Miscellanea Curiosa. (continued 3)

Let (in Fig. 3. Plate 3.) A be the Sun, B Jupiter, C the first Satellit of Jupiter, which enters into the shadow of Jupiter, to come out at D, and let EFGHKL be the Earth, placed at divers distances from Jupiter.

Now suppose the Earth, being in L, towards the second Quadrature of Jupiter, hath seen the first Satellit, at the time of its emersion, or issuing out of the shadow at D, and that about 42½ Hours after (viz. after one Revolution of this Satellit) the Earth being in K, do see it return'd in D: It is manifest, that if the Light require time to traverse the Interval LK, the Satellit will be seen return'd later in D, than it would have been if the Earth had remained in L. So that the Revolution of the Satellit being thus observ'd by the Emersions, will be retarded by so much time, as the Light shall have taken in passing from L to K; and that on the contrary, in the other Quadrature FG, where the Earth by approaching goes to meet the Light, the Revolutions of the Emersions will appear to be shortned, by so much as those of the Emersions had appear'd to be lengthned. And because 42½ Hours, which this Satellit very near takes to make one Revolution, the distance between the Earth and Jupiter, in both the Quadratures, varies at least 210 Diameters of the Earth: It follows, that if for the Account of every Diameter of the Earth there were required a Second of Time, the Light would take 3½ Minutes for each of the Intervals GF, KL; which would cause near half a quarter of an Hour between two Revolutions of the first Satellit, one observ'd in FG, and the other in KL, whereas there is not observed any sensible difference.

Yet doth it not follow hence, that Light demands no time. For after M. Romer had examin'd the thing more nearly, he found that what was not sensible in two Revolutions, became very considerable in many being taken together; and that, for Example, forty Revolutions observed on the side F, might be sensibly shorter, than forty others observ'd in any place of the Zodiack where Jupiter may be met with; and that in proportion of Twenty two for the whole Interval of HE, which is the double of the Interval that is from hence to the Sun.

The necessity of this new Equation of the Retardment of Light, is establish'd by all the Observations that have been made in the Royal Academy, and in the Observatory, for the space of eight Years; and it hath been lately confirmed by the Emersion of the first Satellit observ'd at Paris, the 9th of November last, at 5 a-clock 35' 45" at Night, 10 Minutes later than it was to be expected, by deducting it from those that had been observ'd in the Month of August, when the Earth was much nearer to Jupiter; which M. Romer had predicted to the said Academy from the beginning of September.

But to remove all doubt, that this Inequality is caused by the Retardment of the Light, he demonstrates, that it cannot come from any Excentricity, or other Cause of those that are commonly alledged to explicate the Irregularities of the Moon, and the other Planets; though he be well aware, that the first Satellit of Jupiter was Excentrick; and that, besides his Revolutions were advanced or retarded, according as Jupiter did approach to or recede from the Sun; as also, that the Revolutions of the Primum Mobile were unequal: Yet, saith he, these three last Causes of Inequality do not hinder the first from being manifest.

An introductory Essay to the Doctrine of Sounds, containing some Proposals for the improvement of Acousticks; As it was presented to the Dublin Society, Nov. 12. 1683, by the Right Reverend Father in God Narcissus Lord Bishop of Ferns and Leighlin.

BEing to treat of the Doctrine of Sounds, I hold it convenient to premise something in the general, concerning this Theory; which may serve at once to ingage your Attention, and excuse my Pains, when I shall have recommended them, as bestow'd on a Subject not altogether useless and unfruitful.

And for this purpose I shall omit to speak any thing of the Excellency of the Matter in Hand; though it might be celebrated by Arguments drawn from several Topicks, and particularly from this, that new Discoveries and Improvements may be made, both as to the Generation, Propagation and Reception of Sounds into the Sense; which, in a peculiar manner agrees to this, above the Object of any other Sense whatsoever. I shall, I say, omit these things, and apply my self wholly to the Usefulness of the Theory, that we are now falling upon, which I think cannot better be discovered, than by making a comparison 'twixt the Senses of Seeing and Hearing, as to their Improvements. I mean, by shewing, that this latter of Hearing is capable of all those improvements which the Sense of Seeing has receiv'd from Art, besides many more advantages that the Ear may enjoy, by the help of our Doctrine, above the Eye; all which moreover will be of as great benefit to Mankind, as any thing that Opticks have yet discover'd, if not of greater; which, with some other pre-eminencies that it has upon another Score, will happily render Acousticks the nobler Science of the two.

In order to the making good what I but now premised of the Comparison of these two Faculties of Seeing and Hearing, as to their Improvements, I observe;

That Vision is threefold, Direct, Refracted, and Reflex'd; answerable whereunto we have Opticks, Dioptricks, and Catoptricks.

In like manner Hearing may be divided into Direct, Refracted and Reflex'd; whereto answer three parts of our Doctrine of Acousticks, which are yet nameless, unless we call them Acousticks, Diacousticks, and Catacousticks, or (in another Sense, but to as good Purpose) Phonicks, Diaphonicks, and Cataphonicks.

I. Direct Vision has been improv'd two ways, ex parte Objecti, and ex parte Organi vel Medii.

1. Ex parte Objecti, Direct Vision has receiv'd advantages by the Arts of Producing, Conserving and Imitating Light and Colours, which are the Objects of Vision.

1. For the Art of Producing Light, we have the Frication of all hard Bodies that beget Fire; especially of the Flint and Steel; and instead of the Flint, most hard Stones (as well as the Cane) may be us'd to the same effect, as upon trial I have found. Add hereto the lately invented Phosphorus, which is a new and admirable way of producing a Lucid Substance by Art, out of a Body in itself not Lucid; and therefore may not unfitly be term'd an Artificial production of Light.

And then of the Art of Conserving Light, the Lapis Bononiensis is a notable Instance; and so happily were the Sepulchral Lamps of the Ancients.

2. As to Colours, 'tis the greatest part of the Art of Dying to be able to make and fix (that is preserve) them; and the Painters and Limners will own it to be no small part of their Skill to be able well to Mix (that is, in effect, to Generate) Colours.

3. For Imitation of Light and Colours, 'tis well known how far Perspective with the Art of Limning and Shadowing have gone therein, which all tend some way to the Advance or Improvement of Direct Vision.

Add to all these, That a due Application of Light to the Object renders it Visible, if it were not so before; as appears from a dark Room illuminated; or else makes it better and more truly discernable by the Sense of Seeing, if before it might have been discern'd.

Hence the same Colour, in a diverse Light, will appear different, and no Picture can well be discern'd or judg'd of but by its true Light. Besides, the Limner will assure you, that he can hardly make true Work, or hit the Air of a Face exactly, unless he draw by a North-Light, by reason of the steadiness of that, and the uncertainty of all other Lights whatsoever. Which things shew, that the Art of duly applying Light to the Object does very much help and improve Vision. So also does the due placing of the Object, as to Height and Distance. But to enumerate all things that help Direct Vision, would be infinite.

2. Ex parte Organi vel Medii, Direct Vision has been improv'd by making use of a Tube, without Glasses, or a Man's clos'd Hand, to look thro'; which admitting into the Eye only the principal Rays, that come directly from the Object, do very much strengthen and clear the Sight, by excluding all the Collateral Rays, that crouding into the Eye, together with the direct ones, would confound and disturb it, partly by mixing and interfering with the direct Rays, and partly (or rather chiefly) by too much enlightning the fund of the Eye, wherein Vision is truly (tho' then imperfectly) made.

On this is founded the Art of making Spectacles without Glasses; (as well as Tubes) which is done by putting into the Glass-holes (instead of Glasses) two short Tubes of between three and four Inches long (for their length is to be vary'd according to the Age or Eye of the Beholder, and so also is the Diameter of the extream ends) which Tubes being made of Spanish Leather (or Past-board, or some such like Matter) and black'd on the inside, are so to be placed, as that the visual Rays, receiv'd thro' them, may meet in one point (or rather issue out from one Point) of the Object standing at such a due distance, as the Person may clearly and distinctly see it, or according to his length of Sight (as ABC, in the 4th Fig. Tab. 3.)

And these Spectacles may be suppos'd better for preserving the Sight, than the ordinary ones with Glasses, because they represent the Object more naturally, and withal more clearly and distinctly to the Eye, than the other, whose refracted Rays being collected together with the right ones in the Glasses, do somewhat confound good Vision, as before: Especially if the visive Power be strong enough to be sufficiently determin'd by the right Rays alone.

For I speak now of preserving a good Eye by these Spectacles, which holds in proportion true also of a bad one. Because those Rays (both right and refracted) being collected and brought so near the Eye (whether good or bad) as the Spectacles are usually plac'd, do too much affect it, both by their own brightness, and also by the brightness of the Colours of the Object (when they are bright) which is brought very near also; whereby the Eye is dazl'd and confounded, unless there be a strong attention and conatus of the Spirits, whereto the bright Rays do certainly engage them, which of necessity weakens Vision, especially if these Glass-spectacles be much us'd.

Wherefore the now describ'd new Tube-spectacles, contributing so much to the help and preservation of Sight, may well be counted an improvement of Direct Vision, because they convey the Rays to the Eye without any kind of Refraction whatsoever. Seeing the same Object also through various holes, plac'd at certain distances, does somewhat alter Vision; but of this perhaps more hereafter.

Now as Direct Vision has thus been improved, so likewise Direct Hearing partly has already receiv'd, and partly may by the Doctrine whereof we are treating, (if well cultivated) farther receive as great and notable Improvements, both ex parte Objecti, and ex parte Organi vel Medii.

1. As to the Object of Hearing, which is Sound, improvement has been and may be made, both as to the Begetting, and as to the Conveying and Propagating (which is a kind of Conserving) of Sounds.

