very large, and the vessels whence they come very full of bloud, are rarified and dilated because of the heat which they find therein. By means whereof, causing all the heart to swel, they drive and shut the five little doors which are at the entry of the two vessels whence they come, hindering thereby any more bloud to fall down into the heart, and continuing more and more to rarifie themselves, they drive and open the six other little doors which are at the entry of the other two vessels whence they issue, causing by that means all the branches of the arterious vein, and of the great artery, to swel (as it were) at the same time with the heart: which presently after fals, as those arteries also do, by reason that the bloud which is entred therein grows colder, and their six little doors shut up again, and those five of the _vena cava_, and of the veinous artery open again, and give way to two other drops of bloud, which again swell the heart and the arteries in the same manner as the preceding did. And because the bloud which thus enters into the heart, passeth thorow those two purses, which are call'd the ears; thence it comes, that their motion is contrary to the heart's, and that they fall when that swels.

Lastly, That they who know not the force of Mathematical demonstrations, and are not accustomed to distinguish true reasons from probable ones, may not venture to deny this without examining it, I shall advertise them, that this motion which I have now discovered, as necessarily follows from the onely disposition of the organs (which may plainly be seen in the heart,) and from the heat (which we may feel with our fingers,) and from the nature of the bloud (which we may know by experience,) as the motions of a clock doth by the force, situation and figure of its weight and wheels.

But if it be asked, how it comes that the bloud of the veins is not exhausted, running so continually into the heart; and how that the arteries are not too full, since all that which passeth thorow the heart dischargeth it self into them: I need answer nothing thereto but what hath been already writ by an English Physician, to whom this praise must be given, to have broken the ice in this place, and to be the first who taught us, That there are several little passages in the extremity of the arteries whereby the bloud which they receive from the heart, enters the little branches of the veins; whence again it sends it self back towards the heart: so that its course is no other thing but a perpetuall circulation. Which he very wel proves by the ordinary experience of Chirurgians, who having bound the arm indifferently hard above the the place where they open the vein, which causeth the bloud to issue more abundantly, then if it had not been bound. And the contrary would happen, were it bound underneath, between the hand and the incision, or bound very hard above. For its manifest, that the band indifferently tyed, being able to hinder the bloud which is already in the arm to return towards the heart by the veins; yet it therefore hinders not the new from coming always by the arteries, by reason they are placed under the veins, and that their skin being thicker, are less easie to be press'd, as also that the bloud which comes from the heart, seeks more forcibly to passe by them towards the hand, then it doth to return from thence towards the heart by the veins. And since this bloud which issues from the arm by the incision made in one of the veins, must necessarily have some passage under the bond, to wit, towards the extremities of the arm, whereby it may come thither by the arteries, he also proves very well what he sayes of the course of the bloud through certain little skins, which are so disposed in divers places along the veins, which permit it not to pass from the middle towards the extremities, but onely to return from the extremities towards the heart. And besides this, experience shews, That all the bloud which is in the body may in a very little time run out by one onely artery's being cut, although it were even bound very neer the heart, and cut betwixt it and the ligature: So that we could have no reason to imagine that the bloud which issued thence could come from any other part.

But there are divers other things which witness, that the true cause of this motion of the bloud is that which I have related. As first, The difference observed between that which issues out of the veins, and that which comes out of the arteries, cannot proceed but from its being rarified and (as it were) distilled by passing thorow the heart: its more subtil, more lively, and more hot presently after it comes out; that is to say, being in the arteries, then it is a little before it enters them, that is to say, in the veins. And if you observe, you will finde, that this difference appears not well but about the heart; and not so much in those places which are farther off. Next, the hardnesse of the skin of which the artery vein and the great artery are composed, sheweth sufficiently, that the bloud beats against them more forcibly then against the veins. And why should the left concavity of the heart, and the great artery be more large and ample then the right concavity, and the arterious vein; unless it were that the bloud of the veinous artery, having bin but onely in the lungs since its passage thorow the heart, is more subtil, and is rarified with more force and ease then the bloud which immediately comes from the _vena cava_. And what can the Physicians divine by feeling of the pulse, unlesse they know, that according as the bloud changeth its nature, it may by the heat of the heart be rarified to be more or lesse strong, and more or lesse quick then before. And if we examine how this heat is communicated to the other members, must we not avow that 'tis by means of the bloud, which passing the heart, reheats it self there, and thence disperseth it self thorow the whole body: whence it happens, that if you take away the bloud from any part, the heat by the same means also is taken a way. And although the heart were as burning as hot iron, it were not sufficient to warm the feet and the hands so often as it doth, did it not continue to furnish them with new bloud.

