Chapter 27

CHAP. II.Of the Eye.

Of the Eye.

For our clearer Proceeding in the Consideration of this noble Part[a], and understanding its Oeconomy, I shall consider:

1. TheFormof the Eye.

2. ItsSituationin the Body.

3. ItsMotions.

4. ItsSize.

5. ItsNumber.

6. ItsParts.

7. TheGuardandSecurityNature hath provided for this so useful a Part.

As this eminent Part hath not been pretermitted by Authors, that have made it their particular Design and Business to speak of the Works of God; so divers of the aforesaid Particulars have been touched upon by them. And therefore I shall take in as little as possible of what they have said, and as near as I can, mention chiefly what they have omitted. And,

1. For theFormof the Eye; which is for the most part Globous, or somewhat of the sphæroidal Form: Which is far the most commodious optical Form, as being fittest to contain the Humours within, and to receive the Images of Objects from without[b]. Was it a Cube, or of any multangular Form, some of its Parts would lie too far off[c], and some too nigh those lenticular Humours, which by their Refractions cause Vision. But by Means of the Form before-mentioned, the Humours of the Eye are commodiously laid together, to perform their Office of Refraction; and theRetina, and every other Part of that little darkned Cell, is neatly adapted regularly to receive the Images from without, and to convey them accordingly to the common Sensory in the Brain.

To this we may add the aptitude of this Figure to the Motion of the Eye, for it is necessary for the Eye to move this way, and that way, in order to adjust it self to the Objects it would view; so by this Figure it is well prepared for such Motions, so that it can with great Facility and Dexterity direct it self as occasion requires.

And as the Figure, so no less commodious is,

2. TheSituationof the Eye, namely in the Head[d], the most erect, eminent Part of the Body, near the most sensible, vital Part, the Brain. By its Eminence in the Body, it is prepar’d to take in the more[e]Objects. And by its Situation in the Head, besides its Proximity to the Brain, it is in the most convenient Place for Defence and Security. In the Hands, it might indeed (in Man) be render’d more eminent than the Head, and be turned about here and there at pleasure. But then it would be exposed to many Injuries in that active Part, and the Hands[f]render’d a less active and useful Part. And the like may be said to its Sight, in any other Part of the Body, but where it is. But in the Head, both of Man, and other Animals, it is placed in a Part that seems to be contrived, and made chiefly for the Action of the principal Senses.

Another Thing observable in the Sight of the Eye, is the Manner of its Situation in the Head, inthe Fore-part, or Side-part thereof; according to the particular Occasions of particular Animals. In Man, and some other Creatures, it is placed to look directly forward chiefly; but withal it is so order’d, as to take in near the Hemisphere before it. In Birds, and some other Creatures, the Eyes are so seated, as to take in near a whole Sphere, that they may the better seek their Food, and escape Dangers. And in some Creatures they are seated, so as to see best behind them[g], or on each Side, whereby they are enabled to see their Enemy that pursues them that way, and so make their Escape.

And for the Assistance of the Eyes, and some of the other Senses in their Actions; the Head is generally made to turn here and there, and move as Occasion requires. Which leads me to the

3. Thing to be remarked upon, theMotionsof the Eye it self. And this is generally upwards, downwards, backwards, forwards, and every way[h], for the better, more easy, and distinct Reception of the visual Rays.

But where Nature any way deviateth from this Method, either by denying Motion to the Eyes, or the Head[i], it is a very wonderful Provision shehath made in the Case. Thus for a Remedy of this Inconvenience, in some Creatures their Eyes are set out at a Distance[k]from the Head, to be circumvolved here and there, or one this, the other that way, at Pleasure. And in Creatures, whose Eyes are without Motion, as in divers Insects; in this Case, either they have more than two Eyes, or their Eyes are nearly two protuberant Hemispheres, and each Hemisphere often consisting of a prodigious number of other little Segments of a Sphere[l]. By which Means those Creatures are so far from being deny’d any Benefit, of that noble and most necessary Sense of Sight, that they have probablymore of it than other Creatures, answerable to the Rapidity of their Flight, and brisk Motion; and to their Inquests after Food, Habitation, or Repositories of Generation, or such other Necessity of the Animal.

4. Another admirable Provision in the Eye, is, its Size; in some Animals large, in some little. It would be endless here to enumerate Particulars; as thole of Quadrupeds, Birds, Insects, and other terrestrial Animals. And as for Fishes, they will fall under another Part of my Survey.

I shall therefore only take Notice of its Size in one Creature, theMole[m]. As the Habitation ofthat uncouth Animal is wholly subterraneous, its Lodging, its Food, its Exercises, nay, even all its Pastimes and Pleasures, are in those subterraneous Recesses and Passages, which its own Industry hath made for it self; so it is an admirable Provision made in the Size of the Eye of that little Creature, to answer all its Occasions, and at the same time to prevent Inconveniences. For as a little Light will suffice an Animal living always under Ground; so the smallest Eye will abundantly supply that Occasion. And as a large protuberant Eye, like that of other Animals, would much annoy this Creature in its principal Business, of digging for its Food and Passage; so it is endow’d with a very small one, commodiously seated in the Head, and well fenced and guarded against the Annoyances of the Earth.

5. Another Thing remarkable in this noble Part of Animals, is, itsNumbers; no less than two[n]in any Instance, that I know of; and in some Animals more, as I have already hinted[o].

Now this is an admirable Provision; first, for the Convenience of taking in the larger Angle or Space: And in the next Place, the Animal is by this Provision, in some Measure prepar’d for theMisfortune of the Loss of one of these noble, and necessary Organs of its Body.

But then besides all this, there is another Thing considerable in this multiplicate Number of the Eye; and that is, that the Object seen is not multiplied as well as the Organ, and appears but one, though seen with two or more Eyes[p]. A manifestSign of the infinite Skill of the Contriver of this so noble a Part, and of the exquisite Art he employed in the Formation thereof. But the Design and Skill of the infinite Workman, will best be set forth by

6. Surveying thePartsandMechanismof this admirable Organ the Eye. And here indeed we cannot but stand amazed, when we view its admirable Fabrick, and consider the prodigious Exactness, and the exquisite Skill employed in every part ministring to this noble and necessary Sense. To pass by its Arteries and Veins, and such other Parts common to the rest of the Body, let us cast our Eye on itsMuscles. These we shall find exactly and neatly placed for every Motion of the Eye. Let us view itsTunicks, and these we shall find so admirably seated, so well adapted, and of so firm a Texture, as to fit every Place, to answer every Occasion, and to be Proof against all commonInconveniences and Annoyances. Let us examine its threeHumours, and these we shall find all of exquisite Clearness and Transparency, for an easy Admission of the Rays; well placed for the refracting of them, and formed (particularly theCrystalline Humour) by the nicest Laws of Opticks, to collect the wandring Rays into a Point. And to name no more, let us look into its darkned Cell, where those curious Humours lie, and into which the Glories of the Heavens and the Earth are brought, and exquisitely pictured; and this Cell we shall find, without, well prepared by Means of its Texture, Aperture, and Colour, to fence off all the useless or noxious Rays; and within, as well coated with a dark Tegument, that it may not reflect, dissipate, or any way confuse or disturb the beneficial Rays[q].

But to descend to Particulars, although it would be a great Demonstration of the Glory of God, yet would take up too much Time, and hath been in some Measure done by others that have written of God’s Works. Passing over therefore what they have observed, I shall under each principal Part take a transient Notice of some Things they have omitted, or but slightly spoken of.

And my first Remark shall be concerning theMusclesof the Eye, and their Equilibration. Nothing can be more manifestly an act of Contrivance and Design, than theMusclesof the Eye, admirably adapted to move it any, and every way; upwards, downwards, to this side or that, or howsoeverwe please, or there is occasion for, so as to always keep that Parallelism of the Eye, which is necessary to true Vision. For the Performance of which Service, the Form, the Position, and the due Strength of each Muscle is admirable. And here I might Instance the peculiar and artificial Structure of theTrochlearis, and the Augmentation of its Power by theTrochlea[r]; the Magnitude and Strength of theAttollent Muscle, somewhat exceeding that of its Antagonist; the peculiar Muscle, called theSeventh, orSuspensory Muscle[s], given to Brutes, by reason of the prone Posture of theirBodies, and frequent Occasions to hang down their Heads: And I might speak also of the peculiar Origine and Insertion of thelower Oblique Muscle[t], which is very notable, and many other Things relating to these Parts; but it would be tedious to descend too much to those admirable Particulars. And therefore to close up these Remarks, all I shall farther take Notice of, shall be only the exquisite Equilibration of all theseOppositeandAntagonist Muscles, affected partly by the Equality of the Strength; which is the Case of theAdducentandAbducent Muscles; partly by their peculiar Origine, or the Addition of theTrochlea, which is the Case of theOblique Muscles[u]: and partly by the natural Posture of the Body, and the Eye, which is the Case of theAttollentandDepriment Muscles. By this so curious and exact a Libration, not only unseemly Contortions, and incommodious Vagations of theEye are prevented, but also it is able with great Readiness and Exactness to apply it self to every Object.

As to theTunicksof the Eye, many Things might be taken notice of, the prodigious Fineness of theArachnoïdes, the acute Sense of theRetina, the delicate Transparency of theCornea[w], and the firm and strong Texture of that and theScleroticatoo; and each of them, in these and every other respect, in the most accurate manner adapted to the Place in which it is, and the Business it is there to perform. But for a Sample, I shall only take notice of that part of theUveawhich makes thePupil. It hath been observed by others, particularly by our Honourable Founder[x], That as we are forced to use various Apertures to our Optick Glasses, so Nature hath made a far more compleat Provision in the Eyes of Animals, to shut out too much, and to admit sufficient Light, by the Dilatation and Contraction of the Pupil[y]. But it deserveth our especial Remark, that these Pupils are in divers Animals of divers Forms, according to theirpeculiar Occasions. In some (particularly in Man) it is round; that being the most proper Figure for the Position of our Eyes, and the Use we make of them both by Day and Night. In some other Animals it is of a longish Form; in some Transverse[z], with its Aperture large, which is an admirable Provision for such Creatures to see the better laterally, and thereby avoid Inconveniencies, as well as help them to gather their Food on the Ground, both by Day and Night. In other Animals the Fissure of the Pupil is erect[aa], and also capable of opening wide, and shutting up close. The latter of which serveth to exclude the brighter Light of the Day, and the former to take in the more faint Rays of the Night, thereby enabling those Nocturnal Animals (in whom generally this erect Form of the Pupil is) to catch their Prey with the greater Facility in the dark[bb], to see upwards and downwards, to climb,&c. Thus much for theTunicks.

The next Thing I shall take notice of, will relate to theHumoursof the Eye, and that only concerning the Mechanism of theCrystalline Humour; not its incomparable Transparency; nor its exact lenticular Form; nor its curious araneous Membrane[cc], that constringeth and dilateth it, andso varieth itsFocus, (if any such Variation there be, as some affirm with great Probability,) nor lastly,its admirable Approach to or from theRetina, by help of theCiliar Ligament[dd], according asObjects are far off or near, because these Things are what are usually taken notice of; but that which I shall observe is, the prodigious Art and Finery of its constituent Parts, it being, according to some late nice Microscopical Observations[ee], composedof divers thin Scales, and these made up of one single minutest Thread or Fibre, wound round and round, so as not to cross one another in any one Place, and yet to meet, some in two, and some in more different Centers; a Web not to be woven, anOptick Lens, not to be wrought by any Art less than infinite Wisdom.

Lastly, To conclude the Parts of this admirable Organ, I shall make only one Remark more, and that is about itsNerves. And here, among others, the admirable Make of theOptick Nervesmight deserve to be taken notice of in the first Place, theirMedullaryPart[ff]terminating in the Brain it self, the Teguments propagated from theMeninges, and terminating in the Coats of the Eye, and their commodious Insertions into the Ball of the Eye, in some directly opposite to the Pupil of the Eye, in othersobliquely towards one Side[gg]. But most of these Things have been treated of, and the Convenience hereof set forth by others that have written of God’s Works. I shall therefore take notice only of one wise Provision the Creator hath made about the Motion of the Eye, by uniting into one theThird Pairof Nerves, called theMotory Nerves[hh], each of which sending its Branches into each Muscle of each Eye, would cause a Distortion in the Eyes; but being united into one, near their Insertion into the Brain, do thereby cause both Eyes to have the same Motion; so that when one Eye is moved this way and that way, to this and that Object, the other Eye is turned the same way also.

Thus from this transient and slight View (I may call it) of the Parts of the Eye, it appears what an admirable Artist was the Contriver thereof. And now in the

Seventhand last Place, Let us consider what Provision this admirable Artist hath made for theGuardandSecurityof this so well formed Organ[ii]. Andhere we shall find the Guard equivalent to the Use and Excellency of the Part. The whole Organ fortified and fenced with strong, compact Bones, lodged in a strong, well made Socket, and the Eye it self guarded with a nice made Cover[kk]. Its Humours, and its inward Tunicks, are indeed tender,proportionate to their tender, curious Uses; but the Coats without, are context and callous, firm and strong. And in some Animals, particularlyBirds[ll], some Part of those Tunicles have the Nature and Hardness of Bone or Horn.

But for Creatures, whose Eyes, like the rest of their Body, are tender, and without the Guard of Bones; there Nature hath provided for this necessary and tender Sense, a wonderful kind of Guard, by endowing the Creature with a Faculty of withdrawingits Eyes into its Head[mm], and lodging them in the same Safety with the Body.