1. As to the Begetting of Sounds. The Art of imitating any Sound, whether by Speaking (that is pronouncing) any kind of Language, (which really is an Art, and the Art of Speaking, perhaps one of the greatest) or by Whistling, or by Singing (which are allow'd Arts) or by Hollowing or Luring (which the Huntsman or Faulkner would have to be an Art also) or by imitating with the Mouth (or otherwise) the Voice of any Animal, as of Quails, Cats, and the like; or by representing any Sound begotten by the Collision of Solid Bodies, or after any other manner; these are all Improvements of Direct Hearing, and may be improv'd.

Moreover the Skill to make all sorts of Musical Instruments, both Ancient and Modern, whether Wind Instruments or String'd, or of any other sort, whereof there are very many (as Drums, Bells, the Systrum of the Egyptians, and the like) that beget (and not only propagate) Sounds; the Skill of making these, I say, is an Art, that has as much improv'd Direct Hearing, as an Harmonious Sound exceeds a single and rude one, that is, an immusical Tone; which Art is yet capable of farther improvement. And I do hope, that by the Rules, which may happily be laid down concerning the Nature, Propagation and Proportion, or Adapting of Sounds, a way may be found out, both to improve Musical Instruments already in use, and to invent new ones, that shall be more sweet and luscious, than any yet known. Besides that, by the same means Instruments may be made, that shall imitate any Sound in Nature, that is not Articulate, be it of Bird, Beast, or what thing else soever.

2. The Conveying and Propagating (which is a kind of Conserving) of Sounds, is much help'd by duly placing the Sonorous Body, and also by the Medium.

For if the Medium be Thin and Quiescent, and the Sounding Body plac'd conveniently, the Sound will be easily and regularly propagated, and mightily conserv'd. I say,

1. If the Medium be Thin and Quiescent, because it otherwise causes a Refracted Sound, of which afterwards. Hence in a still Evening, or the dead of the Night (when the Wind ceases) a Sound is better sent out, and to a greater distance than otherwise, tho' much of this may be ascrib'd to its Refraction also.

2. I say, that the Sonorous Body must be plac'd conveniently, near a Smooth Wall, near Water, or a Plain, whose Surface is even.

1. Near a Smooth Wall, either Plain or Arch'd (Cycloidically or Elliptically, rather than otherwise, tho' a Circular or any Arch will do, but not so well.)

Hence in a Church, the nearer the Preacher stands to the Wall (and certainly 'tis much the best way to place Pulpits near the Wall) the better is he heard, especially by those who stand near the Wall also, though at a greater distance from the Pulpit; those at the remotest end of the Church, by laying their Ears somewhat close to the Wall, may hear him easier than those in the middle.

Hence also do arise Whispering Places. For the Voice being apply'd to one end of an Arch, easily rowls to the other. And indeed were the Motion and Propagation of Sounds but rightly understood, 'twould be no hard matter to contrive Whispering Places of infinite variety and use. And perhaps there could be no better or more pleasant hearing a Consort of Musick than at such a place as this, where the Sounds rowling along together, before they come to the Ear, must needs consolidate and imbody into one; which becomes a true composition of Sounds, and is the very Life and Soul of Consort.

2. If the Sonorous Body be plac'd near Water, the Sound will easily be convey'd, yet mollified; as Experience teacheth us from a Ring of Bells near a River, and a great Gun shot off at Sea, which yet differ much in the strength, and softness and continuance, or propagation of their Sounds, from the same at Land, where the Sound is more harsh and more perishing, or much sooner decays.

3. In a Plain a Voice may be heard at a far greater distance than in uneven Ground.

The Reason of all which last nam'd Phænomena is the same; because the Sonorous Air meeting with little or no resistance upon a Plane (much less upon an Arch'd) smooth Superficies, easily rowls along it, without being let or hinder'd in its Motion, and consequently without having its parts disfigured, and put into another kind of Revolution, than what they had at the first begetting of the Sound. Which is the true cause of its Preservation or Progression, and fails much when the Air passes over an uneven Surface, according to the degrees of its inequality, and somewhat also, when it passes over the plain Superficies of a Body that is hard and resisting.

Wherefore the smooth Top of the Water (by reason of its yielding to the Arch'd Air, and gently arising again with a kind of Resurge, like to Elasticity, tho' it be not so, by which Resurge it quickens and hastens the motion of the Air rowling over it, and by its yielding preserves it in its Arch'd Cycloidical or Elliptical Figure) the smooth Top of the Water, I say, for these Reasons, and by these Means, conveys a Sound more entire, and to a greater distance than the plain Surface of a piece of Ground, a Wall, or any other Solid Body whatever, can do.

As for the Speaking Trumpet, by which a Voice may be convey'd to a considerable distance, I refer its consideration to that of Refracted Sounds, or Refracted Audition.

Thus much of the Improvements of Hearing, that respect its Object, which is Sound.

2. The Organ and Medium are to be consider'd. And, 1. The Organ, which is the Ear, is helpt much by placing it near a Wall (especially at one end of an Arch, the Sound being begotten at the other) or near the Surface of Water, or of the Earth, along which the Sounds are most easily and naturally convey'd, as was before declar'd. And 'tis incredible how far a Sound made upon the Earth (by the trampling of a Troop of Horses, for Example) may be heard in a still Night, if a Man lays his Ear close to the Ground in a large Plain.

Otacousticks here come in for helping the Ear; which may be so contriv'd (by a right understanding the Progression of Sounds, which is the principal thing to be known for the due regulating all such kinds of Instruments) as that the Sound might enter the Ear without any Refraction, but as now they are generally made I refer them to Refracted Audition.

2. As to the Medium, I know not how that, by any contrivance of Art, can advantage Direct Hearing, otherwise than I have declar'd already in the propagation or conveyance of Sounds, though to the Refracting or Reflecting of them it may very much conduce; of which presently.

And so I have done with the first part of my present undertaking, which is the Comparison of Direct Vision and Audition, as to their Improvements from Art. The rest follow. Wherefore,

II. Concerning Refracted Vision and its Comparison, I observe, That Refracted Vision is always made Ex parte Medii, as Reflected is ex parte Objecti. And therefore, though Direct Vision may be help'd ex parte Objecti, Medii vel Organi, yet Refracted can be improv'd only ex parte Medii, and Reflected ex parte Corporis oppositi alone. Unless it be in a mixt or compound Vision, that is Refracto-Reflext, when the reflext Rays pass to the Eye through a refracting Medium, such as the Medium Internum, contain'd in the Body of the Eye, always is. So that in truth, all Vision is Refracted by an internal Refraction made in ipso Oculo.

And all that I have spoken of Vision holds true of Hearing also, both Refracted and Reflext, and therefore need not be repeated.

Refracted Vision arises from the different Density, Figure, and Magnitude of the Medium, which is somewhat alter'd also by the diverse incidence of the visible Rays. And so it is in Refracted Hearing, all these Causes concur to its Production, and some others to be hereafter consider'd.

Now as any Object (a Man for example) seen through a thicken'd Air, by Refraction appears greater than really he is: So likewise a Sound, heard through the same thicken'd part of the Atmosphere, will be considerably vary'd from what it would seem to be, if heard through a thinner Medium.

And this I call a Refracted Sound: But what this Refraction of Sound is, and how caus'd, may hereafter be discuss'd, when the Nature, and Motion, or Progression of Sounds are well stated.

For the Improvement of Refracted Vision artificial Instruments have been made, by grinding or blowing Glasses, into a certain Figure, and placing them at due distances, whereby the Object may be (as 'twere) enabled to send forth its Rays more vigorously, and the Visive Faculty impower'd the better to receive them. And thus also Instruments may be contriv'd for the assisting both the Sonorous Body, to send forth its Sound more strongly, and the Acoustick Faculty, to receive and discern it more easily and clearly. For,

1. As a fine Glass Bubble, fill'd with clear Water, and placed before a burning Candle or Lamp, does help it to dart forth its Rays to a prodigious Length and Brightness: So an Instrument may be invented, that apply'd to the Mouth (or any Sonorous Body) shall send forth the Voice distinctly to as prodigious a Distance and Loudness.

For if the Stentoro-phonecon (which is but a rude and unartificial Instrument) does such great feats, what might be done with one compos'd according to the Rules of Art? whose make should comply with the Laws of Sonorous Motion (which that does not) and therefore not so much Refract, as to alter and confound the Tone of the Voice and Words (as that somewhat does.)

Now of what use such an Instrument might be for speaking clearly and articulately at a distance (and that without altering the Tone of the Voice) whether it be at Sea or at Land (but especially at Sea in tempestuous Weather and in the Night) is obvious to any Man to conceive.

2. As Instruments have been invented to help the Eye, So likewise are there some, and more such there may be, for the Ear.

For,

1. As Spectacles and other Glasses are made to help the Purblind and weak Eyes, to see at any competent distance: So there are Otacousticks (and better may be made) to help weak Ears to hear at a reasonable distance also. Which would be as great a help to the infirmity of Old Age, as the other invention of Spectacles is, and perhaps greater; forasmuch as the Hearing what's spoken is of more daily use and concern to such Men, then to be able to read Books or to view Pictures.

2. As Perspective-Glasses and Telescopes help the Eye to see Objects at a very great distance, which otherwise would not be discernable; in like manner may a sort of Otacousticks be so contriv'd, as that they shall receive in Sounds made at a very great distance also, but with so much advantage, that the Ear shall be able to hear them, which otherwise would have been inaudible.

And these Otacousticks in some respects would be of greater use than Perspectives. For whereas at Land Perspectives are many times render'd almost useless, by the interposition of Woods and Mountains, which hinder the Sight from reaching very far: Our Otacousticks would, notwithstanding these Obstacles, take in a Sound made some Leagues off. Which might be of notable use in the time of War, for discovering the Enemy at a good distance, when he marches or lyes incamp'd behind a Mountain or Wood, or any such place of shelter.