Besides, from thence we know also that the true use of respiration is to bring fresh air enough to the lungs, to cause that bloud which comes from the right concavity of the heart, where it was rarified, and (as it were) chang'd into vapours, there to thicken, and convert it self into bloud again, before it fall again into the left, without which it would not be fit to serve for the nourishment of the fire which is there. Which is confirm'd, for that its seen, that animals which have no lungs have but one onely concavity in the heart; and that children, who can make no use of them when they are in their mothers bellies, have an opening, by which the bloud of the _vena cava_ runs to the left concavity of the heart, and a conduit by which it comes from the arterious vein into the great artery without passing the lungs.

Next, How would the concoction be made in the stomach, unlesse the heart sent heat by the arteries, and therewithall some of the most fluid parts of the bloud, which help to dissolve the meat receiv'd therein? and is not the act which converts the juice of these meats into bloud easie to be known, if we consider, that it is distill'd by passing and repassing the heart, perhaps more then one or two hundred times a day? And what need we ought else to explain the nutrition and the production of divers humours which are in the body, but to say, that the force wherewith the bloud in rarifying it self, passeth from the heart towards the extremities or the arteries, causeth some of its parts to stay amongst those of the members where they are, and there take the place of some others, which they drive from thence? And that according to the situation, or the figure, or the smalnesse of the pores which they meet, some arrive sooner in one place then others. In the same manner as we may have seen in severall sieves, which being diversly pierc'd, serve to sever divers grains one from the other. And briefly, that which is most remarkable herein, is the generation of the animal spirits, which are as a most subtil wind, or rather, as a most pure and lively flame, which continually rising in great abundance from the heart to the brain, dischargeth it self thence by the nerves into the muscles, and gives motion to all the members; without imagining any other reason which might cause these parts of the bloud, which being most mov'd, and the most penetrating, are the most fit to form these spirits, tend rather towards the brain, then to any other part. Save onely that the arteries which carry them thither, are those which come from the heart in the most direct line of all: And that according to the rules of the Mechanicks, which are the same with those of Nature, when divers things together strive to move one way, where there is not room enough for all; so those parts of bloud which issue from the left concavity of the heart tend towards the brain, the weaker and less agitated are expell'd by the stronger, who by that means arrive there alone.