Thus have I survey’d this first Sense of Animals, I may say in a cursory, not accurate, strict manner, considering the prodigious Workmanship thereof; but so, as abundantly to demonstrate it to be the Contrivance, the Work of no less a Being than the infinite Wise, Potent, and Indulgent Creator[nn]. For none less could compose so admirable an Organ, so adapt all its Parts, so adjust it to all Occasions, so nicely provide for every Use, and for every Emergency: In a word, none less thanGod, could, I say, thus contrive, order, and provide an Organ, as magnificent and curious as the Sense is useful; a Sense without which, as all the Animal World would be in perpetual Darkness, so it would labour under perpetual Inconveniencies, be exposed to perpetual Harms, and suffer perpetual Wants and Distresses. But now by this admirable Sense, the greatGod, who hath placed us in this World, hath as well provided for our comfortable Residence in it; enabled us to see and chuse wholsome, yea delicate Food, to provide our selves useful, yea gaudy Cloathing, and commodious Places of Habitation and Retreat. We can now dispatch our Affairs with Alacrityand Pleasure, go here and there as our Occasions call us. We can, if need be, ransack the whole Globe, penetrate into the Bowels of the Earth, descend to the bottom of the Deep, travel to the farthest Regions of this World, to acquire Wealth, to encrease our Knowledge, or even only to please our Eye and Fancy. We can now look about us, discern and shun the Precipices and Dangers which every where enclose us, and would destroy us. And those glorious Objects which fill the Heavens and the Earth, those admirable Works of God which every where surround us, and which would be as nothing to us, without being seen, do by means of this noble Sense present their Glories to us[oo], andfill us with Admiration and Pleasure. But I need not expatiate in the Usefulness and Praises of this Sense, which we receive the Benefit of every Moment, and the want, or any defect of which, we lament among our greatest Misfortunes.

Leaving then this Sense, I shall proceed to the other four, but more briefly treat of them, by reason we have so ample a Sample of the divine Art in the last, and may presume that the same is exerted in all as well as one. For a Demonstration of which, let us in the next Place carry our Scrutiny to the Sense ofHearing.