Yea, even at Sea also, where Perspectives are of most use, by reason of the plainess of the Surface of the Water; yet sometimes there Otacousticks may be of more benefit, when in dark hazy Weather the Air is too thick, or in Stormy Tempestuous Weather the Waves arise too high for the Perspective to be made use of.

But, whether at Sea or Land, Perspectives become altogether insignificant in the Night-time (unless it be for viewing the Stars) which is the chief time for using Otacousticks; as it is generally, for Soldiers to take their March, when they would surprise their Enemies.

And therefore this sort of Otacousticks have then their chief use, when Perspectives are of no use at all; besides that they may be imploy'd in the Day-time, as well as Perspectives, whence they may (not unfitly) be term'd the most useful Instrument of the two.

3. As Microscopes or Magnifying-Glasses help the Eye to see near Objects, that by reason of their smallness were Invisible before; which Objects they Magnify to a strange greatness: So Microphones or Micracousticks, that is Magnifying Ear Instruments, may be contriv'd after that manner, that they shall render the most minute Sound in nature distinctly audible, by Magnifying it to an unconceivable loudness.

By the help hereof we may hear the different Cries and Tones, as well as by Microscopes see the divers Shapes and Figures of the smallest Animals.

4. As by Polyscopes or Multiplying-Glasses, one thing is represented to the Eye as many, whether in the same or different Shapes (for so Multiplying-Glasses may be contriv'd:) So by a Polyphone or Polyacoustick well order'd, one Sound may be heard as many, either of the same or a different Note. Insomuch, that who uses this Instrument, he shall, at the Sound of a single Viol, seem to hear a whole Consort and all true Harmony. By which means this Instrument has much the advantage of the Polyscope.

And thus much may suffice for comparing the Improvements made upon Refracted Seeing and Hearing; I call it Refracted Hearing, because made through a Medium, viz. thick Air, or an Instrument, through which the Sound passing is broken or refracted.

III. Reflected Vision has been improv'd by the Invention of Looking-glasses and Polished Metals, whether Plane, Concave, or Convex; and these two last, either Spherical, Oval, Cylindrical, Conical, Hyperbolical, or of several other shapes; all which cause a different Reflection, and vary the Phænomena.

Thus also Reflext Audition, made by Ecchoes, may be improv'd, by contriving several sorts of Artificial Ecchoes; as 'tis no hard matter to do in almost any place.

For (speaking in the general) Any Sound, falling directly or obliquely upon any dense Body, of a smooth (whether Plane or Arch'd) Superficies, is beat back again and reflected, or does eccho more or less.

I say (1.) falling directly or obliquely; because, if the Sound be sent out and propagated parallel to the Surface of the Dense Body, or be made so far off and so weak, that it cannot reach it, there will be no Reflection of Sound, no Eccho.

I say (2.) upon a Body of a smooth Superficies; because if the Surface of the Corpus Obstans be uneven, the Air by reverberation will be put out of its regular Motion, and the Sound thereby broken and extinguish'd: So that tho' in this case also the Air be beaten back again, yet Sound is not reflected, nor is there any Eccho.

I say (3.) it does eccho more or less, to shew, that when all things are, as is before describ'd, there is still an Ecchoing, though it be not always heard; either because the direct Sound is too weak to be beaten quite back again to him that made it; or that it does return home to him, but so weak, that without the help of a good Otacoustick, it cannot be discern'd; or that he stands in a wrong place, to receive the reflected Sound, which passes over his head, under his Feet, or to one side of him; which therefore may be heard by a Man standing in that place, where the reflected Sound will come, provided no interpos'd Body does intercept it; but not by him, that first made it.

I shall further make out the comparison 'twixt Reflex'd Vision and Audition, by these following Propositions.

1. As a Plain Speculum reflects the Object in its due Dimensions and Colours; allowing for their difference of appearance, according to their distance: So a Plane Corpus Obstans reflects the Sound back in its due Tone and Loudness; if allowance be likewise made for the proportionable decrease of the Sound, according to its distance.

2. As a Convex Speculum reflects the Object less, but somewhat brighter or clearer: So a Convex Corpus Obstans repels the Sound (insensibly) smaller; but somewhat quicker (though weaker) than otherwise it would be.

3. As a Concave Speculum reflects the Object bigger, more obscure and Inverted: So a Concave Corpus Obstans ecchoes back the Sound (insensibly) bigger, slower (though stronger) and also inverted; but never according to the order of Words. Nor do I think it possible for the Art of Man to contrive a Single Eccho, that shall invert the Sound, and repeat backwards; because then the Words last spoken, that is, which do last occur to the Corpus Obstans, must first be repell'd; which cannot be: For where, in the mean time, should the first Words hang, and be conceal'd, or lie dormant? Or how, after such a pause, be reviv'd and animated again into Motion? Yet in complicated or Compound Ecchoes, where many receive from one another, I know not whether something that way may not be done.

From the determinate Concavity or Archedness of these reflecting Bodies, it comes to pass, that some of them, from a certain distance or posture, will eccho back but one determinate Note, and from no other place will they reverberate any; because of the undue Position of the sounding Body. Such an one (as I remember) is the Vault in Merton College in Oxford.

4. As a Speculum takes in and reflects more of its Object, when plac'd at a great distance from it, than when nearer; because it reflects according to the apparent Magnitude of the Body at such a distance, which is less: So also the Ecchoing Body, being remov'd farther off, reflects more of the Sound, than when nearer. And this is the reason, why some Ecchoes repeat but one Syllable, some one Word, and some many.

5. As Specula's may be so plac'd, that reflecting one upon or into the other, either directly or obliquely, one Object shall appear many; as in Sir Samuel Moreland's Glass-room: After the same manner Ecchoing Bodies may be so contriv'd and plac'd, as that reflecting the Sound from one to the other, either directly and mutually, or obliquely and by Succession, out of one Sound shall many Ecchoes be begotten; which in the first case will be all together, and somewhat involv'd or swallow'd up of each other, and thereby confus'd (as a Face in Looking-glasses obverted) in the other they will be distinct, separate, and succeeding one another; as most multiple Ecchoes do.

Moreover a Multiple-Eccho may be made, by so placing the Ecchoing Bodies, at unequal distances, that they reflect all one way, and not one on the other; by which means a manifold successive Sound will be heard (not without astonishment) one Clap of the hands like many, one Ha, like a laughter, one single Word like many of the same Tone and Accent, and so one Viol like many of the same kind imitating each other.

Furthermore, as Specula's may be so order'd, that by Reflection they shall make one single thing appear many different things; as one single Man to seem many Men, differing as to Shape and Complexion (or a company of Men) which I think Sir Samuel Moreland's Contrivance does not: So may Ecchoing Bodies also be order'd, that from any one Sound given, they shall produce many Ecchoes, different both as to their Tone and Intension. (The ground whereof has elsewhere been laid down in a Treatise concerning the Sympathy of Lute-strings.)

By this means a Musical Room may be so contriv'd, that not only one Instrument, play'd on in it shall seem many of the same sort and size; but even a Consort of (somewhat) different ones; only by placing certain Ecchoing Bodies so, as that any Note (play'd) shall be return'd by them in 3ds, 5ths, and 8ths, which is possible to be done otherwise than was mention'd before in Refracted Audition.

I have now done with my Comparison of the two Noblest Senses, and Sciences, as to their Improvements; wherein I have been thus large, that I might give you a little prospect into the Excellency and Usefulness of Acousticks; and that thereby I might excite all that hear me, to bend their Thoughts towards the making of Experiments for the compleating this (yet very imperfect, tho' noble) Science; a Specimen whereof I will give you in three Problems, and then present you with the Semiplane of an Acoustick or Phonical Sphere, as an Attempt to explicate the great Principle in this Science, which is The Progression of Sounds.

The Problems are these:

1. Sonum intendere quousque velis; or, Datum sonum ad datum gradum intendere.

2. Sonum extendere quousque velis; or, Datum sonum ad datum distantiam extendere seu propagare.

3. Sonum transire ab extremo ad extremum & non per Medium.

1. The first is, To make the least Sound (by the help of Instruments) as loud as the greatest; a whisper to become as loud as the shot of a Cannon.

By the help of this Problem, the most minute Sounds in Nature may be clearly and distinctly heard.

2. The second is, To propagate any (the least) Sound to the greatest distance.

By the help hereof any Sound may be convey'd to any, and therefore heard at any distance, (I must add, within a certain, tho' very large Sphere.)

Moreover, by this means, a Weather-cock may be so contriv'd, as that with an ordinary blast of Wind it shall cry (or whistle) loud enough to be heard many Leagues: Which happily may be found of some use, not only for Pilots in mighty tempestuous Weather, when light Houses are render'd almost useless, but also for the measuring the strength of Winds, if allowance be made for their different moisture. For I conceive, that the more dry any Wind is, the louder it will whistle cæteris paribus; I say, cæteris paribus, because, besides the strength and dryness of Winds or Breath, there are a great many other things (hereafter to be considered) that concur to the increase or magnifying of Sounds, begotten by them in an Instrument exposed to their Violence, or blown into.

3. The third Problem, is, That a Sound may be convey'd from one extreme to the other (or from one distant place to another) so as not to be heard in the middle.

By the help of this Problem a Man may talk to his Friend at a very considerable distance, so that those in the middle space shall hear nothing of what passed betwixt them.

FIG. V. TAB. III.

Semiplanum Sphæræ Phonicæ seu Acousticæ.