I had particularly enough expounded all these things in a Treatise which I formerly had design'd to publish: In pursuit whereof, I had therein shewed what ought to be the fabrick of the nerves and muscles of an humane body, to cause those animall spirits which were in them, to have the power to move those members. As we see that heads a while after they are cut off, yet move of themselves, and bite the ground, although they are not then animated. What changes ought to be made in the brain to cause waking, sleeping, and dreaming: how light, sounds, smels, tasts, heat, and all other qualities of exteriour objects, might imprint severall _Ideas_ by means of the senses. How hunger and thirst, and the other interiour passions might also send theirs thither. What ought to be taken therein for common sense, where these _Ideas_ are received; for memory which preserves them; and for fancy, which can diversly change them, and form new ones of them; and by the same means, distributing the animal spirits into the muscles, make the members of the body move in so many severall fashions, and as fitly to those objects which present themselves to its senses; and to the interiour passions which are in them, as ours may move themselves without the consent of the Wil. Which wil seem nothing strange to those, who knowing how many _Automatas_ or moving Machines the industry of men can make, imploying but very few pieces, in comparison of the great abundance of bones, muscles, nerves, arteries, veins, and all the other parts which are in the body of every Animal, will consider this body as a fabrick, which having been made by the hands of God, is incomparably better ordered, and hath more admirable motions in it then any of those which can be invented by men. And herein I particularly insisted, to make it appear, that if there were such Machines which had organs, and the exteriour figure of an Ape, or of any other unreasonable creature, we should finde no means of knowing them not to be altogether of the same nature as those Animals: whereas, if there were any which resembled our bodies, and imitated our actions as much as morally it were possible, we should always have two most certain ways to know, that for all that they were not reall men: The first of which is, that they could never have the use of speech, nor of other signes in framing it, as we have, to declare our thoughts to others: for we may well conceive, that a Machine may be so made, that it may utter words, and even some proper to the corporal actions, which may cause some change in its organs; as if we touch it in some part, and it should ask what we would say; or so as it might cry out that one hurts it, and the like: but not that they can diversifie them to answer sensibly to all what shall be spoken in its presence, as the dullest men may do. And the second is, That although they did divers things aswel, or perhaps better, then any of us, they must infallibly fail in some others, whereby we might discover that they act not with knowledge, but onely by the disposition of their organs: for whereas Reason is an universal instrument which may serve in all kinde of encounters, these organs have need of some particular disposition for every particular action: whence it is, that its morally impossible for one Machine to have severall organs enough to make it move in all the occurrences of this life, in the same manner as our Reason makes us move. Now by these two means we may also know the difference which is between Men and Beasts: For 'tis a very remarkable thing, that there are no men so dull and so stupid, without excepting those who are out of their wits, but are capable to rank severall words together, and of them to compose a Discourse, by which they make known their thoughts: and that on the contrary, there is no other creature, how perfect or happily soever brought forth, which can do the like. The which happens, not because they want organs; for we know, that Pyes and Parrots can utter words even as we can, and yet cannot speak like us; that is to say, with evidence that they think what they say. Whereas Men, being born deaf and dumb, and deprived of those organs which seem to make others speak, as much or more then beasts, usually invent of themselves to be understood by those, who commonly being with them, have the leisure to learn their expressions. And this not onely witnesseth, that Beasts have lesse reason than men, but that they have none at all. For we see there needs not much to learn to speak: and forasmuch as we observe inequality amongst Beasts of the same kind, aswell as amongst men, and that some are more easily managed then others; 'tis not to be believed, but that an Ape or a Parrot which were the most perfect of its kinde, should therein equall the most stupid child, or at least a child of a distracted brain, if their souls were not of a nature wholly different from ours. And we ought not to confound words with naturall motions, which witness passions, and may be imitated by Machines aswell as by Animals; nor think (as some of the Ancients) that beasts speak, although we do not understand their language: for if it were true, since they have divers organs which relate to ours, they could aswell make themselves understood by us, as by their like. Its likewise very remarkable that although there are divers creatures which express more industry then we in some one of their actions; yet we may well perceive, that the same shew none at all in many others: So that what they do better then we, proves not at all that they have reason; for by that reckoning they would have more then any of us, and would do better in all other things; but rather, that they have none at all, and that its Nature onely which works in them according to the disposition of their organs. As wee see a Clock, which is onely composed of wheels and springs, can reckon the hours, and measure the times more exactly then we can with all our prudence.

After this I had described the reasonable Soul, and made it appear, that it could no way be drawn from the power of the Matter, as other things whereof I had spoken; but that it ought to have been expresly created: And how it suffiseth not for it to be lodg'd in our humane body as a Pilot in his ship, to move its members onely; but also that its necessary it be joyned and united more strongly therewith to have thoughts and appetites like ours, and so make a reall man.

I have here dilated my self a little on the subject of the Soul, by reason 'tis of most importance; for, next the errour of those who deny God, which I think I have already sufficiently confuted, there is none which sooner estrangeth feeble minds from the right way of vertue, then to imagine that the soul of beasts is of the same nature as ours, and that consequently we have nothing to fear nor hope after this life, no more then flies or ants. Whereas, when we know how different they are, we comprehend much better the reasons which prove that ours is of a nature wholly independing from the body, and consequently that it is not subject to die with it. And that when we see no other cause which destroys it, we are naturally thence moved to judge that it's immortall.

PART. VI.

Its now three years since I ended the Treatise which contains all these things, and that I began to review it, to send it afterwards to the Presse, when I understood, that persons to whom I submit, and whose authority can no lesse command my actions, then my own Reason doth my thoughts, had disapproved an opinion in Physicks, published a little before by another; of which I will not say that I was, but that indeed I had observed nothing therein, before their censure, which I could have imagined prejudiciall either to Religion or the State; or consequently, which might have hindred me from writing the same, had my Reason perswaded mee thereto. And this made me fear, lest in the same manner there might be found some one amongst mine, in which I might have been mistaken; notwithstanding the great care I always had to admit no new ones into my belief, of which I had not most certain demonstrations; and not to write such as might turn to the disadvantage of any body. Which was sufficient to oblige me to change my resolution of publishing them. For although the reasons for which I had first of all taken it, were very strong; yet my inclination, which alwayes made me hate the trade of Book-making, presently found me out others enough to excuse my self from it. And these reasons on the one and other side are such, that I am not only somewhat concern'd to speak them; but happily the Publick also to know them.