FOOTNOTES:[a]In Dissectionibus anatomicis vix aliquid admirabilius, aut artificiosius structurâ Oculi humani, meo quidem judicio, occurrit: ut meritò, per excellentiam, Creatoris appelletur Miraculum.Gul. Fabr. Hildan. Cent. 2. Observ. 1.So likewise that accurate Surveyor of the Eye, Dr.Briggs, whoseOphthalmographyI have met with since my penning this part of my Survey. His Character of this curious piece of God’s Work is,Inter præcipuas corporis animati partes, quæ magni Conditoris nostri sapientiam ostendunt, nulla sanè reperitur, quæ majori pompâ elucet quàm ipse Oculus, aut quæ elegantiori formâ concinnatur. Deum enim aliæ partes vel minori satellitio stipantur, vel in tantam venustatem haud assurgunt; Ocelli peculiarem honorem & decus à supremo Numine efflatum referunt, & nunquam non stupendæ suæ Potentia characteres repræsentant. Nulla sanè pars tam divino artificio & ordine,&c.Cap. 1. §. 1.[b]It is a good ReasonFrier Baconassigns for the Sphæricity of the Eye:Nam si esset planæ figuræ, species rei majoris oculo non posset cadere perpendiculariter super eum——Cùm ergò Oculus videt magna corpora, ut ferè quartam cœli uno aspectu, manifestum est, quòd non potest esse planæ figuræ, nec alicujus nisi sphæricæ, quoniam super sphæram parvam possunt cadere perpendiculares infinitæ, quæ à magno corpore veniunt, & tendunt in centrum Sphæræ: Et sic magnum corpus potest ab oculo parvo videri.For the Demonstration of which he hath given us a Figure.Rog. Bacon. Perspect. Distinct. 4. Cap. 4.Dr.Briggssaith,Pars antica, (sive Cornea,) convexior est posticâ: hâc enim ratione radii meliùs in pupillam detorquentur, & Oculi fundus ex altarâ parte in majorem (propter imagines rerum ibidem delineandos) expanditur.Ibid. §. 2.[c]Suppose the Eye had theRetina, or back part flat for the Reception of the Images, as inFig. 1.ABA: it is manifest, that if the Extremes of the Image AA were at a due focal distance, the middle B would be too nigh the Crystalline, and consequently appear confused and dim; but all Parts of theRetinalying at a due focal distance from the Crystalline, as at ACA, therefore the Image painted thereon is seen distinct and clear. Thus in a dark Room, with a Lens at a Hole in the Window, (whichSturmiuscalls his Artificial Eye, in hisExercit. Acad.one of which he had made for his Pupils, to run any where on Wheels). In this Room, I say, if the Paper that receives the Images be too nigh, or too far off the Lens, the Image will be confused and dim; but in the Focus of the Glass, distinct, clear, and a pleasant Sight.[d]Blemmyis traduntur capita abesse, Ore & Oculis pectori affixis.Plin. Nat. Hist. l. 5. c. 8.Occidentem versus quosdam sine cervice Oculos in humeris habentes.Ib. l. 7. c. 2. From these, and other such like Fables, in this last cited Chapter ofPliny, no doubt our famous Romancer SirJ. Mandevile, had his Romnantick Stories related in his Travels.[e]SeeBook V. Chap. 2. Note (e).[f]Galendeserves to be here consulted, who in his BookDe Usu Partium, from many Considerations of the Hand, such as what is here mentioned, as also its Structure, Site and Use, largely proves and reflects upon the Wisdom and Providence of the Contriver and Maker of that Part.[g]Thus inHaresandConies, their Eyes are very protuberant, and placed so much towards the sides of their Head, that their two Eyes take in nearly a whole Sphere: Whereas inDogs, (that pursue them) the Eyes are set more forward in the Head, to look that way more than backward.[h]Sed lubricos Oculos fecit[Natura]& mobiles, ut & declinarent siquid noceret; & aspectum, quo vellent, facile converterent. Cicer. de Nat. Deor. l. 2. c. 57.[i]The Eyes ofSpiders,(in some four, in some six, and in some eight)are placed all in the fore-front of their Head, (which is round, and without any Neck) all diaphanous and transparent, like a Locket of Diamonds,&c.neither wonder why Providence should be so anomalous in this Animal, more than in any other we know of. For, 1. Since they wanting a Neck, cannot move their Head, it is requisite that Defect should be supplied by the multiplicity of Eyes. 2. Since they were to live by catching so nimble a Prey as a Fly is, they ought to see her every way, and to take herper saltum, (as they do) without any Motion of the Head to discover her: Which Motion would have scared away so timorous an Insect.Power’sMicros. Observ. pag. 11.The Eyes of theCameleonresemble a Lens, or Convex Glass, set in a versatile globular Socket, which she turneth backward, or any way, without moving her Head; and ordinarily the one a contrary, or quite different way from the other.Dr.Goddardin Phil. Tran. Nᵒ. 137.But what is more extraordinary in this Motion[of the Cameleon’s Eye]is to see one of the Eyes move, whilst the other remains immoveable; and the one to turn forward, at the same time that the other looketh behind; the one to look up to the Sky, when the other is fixed on the Ground. And these Motions to be so extreme, that they do carry thePupillaunder the Crest which makes the Eye-brow, and so far into theCanthi, or Corners of the Eyes, that the Sight can discern whatever is done just behind it, and directly before, without turning the Head, which is fastned to the Shoulders.Mem. for a Nat. Hist. in Anatom. Dissect. at Paris. Diss. of Camel. pag. 22.[k]Snailssend out their Eyes at a distance, they being contained in their four Horns,like atramentous Spots, fitted to the end of their Horns, or rather to the ends of those black Filaments or optick Nerves, which are sheathed in her Horns, as Dr.Powerwordeth it.Obs. 31. pag. 36.So the ingenious Dr.Lister.Exercit. Anat. Cochl. & Limac.[l]Vid.l. 8. c. 3. Note (a).[m]Severinusis ofAristotle’s,Pliny’s, andAlb. Magnus’s Opinion, that theMolehath no Sight;G. Segerdenies any Humour to be therein, but thinks they may probably see, because Nature made nothing in vain. ButBorrichiussaith, their Eyes haveappendiculam nerveam in cerebrum euntem, cujus beneficio globuli illi[the little Eyes]extra pellem facilè poterant exseri, retrahique pro arbitrio——In illis oculorum globulis humor aqueus copiose satis natabat; cæterorum non nisi tenue vestigiem.Blas. Anat. Anim. c. 35.Et quoniam Natura hoc vitæ genus ipsi destinavit, etiam perquàm exiguos Oculos——dedit eo concilio, ut ii, pretiosissima corporis pars, à terræ pulvere nè affligerentur. Ii insuper pilis recti,&c.Humores illis oculis insunt, & tunica nigra, uvea, se prodit. Ad hos tramite alio nervus venit.Schneider in Blas. ibid.Some time since I made divers accurate Dissections of theEyesofMoles, with the help of Microscopes, having a doubt whether what we take to be Eyes, were such or no. And upon a strict Scrutiny I plainly could distinguish theVitreousandCrystallineHumours, yea, theLigamentum Ciliare, and the atramentaceousMucus. ThePupilI could manifestly discern to be round, and theCorneacopped, or conical: The Eye is at a great distance from the Brain, the Optick Nerve very slender and long, reaching from the Eye through the intermediate Flesh, and so passeth to the Brain, along with the pair of Nerves reaching to the Nose, which are much the largest that are in all the Animal. These Creatures, I imagine, have the Faculty of withdrawing their Eyes, if not quite into the Head, (asSnails) yet more or less within the Hair, as they have more or less Occasion to use or guard their Eyes.Galensaith,Moleshave Eyes, theCrystallineandVitreousHumours, encompassed withTunicks.De Us. Part. l. 14. c. 6.So accurate an Anatomist was he for his Time.[n]Plinytells us of a sort ofHeronwith but one Eye, but ’twas only by hear-say.Inter Aves Ardeolarum genere, quos Leucos vocant, altero oculo carere tradunt.Nat. Hist. l. 11. c. 37. So the King of theNigræthat hath but one Eye, and that in his Forehead,l. 6. c. 30.Which Fables I take notice of more for the Reader’s Diversion, than any Truth in them.[o]Supra,Note (i).[p]The most celebrated Anatomists differ greatly about the Reason why we see not double with two Eyes. ThisGalen, and others after him, generally thought to be from a Coalition or Decussation of the Optick Nerves, behind theOs Sphenoïdes. But whether they decussate, coalesce, or only touch one another, they do not well agree. TheBartholinesexpressly assert they are united,non per simplicem contactum vel intersectionem in homine, sed totalem substantiæ confusionem, Anat. l. 3. c. 2. And whereasVesalius, and some others had found some Instances of their being disunited; they say,sed in plerisque ordinarie confunditur interior substantia, ut accuratâ disquisitione deprehendi.But our Learned Dr.Gibson, (Anat. l. 3. c. 10.) saith, theyare united by the closest Conjunction, but not Confusion of their Fibres.But others think the Reason is not from any Coalescence, Contact, or crossing of the Optick Nerves, but from a Sympathy between them. Thus MonsieurCartesis of Opinion, that theFibrillæconstituting the medullary Part of those Nerves, being spread in theRetinaof each Eye, have each of them corresponding Parts in the Brain; so that when any of thoseFibrillæare struck by any part of an Image, the corresponding Parts of the Brain are thereby affected, and the Soul thereby informed,&c.but see more hereafter underNote (oo), fromCarteshimself.Somewhat like this is the Notion of our judicious Dr.Briggs, who thinks the Optick Nerves of each Eye consist ofHomologous Fibres, having their rise in theThalamus Nervorum Opticorum, and thence continued to both theRetinæ, which are made of them; And farther, that thoseFibrillæhave the same Parallelism, Tension,&c.in both Eyes; and consequently when an Image is painted on the same corresponding, sympathizing Parts of eachRetina, the same Effects are produced, the same Notice or Information is carried to theThalamus, and so imparted to the Soul, or judging Faculty. That there is such an Ὁμοιοπάθεια between theRetina, &c. he makes very probable from the ensuing of double Vision upon the Interruption of the Parallelism of the Eyes; as when one Eye is depressed with the Finger, or their Symphony interrupted by Disease, Drunkenness,&c.And lastly, That simple Vision is not made in the former way,viz.by a Decussation or Conjunction of the Optick Nerves, he proves, because those Nerves are but in few Subjects decussated, and in none conjoined otherwise than by a bare Contact, which is particularly manifest in Fishes; and in some Instances it hath been found, that they have been separated without any double Vision ensuing thereupon.Vid.Brig. Ophthalmogr.cap. 11. & 5. andNov. Vis. Theor.passim.What the Opinion of our justly eminent SirIsaac Newtonis, may be seen in hisOpticks, Qu. 15.Are not the Species of Objects seen with both Eyes, united where the Optick Nerves meet before they come into the Brain, the Fibres on the right side of both Nerves uniting there,&c.For the Optick Nerves of such Animals as look the same way with both Eyes, (as of Men, Dogs, Sheep, Oxen,&c.) meet before they come into the Brain; but the Optick Nerves of such Animals as do not look the same way with both Eyes, (as of Fishes and of the Cameleon) do not meet, if I am rightly informed.Newt. Opt. Q. 15.[q]Nigra est[Uvea]ut radios (ab Oculi fundo ad anteriorem ejus partem reflexos) obumbret; nè hi (ut ait clar. Cartesius) ad Oculi fundum retorti ibidem confusam visionem efficerent. Alia forsan ratio hujus nigredinis statuatur, quòd radii in visione superflui, qui ab objectis lateralibus proveniunt hoc ritu absorbeantur. Ita enim è loco obscuro interdiu objecta optimè intuemur, quia radii tunc temporis circumfuso lumine non diluuntur.Brigg’s Ophthal. c. 3. §. 5.[r]Admirandum Dei artificium ex diversorum animalium comparatione indies evadit manifestiùs. Mirantur omnes Trochlearem in oculis Hominum & Quadrupedum, & quidem jure: sed admirationem omnem superat, quòd sine Trochleâ oculum movens in Avibus novum genus Trochleæ longè artificiosiùs Nictitandi Membranæ dederit.Blas. Anat. Animal. p. 2. c. 4.ex Stenon.[Musculum Trochlearem]per intermedium trochleam traductum, nunquam intueor, quin admirabundus mecum, Ὁ Θεὸς, exclamem ὀυ μόνον ἀεὶ γεωμετρεῖ, ἀλλὰ καὶ ἀεὶ μηχανᾶται.I. C. Sturmii Exercit. Acad. 9. de Vis. Org. & Rat.c. 3. §. 4. p. 446.[s]Observare est quod Quadrupedes, qui oculos in terram pronos, ac pendulos gerunt, Musculum peculiarem habent, quo Oculi globus suspenditur——Hoc Musculo Bos, Equus, Ovis, Lepus, Porcus, &c. præditi sunt: hoc etiam Canis instruitur, sed alio modo conformatum habet.Willis de An. Brut. p. 1. c. 15.Of this Opinion also wasBartholine Anat.l. 3. c. 8. and divers other eminent Anatomists.But Dr.Briggsis of Opinion that theAdnata, and the other Muscles sufficiently answer all those Ends ascribed to that Muscle by former Anatomists, and thinksProbabiliùs itaque esse hunc Musculum nervi Optici actionem (per vices) confirmare, nè à prono Brutorum incessu & copioso affluxu humorum debilitetur, Ophthal. c. 2. §. 2.TheMusculus Suspensoriusbeing in thePorpess, as well as Brutes, Dr.Tysonthinks the Use of it is not to suspend the Bulk of the Eye; but rather by its equal Contraction of theSclerotis, to render the Ball of the Eye more or less Spherical, and so fitter for Vision.Tyson’s Anat. of the Porpess, p. 39.[t]Musculus obliquus inferior oritur à peculiari quodam foramine in latere Orbitæ ocularis facto, (contra quam in cæteris,&c.) quo fit ut ex unâ parte à Musculo trochleari, ex alterâ verò ab hujus Musculi commodissimâ positione, Oculus in æquilibrio quodam constitutus, irretorto obtutu versus objecta feratur, nec plus justo accedat versus internum externumve canthum; quæ quidem Libratio omnino nulla fuisset, absque hujus Musculi peculiari originatione (cujus ratio omnes hucusque Anatomicos latuit).And so this curious Anatomist goes on to shew farther the stupendous Artifice of the great Creator in this Position of theOblique Muscles. Brigg’sNova Vis. Theor.p. 11.meo libro.[u]Besides those particular Motions which the Eye receives from theOblique Muscles, and I may add its Libration also in some Measure, some Anatomists ascribe another no less considerable Use to them; namely, to lengthen and shorten the Eye (by squeezing and compressing it) to make it correspond to the Distances of all Objects, according as they are nigh or far off. Thus the ingenious Dr.Keil;The Aqueous Humour being the thinnest and most liquid, easily changeth its Figure, when either theLigamentum Ciliatecontracts, or both theOblique Musclessqueeze the middle of the Ball of the Eye, to render it Oblong when Objects are too near us.Keil’s Anat. Chap. 4. Sect. 4.SeeNote (y).[w]Quis verò opifex præter Naturam, quâ nihil potest esse callidiùs, tantam solertiam persequi potuisset in Sensibus? quæ primùm Oculos membranis tenuissimis vestivit, & sepiit; quas primum perlucidas fecit, ut per eas cerni posset: firmas aurem, ut continerentur.Cic. de Nat. Deor. l. 2. c. 57.[x]BoylofFinal Causes.[y]It is easy to be observed, that thePupilopeneth in dark Places; as also when we look at far distant Objects, but contracts by an Increase of Light, and when the Objects are nigh. This Motion of thePupilsome say, is effected by the circular and strait Fibres of theUvea, and some attribute it to theLigamentum Ciliare. Yet I have no great doubt but that they both concur in that Action, and that theLigamentum Ciliaredoth, at the same time the Pupil opens or shuts, dilate or compress theCrystalline, and bring it nigher unto, or carry it farther off theRetina. For the Structure of theLigamentum Ciliare, and its two Sorts of Fibres, drawn with the Help of a Microscope, I shall refer to Mr.Cowper’s Anat.T. 11.[z]In Bove, Caprâ, Equo, Ove, & quibusdam aliis elliptica est(Pupilla)ut eo magis in hisce forsan animalibus, quæ prono incessu victum in agris quæritant, radios laterales ad mala & incommoda utrinque devitanda admittat.Briggs’s Ophthal.c. 7. §. 6.Homini erecto, aliisque,&c.caput erigere, & quaquaversus circumspicere solitis, plurima simul objecta, tum suprà, tum infrà, tum è latere utroque——visu excipiuntur; quapropter Oculi Pupilla rotunda esse debet.——Attamen bovi,&c.caput ferè semper pronum——gerentibus, tantùm quæ coràm, & paulo à latere obversantur, intuitu opus est: quapropter Pupilla——oblonga est,&c.Willisde Anim. Brut.p. 1. c. 15.[aa]ThusCats(their Pupils being erect, and the shutting of their Eye-lids transverse thereunto) can so close their Pupil, as to admit of, as it were, one only single Ray of Light; and by throwing all open, they can take in all the faintest Rays. Which is an incomparable Provision for these Animals, that have occasion to watch and way-lay their Prey both by Day and Night.[bb]There is besides this large opening of the Pupil, in some nocturnal Animals, another admirable Provision, enabling them to catch their Prey in the Dark; and that is a Radiation of the Eyes: Of which Dr.Willisthus;Hujus usus est Oculi Pupillam, quasi jubare insito, illuminare, ut res noctu, & in tenebris positas conspicere valeat: quare in Fele plurimùm illustris est: at Homini, Avibus, & Piscibus deest.This Illumination he speaks of, is from theTapetum, in the Bottom of the Eye, or the shining of theRetina, round the optick Nerve.Besides which, he saith, theIrishath a Faculty also, in some, of darting out Rays of Light, so as to enable them to see in the Dark: Of which he tells this Story;Novi quendam cerebro calidiori præditum, qui post uberiorem vini generosi potum in nocte atratâ, sive tenebris profundis, literas distincte legere potuit. Cujus ratio videtur esse, quòd spiritus animales velut accensi, adeòque ab hâc Iride irradiantes, jubare infito Medium illuminabant.Willis Ibid.Such another Thing,Plinytells us, was reported ofTiberius Cæsar:Ferunt Tib. Cæs. nec alii genitorum mortalium, fuisse naturam, ut expergefactus noctu paulisper, haud alio modo quam luce clarâ, contueretur omnia.Nat. Hist. l. 11. c. 37.So Dr.Briggs:Virum sanè calidæ indolis novi in Comitatu Bedfordiensi degentem, qui oculis felineis——donatus est: adeò ut epistolam——mirè admodùm in loco obscuro (ubi eadem mihi vix apparuit) perlegit. Hujus verò Oculi (nisi quod Pupillas insigniores obsinuere) ab aliorum formatione neutiquam discrepabant.Ophthal. c. 5. §. 12.[cc]TheTunica Araneais taken notice of byFrier Bacon, who calls it,Tela Aranea, and saith,in hâc continetur——glaciale vel Crystallinum.Rog. Bacon’s Perspect. Distinct. 2. c. 3.The wrinkling of this, and theCornea(as the Skin is of old Persons) he thinks is the Cause of the Obscurity of the Sight in such Persons.BaconIb. par. 2. cap. 2. But thisTunicksome deny, and others allow of: Dr.A. M.ofTrinity-College, Dublin, (in hisRelat. of Anat. Obs.in the Eyes of Animals, in a Letter to Mr.Boyl,Ann. 1682.annexed to hisAnat. Account of the Elephant burnt inDublin, p. 57.) affirms theTunica Aranea, and saith,I have often seen it before ’twas exposed to the Air one Minute, notwithstanding what Dr.Briggssaith to the contrary,&c.But Dr.Briggshis Opinion is,Humor Crystallinus, nisi aeri diutiùs expositus, vel lenitèr coctus (instar lactis) cuticulam non acquirit: quæ verò impropriè, Tunica Aranea dicitur, cùm si tantùm adventitia, ut in Oculo Bovis recens execto appareat.Briggs’s Ophthalm. c. 3.TheCrystalline Humourbeing of a double Substance, outwardly like a Gelly, towards the Center as consistent as hard Suet, upon occasion whereof its Figure may be varied; which Variation may be made by theLigamentum Ciliare; Dr.Grewdoth, upon these Accounts, not doubt to ascribe to theLigamentum Ciliare, a Power of making theCrystallinemore Convex, as well as of moving it to, or from theRetina. SeeGrew’sCosmolog. Sacr.l. 1. c. 4. Now it is certain by the Laws of Opticks, that somewhat of this is absolutely necessary to distinct Vision, inasmuch as the Rays proceeding from nigh Objects do more diverge, and those from distant Objects less: Which requires either that theCrystalline Humourshould be made more Convex, or more flat; or else an Elongation, or shortning of the Eye, or of the Distance between theCrystalline Humourand theRetina.But although Dr.Briggs(so good a Judge) denies theTunica Crystallina, contrary to the Opinion of most former Anatomists; yet there is great Reason to conclude he was in a Mistake, in my Opinion, from the Observations of theFrench Anatomists, of theCrystallineof the Eye, of theGemporChamois, who say,The Membrana Arachnoïdes was very thick, and hard, so that it was easily separated from the Crystallinus, p. 145.The same Anatomists also favour the Surmise of Dr.Grew, This [Contraction of the Fibres of theLigamentum Ciliareon one side, and Dilatation on the other]would make us think that these Fibres of theLigamentum Ciliare, are capable of Contraction, and voluntary Dilatation, like that of the Fibres of the Muscles; and that this Action may augment, or diminish the Convexity of theCrystallinus, according as the Need which the Distance of the Objects may make it to have on the Eye, to see more clearly and distinctly.Anat. Descrip. of aBear, p. 49.Since my penning the foregoing Notes, having as critically as I could, dissected many Eyes of Birds, Beasts and Fishes, I manifestly found theMembrana Arachnoïdes, and will undertake to shew it any one, with great Ease and Certainty. It is indeed so transparent, as not to be seen distinct from theCrystalline. But if theCorneaandUveabe taken off before, or thevitreous Humourbehind it, and the out-side of theCrystallinebe gently cut, theArachnoïdesmay be seen to open, and theCrystallinewill easily leap out, and part from theLigamentum Ciliare; which otherwise it would not do: For it is by theArachnoïdesbraced to theLigamentum Ciliare. This Membrane or Tunick, in the Ox, is so substantial and strong, though thin, that it yields to, or sinks under the sharpest Lancet, and requires (for so thin and weak a Membrane in appearance) a strong Pressure to pierce it.[dd]As Birds and Fishes are in divers Things conformable, so in some sort they are in their Eye; to enable it to correspond to all the Convergences, and Divergences of the Rays, which the Variations of each of the Mediums may produce. For this Service theTunica Choroeides, (in Fishes) hath a musculous Substance at the Bottom of it, lying round the optick Nerve, at a small Distance from it; by which Means I imagine they are able to contract, and dilate theChoroeides, and thereby to lengthen and shorten the Eye: For the helping in which Service, I imagine it is that theChoroeides, andSclerotica, are in a great Measure parted, that theChoroeidesmay have the greater Liberty of acting upon the Humours within.But in Birds, I have my self found, that although theChoroeidesbe parted from theSclerotica; yet theChoroeideshath no Muscle, but instead thereof, a curious pectinated Work, seated on the optick Nerve, represented inFig. 2.In whichc.a.e.b.d.represents theChoroeidesandSclerotica:a.b.the Part of theoptick Nerve, that is within the Eye:v.v.v.thevitreous Humour:a.f.g.b.thePecten:h.i.theCrystalline. For the Reception of thisPecten, theoptick Nervecomes farther within the Eye, than in other Creatures. The Structure of thisPecten, is very like that of theLigamentum Ciliare; and in the Eye of aMagpy, and some others, I could perceive it to be musculous towards the Bottom. ThisPectenis so firmly fixed unto, or embodied in thevitreous Humour, that thevitreous Humourhangs firmly to it, and is not so easily parted from it. By which Means all the Motions of thePectenare easily communicated to thevitreous Humour, and indeed to all contained in theChoroeides. And forasmuch as theCrystallineis connected to thevitreous Humour, therefore also the Alterations in thevitreous Humouraffect also theCrystalline; and theCrystallineis hereby brought nearer unto, or farther from theRetina, as occasion is. Besides all which Observables in theChoroeides, and inner Eye, I have also found this farther remarkable in theSclerotica, and outer-part of the Eye of Birds,viz.That the fore-part of theScleroticais horny and hard, the middle-part thin and flexible, andBracesintervene between the fore and hind-part, running between theChoroeidesandSclerotica; by which Means theCornea, and back-part of the Eye, are brought to the same Conformity, that the rest of the Eye hath.The great End and Design of this singular and curiousApparatusin the Eyes, both of Birds and Fishes, I take to be, 1. To enable those Creatures to see at all Distances, far off, or nigh; which (especially in the Waters) requireth a different Conformation of the Eye. In Birds also, this is of great Use, to enable them to see their Food at their Bill’s End, or to reach the utmost Distances their high Flights enable them to view; as to see over great Tracts of Sea or Land, whither they have occasion to fly; or to see their Food or Prey, even small Fishes in the Waters, and Birds, Worms,&c.on the Earth, when they sit upon Trees, high Rocks, or are hovering high in the Air. 2. To enable those Animals to adapt their Eye to all the various Refractions of theirMedium. Even the Air it self varies the Refractions, according as it is rarer or denser, more or less compressed; as is manifest from the learned and ingenious Mr.Lowthorp’s Experiment inPhil. Trans.Nᵒ. 257. and some other Experiments since of the before-commended Mr.Hawksbee, both in natural, rarify’d and compressed Air; in each of which, the Refractions constantly varied in exact Proportion to the Rarity or Density of the Air.Vid.Hawksbee’sExp.pag. 175,&c.Besides this Conformity in general, between the Eyes of Birds and Fishes,Du Hameltells us of a singular Conformity in theCormorant’s Eye, and that is, that theCrystallineis globous, as in Fishes, to enable it to see and pursue its Prey under Water: WhichJ. Faber, in Mr.Willoughbysaith, they dowith wonderful Swiftness, and for a long Time. Will. Ornithol. p. 329.[ee]TheCrystalline Humour, when dry’d, doth manifestly enough appear to be made up of many very thin sphericalLaminæ, or Scales lying one upon another. Mr.Lewenhockreckons there may be 2000 of them in oneCrystalline, from the outermost to the Center. Every one of these Scales, he saith, he hath discovered to be made up of one single Fibre, or finest Thread wound, in a most stupendous Manner, this way, and that way, so as to run several Courses, and meet in as many Centers, and yet not to interfere, or cross one another, in any one Place. InOxen,Sheep,Hogs,DogsandCats, the Thread spreads into three several Courses, and makes as many Centers: InWhalesfive; but inHaresandRabbetsonly two. In the whole Surface of anOx’sCrystalline, he reckons there are more than 12000 Fibres juxtaposited. For the right and clear Understanding of the Manner of which admirable Piece of Mechanism, I shall refer to his Cuts and Descriptions inPhilos. Trans.Nᵒ. 165. and 293. The Truth hereof I have heard some ingenious Men question; but it is what I my self have seen, and can shew to any Body, with the Help of a good Microscope.[ff]S. Malpighiobserved the Middle of theoptick Nerveof theSword-Fish, to be nothing else but a large Membrane, folded according to its Length in many Doubles, almost like a Fan, and invested by theDura mater; whereas in Land-Animals it is a Bundle of Fibres.V.Phil. Trans.Nᵒ. 27.[gg]Certissimum est, quòd in omnibus Oculis humanis (quos saltem mihi dissecare contigit) Nervus opticus Pupillæ è diametro apponitur,&c.Briggs’s Ophthal. c. 3. §. 15. ItaWillis de Anim. Brut.p. 1. c. 15.Nervi Optici in nobis, item in Cane, Fele (& in cateris forsan animalibus calidis) ad fundum Oculi delati Pupilla regioni prospiciunt, dum interim in aliis Quadrupedibus, uti etiam in Piscibus & Volueribus, obliquè semper Tunica Sclerotidi inseruntur. Unde,&c.Willis Ib.c. 7. §. 11.[hh]This Pair is united at its Rise; whence is commonly drawn a Reason why one Eye being mov’d towards an Object, the other is directed also to the same.Gibson’s Anat.Book III. Chap. 11.SoBartholine Anat.Libellus 3. c. 2.[ii]Among all the other Security the Eye hath, we may reckon the Reparation of theaqueous Humour; by which Means the Eye when wounded, and that in all Appearance very dangerously too, doth often recover its Sight: Of whichBern. Verzaschagives divers Examples ancient and modern. One is fromGalen, of a Boy so wounded, that theCorneafell, and became flaccid, but yet recovered his Sight. Other such like Instances also he gives fromRealdus Columbus,Rhodius, andTulpius; and one that he cured himself in these Words,Ego in Nobilissimi viri filiolâ similem casum observavi: hæc dum levibus de causis cum fratre altercaret, iste iracundiâ percitus cultellum Scriptorium apprehendit, & sororis oculo vulnus infligit, inde humor aqueus effluxit. Vocatus præsentem Chirurgum jussi sequens collyrium anodynum & exsiccans tepidè sæpiùs admovere.℞aq. Plantag.℥iv.Rosar. Sanicul. Euphras.anaTrochisc. alb. Rhaf. cum Opio℈ii.Tutiæ pp.℈i.Croci orient.℈ss. M.Hoc Collyrium inflammationem compescuit, vulnus siccavit & sanavit. Hinc post aliquot menses Humor aqueus succrevit. Nam visus, sed dibilior, cum summo parentum gaudio redivit.B. Verzaschæ Observ. Medicæ. Obs. 14.Another Cure of this kind, was experimented by Dr.Daniel Major, upon a Goose, Ann. 1670, theaqueous Humourof both whose Eyes they let out, so that the Eyes fell, and theGoosebecame quite blind: But without the Use of any Medicine, in about two Days Time, Nature repaired the watery Humour again, the Eyes returned to their Former Turgency, and theGoosewas in a Week after produced seeing before twenty eight or thirty Spectators.Ephem. Germ.T. 1. Add. ad. Obs. 117.From the same Cause, I doubt not, it was that the Eye of a Gentleman’s Daughter, and those of a Cock, when wounded, so that theCorneasunk, were restored by aLithuanianChymist, that passed for a Conjurer, by the Use of a Liquor found inMay, in the Vesiculæ ofElm. Of which see Mr.Ray’s Catal. Cantab.inUlmusfromHenr. ab Heers.[kk]Palpebræ, quæ sunt tegumenta Oculorum, mollissimæ tactu, nè lederent aciem, aptissimæ factæ, & ad claudendas Pupillas, nè quid incideret, & ad aperiendas; idque providit, ut identidem fieri posset cum maximâ celeritate. Munitæque sunt Palpebræ tanquàm vallo pilorum: quibus & apertis Oculis, si quid incideret, repelleretur, & somno conniventibus, cùm Oculis ad cernendum non egerimus, ut qui, tanquàm involuti, quièscerent. Latent prætereà utiliter, & excelsis undique partibus sepiuntur. Primùm enim superiora Superciliis obducta sudorem à capitæ, & fronte destuentem repellunt. Genæ deinde ab inferiore parte tutantur subjectæ, leviterque eminentes.Cicer. de Nat. Deor. L. 2. c. 57.Tully, in the Person of aStoick, having so well accounted for the Use of theEye-Lids, I shall for a further Manifestation of the Creator’s Contrivance and Structure of them, take notice of two or three Things: 1. They consist of a thin and flexible, but strong Skin, by which means they the better wipe, clean, and guard theCornea. 2. Their Edges are fortified with a softCartilage, by which means they are not only enabled the better to do their Office, but also to close and shut the better. 3. Out of these Cartilages grow a Pallisade of stiff Hairs, of great Use to warn the Eye of the Invasion of Dangers, to keep off Motes, and to shut out too excessive Light,&c.and at the same time to admit of (through their Intervals) a sufficient Passage for Objects to approach the Eye. And it is remarkable, that these Hairs grow but to a certain, commodious Length, and need no cutting, as many other Hairs of the Body do: Also, that their Points stand out of the way, and in the upper-lid bend upwards, as they do downwards in the lower lid, whereby they are well adapted to their Use. From which last Observables, we may learn how critical and nice the great Author of Nature hath been, in even the least and most trivial Conveniencies belonging to Animal Bodies; for which Reason I have added it toTully’s Remarks. And more might have been added too, as particularly concerning the curious Structure and Lodgment of theRight Muscle, which opens the Eye-Lids; and theOrbicularis, orCircularone, that shuts them; the niceApparatusof Glands that keep the Eye moist, and serve forTears; together with the Reason why Man alone, who is a social Animal, doth exhibit his social Affections by such outward Tokens asTears; theNervesalso, and other Organs acting in this Ministry. I might also speak of the Passages for discharging the superfluous Moisture of the Eyes through the Nostrils, and much more of the like kind. But it would take up too much Room in these Notes; and therefore it shall suffice to give only such Hints as may create a Suspicion of a noble Œconomy and Contrivance in this (I had almost said) least considerable part of the Eye. But for Particulars I shall refer to the Anatomists; and for some of these Things, particularly to Dr.Willis’sCereb. Anat.andde Anim. Brut.and Mr.Cowper’s Elegant Cuts in the 11ᵗʰTab.of hisAnatomy.To the Eye-Lids we may add another Guard afforded the Eyes of most Quadrupeds, Birds, and Fishes, by thenictitating Membrane, which Dr.Willisgives this Account of,Plurimis[Animalibus]quibus Musculus suspensorius adest(which Limitation he needed not to have added)etiam alter Membranosus conceditur, qui juxta interiorem oculi canthum situs, quando elevatur, Oculi globum ferè totum obtegit. Hujus usus esse videtur, ut cùm Bestiæ inter gramina,&c.capita sua propter victum capessendum demergunt, hic Musculus Oculi Pupillam, nè à stipularum incursu seriatur, oculit, munitque.De Anim. Brut. p. 1. c. 15.This Membrane Man hath not, he having little Occasion to thrust his Head into such Places of Annoyance, as Beasts and other Animals; or if he hath, he can defend his Eyes with his Hands. But Birds (who frequent Trees and Bushes) and Quadrupeds, (Hedges and long Grass) and who have no part ready, like the Hand, to fence off Annoyances; these, I say, have this incomparable Provision made for the Safety of their Eyes. And for Fishes, as they are destitute of Eye-Lids, because in the Waters there is no occasion for a Defensative against Dust and Motes, offensive to the Eyes of Land Animals, nor to moisten and wipe the Eyes, as the Eye-Lids do, so theNictitating-Membraneis an abundant Provision for all their Occasions, without the Addition of the Eye-Lids.And now, if we reflect, are these the Works of any Thing but a wise and indulgent Agent?[ll]Although the Hardness and Firmness of theAdnata, orScleroticain Birds, is a good Guard to their Eyes, yet I do not think it is made thus, so much for a Defence, as to minister to the lengthning and shortning the Eye, mentioned before inNote (cc).[mm]Cochleis oculorum vicem Cornicula bina pratentu implent.Plin. Nat. Hist. l. 11. c. 37. See more of the Eyes ofSnailsbefore inNote (k); and inNote (l), I said that I suspectedMolesalso might thrust out, or withdraw their Eyes more or less within the Hair or Skin.[nn]The diligentSturmiuswas fully persuaded there could not be any speculative Atheism in any one that should well survey the Eye.Nobis, saith he,fuit persuasissimum. Atheismum, quem vocant speculativum, h. e. obsirmatam de Deitate in Universo nullâ persuasionem, habere locum aut inveniri non posse in eo homine, qui vel unius corporis organici, & speciatim Oculi fabricam attento animo aspexerit.Sturm. Exerc. Acad. 9. De Vis. Organ. & Rat. in Epilogo.[oo]The glorious Landskips, and other Objects that present themselves to the Eye, are manifestly painted on theRetina, and that not erect, but inverted as the Laws of Opticks require; and is manifest to the Eye fromMonsieur Cartes’s Experiment, of laying bare the vitreous Humour on the back part of the Eye, and clapping over it a Bit of white Paper, or the Skin of an Egg; and then placing the fore-part of the Eye to the Hole of the Window of a darkned Room. By which means we have a pretty Landskip of the Objects abroad invertedly painted on the Paper, on the back of the Eye. But now the Question is, How in this Case the Eye comes to see the Objects erect?Monsieur Cartes’s Answer is,Notitia illius ex nullâ imagine pendet, nec ex ullâ actione ab objectis veniente, sed ex solo situ exiguarum partium cerebri, è quibus Nervi expullulant.——E.g. cogitandum in Oculo——situm capillamenti nervi optici——respondere ad alium quendam partis cerebri——qui facit ut Anima singula loca cognoscat, quæ jacent in rectâ, aut quasi rectâ lineæ; ut ita mirari non debeamus corpora in naturali situ videri, quamvis imago in oculo delineata contrarium habeat.Dioptr. c. 6. But our most ingenious Mr.Molyneuxanswereth thus,The Eye is only the Organ or Instrument, ’tis the Soul that sees by means of the Eye. To enquire then how the Soul perceives the Object erect, by an inverted Image, is to enquire into the Soul’s Faculties——But erect and inverted are only Terms of Relation to up and down; or farther from, or nigher to the Center of the Earth, in Parts of the same Thing.——But the Eye, or visive Faculty takes no notice of the internal Posture of its own Parts, but useth them as an Instrument only, contrived by Nature for the Exercise of such a Faculty.——Let us imagine, that the Eye(on its lower Part)receives an Impulse[by a Ray from the upper part of the Object]must not the visive Faculty be necessarily directed hereby to consider this Stroke, as coming from the top rather than the bottom[of the Object]and consequently be directed to conclude it the Representation of the top? Hereof we may be satisfied, by supposing a Man standing on his Head. For here, though the upper Parts of Objects are painted on the upper Parts of the Eye, yet the Objects are judged to be erect. What is said of Erect and Reverse, may be understood of Sinister and Dexter.Molyneux’s Dioptr. Nov. Part I. Prop. 28.