You are to conceive that (rude) Semiplane, as parallel to the Horizon: For if it be perpendicular thereunto, I suppose the upper extremity will be no longer Circular, but Hyperbolical, and the lower part of it suited to a greater Circle of the Earth. So that the whole Phonical Sphere (if I may so call it) will be a solid Hyperbola, standing upon a Concave Spherical Base. I speak this concerning Sounds made (as usually they are) nigh the Earth, and whose Sonorous Medium has a free passage every way. For if they are generated high in the Air, or directed one way, the case will be different; which is partly design'd in the inequality of that Draught.

A Discourse concerning the Modern Theory of Generation, by Dr. George Garden of Aberdeen, being part of a Letter to Dr. William Musgrave, L. L. D. Reg. Soc. S. and by him communicated the Royal Society.

THE Subject I pitch upon, is that of the Formation of Animals. You know how wide and unsatisfying Men's Conjectures were upon this Head, until this Age, in which first the deservedly Famous Dr. Harvey discovered the proper place of the Formation of the Chick in the Cicatricula of the Egg, and the Formation of the Parts so far as was discernable by the naked Eye; and after him Malpighius, by the help of exact Glasses, observ'd the first Rudiments of it there, both before and after Incubation: And R. de Graef, and others, having upon many Observations concluded, that the Testes Fœminei were the Ovaries of Females, and consequently that all Animals were ex ovo; they began from hence to infer, that the Rudiments of each Animal were originally in the respective Females, and that the Male contributed only to give a new Ferment to the Mass of the Blood and Spirits, by which means a spirituous Liquor (which the Blood in its ordinary Ferment could not produce) did insinuate it self into the same Ducts and Pores of the Rudiments of those Animals, which were in greatest forwardness in the Ovary, and so extend and enlarge all their Parts, and at last bring them to perfection, as Mr. Perrault does ingeniously discourse in the third Part of his Essais de Physique; till now at last Leowenhoek has discover'd an infinite number of Animalcula in semine marium of all kinds, which has made him condemn the former Opinions about the Propagation of all Animals ex Ovo.

Now upon comparing the Observations and Discoveries which have been made with one another, these three things seem to me very probable. 1. That Animals are ex Animalculo. 2. That these Animalcles are originally in semine Marium & non in Fœminis. 3. That they can never come forward, nor be formed into Animals of the respective kind, without the Ova in Fœminis.

The first of these seems probable from these three Observations. 1. That some such thing has been so often observ'd by Malpighius, in the Cicatricula of an Egg before Incubation, as the Rudiments of an Animal in the shape of a Tadpole, as may be seen in his first, and in his repeated Observations de formatione Pulli in Ovo. 2. The sudden appearance and displaying of all the Parts after Incubation, makes it probable, that they are not then actually formed out of a fluid, but that the Stamina of them have been formerly there existent, and are now expanded. The first Part of the Chick which is discovered with the naked Eye, is, you know, the Punctum saliens, and that not till three days and nights of Incubation be past; and then, on the fifth day, the Rudiments of the Head and Body do appear. This made Dr. Harvey conclude, that the Blood had a being before any other Part of the Body; and that from it, all the Organs of the Fœtus were both form'd and nourished: But by Malpighius's Observations we find that the Parts are then only so far extended, as to be made visible to the naked Eye, and that they were actually existent before, and discernable by Glasses. After an Incubation of thirty hours, are to be seen the Head, the Eyes, and the Carina with the Vertebræ, distinct, and the Heart. After forty hours its Pulse is visible, and all the other Parts more distinct, which cannot be discerned by the naked Eye before the beginning of the fifth day; from whence it seems probable, that even the so early discovery of those Parts of the Fœtus by the Microscope, is not the discerning of Parts newly formed, but only more dilated and extended by receiving of Nutriment from the Colliquamentum; so that they seem all to have been actually existent before the Incubation of the Hen. And what Swammerdam has discovered in the transformation of Insects, gives no small light to this; whilst he makes appear in the Explanation of the 13th Table of the General History of Insects, that in those large Eruca's which feed upon Cabbage, if they be taken about the time they retire to be transformed into Aurelia's, and plung'd often in warm Water to make a Rupture of the outer Skin, you will discern through the transparency of their second Membrane, all the Parts of the Butterfly, the Trunk, Wings, Feelers, &c. folded up. But that after the Eruca is chang'd into an Aurelia, none of these Parts can be discern'd, they are so drencht with moisture, tho' they be there actually form'd. Another Consideration is from the Analogy, which we may suppose between Plants and Animals. All Vegetables we do see proceed ex Plantula, the Seeds of Vegetables being nothing else but little Plants of the same kind folded up in Coats and Membranes; and from hence we may probably conjecture, that so curiously an organized Creature as an Animal, is not the sudden Product of a Fluid or Colliquamentum, but does much rather proceed from an Animalcle of the same kind, and has all its little Members folded up according to their several Joints and Plicatures, which are afterwards enlarged and distended, as we see in Plants. Now tho' this Consideration alone may seem not to bear much weight; yet being join'd to the two former, they do mutually strengthen each other. And indeed all the Laws of Motion, which are as yet discovered, can give but a very lame account of the forming of a Plant or Animal. We see how wretchedly Des Cartes came off when he began to apply them to this Subject; they are formed by Laws yet unknown to Mankind; and it seems most probable, that the Stamina of all the Plants and Animals that have been, or ever shall be in the World, have been form'd, ab Origine Mundi, by the Almighty Creator within the first of each respective kind. And he who considers the Nature of Vision, that it does not give us the true magnitude, but the proportion of things; and that what seems to our naked Eye but a Point, may truly be made up of as many Parts as seem to us to be in the whole visible World, will not think this an absurd or impossible thing.

But the second thing which later Discoveries have made probable, is, that these Animalcles are originally in Semine Marium & non in Fœminis. And this I collect from these Considerations: 1. That there are innumerable Animalcula discover'd in Semine Masculo omnium Animalium. Mr. Leewenhoeck has made this so evident by so many Observations, that I do not in the least question the truth of the thing. The reason of their Multitude, and some of the Difficulties which arise thereupon, he has cleared to very good Purpose, so that I shall not repeat them. 2. The observing the Rudiments of the Fœtus in Eggs, which have been fecundated by the Male, and the seeing no such thing in those which are not fecundated, as appears from Malpighius his Observations, make it very probable that these Rudiments proceed originally from the Male, and not from the Female. 3. The resemblance between the Rudiments of the Fœtus in Ovo, both before and after Incubation, and the Animalcle, makes it very probable, that they are one and the same. The same Shape and Figure which Mr. Leewenhoeck gives us of the Animalcle, Malpighius likewise gives of the Rudiments of the Fœtus, both before and after Incubation; yea, and even the Fœtus's of Animals do appear so at first to the naked Eye, so that Dr. Harvey does acknowledge that all Animals, even the most perfect, are begotten of a Worm, De Gen. Anim. Ex. 18. 4. This gives a rational account of many Fœtus's at one Birth, especially that of the Countess of Holland, and how at least a whole Cluster of Eggs in a Hen are fecundated by one Coition of the Male. 5. This gives a new light, as it were, to the first Prophecy concerning the Messiah, that the Seed of the Woman shall bruise the Head of the Serpent, all the rest of Mankind being thus most properly and truly the Seed of the Man. 6. The Analogy I have already mentioned, which we may rationally suppose between the manner of the propagation of Plants and Animals, does likewise make this probable. Every Herb and Tree bears its Seed after its kind; which Seed is nothing else but a little Plant of the same kind, which being thrown into the Earth, as into its Uterus, spreads forth its Roots, and receives its Nourishment, but has its form within its self, and we may rationally conjecture some such Analogy in the Propagation of Animals.

The third Particular which later Discoveries make probable, is, that Animals cannot be formed of these Animalcula without the Ova in fœminis, which are necessary for supplying of them with proper Nutriment: And this these Considerations seem to evince. 1. It is probable that an Animalcle cannot come forward, if it do not fall into a proper Nidus. This we see is the Cicatricula in Eggs; and tho' a Million of them should fall into an Egg, none of them would come forward, but what were in the Center of the Cicatricula; and perhaps the Nidus necessary for their formation is so proportion'd to their bulk, that it can hardly contain more than one Animalcle; and this may be the reason why there are so few Monsters. This we see is absolutely necessary in Oviparis; and the only difference which seems to be between them and the Vivipara, in this matter, is in this, that in the latter the Ova are properly nothing more but the Cicatricula, with its Colliquamentum, so that the Fœtus must spread forth its Roots into the Uterus to receive its nourishment; but the Eggs in Oviparis may be properly term'd an Uterus, in relation to the Fœtus; for they contain not only the Cicatricula, with its Amnion and the Colliquamentum, which is the immediate nourishment of the Fœtus, but also the materials which are to be converted into that Colliquamentum; so that the Fœtus spreads forth its Roots no farther than into the White and Yolk of the Egg, from whence it derives all its nourishment. Now that an Animalcle cannot come forward without some such proper Nidus, Mr. Leewenhoeck will not readily deny; for if there were nothing needful, but their being thrown into the Uterus, I do not see why many hundreds of them should not come forward at once; for as to what Mr. Leewenhoeck says, that one of them would be-dwarf and choak the rest; this might fall out in process of time: But at first I do not see why many of them should not grow together, whilst scatter'd in so large a Field (and yet no such thing is observed) if there were not an absolute necessity of a Cicatricula for their growth and thriving. Now, 2. That this Cicatricula is not originally in Utero, seems evident from the frequent Conceptions which have been found extra Uterum: Such as the Child which continued Twenty six Years in the Woman of Tholouse's Belly, mention'd Numb. 139. of the Philos. Trans. And the little Fœtus found in the Abdomen de St. Mere, together with the Testicle torn and full of clotted Blood, recorded Numb. 150. both taken out of the Journals des Savans: Such also seem to be the Fœtus in the Abdomen of the Woman of Copenhagen, mention'd in the Nouvelles des Lettres, for Sept. 85. pag. 996. all the Members of which were easily to be felt through the Skin of the Belly, and which she had carried in her Belly for four Years; and the seven Years Gravidation, related by Dr. Cole, Numb. 172. of the Transact. That these two were undoubtedly extra Uterum, is uncertain, because the last was not open'd after her death, and the former may be yet still alive. Now granting once the necessity of a proper Nidus, for the formation of an Animalcle into the Animal of its respective kind; these Observations make it probable, that the Testes are the Ovaria appropriated for this use; for tho' the Animalcles coming thither in such Cases may seem to be extraordinary, and that usually the Impregnation is in Utero; yet it may be collected from hence, that the Cicatriculæ or Ova to be impregnated, are in Testibus fœmineis; for if it were not so, the accidental coming of Animalcles thither could not make them come forward more than in any other part of the Body, since they cannot be formed and nourished without a proper Nidus. But 3. It is acknowledg'd by all, that the Fœtus in Utero, for some considerable time after Conception, has no connexion with the Womb, that it sits wholly loose to it, and is perfectly a little round Egg with the Fœtus in the midst, which sends forth its Umbilical Vessels by degrees, and at last lays hold on the Uterus. Now from hence it seems evident, that the Cicatricula, which is the Fountain of the Animalcles nourishment, does not sprout from the Uterus, but has its Origin elsewhere, and falls in thither as into a fit Soil, from whence it may draw Nutriment for the growth of the Fœtus, else it cannot be easily imagin'd, how it should not have an immediate Connexion with the Uterus from the time of Conception. If you join all these three Considerations together, viz. that an Animalcle cannot come forward without a proper Nidus or Cicatricula; that there have been frequent Fœtus's extra Uterum; and that they have no Adhæsion to the Uterus, for a considerable time after Conception, they seem to make it evident, that Animals cannot be form'd ex Animalculis without the Ova in Fœminis. To all these I shall subjoin the Proposal of an Experimentum Crucis, which may seem to determine, whether the Testes Fœmineæ be truly the Ovaria, viz. Open the Abdomen of the Females of some kinds, and cut out these Testicles, and this will determine, whether they be absolutely necessary for the formation of Animals.