[a]In Dissectionibus anatomicis vix aliquid admirabilius, aut artificiosius structurâ Oculi humani, meo quidem judicio, occurrit: ut meritò, per excellentiam, Creatoris appelletur Miraculum.Gul. Fabr. Hildan. Cent. 2. Observ. 1.So likewise that accurate Surveyor of the Eye, Dr.Briggs, whoseOphthalmographyI have met with since my penning this part of my Survey. His Character of this curious piece of God’s Work is,Inter præcipuas corporis animati partes, quæ magni Conditoris nostri sapientiam ostendunt, nulla sanè reperitur, quæ majori pompâ elucet quàm ipse Oculus, aut quæ elegantiori formâ concinnatur. Deum enim aliæ partes vel minori satellitio stipantur, vel in tantam venustatem haud assurgunt; Ocelli peculiarem honorem & decus à supremo Numine efflatum referunt, & nunquam non stupendæ suæ Potentia characteres repræsentant. Nulla sanè pars tam divino artificio & ordine,&c.Cap. 1. §. 1.

So likewise that accurate Surveyor of the Eye, Dr.Briggs, whoseOphthalmographyI have met with since my penning this part of my Survey. His Character of this curious piece of God’s Work is,Inter præcipuas corporis animati partes, quæ magni Conditoris nostri sapientiam ostendunt, nulla sanè reperitur, quæ majori pompâ elucet quàm ipse Oculus, aut quæ elegantiori formâ concinnatur. Deum enim aliæ partes vel minori satellitio stipantur, vel in tantam venustatem haud assurgunt; Ocelli peculiarem honorem & decus à supremo Numine efflatum referunt, & nunquam non stupendæ suæ Potentia characteres repræsentant. Nulla sanè pars tam divino artificio & ordine,&c.Cap. 1. §. 1.

[b]It is a good ReasonFrier Baconassigns for the Sphæricity of the Eye:Nam si esset planæ figuræ, species rei majoris oculo non posset cadere perpendiculariter super eum——Cùm ergò Oculus videt magna corpora, ut ferè quartam cœli uno aspectu, manifestum est, quòd non potest esse planæ figuræ, nec alicujus nisi sphæricæ, quoniam super sphæram parvam possunt cadere perpendiculares infinitæ, quæ à magno corpore veniunt, & tendunt in centrum Sphæræ: Et sic magnum corpus potest ab oculo parvo videri.For the Demonstration of which he hath given us a Figure.Rog. Bacon. Perspect. Distinct. 4. Cap. 4.Dr.Briggssaith,Pars antica, (sive Cornea,) convexior est posticâ: hâc enim ratione radii meliùs in pupillam detorquentur, & Oculi fundus ex altarâ parte in majorem (propter imagines rerum ibidem delineandos) expanditur.Ibid. §. 2.

Dr.Briggssaith,Pars antica, (sive Cornea,) convexior est posticâ: hâc enim ratione radii meliùs in pupillam detorquentur, & Oculi fundus ex altarâ parte in majorem (propter imagines rerum ibidem delineandos) expanditur.Ibid. §. 2.

[c]Suppose the Eye had theRetina, or back part flat for the Reception of the Images, as inFig. 1.ABA: it is manifest, that if the Extremes of the Image AA were at a due focal distance, the middle B would be too nigh the Crystalline, and consequently appear confused and dim; but all Parts of theRetinalying at a due focal distance from the Crystalline, as at ACA, therefore the Image painted thereon is seen distinct and clear. Thus in a dark Room, with a Lens at a Hole in the Window, (whichSturmiuscalls his Artificial Eye, in hisExercit. Acad.one of which he had made for his Pupils, to run any where on Wheels). In this Room, I say, if the Paper that receives the Images be too nigh, or too far off the Lens, the Image will be confused and dim; but in the Focus of the Glass, distinct, clear, and a pleasant Sight.

[d]Blemmyis traduntur capita abesse, Ore & Oculis pectori affixis.Plin. Nat. Hist. l. 5. c. 8.Occidentem versus quosdam sine cervice Oculos in humeris habentes.Ib. l. 7. c. 2. From these, and other such like Fables, in this last cited Chapter ofPliny, no doubt our famous Romancer SirJ. Mandevile, had his Romnantick Stories related in his Travels.

[e]SeeBook V. Chap. 2. Note (e).

[f]Galendeserves to be here consulted, who in his BookDe Usu Partium, from many Considerations of the Hand, such as what is here mentioned, as also its Structure, Site and Use, largely proves and reflects upon the Wisdom and Providence of the Contriver and Maker of that Part.

[g]Thus inHaresandConies, their Eyes are very protuberant, and placed so much towards the sides of their Head, that their two Eyes take in nearly a whole Sphere: Whereas inDogs, (that pursue them) the Eyes are set more forward in the Head, to look that way more than backward.

[h]Sed lubricos Oculos fecit[Natura]& mobiles, ut & declinarent siquid noceret; & aspectum, quo vellent, facile converterent. Cicer. de Nat. Deor. l. 2. c. 57.

[i]The Eyes ofSpiders,(in some four, in some six, and in some eight)are placed all in the fore-front of their Head, (which is round, and without any Neck) all diaphanous and transparent, like a Locket of Diamonds,&c.neither wonder why Providence should be so anomalous in this Animal, more than in any other we know of. For, 1. Since they wanting a Neck, cannot move their Head, it is requisite that Defect should be supplied by the multiplicity of Eyes. 2. Since they were to live by catching so nimble a Prey as a Fly is, they ought to see her every way, and to take herper saltum, (as they do) without any Motion of the Head to discover her: Which Motion would have scared away so timorous an Insect.Power’sMicros. Observ. pag. 11.The Eyes of theCameleonresemble a Lens, or Convex Glass, set in a versatile globular Socket, which she turneth backward, or any way, without moving her Head; and ordinarily the one a contrary, or quite different way from the other.Dr.Goddardin Phil. Tran. Nᵒ. 137.But what is more extraordinary in this Motion[of the Cameleon’s Eye]is to see one of the Eyes move, whilst the other remains immoveable; and the one to turn forward, at the same time that the other looketh behind; the one to look up to the Sky, when the other is fixed on the Ground. And these Motions to be so extreme, that they do carry thePupillaunder the Crest which makes the Eye-brow, and so far into theCanthi, or Corners of the Eyes, that the Sight can discern whatever is done just behind it, and directly before, without turning the Head, which is fastned to the Shoulders.Mem. for a Nat. Hist. in Anatom. Dissect. at Paris. Diss. of Camel. pag. 22.

The Eyes of theCameleonresemble a Lens, or Convex Glass, set in a versatile globular Socket, which she turneth backward, or any way, without moving her Head; and ordinarily the one a contrary, or quite different way from the other.Dr.Goddardin Phil. Tran. Nᵒ. 137.

But what is more extraordinary in this Motion[of the Cameleon’s Eye]is to see one of the Eyes move, whilst the other remains immoveable; and the one to turn forward, at the same time that the other looketh behind; the one to look up to the Sky, when the other is fixed on the Ground. And these Motions to be so extreme, that they do carry thePupillaunder the Crest which makes the Eye-brow, and so far into theCanthi, or Corners of the Eyes, that the Sight can discern whatever is done just behind it, and directly before, without turning the Head, which is fastned to the Shoulders.Mem. for a Nat. Hist. in Anatom. Dissect. at Paris. Diss. of Camel. pag. 22.

[k]Snailssend out their Eyes at a distance, they being contained in their four Horns,like atramentous Spots, fitted to the end of their Horns, or rather to the ends of those black Filaments or optick Nerves, which are sheathed in her Horns, as Dr.Powerwordeth it.Obs. 31. pag. 36.So the ingenious Dr.Lister.Exercit. Anat. Cochl. & Limac.

[l]Vid.l. 8. c. 3. Note (a).

[m]Severinusis ofAristotle’s,Pliny’s, andAlb. Magnus’s Opinion, that theMolehath no Sight;G. Segerdenies any Humour to be therein, but thinks they may probably see, because Nature made nothing in vain. ButBorrichiussaith, their Eyes haveappendiculam nerveam in cerebrum euntem, cujus beneficio globuli illi[the little Eyes]extra pellem facilè poterant exseri, retrahique pro arbitrio——In illis oculorum globulis humor aqueus copiose satis natabat; cæterorum non nisi tenue vestigiem.Blas. Anat. Anim. c. 35.Et quoniam Natura hoc vitæ genus ipsi destinavit, etiam perquàm exiguos Oculos——dedit eo concilio, ut ii, pretiosissima corporis pars, à terræ pulvere nè affligerentur. Ii insuper pilis recti,&c.Humores illis oculis insunt, & tunica nigra, uvea, se prodit. Ad hos tramite alio nervus venit.Schneider in Blas. ibid.Some time since I made divers accurate Dissections of theEyesofMoles, with the help of Microscopes, having a doubt whether what we take to be Eyes, were such or no. And upon a strict Scrutiny I plainly could distinguish theVitreousandCrystallineHumours, yea, theLigamentum Ciliare, and the atramentaceousMucus. ThePupilI could manifestly discern to be round, and theCorneacopped, or conical: The Eye is at a great distance from the Brain, the Optick Nerve very slender and long, reaching from the Eye through the intermediate Flesh, and so passeth to the Brain, along with the pair of Nerves reaching to the Nose, which are much the largest that are in all the Animal. These Creatures, I imagine, have the Faculty of withdrawing their Eyes, if not quite into the Head, (asSnails) yet more or less within the Hair, as they have more or less Occasion to use or guard their Eyes.Galensaith,Moleshave Eyes, theCrystallineandVitreousHumours, encompassed withTunicks.De Us. Part. l. 14. c. 6.So accurate an Anatomist was he for his Time.

Et quoniam Natura hoc vitæ genus ipsi destinavit, etiam perquàm exiguos Oculos——dedit eo concilio, ut ii, pretiosissima corporis pars, à terræ pulvere nè affligerentur. Ii insuper pilis recti,&c.Humores illis oculis insunt, & tunica nigra, uvea, se prodit. Ad hos tramite alio nervus venit.Schneider in Blas. ibid.

Some time since I made divers accurate Dissections of theEyesofMoles, with the help of Microscopes, having a doubt whether what we take to be Eyes, were such or no. And upon a strict Scrutiny I plainly could distinguish theVitreousandCrystallineHumours, yea, theLigamentum Ciliare, and the atramentaceousMucus. ThePupilI could manifestly discern to be round, and theCorneacopped, or conical: The Eye is at a great distance from the Brain, the Optick Nerve very slender and long, reaching from the Eye through the intermediate Flesh, and so passeth to the Brain, along with the pair of Nerves reaching to the Nose, which are much the largest that are in all the Animal. These Creatures, I imagine, have the Faculty of withdrawing their Eyes, if not quite into the Head, (asSnails) yet more or less within the Hair, as they have more or less Occasion to use or guard their Eyes.

Galensaith,Moleshave Eyes, theCrystallineandVitreousHumours, encompassed withTunicks.De Us. Part. l. 14. c. 6.So accurate an Anatomist was he for his Time.

[n]Plinytells us of a sort ofHeronwith but one Eye, but ’twas only by hear-say.Inter Aves Ardeolarum genere, quos Leucos vocant, altero oculo carere tradunt.Nat. Hist. l. 11. c. 37. So the King of theNigræthat hath but one Eye, and that in his Forehead,l. 6. c. 30.Which Fables I take notice of more for the Reader’s Diversion, than any Truth in them.

[o]Supra,Note (i).

[p]The most celebrated Anatomists differ greatly about the Reason why we see not double with two Eyes. ThisGalen, and others after him, generally thought to be from a Coalition or Decussation of the Optick Nerves, behind theOs Sphenoïdes. But whether they decussate, coalesce, or only touch one another, they do not well agree. TheBartholinesexpressly assert they are united,non per simplicem contactum vel intersectionem in homine, sed totalem substantiæ confusionem, Anat. l. 3. c. 2. And whereasVesalius, and some others had found some Instances of their being disunited; they say,sed in plerisque ordinarie confunditur interior substantia, ut accuratâ disquisitione deprehendi.But our Learned Dr.Gibson, (Anat. l. 3. c. 10.) saith, theyare united by the closest Conjunction, but not Confusion of their Fibres.But others think the Reason is not from any Coalescence, Contact, or crossing of the Optick Nerves, but from a Sympathy between them. Thus MonsieurCartesis of Opinion, that theFibrillæconstituting the medullary Part of those Nerves, being spread in theRetinaof each Eye, have each of them corresponding Parts in the Brain; so that when any of thoseFibrillæare struck by any part of an Image, the corresponding Parts of the Brain are thereby affected, and the Soul thereby informed,&c.but see more hereafter underNote (oo), fromCarteshimself.Somewhat like this is the Notion of our judicious Dr.Briggs, who thinks the Optick Nerves of each Eye consist ofHomologous Fibres, having their rise in theThalamus Nervorum Opticorum, and thence continued to both theRetinæ, which are made of them; And farther, that thoseFibrillæhave the same Parallelism, Tension,&c.in both Eyes; and consequently when an Image is painted on the same corresponding, sympathizing Parts of eachRetina, the same Effects are produced, the same Notice or Information is carried to theThalamus, and so imparted to the Soul, or judging Faculty. That there is such an Ὁμοιοπάθεια between theRetina, &c. he makes very probable from the ensuing of double Vision upon the Interruption of the Parallelism of the Eyes; as when one Eye is depressed with the Finger, or their Symphony interrupted by Disease, Drunkenness,&c.And lastly, That simple Vision is not made in the former way,viz.by a Decussation or Conjunction of the Optick Nerves, he proves, because those Nerves are but in few Subjects decussated, and in none conjoined otherwise than by a bare Contact, which is particularly manifest in Fishes; and in some Instances it hath been found, that they have been separated without any double Vision ensuing thereupon.Vid.Brig. Ophthalmogr.cap. 11. & 5. andNov. Vis. Theor.passim.What the Opinion of our justly eminent SirIsaac Newtonis, may be seen in hisOpticks, Qu. 15.Are not the Species of Objects seen with both Eyes, united where the Optick Nerves meet before they come into the Brain, the Fibres on the right side of both Nerves uniting there,&c.For the Optick Nerves of such Animals as look the same way with both Eyes, (as of Men, Dogs, Sheep, Oxen,&c.) meet before they come into the Brain; but the Optick Nerves of such Animals as do not look the same way with both Eyes, (as of Fishes and of the Cameleon) do not meet, if I am rightly informed.Newt. Opt. Q. 15.

But our Learned Dr.Gibson, (Anat. l. 3. c. 10.) saith, theyare united by the closest Conjunction, but not Confusion of their Fibres.

But others think the Reason is not from any Coalescence, Contact, or crossing of the Optick Nerves, but from a Sympathy between them. Thus MonsieurCartesis of Opinion, that theFibrillæconstituting the medullary Part of those Nerves, being spread in theRetinaof each Eye, have each of them corresponding Parts in the Brain; so that when any of thoseFibrillæare struck by any part of an Image, the corresponding Parts of the Brain are thereby affected, and the Soul thereby informed,&c.but see more hereafter underNote (oo), fromCarteshimself.