There are some Difficulties proposed against this Conjecture, which I think may be easily resolved. Some object the distance between the Tubæ or Cornua Uteri, and the Testicles; but to this is opposed by Swammerdam, and others, the like distance between the Infundibulum, in Hens and Frogs, and the Ovary; and yet it cannot be denied that the Eggs are transmitted thro' this into the Uterus: And besides R. de Graef, and others, have by repeated Observations found that the Cornua Uteri do at certain times after Conception, embrace the Testes on both sides the Uterus. They object in the second place the great disproportion between the pretended Eggs in the Ovary, and the Aperture of the Tubæ or Cornua Uteri, the former being a great deal bigger than the latter: But both R. de Graef and Malpighius have clear'd that Matter, by making appear, that these Bladders in the Ovary are not the Ova, but serve to form the Glandules within which the Ova are formed, which break through a small Papilla opening in the Glandule, which bears a proportion to the Aperture of the Tube. They object 3, The difficulty to conceive how these Eggs should be impregnated per semen Maris, both because there is no Connexion between the Tubæ and the Ovary for its transmission, and for that Dr. Harvey could never discover any thing of it in Utero. As to the last, Mr. Leewenhoeck has cleared that difficulty, by the discovery of innumerable Animalcula Seminis Maris in Cornubus Uteri, and those living a considerable time after Coition. Numb. 174. of the Transact. And as to the former, we may either suppose that there is such an Inflation of the Tubæ or Cornua Uteri tempore Coitionis, as makes them embrace the Ovaria, and such an approach of the Uterus and its Cornua, as that I may easily transmit the Seed into the Ovary; or else, that the Ova are impregnated by the Animalcles after they descend into the Uterus, and not in the Ovary; the former seems probable for this Reason, that at least a whole Cluster of Eggs in a Hen will be fecundated by one Tread of the Cock: Now this Fecundation seems to be in the Vitellary, and not in the Uterus, as the Eggs pass along from day to day; for it can hardly be supposed that the Animalcles should subsist so long, being scattered loosely in the Uterus, as to wait there for many days for the Fecundation of the Eggs as they pass along. The latter Conjecture has this to strengthen it, that the Animalcles are found to live a considerable time in the Uterus; and that if they should impregnate the Ova in the Ovary it self, the Fœtus would increase so fast, that the Ova could not pass through the Tubæ Uteri, but would either burst the Ovary, or fall down into the Abdomen from the Orifices of the Tubæ; and that from hence proceed those extraordinary Conceptions in Abdomine extra Uterum. But, 4. Mr. Leewehoeck, Numb. 147. of the Transact. to weaken the third Consideration about the Conceptions, being like unto an Ovum in the Womb, proposes a Parallel between these Animalcles and Insects; and insinuates, that as the latter cast their Skins, and appear of another Shape, so the other which at first seem like Tadpoles, may cast their outer Skin, and then be round; and that this may be the occasion of the round Figure of the Conception in the Womb. To this it may be replied, that according to Mr. Leewenhoeck's own Sentiment, the Animalcles cannot come forward, if they do not find the Punctum or proper place for their Nourishment, to which it seems they must have some Adhæsion. Now the Conception in Viviparis is not fastned unto the Womb for many days, nor does adhere to any point of it; so that it seems this roundish Body is not the Animalcle thus chang'd after having cast an outer Skin, but is rather the Cicatricula or little Egg, into which the Animalcle has entred as its Punctum or place of nourishment; else I do not see why they should not be adhering to the Womb from the first Conception, or why (as I have said) many hundreds of them are not conceiv'd and formed together, &c.

A short Discourse concerning Concoction: Read at a Meeting of the Royal Society, May ... 1699, by Clopton Havers, M. D. Fellow of the Royal Society.

THE manner in which the Digestion of the Aliment is performed, is a thing not very easie to be understood and explained. However, it has not escap'd the Conjectures of some Philosophical Men, who having curiously observ'd the Phænomena of Nature, and enquired into their Causes, have, amongst other things, endeavour'd to account for this. But their Sentiments about it have been various, and the Hypothesis, by which they have studied to explain it, very different. Some have thought the Concoction of the Food to be a kind of Elixation; and that the grosser and more solid Parts being, as it were, boil'd in the Liquid by the Heat of the Stomach, and the Parts adjacent to it, as the Liver, Spleen, and Omentum, are by a long and continued Elixation, first render'd more tender, and then colliquated, and dissolved into minuter Particles, so as to mix more equally with the Fluid, and with that to make one Pulpament, or chylous Mass. And Hippocrates, tho' he does not plainly call it an Elixation, yet seems to attribute the Concoction of the Food to the Heat of the Stomach, as the Cause of it, Sect. 4. Libro de salubri victus ratione. So where he takes notice of the voiding of such Fæces, as appear to be like the Food that has been eaten; he adds, Constat enim, sane ventriculum, ciborum copiam, ut concoquat, calefacere non posse. And there are other Passages in the same Book, from which we may conclude, that he suppos'd the Heat of the Stomach to be the great Cause of the Digestion of the Food.

There are others that make the Stomach itself to be the great Instrument of Digestion, but in a different manner: And they suppose it to be perform'd by an Attrition, as if the Stomach, by those repeated Motions, which are the necessary Effects of Respiration, when it is distended by the Aliment, did both rub or grind off some minuter Particles from the grosser Parts; and by continually agitating the Mass of Food, make those Parts, which are not contiguous to the Stomach, strike one against another, and break one another in pieces, until they are all attenuated. It is evident enough, that the sides of the Stomach do in Expiration press upon the Contenta, so as to oblige, at least some Parts of them, every time the Muscles of the Abdomen are contracted, to move and shift their places. So in Inspiration, when the Diaphragm and Liver press upon the upper part of the Stomach, the Aliment must be moved again. So that by these reciprocal Motions, that part of the Food which is contiguous to the Stomach, and moves in a Line parallel to it, must rub against it; and all the other Parts being moved by such a Compression, as gives them a different Tendency, it is certain they must be continually striking one against another. And for Bread, and such things as are made of Flower, that will be softned and dissolv'd with any common Liquid, that Agitation of the Stomach which moves them in Respiration, might seem sufficient to break and dissolve them, when they are sufficiently moisten'd with a Fluid. Yet this cannot be thought enough to break and digest Flesh-meat, Fruits, or any other thing that will not be softned and dissolv'd in Water, or some such Liquid. But although this Motion of the Aliment, caused by Respiration, does not actually digest it, yet it has a great and necessary Use in Concoction, and makes all the grosser Parts, as they are attenuated, mix equally with the Fluid.

Some think that the Bilious Juice; others, that the Spirits are chiefly concern'd in this Affair. Galen, in his Book de Neutralibus Facultatibus, makes it to be the Effect, not of one, but of several Causes; as a pituitous Juice in the Stomach, the Bile, &c. which appears from what he has said, and the Translator thus render'd: 'Verum quanto ii (cibi) qui mansi sunt, iis, qui inhæserunt, magis sunt alterati; tanto etiam his magis ii, qui devorati sunt. Siquidem incomparabilis erit horum alterationis excessus, si & quæ in ventre est Pituita & Bilis, & Spiritus, & Calor, & tota Ventris substantia, æstimentur.'

Some there are that will have the Food to be dissolv'd by a Menstruum, which is supply'd from the Glands of the Stomach, or some other way: But those that do so far agree in the General, as to think Concoction is perform'd by a Dissolvent, do differ in their Notions of the Nature of the Menstruum: For there are some that suppose it to be an Acid, which does erode the grosser parts of the Food, and dissolves them in the same manner as Vinegar, Spirit of Vitriol, or any such-like Acid, will dissolve even so solid a Body as Iron. And it cannot be deny'd, but that Oil of Vitriol will dissolve Flesh-meat, and reduce it to a Pulp; but it is not to be suppos'd, that the Fibres of the Stomach can admit any such strong and corroding Acid, without something to correct it, but it must be injur'd in its Tone, and labour under great and extraordinary Pains. Neither does such a Menstruum, tho' it will digest some things, seem capable of dissolving so great a Variety of Things as we eat, especially when a great many of them are of a contrary Nature. Some will have the Menstruum to be a nitro-aerius Spirit, that is, quick, and very penetrating, and included in its proper Vehicle; which, being in its own Nature apt to penetrate the Mass of the Aliment, does diffuse it self through the Whole, and breaking the Vinculum of the more solid Parts, does dissolve their Compages. By others, it is thought to be some saline Juice in the Stomach, by which the Parts of the Aliment are divided and dissolved, and those which are fit for Nourishment, are volatiliz'd.

Lastly, There are some others who reject the Opinions I have already mention'd, and suppose the Digestion of the Food to be perform'd by the Benefit of a Ferment; which, when it is mixed with the Aliment, excites in the Mass an intestine motion; and the different and contrary motions and tendency of the Parts, making some kind of Collision, gradually break off Particles from the grosser, and more solid Parts, till they are so attenuated as to be apt to mix more equally with the Fluid, and with them to make one soft or chylous Substance. But yet there is not amongst them an universal Consent, either about the Nature of this Ferment, or the manner how it is supply'd. For first, some think it to be the Remains of the Food that was last digested; which having lain some time in the Stomach, after the rest is carried down into the Intestines, contracts an Acid, or some other Quality, and is so alter'd, as to partake of the Nature of a Leaven. And this Leaven being a part of the Food, which has been already digested, is so soft and liquid as to be capable of mixing with the Aliment, which is next taken into the Stomach; and being agitated with it by the repeated Pressures of the Diaphragm, Liver, and Abdominal Muscles upon the Stomach in Respiration, does diffuse it self through the whole Mass; and being mixed with it, like Leaven, or Yest added to new Wort, &c. puts it into a State of Fermentation; and by this Fermentation, or the Expansion of the Ferment, and the more tenuious Parts, which are first put into motion by it, those which are more solid, and with which they are intermixed, are rent, and divided, and so attenuated, as to become a soft and pulpous matter. And altho' the greatest part of the Food, that is thus broken and concocted, is by the Contraction of the Fibres of the Stomach press'd into the Duodenum; yet they do not contract themselves so as to force out all the Aliment, but leave between the Rugæ or Folds, on the inside of the Stomach, a sufficient Quantity to be a Leaven to the next Meal; and so from time to time.

Some have a Notion, That this Ferment, or Principle of Fermentation, is in the Aliment it self; which being a Congeries of Matter, consisting of various Parts of a different Nature, is no sooner enclosed in the Stomach, and digested in the Heat of that, and the adjacent Parts, but the more spirituous and subtil Particles are put into motion both from that Warmth, and the difference of their Natures, and enter upon a Fermentation. And so by their intestine Commotion, and the Violence they offer to those Parts which oppose the tendency of any of them, they break and dissolve what is more solid.

Again: Some suppose, that this Ferment is supply'd from the Glands of the Stomach.

And Lastly, Others, and perhaps with much better Reason, contend for the Saliva, and make that to be the Ferment, which serves principally for the Digestion of the Food; which in Mastication being mix'd with our Aliment, is with that carried down into the Stomach, where the Parts of it being put into motion by a kindly and agreeable Heat, they do ferment with, and exagitate first those Parts of the Food which are most apt to ferment with it, and then both conspire to break and dissolve the grosser and more stubborn Parts. And Galen, in the Book I have before-mention'd, plainly allows that the Saliva is concern'd in the business of Concoction, tho' he supposes the Alteration, which is produc'd by this Juice, to be made in the Mouth, as appears from these Words: Quæ (alteratio) in ore agitur mutat quidem id (nutrimentum) in alteram speciem manifestè, non tamen ad perfectionem transmutat--Qui mansi sunt cibi primum quidem hac Pituita (oris) imbuunter, & cum ea miscentur----Itaque majorem mutationem consecuti sunt, quam ii, qui in vacuis dentium intervallis fuere impacti.

Now I have given this short Account of the various Opinions of some Ingenious Men, concerning the manner how Concoction is perform'd; I come now to propose my own Hypothesis, by which I shall endeavour to explain it.

In order to the more easie and effectual Digestion of the Food, Nature has appointed some Parts for the breaking our Aliment, and reducing whatever is gross into smaller Parts, before it is put upon Digestion: Others to supply the Ferment, by which it is to be dissolv'd and concocted, and which, before it comes to be included in the Stomach, does moisten, and make it more soft, that it may more easily be penetrated, and broken by those Parts which serve to divide every Morsel into smaller Pieces, and prevents the Inconvenience and Trouble which would arise from the Nourishment sticking about or between them, when it is dry or viscous.

For the breaking of that part of our Food, which is not liquid, Nature has furnish'd us with Teeth, and those of two sorts: For some are ordain'd to divide and break off smaller Morsels from a larger Mass; others are made for the grinding those Morsels into much smaller parts. The Teeth, which serve to break off Pieces of a convenient Magnitude from a larger Mass, are of two sorts, accommodated to the Nature of the Substance which we eat. These are the Incisores, and the Dentes Canini. If the Substance, which we have to eat, be not hard, but more easily penetrated and divided, then the Incisores are capable of making an Impression upon it, and fix'd firmly enough in the Jaws to break off that part which they take hold of. But if it be more solid, and not easily penetrated, nor any Piece without difficulty to be separated from that Body, whereof it is a part; then we apply the Dentes Canini, or Eye-Teeth, to it, which are not spread, nor have such an edge as the Incisores, but are sharp and pointed like an Awl, and so do more readily penetrate a Substance that is hard, and which the Incisores can scarcely make any Impression upon. And as the Parts of a more solid Body are commonly with more difficulty separated, and there must be a greater stress put upon those Teeth which pull it into pieces; so these Teeth are much more firmly fixed in the Jaws than the Incisores, tho' they have but one single Root. Besides, the Position of all these Teeth is accommodated to their use, as being planted opposite to the Aperture of the Mouth; so that they may be conveniently apply'd to the Substance which we have to eat, before it is broken, and when it is too large to be admitted within the Mouth.

The Teeth which do by a Compression and Attrition reduce the little Morsels to smaller Parts, are from the manner in which they break the Aliment, called Dentes Molares, because they do, like so many Mill-stones, grind the Food between them. And that they might be render'd fit for this purpose, they are made broad at that Extremity, which stands out of the Gums, by which means they retain some Quantity of the Food between them every time the lower Jaw is pulled up and forc'd against the Maxilla superior. And as they are broad, so they are formed with Inequalities and Protuberances; and by the motion of the lower Jaw, from one side towards the other, they grind what they have between them into pieces. The Position of these Teeth too is as convenient as that of the Incisores, and the Dentes Canini: For being design'd to break those pieces of our solid Food, which are taken into the Mouth, and these pieces, when they are compress'd, and mov'd by the Dentes Molares, being apt to fly out of the Mouth, if there were no Contrivance to prevent it, they are placed beyond the Aperture of the Mouth, and opposite to the Cheeks, which keep the Food within that Cavity, and not only so, but press it in between the Dentes Molares on one side, as the Tongue does on the other, until they have sufficiently broken and divided it.

At the same time, whilst the Dentes Molares are breaking the Food, there flows into the Mouth a Salival Juice, which mixes with it, and not only serves to moisten it, and to render it more apt and easie to be divided, but seems to be the Ferment, by the Benefit of which the Food is dissolved and digested. And therefore it is intimately mixed with it, by the Teeth agitating or stirring them together in Mastication.

This Liquor, which we commonly call the Saliva, or Spittle, seems to be a Composition made of two several Juices, very different in their Nature: And therefore the several Parts of it are separated by their proper Glands, and Nature has planted no fewer than four Pair about the Mouth, which supply the Juices that make the Saliva; to wit, the Parotides, and the Glandulæ Nuckianæ, the Glandulæ Maxillares internæ, and Sublinguales. Whereas if the Saliva were but one more simple Liquor, a less number of Glands might have been sufficient. At least there appears no Reason why one of every Pair should disembogue itself into the Mouth so very near to the Orifice, by which a Gland of some other Pair throws in its Juice; and they are not rather all planted at more equal distances from one another, so to flow in upon every part of the Aliment at the same time.

Not that I suppose, as there are four Pair of salivatory Glands, so there are four sorts of Juices supply'd from them, to make the Saliva; but, as I hinted before, that there are only two different Juices that constitute it. And these are not only sufficient, but more proper to excite and secure that Fermentation, which is necessary to Concoction. For we find that most of those Fermentations, which arise upon Mixtures made for Experiments, are produced from the mixture of two things; and it is not so easie to find out three or four such Liquors of a different Nature, as will, upon the mixtion of them all, produce a Fermentation, and from the omission of any one of them discover no Discord or Disposition to ferment: Besides, it is certain that two do better secure the End, which Nature designs. For, if there were three or four different Juices, of which the Saliva naturally consists, these must all have their proper Qualities preserved to them, or else the Fermentation, which should arise between them, will not necessarily follow upon their mixture; and it is certain, that there would be more Danger, that one of three or four should be deprived of its Natural Quality, than one of two.

What Nature these two Juices are of, I do not pretend positively to determine; but so far as I have been able to make my Conjectures about it from Experiments, I do think one of them to be an acid Juice; the other an oleaginous Liquor, something like Oil of Turpentine. For amongst the many Experiments I have made, there was no one that gave me so much Satisfaction, as that which I made with Oil of Turpentine, and Oil of Vitriol, though I try'd several other things, that will produce a Fermentation upon their Mixture. And it was for this Reason, that I made the Experiment with Oil of Turpentine and the other Oil.