Somewhat like this is the Notion of our judicious Dr.Briggs, who thinks the Optick Nerves of each Eye consist ofHomologous Fibres, having their rise in theThalamus Nervorum Opticorum, and thence continued to both theRetinæ, which are made of them; And farther, that thoseFibrillæhave the same Parallelism, Tension,&c.in both Eyes; and consequently when an Image is painted on the same corresponding, sympathizing Parts of eachRetina, the same Effects are produced, the same Notice or Information is carried to theThalamus, and so imparted to the Soul, or judging Faculty. That there is such an Ὁμοιοπάθεια between theRetina, &c. he makes very probable from the ensuing of double Vision upon the Interruption of the Parallelism of the Eyes; as when one Eye is depressed with the Finger, or their Symphony interrupted by Disease, Drunkenness,&c.And lastly, That simple Vision is not made in the former way,viz.by a Decussation or Conjunction of the Optick Nerves, he proves, because those Nerves are but in few Subjects decussated, and in none conjoined otherwise than by a bare Contact, which is particularly manifest in Fishes; and in some Instances it hath been found, that they have been separated without any double Vision ensuing thereupon.Vid.Brig. Ophthalmogr.cap. 11. & 5. andNov. Vis. Theor.passim.

What the Opinion of our justly eminent SirIsaac Newtonis, may be seen in hisOpticks, Qu. 15.Are not the Species of Objects seen with both Eyes, united where the Optick Nerves meet before they come into the Brain, the Fibres on the right side of both Nerves uniting there,&c.For the Optick Nerves of such Animals as look the same way with both Eyes, (as of Men, Dogs, Sheep, Oxen,&c.) meet before they come into the Brain; but the Optick Nerves of such Animals as do not look the same way with both Eyes, (as of Fishes and of the Cameleon) do not meet, if I am rightly informed.Newt. Opt. Q. 15.

[q]Nigra est[Uvea]ut radios (ab Oculi fundo ad anteriorem ejus partem reflexos) obumbret; nè hi (ut ait clar. Cartesius) ad Oculi fundum retorti ibidem confusam visionem efficerent. Alia forsan ratio hujus nigredinis statuatur, quòd radii in visione superflui, qui ab objectis lateralibus proveniunt hoc ritu absorbeantur. Ita enim è loco obscuro interdiu objecta optimè intuemur, quia radii tunc temporis circumfuso lumine non diluuntur.Brigg’s Ophthal. c. 3. §. 5.

[r]Admirandum Dei artificium ex diversorum animalium comparatione indies evadit manifestiùs. Mirantur omnes Trochlearem in oculis Hominum & Quadrupedum, & quidem jure: sed admirationem omnem superat, quòd sine Trochleâ oculum movens in Avibus novum genus Trochleæ longè artificiosiùs Nictitandi Membranæ dederit.Blas. Anat. Animal. p. 2. c. 4.ex Stenon.[Musculum Trochlearem]per intermedium trochleam traductum, nunquam intueor, quin admirabundus mecum, Ὁ Θεὸς, exclamem ὀυ μόνον ἀεὶ γεωμετρεῖ, ἀλλὰ καὶ ἀεὶ μηχανᾶται.I. C. Sturmii Exercit. Acad. 9. de Vis. Org. & Rat.c. 3. §. 4. p. 446.

[Musculum Trochlearem]per intermedium trochleam traductum, nunquam intueor, quin admirabundus mecum, Ὁ Θεὸς, exclamem ὀυ μόνον ἀεὶ γεωμετρεῖ, ἀλλὰ καὶ ἀεὶ μηχανᾶται.I. C. Sturmii Exercit. Acad. 9. de Vis. Org. & Rat.c. 3. §. 4. p. 446.

[s]Observare est quod Quadrupedes, qui oculos in terram pronos, ac pendulos gerunt, Musculum peculiarem habent, quo Oculi globus suspenditur——Hoc Musculo Bos, Equus, Ovis, Lepus, Porcus, &c. præditi sunt: hoc etiam Canis instruitur, sed alio modo conformatum habet.Willis de An. Brut. p. 1. c. 15.Of this Opinion also wasBartholine Anat.l. 3. c. 8. and divers other eminent Anatomists.But Dr.Briggsis of Opinion that theAdnata, and the other Muscles sufficiently answer all those Ends ascribed to that Muscle by former Anatomists, and thinksProbabiliùs itaque esse hunc Musculum nervi Optici actionem (per vices) confirmare, nè à prono Brutorum incessu & copioso affluxu humorum debilitetur, Ophthal. c. 2. §. 2.TheMusculus Suspensoriusbeing in thePorpess, as well as Brutes, Dr.Tysonthinks the Use of it is not to suspend the Bulk of the Eye; but rather by its equal Contraction of theSclerotis, to render the Ball of the Eye more or less Spherical, and so fitter for Vision.Tyson’s Anat. of the Porpess, p. 39.

Of this Opinion also wasBartholine Anat.l. 3. c. 8. and divers other eminent Anatomists.

But Dr.Briggsis of Opinion that theAdnata, and the other Muscles sufficiently answer all those Ends ascribed to that Muscle by former Anatomists, and thinksProbabiliùs itaque esse hunc Musculum nervi Optici actionem (per vices) confirmare, nè à prono Brutorum incessu & copioso affluxu humorum debilitetur, Ophthal. c. 2. §. 2.

TheMusculus Suspensoriusbeing in thePorpess, as well as Brutes, Dr.Tysonthinks the Use of it is not to suspend the Bulk of the Eye; but rather by its equal Contraction of theSclerotis, to render the Ball of the Eye more or less Spherical, and so fitter for Vision.Tyson’s Anat. of the Porpess, p. 39.

[t]Musculus obliquus inferior oritur à peculiari quodam foramine in latere Orbitæ ocularis facto, (contra quam in cæteris,&c.) quo fit ut ex unâ parte à Musculo trochleari, ex alterâ verò ab hujus Musculi commodissimâ positione, Oculus in æquilibrio quodam constitutus, irretorto obtutu versus objecta feratur, nec plus justo accedat versus internum externumve canthum; quæ quidem Libratio omnino nulla fuisset, absque hujus Musculi peculiari originatione (cujus ratio omnes hucusque Anatomicos latuit).And so this curious Anatomist goes on to shew farther the stupendous Artifice of the great Creator in this Position of theOblique Muscles. Brigg’sNova Vis. Theor.p. 11.meo libro.

[u]Besides those particular Motions which the Eye receives from theOblique Muscles, and I may add its Libration also in some Measure, some Anatomists ascribe another no less considerable Use to them; namely, to lengthen and shorten the Eye (by squeezing and compressing it) to make it correspond to the Distances of all Objects, according as they are nigh or far off. Thus the ingenious Dr.Keil;The Aqueous Humour being the thinnest and most liquid, easily changeth its Figure, when either theLigamentum Ciliatecontracts, or both theOblique Musclessqueeze the middle of the Ball of the Eye, to render it Oblong when Objects are too near us.Keil’s Anat. Chap. 4. Sect. 4.SeeNote (y).

[w]Quis verò opifex præter Naturam, quâ nihil potest esse callidiùs, tantam solertiam persequi potuisset in Sensibus? quæ primùm Oculos membranis tenuissimis vestivit, & sepiit; quas primum perlucidas fecit, ut per eas cerni posset: firmas aurem, ut continerentur.Cic. de Nat. Deor. l. 2. c. 57.

[x]BoylofFinal Causes.

[y]It is easy to be observed, that thePupilopeneth in dark Places; as also when we look at far distant Objects, but contracts by an Increase of Light, and when the Objects are nigh. This Motion of thePupilsome say, is effected by the circular and strait Fibres of theUvea, and some attribute it to theLigamentum Ciliare. Yet I have no great doubt but that they both concur in that Action, and that theLigamentum Ciliaredoth, at the same time the Pupil opens or shuts, dilate or compress theCrystalline, and bring it nigher unto, or carry it farther off theRetina. For the Structure of theLigamentum Ciliare, and its two Sorts of Fibres, drawn with the Help of a Microscope, I shall refer to Mr.Cowper’s Anat.T. 11.

[z]In Bove, Caprâ, Equo, Ove, & quibusdam aliis elliptica est(Pupilla)ut eo magis in hisce forsan animalibus, quæ prono incessu victum in agris quæritant, radios laterales ad mala & incommoda utrinque devitanda admittat.Briggs’s Ophthal.c. 7. §. 6.Homini erecto, aliisque,&c.caput erigere, & quaquaversus circumspicere solitis, plurima simul objecta, tum suprà, tum infrà, tum è latere utroque——visu excipiuntur; quapropter Oculi Pupilla rotunda esse debet.——Attamen bovi,&c.caput ferè semper pronum——gerentibus, tantùm quæ coràm, & paulo à latere obversantur, intuitu opus est: quapropter Pupilla——oblonga est,&c.Willisde Anim. Brut.p. 1. c. 15.

Homini erecto, aliisque,&c.caput erigere, & quaquaversus circumspicere solitis, plurima simul objecta, tum suprà, tum infrà, tum è latere utroque——visu excipiuntur; quapropter Oculi Pupilla rotunda esse debet.——Attamen bovi,&c.caput ferè semper pronum——gerentibus, tantùm quæ coràm, & paulo à latere obversantur, intuitu opus est: quapropter Pupilla——oblonga est,&c.Willisde Anim. Brut.p. 1. c. 15.

[aa]ThusCats(their Pupils being erect, and the shutting of their Eye-lids transverse thereunto) can so close their Pupil, as to admit of, as it were, one only single Ray of Light; and by throwing all open, they can take in all the faintest Rays. Which is an incomparable Provision for these Animals, that have occasion to watch and way-lay their Prey both by Day and Night.

[bb]There is besides this large opening of the Pupil, in some nocturnal Animals, another admirable Provision, enabling them to catch their Prey in the Dark; and that is a Radiation of the Eyes: Of which Dr.Willisthus;Hujus usus est Oculi Pupillam, quasi jubare insito, illuminare, ut res noctu, & in tenebris positas conspicere valeat: quare in Fele plurimùm illustris est: at Homini, Avibus, & Piscibus deest.This Illumination he speaks of, is from theTapetum, in the Bottom of the Eye, or the shining of theRetina, round the optick Nerve.Besides which, he saith, theIrishath a Faculty also, in some, of darting out Rays of Light, so as to enable them to see in the Dark: Of which he tells this Story;Novi quendam cerebro calidiori præditum, qui post uberiorem vini generosi potum in nocte atratâ, sive tenebris profundis, literas distincte legere potuit. Cujus ratio videtur esse, quòd spiritus animales velut accensi, adeòque ab hâc Iride irradiantes, jubare infito Medium illuminabant.Willis Ibid.Such another Thing,Plinytells us, was reported ofTiberius Cæsar:Ferunt Tib. Cæs. nec alii genitorum mortalium, fuisse naturam, ut expergefactus noctu paulisper, haud alio modo quam luce clarâ, contueretur omnia.Nat. Hist. l. 11. c. 37.So Dr.Briggs:Virum sanè calidæ indolis novi in Comitatu Bedfordiensi degentem, qui oculis felineis——donatus est: adeò ut epistolam——mirè admodùm in loco obscuro (ubi eadem mihi vix apparuit) perlegit. Hujus verò Oculi (nisi quod Pupillas insigniores obsinuere) ab aliorum formatione neutiquam discrepabant.Ophthal. c. 5. §. 12.

Besides which, he saith, theIrishath a Faculty also, in some, of darting out Rays of Light, so as to enable them to see in the Dark: Of which he tells this Story;Novi quendam cerebro calidiori præditum, qui post uberiorem vini generosi potum in nocte atratâ, sive tenebris profundis, literas distincte legere potuit. Cujus ratio videtur esse, quòd spiritus animales velut accensi, adeòque ab hâc Iride irradiantes, jubare infito Medium illuminabant.Willis Ibid.

Such another Thing,Plinytells us, was reported ofTiberius Cæsar:Ferunt Tib. Cæs. nec alii genitorum mortalium, fuisse naturam, ut expergefactus noctu paulisper, haud alio modo quam luce clarâ, contueretur omnia.Nat. Hist. l. 11. c. 37.

So Dr.Briggs:Virum sanè calidæ indolis novi in Comitatu Bedfordiensi degentem, qui oculis felineis——donatus est: adeò ut epistolam——mirè admodùm in loco obscuro (ubi eadem mihi vix apparuit) perlegit. Hujus verò Oculi (nisi quod Pupillas insigniores obsinuere) ab aliorum formatione neutiquam discrepabant.Ophthal. c. 5. §. 12.