I took a piece of raw Flesh, and having cut it into pieces, but much larger than what our more solid Food is reduc'd to by due Mastication, I mix'd some Crums of Bread with it, then I pour'd in the Oil of Turpentine to them, and upon that the Oil of Vitriol; and having shak'd them together, I digested them about four Hours in Balneo Mariæ, and then shaking them again in the Glass, I found the Meat dissolv'd, and they all became a thickish Pulp. I could not but take notice, that Oil of Camphire (though it does not otherwise seem much different in its Nature from Oil of Turpentine) and Oil of Vitriol, which upon mixture will produce an Effervescence as well as the Oil of Turpentine and Oil of Vitriol, yet did not touch the Meat, upon which I poured them, so as in the least to dissolve them. I cannot deny but that an Acid, and a Solution of Salt of Tartar, did dissolve some part of the Flesh-meat, which I mix'd them with, but yet neither so soon, nor so perfectly as the two forementioned Oils. And I do the rather think one of those Juices, which constitute the Saliva, to be of the Nature of Oil of Turpentine, than of a fix'd Salt, because it will correct and temper even Oil of Vitriol, so as to render it more tolerable to the Fibres of the Stomach. Not that I suppose the acid part of the Saliva to come near to the Acidity of Oil of Vitriol. For though, when they are mix'd, they will make a Liquor that may not be injurious to the Stomach; yet the acid Juice, if it were so corrosive as Oil of Vitriol, would certainly be injurious and painful to the Salivatory Ducts, which convey it to the Mouth before it is mix'd with the oleaginous Liquor. But I only say it is an Acid, and in some degree approaches to the Nature of that Oil. And Nature, which can much better adapt several Causes for the Production of such an Effect than Art, may attain her End by a more temperate Acid; though, at the same time, we may be able to make some probable and true Conjectures about the Nature of those Causes from Experiments.

It being most reasonable to suppose, that there are but two sorts of Juices, of a different Quality, that make the Saliva, I do conceive, that four of the eight Salivatory Glands, or two Pair of the four, do supply one of these Juices, and the other four Glands the other. And this seems to be a very good Reason, why they are so planted, and the Orifice of their Ducts so order'd, that the Juice, which is supply'd by one Gland, is discharg'd into the Mouth, very near to the Orifice, by which the Juice of a different Nature is transmitted from another, so that they must necessarily meet and mix together. Thus the Glandulæ Nuckianæ, and Parotides, throw in two different Juices by Orifices, which open into the Mouth very near to one another; and the Glandulæ Maxillares internæ, and Sublinguales, do below supply the same kind of Juices by Orifices, that open so near to one another as to secure the mixture of the two different Juices.

These Glands, I say, do between them afford two divers sorts of Liquors, of such a Nature as are apt to ferment upon their first Mixture, but perhaps more considerably when they come to be digested by the Heat of the Stomach. So that the Colluctation, or Fermentation, which attenuates and concocts the Food in the Stomach, does not ordinarily arise between the Aliment and the Saliva, but between the several Parts of the Saliva it self. And indeed, if the Saliva did not consist of two Juices, whose Nature is in such a manner different, as to render them apt to ferment upon their mixture, it would be very hard to conceive how it should so readily and indifferently serve for the Digestion of all Eatables; how it should ferment with, and dissolve so great a variety of Things, not only of a different, but of a contrary Nature; how it should ferment with Acids as well as Alkalies, digest things that are cold, as well as hot or temperate; some things that are salt, others that are insipid, bitter and sweet, mucilaginous, oily, &c. But if we suppose, that the Fermentation, which serves for the Digestion of the Food, arises from a peculiar difference in the Nature of two Juices, which constitute the Saliva, it will be easie to give a rational Account of our Concoction of innumerable things of a different Nature. And this seems to be as effectual, and a more certain way to attenuate and dissolve the grosser Parts of our Food, than if the Fermentation were made only between the Saliva and the Aliment: Besides, the Saliva seems to discover a Fermentation upon the mixture of its constituent Juices, even at those times when we do not actually eat; for it is always attended with Bubbles, and a Froth, when it has not been at all agitated in the Mouth, and many of those Bubbles will remain for some considerable time after we have spit it out.

Nature therefore having appointed the Saliva for the digestion of the Food, has taken care that it shall be thrown in upon the Aliment on every side. Thus the Glandulæ Nuckianæ, and the Parotides, supply their Juices to that part of the Food, which lies on the outside of the Gums, between the Cheeks and the Teeth, and the Glandulæ Maxillares internæ, and Sublinguales, do bestow their Liquor upon the Meat, which is within the Teeth and Gums. Neither has she had a Regard only to that Supply, which is due to all the parts of our Food, but likewise to the mixture of the two different Juices of the Saliva, which is necessary to its Fermentation. And therefore, as I have already observ'd, the Orifices of the Ducts, which belong to one sort of Glands, are placed near the Aperture of a Duct, which conveys a Juice from one of the other Glands. So the Ducts of the Glandulæ Nuckianæ, and the Ductus Stenoniani, do on each side open into the Mouth, near one another; and the salivatory Ducts of the Glandulæ Sublinguales, and the Maxillares internæ, though they have distinct Orifices, empty themselves under the same Papillæ, and the Juices, which are supply'd by them, meet there, and flow into the Mouth together.

The several Parts of the Saliva being discharg'd into the Mouth in such a manner as to meet and begin a Fermentation, the Saliva does, partly as it is agitated, with the Food by the Teeth, and some other parts of the Mouth; partly by its own Fluidity, insinuate it self into, and mixes with the Food, and not only moistens and softens it, but excites the Fermentation, which is to dissolve it. And when the Aliment is thus mix'd with the Saliva, which serves to ferment the whole Mass, it is then to be convey'd into the Stomach, that great digestive Vessel of the Body, where the Fermentation is not only continued, but improved.

The Nourishment being convey'd into the Cavity of the Stomach, is there kept for some time in a digestive Heat, all which time it is under a Fermentation, produc'd by the different Parts or Juices of the Saliva, which are mix'd with it; which Fermentation does first agitate the more tenuious or subtil parts of the Food, and puts them into motion, and so with the Fermentation of its own, and those Alimentary Parts, which it first communicates a Motion to, improved by the Heat of the Stomach, the Saliva must necessarily act upon the grosser Parts. For the intestine Motion, which is excited in the Mass, does not give the Particles, which are fermented, the same Tendency, but what is so various and confus'd, that they must inevitably strike not only one against another, but against those which are more gross, so as to attenuate them, sometimes by a Collision, which strikes off smaller Particles from the larger Parts; sometimes by a Compression, when the Particles which are in Motion, happen to strike directly against any grosser Part, on every side of it, sometimes by a kind of Explosion. For without doubt the Saliva, which is fluid, insinuates it self into the Interstices of the more crass Parts of the Aliment, and whatever is agitated and expanded in those Interstices, requiring a larger space for the Freedom of its Motion, and offering a Violence to every thing that opposes its Tendency, will, like Gun-powder included in a Shell, force its way out, and tear to pieces that Matter, which does endeavour to confine it.

Thus the grosser Parts are broken and divided, until they are at last so far attenuated as to mix more equally with the Fluid, and with them to make one Pulp or Chylous Mass. And although I do not apprehend how the Stomach should by its reciprocal Motions in Inspiration and Expiration, be able to break and attenuate any Matter, that will not be softned and dissolved by Agitation in a Liquid; yet it is certain that these Motions, caused by the Diaphragm and Abdominal Muscles in Respiration, do make those Parts, which are broken off, as they are dissolv'd, mix intimately with the more Liquid; as the Meat which I digested with Oil of Turpentine, and Oil of Vitriol, did by Agitation mix more equally with the Oils, and became a Pulpament.

As the Juices, which constitute the Saliva, do ferment upon their mixture, so it is probable, that from their Mixture and Fermentation there results such a Tertium quid, as is apt to ferment with the Bile. And therefore, when the Aliment has been under the Fermentation, excited by the Saliva, a sufficient time, it is then thrown into the Duodenum, where it meets with the bilious Juice, which flows into that Intestine from the Liver, from which a new Fermentation seems to begin; and the Commotion of the Parts of the Aliment being still continued, does carry on the Business of Digestion until the Food is perfectly concocted: Though it is probable, that this new Fermentation serves not only for the more perfect Digestion of the Food, but likewise for the Separation of the Chyle from the feculent Parts.

Neither do I by a random Guess, and an ungrounded Conjecture, suppose that from the Mixture and Fermentation of the two Juices, which constitute the Saliva, there results a Matter, which is apt to ferment with the Bile. But to me the Notion seem'd to be confirmed by an Experiment that I made. For considering with my self, that the Bile is generally allow'd to have much of a saponary Nature, I made a Solution of Soap in fair Water, and mix'd it with the Oils of Turpentine and Vitriol first put together, and from their Mixture I observ'd a very easie and gentle Fermentation, which continued for a considerable time.

A Discourse concerning some Influence of Respiration on the Motion of the Heart, hitherto unobserved. By J. Drake, M. D. F. R. S.

THO' divers accurate Treatises of the Heart, and its Action, have been written by Learned Men of several Nations, especially by two of our own Country; the Great Dr. Harvey, to whose happy Sagacity this Nation owes the Glory of the Invention of the Circulation of the Blood; and the incomparable Dr. Lower, to whom we are beholden for a compleat Display of the Mechanical Structure of the Heart, and a most ingenious Rationale of its Action. Yet there remain several Doubts and Difficulties about it (in my Opinion) not sufficiently accounted for; towards the resolving some of which, I shall offer what my own Thoughts have suggested to me, and leave it to the Consideration of the Reader.

The Learned Dr. Lower (whose accurate Piece on this Argument will insure his Reputation so long as Physical Knowledge shall last in esteem) has so well accounted for the Systole, or Contraction of the Heart, from the Mechanical Structure of it, that he seems almost to have exhausted the Subject; and had he been as happy in discovering the true cause of the Diastole, he had left little room for the Industry and Sagacity of others about this Viscus.

But having judiciously and solidly explain'd the Systole, he contents himself to ascribe the Diastole to a motion of Restitution, which account gives me no Satisfaction: Because the Systole being the proper, and (as himself confesses) the only motion of the Heart, a State of Contraction seems to be the natural State, and consequently without External Violence, it shou'd have no Diastole at all.

This will appear more plain, if we consider the Circumstances of it, and its Motion, as a Muscle, with respect to other Muscles. That Contraction is the proper Action, and State of all Muscles, is evident from Experience of Fact, as well as Reason. For, if any Muscle be freed from the power of its Antagonist, it is immediately contracted, and is not by any Action of the Will, or Spirits, to be reduced to a State of Dilatation. Thus, if the Musculi Flexores of any Joint be divided, the Extensores of that Joint being by that means free'd from the contrary Action of their Antagonists, that Joint is immediately extended without any consent of the Will, and in that State it remains; and so Vice versa, if the Extensores be divided. From whence it is plain, that the Muscles have no restitutive Motion, but what they derive from the Action of their Antagonists, by which they are balanc'd. Thus likewise the Sphincters of the Gula, Anus and Vesica, having no proper Antagonists, are always in a State of Contraction, and suffer nothing to pass them, but what is forced through them by the contrary Action of some stronger Muscles, which, though not properly to be call'd Antagonists, yet on all necessary Occasions perform the Office of such.

That the Heart is a Muscle, furnish'd and instructed for Motion like other Muscles, is (in my Opinion at least) demonstrated beyond Contradiction by Dr. Lower and others. And, as it is a Solitary Muscle without any proper Antagonist, and not directly under the power of the Will, nor exercising Voluntary Motion, it approaches nearest to the Sphincter kind, which only has these Conditions in common with it. But in constant and regular Alternations of Contraction and Dilatation, it differs exceedingly from all the Muscles of the Body.

This reciprocal Æstus of the Heart has given the Learned abundance of trouble; who, finding nothing peculiar in the Structure, which shou'd necessarily occasion it, nor any Antagonist, whose re-action should produce it, have been extreamly perplex'd to find out the cause of it.

But passing over the various Opinions of Authors, to avoid being tedious, I shall take notice here only of the very Learned Dr. Lower's, in whose Account of the Systole, however solid and ingenious, I observe something deficient, and whose Hypothesis of the Diastole I think to be precarious and false.

This Excellent Author, having by sound Arguments drawn from the Structure and Mechanism of the Heart, establish'd the Certainty of its Muscular Motion, rests satisfied, without taking notice of any Assistance, that the Heart receives from any other Part, except from the Brain, by the means of the eight pair of Nerves.

Part 2d. Prop. 67. Prop. 73. Prop. 76.

The Accurate Borellus, in his Oeconomia Animalis, computes the Motive Power of the Machine of the Heart to be equal to, or to surmount that of a Weight of 3000l. The Obstacles to the Motion of the Blood thro' the Arteries he esteems equivalent to 180,000l. which is 60 times as much as he rates the Force of the Heart at. Then deducting 45,000l. for the adventitious Help of the Muscular Elastic Coat of the Arteries, he leaves the Heart with a Force of 3,000l. to overcome a resistance of 135,000l. that is, with 1, to remove 45.

This stupendous Effect he contents himself to ascribe to the Energy of Percussion. But, had he proceeded in his Calculation to the Veins, which he allows to contain constantly a quantity of Blood, quadruple to the Contents of the Arteries, and to which this Energy of Percussion does either not reach at all, or but very languidly, he might probably have seen a necessity for some other Expedient to remove so insuperable a Difficulty.

But not to insist rigorously on the Exactness of this Calculation, (though the great Abilities of the Author in this way, and his Ingenuity and Modesty, are a sufficient Warrant for the Accuracy of his Computations, and the Fidelity of his Accounts) we may allow a much greater Deduction, than would be justifiable, without lessening the Difficulty. But this Account I have taken notice of purely for the sake of the Calculation, which may be of use in the Sequel; the account it self being in other respects more defective than Dr. Lower's, to which we will return.

The Doctor, notwithstanding his great Sagacity, appears (to me) to have overlook'd something of very great moment, and importance in the explication of the Action of the Heart. For, tho' it should be granted, that the Muscular Fibres of the Heart acted by the Nerves, are the immediate Instruments of its Constriction or Systole, yet it must not be denied, that the Intercostal Muscles and Diaphragm are of great service to aid and facilitate this Contraction, by opening a Passage for the Blood through the Lungs, which denied would be an invincible Obstacle.

Neither do they promote it that way only. The manner how they farther assist the Heart in its Contraction, will appear manifestly, if we consider the different Posture, Situation, and Capacity of the Blood-Vessels of the Lungs in the several times of Elevation and Depression of the Costæ.

The Pulmonary Artery rises from the right Ventricle of the Heart, and runs in one Trunk, till it comes to the Aspera Arteria, where it is divided, and sends a Branch along with each Division of the Aspera Arteria, according to all the minutest Subdivisions, of which it is likewise subdivided, accompanying all the Bronchi, in their whole progress through the Lungs.

The Pulmonary Vein, which empties itself into the Left Ventricle of the Heart, spreads it self on the Aspera Arteria and Bronchi, in the same manner that the Artery does.

The necessary confluence of this Disposition if, that this Artery and Vein being co-extended with, and fasten'd to the Bronchi, must needs suffer such alteration of Superficial Dimensions, as the Bronchi do in the Elevation or Depression of the Costæ.

While the Ribs are in a State of Depression (whether before Commerce with the External Air or after) the Annular Cartilages of the Bronchi shrink one into another, and by that means their Dimensions are exceedingly contracted. In conformity to this condition of the Bronchi, the Pulmonary Artery and Vein must likewise, either by means of their Muscular Coats, contract themselves to the same Dimensions, or lye in Folds or Corrugations, which is less probable.

On the other hand, when the Ribs are elevated, and the Diaphragm bears downward, the Air rushing into the Lungs, shoots out the Cartilaginous Rings, and divaricates the Branches of the Trachea, and by them extends and divaricates the several Divisions of the Pulmonary Artery and Veins, and thereby lengthens and enlarges their Cavities.

This enlargement of their Cavities is very considerable, not only upon the score of the addition, which they receive in length thereby, but also upon the account of their Divarication. For whereas, when the Ribs are depress'd, and the Lungs subside, the Blood-vessels are not only contracted, (as I have already observ'd) but their Branches, which are exceeding numerous, approach one another, and lie in juxta-position, by which their Cavities are very much compress'd and streighten'd: When the Ribs are elevated, and the Lungs turgid with Air, not only the Fibres, by which their Coats in the opposite state were contracted, are extended; but those innumerable Vessels, which lying before in lines almost parallel upon one another, compress'd one another, making an acute Angle at their Junctures, are divaricated and separated from each other, and make an obtuse, whereby their Channels are widened.

Thus a passage is open'd to the Blood, from the Right Ventricle of the Heart to the Left, through the Lungs, to which it could not otherwise pass; and the opposition, which the Blood contain'd in that Ventricle, must otherwise necessarily have made to its Constriction, is taken off, and the Systole thereby facilitated.

Nor is that all. For the Diastole being caus'd (as I shall in the Sequel shew) by the force of the Blood rushing into the Ventricles, this Ampliation and Extension of the Pulmonary Artery is a sort of Check or Counterpoise to it, and prevents an endeavour towards two contrary Actions at once, which must necessarily frustrate both. For the Heart being a Springy, Compressible Body, whose proper Action, which is Contraction, depends on the influx of certain Fluids into its Fibers, or Substance; and containing besides a Fluid in its Ventricles, or great Cavities, in one of which is the Mouth of this Artery, the action of this Vessel must in great measure resemble that of a Syringe, whose extremity is immers'd in Water, the Enlargement or Expansion of the Chanels of the Artery answering the drawing of the Embolum, as the constrictive motion of the Muscle of the Heart does the pressure of the Atmosphere upon the Surface of the Water, the one making way for the fluid, and the other forcing it to follow, where the resistance is least. In this Sense we may allow a sort of Attraction to the Pulmonary-Artery, depending wholly upon the Action of the Intercostal Muscles and Diaphragm, which we must therefore confess to be very serviceable and instrumental in promoting the Systole of the Heart.

But if the Learned Author be deficient in his Account of the Systole; that is, if he has not observ'd all the Mechanism and Contrivance of Nature for the Contraction of the Heart; much less sufficiently has he accounted for the Diastole, or Dilatation of it, which he ascribes to a motion of Restitution of the over-strain'd Fibres, which yet he confesses are made for Constriction only. 'Tis true, he immediately after joins the Influx of the Blood as a concurrent Cause; but from the slight notice that he takes of it, 'tis plain, that he did not so much as dream of any great share it had in that Action. His Words are these:

De Corde, Pag. 75.

Quin & (ut obiter hoc moneam) omnis motus contractione perficiatur, & Cordis Fibræ ad constrictionem solum factæ sint, apparet quoque Cordis motum totum in Systole positum esse; cumque Fibræ ultra tonum suum in omni constrictione eius tendantur, idcirco ubi nixus iste absolvitur, motu quasi restitutionis Cor iterum relaxatur, & sanguine à Venis influente rursus distenditur; à nullo enim cordis motu, nisi tensionem suam remittente, & ab irruente sanguine Diastole ejus libratis adeo viribus succedit.