[cc]TheTunica Araneais taken notice of byFrier Bacon, who calls it,Tela Aranea, and saith,in hâc continetur——glaciale vel Crystallinum.Rog. Bacon’s Perspect. Distinct. 2. c. 3.The wrinkling of this, and theCornea(as the Skin is of old Persons) he thinks is the Cause of the Obscurity of the Sight in such Persons.BaconIb. par. 2. cap. 2. But thisTunicksome deny, and others allow of: Dr.A. M.ofTrinity-College, Dublin, (in hisRelat. of Anat. Obs.in the Eyes of Animals, in a Letter to Mr.Boyl,Ann. 1682.annexed to hisAnat. Account of the Elephant burnt inDublin, p. 57.) affirms theTunica Aranea, and saith,I have often seen it before ’twas exposed to the Air one Minute, notwithstanding what Dr.Briggssaith to the contrary,&c.But Dr.Briggshis Opinion is,Humor Crystallinus, nisi aeri diutiùs expositus, vel lenitèr coctus (instar lactis) cuticulam non acquirit: quæ verò impropriè, Tunica Aranea dicitur, cùm si tantùm adventitia, ut in Oculo Bovis recens execto appareat.Briggs’s Ophthalm. c. 3.TheCrystalline Humourbeing of a double Substance, outwardly like a Gelly, towards the Center as consistent as hard Suet, upon occasion whereof its Figure may be varied; which Variation may be made by theLigamentum Ciliare; Dr.Grewdoth, upon these Accounts, not doubt to ascribe to theLigamentum Ciliare, a Power of making theCrystallinemore Convex, as well as of moving it to, or from theRetina. SeeGrew’sCosmolog. Sacr.l. 1. c. 4. Now it is certain by the Laws of Opticks, that somewhat of this is absolutely necessary to distinct Vision, inasmuch as the Rays proceeding from nigh Objects do more diverge, and those from distant Objects less: Which requires either that theCrystalline Humourshould be made more Convex, or more flat; or else an Elongation, or shortning of the Eye, or of the Distance between theCrystalline Humourand theRetina.But although Dr.Briggs(so good a Judge) denies theTunica Crystallina, contrary to the Opinion of most former Anatomists; yet there is great Reason to conclude he was in a Mistake, in my Opinion, from the Observations of theFrench Anatomists, of theCrystallineof the Eye, of theGemporChamois, who say,The Membrana Arachnoïdes was very thick, and hard, so that it was easily separated from the Crystallinus, p. 145.The same Anatomists also favour the Surmise of Dr.Grew, This [Contraction of the Fibres of theLigamentum Ciliareon one side, and Dilatation on the other]would make us think that these Fibres of theLigamentum Ciliare, are capable of Contraction, and voluntary Dilatation, like that of the Fibres of the Muscles; and that this Action may augment, or diminish the Convexity of theCrystallinus, according as the Need which the Distance of the Objects may make it to have on the Eye, to see more clearly and distinctly.Anat. Descrip. of aBear, p. 49.Since my penning the foregoing Notes, having as critically as I could, dissected many Eyes of Birds, Beasts and Fishes, I manifestly found theMembrana Arachnoïdes, and will undertake to shew it any one, with great Ease and Certainty. It is indeed so transparent, as not to be seen distinct from theCrystalline. But if theCorneaandUveabe taken off before, or thevitreous Humourbehind it, and the out-side of theCrystallinebe gently cut, theArachnoïdesmay be seen to open, and theCrystallinewill easily leap out, and part from theLigamentum Ciliare; which otherwise it would not do: For it is by theArachnoïdesbraced to theLigamentum Ciliare. This Membrane or Tunick, in the Ox, is so substantial and strong, though thin, that it yields to, or sinks under the sharpest Lancet, and requires (for so thin and weak a Membrane in appearance) a strong Pressure to pierce it.

TheCrystalline Humourbeing of a double Substance, outwardly like a Gelly, towards the Center as consistent as hard Suet, upon occasion whereof its Figure may be varied; which Variation may be made by theLigamentum Ciliare; Dr.Grewdoth, upon these Accounts, not doubt to ascribe to theLigamentum Ciliare, a Power of making theCrystallinemore Convex, as well as of moving it to, or from theRetina. SeeGrew’sCosmolog. Sacr.l. 1. c. 4. Now it is certain by the Laws of Opticks, that somewhat of this is absolutely necessary to distinct Vision, inasmuch as the Rays proceeding from nigh Objects do more diverge, and those from distant Objects less: Which requires either that theCrystalline Humourshould be made more Convex, or more flat; or else an Elongation, or shortning of the Eye, or of the Distance between theCrystalline Humourand theRetina.

But although Dr.Briggs(so good a Judge) denies theTunica Crystallina, contrary to the Opinion of most former Anatomists; yet there is great Reason to conclude he was in a Mistake, in my Opinion, from the Observations of theFrench Anatomists, of theCrystallineof the Eye, of theGemporChamois, who say,The Membrana Arachnoïdes was very thick, and hard, so that it was easily separated from the Crystallinus, p. 145.

The same Anatomists also favour the Surmise of Dr.Grew, This [Contraction of the Fibres of theLigamentum Ciliareon one side, and Dilatation on the other]would make us think that these Fibres of theLigamentum Ciliare, are capable of Contraction, and voluntary Dilatation, like that of the Fibres of the Muscles; and that this Action may augment, or diminish the Convexity of theCrystallinus, according as the Need which the Distance of the Objects may make it to have on the Eye, to see more clearly and distinctly.Anat. Descrip. of aBear, p. 49.

Since my penning the foregoing Notes, having as critically as I could, dissected many Eyes of Birds, Beasts and Fishes, I manifestly found theMembrana Arachnoïdes, and will undertake to shew it any one, with great Ease and Certainty. It is indeed so transparent, as not to be seen distinct from theCrystalline. But if theCorneaandUveabe taken off before, or thevitreous Humourbehind it, and the out-side of theCrystallinebe gently cut, theArachnoïdesmay be seen to open, and theCrystallinewill easily leap out, and part from theLigamentum Ciliare; which otherwise it would not do: For it is by theArachnoïdesbraced to theLigamentum Ciliare. This Membrane or Tunick, in the Ox, is so substantial and strong, though thin, that it yields to, or sinks under the sharpest Lancet, and requires (for so thin and weak a Membrane in appearance) a strong Pressure to pierce it.

[dd]As Birds and Fishes are in divers Things conformable, so in some sort they are in their Eye; to enable it to correspond to all the Convergences, and Divergences of the Rays, which the Variations of each of the Mediums may produce. For this Service theTunica Choroeides, (in Fishes) hath a musculous Substance at the Bottom of it, lying round the optick Nerve, at a small Distance from it; by which Means I imagine they are able to contract, and dilate theChoroeides, and thereby to lengthen and shorten the Eye: For the helping in which Service, I imagine it is that theChoroeides, andSclerotica, are in a great Measure parted, that theChoroeidesmay have the greater Liberty of acting upon the Humours within.But in Birds, I have my self found, that although theChoroeidesbe parted from theSclerotica; yet theChoroeideshath no Muscle, but instead thereof, a curious pectinated Work, seated on the optick Nerve, represented inFig. 2.In whichc.a.e.b.d.represents theChoroeidesandSclerotica:a.b.the Part of theoptick Nerve, that is within the Eye:v.v.v.thevitreous Humour:a.f.g.b.thePecten:h.i.theCrystalline. For the Reception of thisPecten, theoptick Nervecomes farther within the Eye, than in other Creatures. The Structure of thisPecten, is very like that of theLigamentum Ciliare; and in the Eye of aMagpy, and some others, I could perceive it to be musculous towards the Bottom. ThisPectenis so firmly fixed unto, or embodied in thevitreous Humour, that thevitreous Humourhangs firmly to it, and is not so easily parted from it. By which Means all the Motions of thePectenare easily communicated to thevitreous Humour, and indeed to all contained in theChoroeides. And forasmuch as theCrystallineis connected to thevitreous Humour, therefore also the Alterations in thevitreous Humouraffect also theCrystalline; and theCrystallineis hereby brought nearer unto, or farther from theRetina, as occasion is. Besides all which Observables in theChoroeides, and inner Eye, I have also found this farther remarkable in theSclerotica, and outer-part of the Eye of Birds,viz.That the fore-part of theScleroticais horny and hard, the middle-part thin and flexible, andBracesintervene between the fore and hind-part, running between theChoroeidesandSclerotica; by which Means theCornea, and back-part of the Eye, are brought to the same Conformity, that the rest of the Eye hath.The great End and Design of this singular and curiousApparatusin the Eyes, both of Birds and Fishes, I take to be, 1. To enable those Creatures to see at all Distances, far off, or nigh; which (especially in the Waters) requireth a different Conformation of the Eye. In Birds also, this is of great Use, to enable them to see their Food at their Bill’s End, or to reach the utmost Distances their high Flights enable them to view; as to see over great Tracts of Sea or Land, whither they have occasion to fly; or to see their Food or Prey, even small Fishes in the Waters, and Birds, Worms,&c.on the Earth, when they sit upon Trees, high Rocks, or are hovering high in the Air. 2. To enable those Animals to adapt their Eye to all the various Refractions of theirMedium. Even the Air it self varies the Refractions, according as it is rarer or denser, more or less compressed; as is manifest from the learned and ingenious Mr.Lowthorp’s Experiment inPhil. Trans.Nᵒ. 257. and some other Experiments since of the before-commended Mr.Hawksbee, both in natural, rarify’d and compressed Air; in each of which, the Refractions constantly varied in exact Proportion to the Rarity or Density of the Air.Vid.Hawksbee’sExp.pag. 175,&c.Besides this Conformity in general, between the Eyes of Birds and Fishes,Du Hameltells us of a singular Conformity in theCormorant’s Eye, and that is, that theCrystallineis globous, as in Fishes, to enable it to see and pursue its Prey under Water: WhichJ. Faber, in Mr.Willoughbysaith, they dowith wonderful Swiftness, and for a long Time. Will. Ornithol. p. 329.

But in Birds, I have my self found, that although theChoroeidesbe parted from theSclerotica; yet theChoroeideshath no Muscle, but instead thereof, a curious pectinated Work, seated on the optick Nerve, represented inFig. 2.In whichc.a.e.b.d.represents theChoroeidesandSclerotica:a.b.the Part of theoptick Nerve, that is within the Eye:v.v.v.thevitreous Humour:a.f.g.b.thePecten:h.i.theCrystalline. For the Reception of thisPecten, theoptick Nervecomes farther within the Eye, than in other Creatures. The Structure of thisPecten, is very like that of theLigamentum Ciliare; and in the Eye of aMagpy, and some others, I could perceive it to be musculous towards the Bottom. ThisPectenis so firmly fixed unto, or embodied in thevitreous Humour, that thevitreous Humourhangs firmly to it, and is not so easily parted from it. By which Means all the Motions of thePectenare easily communicated to thevitreous Humour, and indeed to all contained in theChoroeides. And forasmuch as theCrystallineis connected to thevitreous Humour, therefore also the Alterations in thevitreous Humouraffect also theCrystalline; and theCrystallineis hereby brought nearer unto, or farther from theRetina, as occasion is. Besides all which Observables in theChoroeides, and inner Eye, I have also found this farther remarkable in theSclerotica, and outer-part of the Eye of Birds,viz.That the fore-part of theScleroticais horny and hard, the middle-part thin and flexible, andBracesintervene between the fore and hind-part, running between theChoroeidesandSclerotica; by which Means theCornea, and back-part of the Eye, are brought to the same Conformity, that the rest of the Eye hath.

The great End and Design of this singular and curiousApparatusin the Eyes, both of Birds and Fishes, I take to be, 1. To enable those Creatures to see at all Distances, far off, or nigh; which (especially in the Waters) requireth a different Conformation of the Eye. In Birds also, this is of great Use, to enable them to see their Food at their Bill’s End, or to reach the utmost Distances their high Flights enable them to view; as to see over great Tracts of Sea or Land, whither they have occasion to fly; or to see their Food or Prey, even small Fishes in the Waters, and Birds, Worms,&c.on the Earth, when they sit upon Trees, high Rocks, or are hovering high in the Air. 2. To enable those Animals to adapt their Eye to all the various Refractions of theirMedium. Even the Air it self varies the Refractions, according as it is rarer or denser, more or less compressed; as is manifest from the learned and ingenious Mr.Lowthorp’s Experiment inPhil. Trans.Nᵒ. 257. and some other Experiments since of the before-commended Mr.Hawksbee, both in natural, rarify’d and compressed Air; in each of which, the Refractions constantly varied in exact Proportion to the Rarity or Density of the Air.Vid.Hawksbee’sExp.pag. 175,&c.

Besides this Conformity in general, between the Eyes of Birds and Fishes,Du Hameltells us of a singular Conformity in theCormorant’s Eye, and that is, that theCrystallineis globous, as in Fishes, to enable it to see and pursue its Prey under Water: WhichJ. Faber, in Mr.Willoughbysaith, they dowith wonderful Swiftness, and for a long Time. Will. Ornithol. p. 329.

[ee]TheCrystalline Humour, when dry’d, doth manifestly enough appear to be made up of many very thin sphericalLaminæ, or Scales lying one upon another. Mr.Lewenhockreckons there may be 2000 of them in oneCrystalline, from the outermost to the Center. Every one of these Scales, he saith, he hath discovered to be made up of one single Fibre, or finest Thread wound, in a most stupendous Manner, this way, and that way, so as to run several Courses, and meet in as many Centers, and yet not to interfere, or cross one another, in any one Place. InOxen,Sheep,Hogs,DogsandCats, the Thread spreads into three several Courses, and makes as many Centers: InWhalesfive; but inHaresandRabbetsonly two. In the whole Surface of anOx’sCrystalline, he reckons there are more than 12000 Fibres juxtaposited. For the right and clear Understanding of the Manner of which admirable Piece of Mechanism, I shall refer to his Cuts and Descriptions inPhilos. Trans.Nᵒ. 165. and 293. The Truth hereof I have heard some ingenious Men question; but it is what I my self have seen, and can shew to any Body, with the Help of a good Microscope.

[ff]S. Malpighiobserved the Middle of theoptick Nerveof theSword-Fish, to be nothing else but a large Membrane, folded according to its Length in many Doubles, almost like a Fan, and invested by theDura mater; whereas in Land-Animals it is a Bundle of Fibres.V.Phil. Trans.Nᵒ. 27.

[gg]Certissimum est, quòd in omnibus Oculis humanis (quos saltem mihi dissecare contigit) Nervus opticus Pupillæ è diametro apponitur,&c.Briggs’s Ophthal. c. 3. §. 15. ItaWillis de Anim. Brut.p. 1. c. 15.Nervi Optici in nobis, item in Cane, Fele (& in cateris forsan animalibus calidis) ad fundum Oculi delati Pupilla regioni prospiciunt, dum interim in aliis Quadrupedibus, uti etiam in Piscibus & Volueribus, obliquè semper Tunica Sclerotidi inseruntur. Unde,&c.Willis Ib.c. 7. §. 11.

Nervi Optici in nobis, item in Cane, Fele (& in cateris forsan animalibus calidis) ad fundum Oculi delati Pupilla regioni prospiciunt, dum interim in aliis Quadrupedibus, uti etiam in Piscibus & Volueribus, obliquè semper Tunica Sclerotidi inseruntur. Unde,&c.Willis Ib.c. 7. §. 11.

[hh]This Pair is united at its Rise; whence is commonly drawn a Reason why one Eye being mov’d towards an Object, the other is directed also to the same.Gibson’s Anat.Book III. Chap. 11.SoBartholine Anat.Libellus 3. c. 2.

[ii]Among all the other Security the Eye hath, we may reckon the Reparation of theaqueous Humour; by which Means the Eye when wounded, and that in all Appearance very dangerously too, doth often recover its Sight: Of whichBern. Verzaschagives divers Examples ancient and modern. One is fromGalen, of a Boy so wounded, that theCorneafell, and became flaccid, but yet recovered his Sight. Other such like Instances also he gives fromRealdus Columbus,Rhodius, andTulpius; and one that he cured himself in these Words,Ego in Nobilissimi viri filiolâ similem casum observavi: hæc dum levibus de causis cum fratre altercaret, iste iracundiâ percitus cultellum Scriptorium apprehendit, & sororis oculo vulnus infligit, inde humor aqueus effluxit. Vocatus præsentem Chirurgum jussi sequens collyrium anodynum & exsiccans tepidè sæpiùs admovere.℞aq. Plantag.℥iv.Rosar. Sanicul. Euphras.anaTrochisc. alb. Rhaf. cum Opio℈ii.Tutiæ pp.℈i.Croci orient.℈ss. M.Hoc Collyrium inflammationem compescuit, vulnus siccavit & sanavit. Hinc post aliquot menses Humor aqueus succrevit. Nam visus, sed dibilior, cum summo parentum gaudio redivit.B. Verzaschæ Observ. Medicæ. Obs. 14.Another Cure of this kind, was experimented by Dr.Daniel Major, upon a Goose, Ann. 1670, theaqueous Humourof both whose Eyes they let out, so that the Eyes fell, and theGoosebecame quite blind: But without the Use of any Medicine, in about two Days Time, Nature repaired the watery Humour again, the Eyes returned to their Former Turgency, and theGoosewas in a Week after produced seeing before twenty eight or thirty Spectators.Ephem. Germ.T. 1. Add. ad. Obs. 117.From the same Cause, I doubt not, it was that the Eye of a Gentleman’s Daughter, and those of a Cock, when wounded, so that theCorneasunk, were restored by aLithuanianChymist, that passed for a Conjurer, by the Use of a Liquor found inMay, in the Vesiculæ ofElm. Of which see Mr.Ray’s Catal. Cantab.inUlmusfromHenr. ab Heers.

Another Cure of this kind, was experimented by Dr.Daniel Major, upon a Goose, Ann. 1670, theaqueous Humourof both whose Eyes they let out, so that the Eyes fell, and theGoosebecame quite blind: But without the Use of any Medicine, in about two Days Time, Nature repaired the watery Humour again, the Eyes returned to their Former Turgency, and theGoosewas in a Week after produced seeing before twenty eight or thirty Spectators.Ephem. Germ.T. 1. Add. ad. Obs. 117.

From the same Cause, I doubt not, it was that the Eye of a Gentleman’s Daughter, and those of a Cock, when wounded, so that theCorneasunk, were restored by aLithuanianChymist, that passed for a Conjurer, by the Use of a Liquor found inMay, in the Vesiculæ ofElm. Of which see Mr.Ray’s Catal. Cantab.inUlmusfromHenr. ab Heers.

[kk]Palpebræ, quæ sunt tegumenta Oculorum, mollissimæ tactu, nè lederent aciem, aptissimæ factæ, & ad claudendas Pupillas, nè quid incideret, & ad aperiendas; idque providit, ut identidem fieri posset cum maximâ celeritate. Munitæque sunt Palpebræ tanquàm vallo pilorum: quibus & apertis Oculis, si quid incideret, repelleretur, & somno conniventibus, cùm Oculis ad cernendum non egerimus, ut qui, tanquàm involuti, quièscerent. Latent prætereà utiliter, & excelsis undique partibus sepiuntur. Primùm enim superiora Superciliis obducta sudorem à capitæ, & fronte destuentem repellunt. Genæ deinde ab inferiore parte tutantur subjectæ, leviterque eminentes.Cicer. de Nat. Deor. L. 2. c. 57.Tully, in the Person of aStoick, having so well accounted for the Use of theEye-Lids, I shall for a further Manifestation of the Creator’s Contrivance and Structure of them, take notice of two or three Things: 1. They consist of a thin and flexible, but strong Skin, by which means they the better wipe, clean, and guard theCornea. 2. Their Edges are fortified with a softCartilage, by which means they are not only enabled the better to do their Office, but also to close and shut the better. 3. Out of these Cartilages grow a Pallisade of stiff Hairs, of great Use to warn the Eye of the Invasion of Dangers, to keep off Motes, and to shut out too excessive Light,&c.and at the same time to admit of (through their Intervals) a sufficient Passage for Objects to approach the Eye. And it is remarkable, that these Hairs grow but to a certain, commodious Length, and need no cutting, as many other Hairs of the Body do: Also, that their Points stand out of the way, and in the upper-lid bend upwards, as they do downwards in the lower lid, whereby they are well adapted to their Use. From which last Observables, we may learn how critical and nice the great Author of Nature hath been, in even the least and most trivial Conveniencies belonging to Animal Bodies; for which Reason I have added it toTully’s Remarks. And more might have been added too, as particularly concerning the curious Structure and Lodgment of theRight Muscle, which opens the Eye-Lids; and theOrbicularis, orCircularone, that shuts them; the niceApparatusof Glands that keep the Eye moist, and serve forTears; together with the Reason why Man alone, who is a social Animal, doth exhibit his social Affections by such outward Tokens asTears; theNervesalso, and other Organs acting in this Ministry. I might also speak of the Passages for discharging the superfluous Moisture of the Eyes through the Nostrils, and much more of the like kind. But it would take up too much Room in these Notes; and therefore it shall suffice to give only such Hints as may create a Suspicion of a noble Œconomy and Contrivance in this (I had almost said) least considerable part of the Eye. But for Particulars I shall refer to the Anatomists; and for some of these Things, particularly to Dr.Willis’sCereb. Anat.andde Anim. Brut.and Mr.Cowper’s Elegant Cuts in the 11ᵗʰTab.of hisAnatomy.To the Eye-Lids we may add another Guard afforded the Eyes of most Quadrupeds, Birds, and Fishes, by thenictitating Membrane, which Dr.Willisgives this Account of,Plurimis[Animalibus]quibus Musculus suspensorius adest(which Limitation he needed not to have added)etiam alter Membranosus conceditur, qui juxta interiorem oculi canthum situs, quando elevatur, Oculi globum ferè totum obtegit. Hujus usus esse videtur, ut cùm Bestiæ inter gramina,&c.capita sua propter victum capessendum demergunt, hic Musculus Oculi Pupillam, nè à stipularum incursu seriatur, oculit, munitque.De Anim. Brut. p. 1. c. 15.This Membrane Man hath not, he having little Occasion to thrust his Head into such Places of Annoyance, as Beasts and other Animals; or if he hath, he can defend his Eyes with his Hands. But Birds (who frequent Trees and Bushes) and Quadrupeds, (Hedges and long Grass) and who have no part ready, like the Hand, to fence off Annoyances; these, I say, have this incomparable Provision made for the Safety of their Eyes. And for Fishes, as they are destitute of Eye-Lids, because in the Waters there is no occasion for a Defensative against Dust and Motes, offensive to the Eyes of Land Animals, nor to moisten and wipe the Eyes, as the Eye-Lids do, so theNictitating-Membraneis an abundant Provision for all their Occasions, without the Addition of the Eye-Lids.And now, if we reflect, are these the Works of any Thing but a wise and indulgent Agent?

Tully, in the Person of aStoick, having so well accounted for the Use of theEye-Lids, I shall for a further Manifestation of the Creator’s Contrivance and Structure of them, take notice of two or three Things: 1. They consist of a thin and flexible, but strong Skin, by which means they the better wipe, clean, and guard theCornea. 2. Their Edges are fortified with a softCartilage, by which means they are not only enabled the better to do their Office, but also to close and shut the better. 3. Out of these Cartilages grow a Pallisade of stiff Hairs, of great Use to warn the Eye of the Invasion of Dangers, to keep off Motes, and to shut out too excessive Light,&c.and at the same time to admit of (through their Intervals) a sufficient Passage for Objects to approach the Eye. And it is remarkable, that these Hairs grow but to a certain, commodious Length, and need no cutting, as many other Hairs of the Body do: Also, that their Points stand out of the way, and in the upper-lid bend upwards, as they do downwards in the lower lid, whereby they are well adapted to their Use. From which last Observables, we may learn how critical and nice the great Author of Nature hath been, in even the least and most trivial Conveniencies belonging to Animal Bodies; for which Reason I have added it toTully’s Remarks. And more might have been added too, as particularly concerning the curious Structure and Lodgment of theRight Muscle, which opens the Eye-Lids; and theOrbicularis, orCircularone, that shuts them; the niceApparatusof Glands that keep the Eye moist, and serve forTears; together with the Reason why Man alone, who is a social Animal, doth exhibit his social Affections by such outward Tokens asTears; theNervesalso, and other Organs acting in this Ministry. I might also speak of the Passages for discharging the superfluous Moisture of the Eyes through the Nostrils, and much more of the like kind. But it would take up too much Room in these Notes; and therefore it shall suffice to give only such Hints as may create a Suspicion of a noble Œconomy and Contrivance in this (I had almost said) least considerable part of the Eye. But for Particulars I shall refer to the Anatomists; and for some of these Things, particularly to Dr.Willis’sCereb. Anat.andde Anim. Brut.and Mr.Cowper’s Elegant Cuts in the 11ᵗʰTab.of hisAnatomy.

To the Eye-Lids we may add another Guard afforded the Eyes of most Quadrupeds, Birds, and Fishes, by thenictitating Membrane, which Dr.Willisgives this Account of,Plurimis[Animalibus]quibus Musculus suspensorius adest(which Limitation he needed not to have added)etiam alter Membranosus conceditur, qui juxta interiorem oculi canthum situs, quando elevatur, Oculi globum ferè totum obtegit. Hujus usus esse videtur, ut cùm Bestiæ inter gramina,&c.capita sua propter victum capessendum demergunt, hic Musculus Oculi Pupillam, nè à stipularum incursu seriatur, oculit, munitque.De Anim. Brut. p. 1. c. 15.

This Membrane Man hath not, he having little Occasion to thrust his Head into such Places of Annoyance, as Beasts and other Animals; or if he hath, he can defend his Eyes with his Hands. But Birds (who frequent Trees and Bushes) and Quadrupeds, (Hedges and long Grass) and who have no part ready, like the Hand, to fence off Annoyances; these, I say, have this incomparable Provision made for the Safety of their Eyes. And for Fishes, as they are destitute of Eye-Lids, because in the Waters there is no occasion for a Defensative against Dust and Motes, offensive to the Eyes of Land Animals, nor to moisten and wipe the Eyes, as the Eye-Lids do, so theNictitating-Membraneis an abundant Provision for all their Occasions, without the Addition of the Eye-Lids.

And now, if we reflect, are these the Works of any Thing but a wise and indulgent Agent?

[ll]Although the Hardness and Firmness of theAdnata, orScleroticain Birds, is a good Guard to their Eyes, yet I do not think it is made thus, so much for a Defence, as to minister to the lengthning and shortning the Eye, mentioned before inNote (cc).

[mm]Cochleis oculorum vicem Cornicula bina pratentu implent.Plin. Nat. Hist. l. 11. c. 37. See more of the Eyes ofSnailsbefore inNote (k); and inNote (l), I said that I suspectedMolesalso might thrust out, or withdraw their Eyes more or less within the Hair or Skin.

[nn]The diligentSturmiuswas fully persuaded there could not be any speculative Atheism in any one that should well survey the Eye.Nobis, saith he,fuit persuasissimum. Atheismum, quem vocant speculativum, h. e. obsirmatam de Deitate in Universo nullâ persuasionem, habere locum aut inveniri non posse in eo homine, qui vel unius corporis organici, & speciatim Oculi fabricam attento animo aspexerit.Sturm. Exerc. Acad. 9. De Vis. Organ. & Rat. in Epilogo.

[oo]The glorious Landskips, and other Objects that present themselves to the Eye, are manifestly painted on theRetina, and that not erect, but inverted as the Laws of Opticks require; and is manifest to the Eye fromMonsieur Cartes’s Experiment, of laying bare the vitreous Humour on the back part of the Eye, and clapping over it a Bit of white Paper, or the Skin of an Egg; and then placing the fore-part of the Eye to the Hole of the Window of a darkned Room. By which means we have a pretty Landskip of the Objects abroad invertedly painted on the Paper, on the back of the Eye. But now the Question is, How in this Case the Eye comes to see the Objects erect?Monsieur Cartes’s Answer is,Notitia illius ex nullâ imagine pendet, nec ex ullâ actione ab objectis veniente, sed ex solo situ exiguarum partium cerebri, è quibus Nervi expullulant.——E.g. cogitandum in Oculo——situm capillamenti nervi optici——respondere ad alium quendam partis cerebri——qui facit ut Anima singula loca cognoscat, quæ jacent in rectâ, aut quasi rectâ lineæ; ut ita mirari non debeamus corpora in naturali situ videri, quamvis imago in oculo delineata contrarium habeat.Dioptr. c. 6. But our most ingenious Mr.Molyneuxanswereth thus,The Eye is only the Organ or Instrument, ’tis the Soul that sees by means of the Eye. To enquire then how the Soul perceives the Object erect, by an inverted Image, is to enquire into the Soul’s Faculties——But erect and inverted are only Terms of Relation to up and down; or farther from, or nigher to the Center of the Earth, in Parts of the same Thing.——But the Eye, or visive Faculty takes no notice of the internal Posture of its own Parts, but useth them as an Instrument only, contrived by Nature for the Exercise of such a Faculty.——Let us imagine, that the Eye(on its lower Part)receives an Impulse[by a Ray from the upper part of the Object]must not the visive Faculty be necessarily directed hereby to consider this Stroke, as coming from the top rather than the bottom[of the Object]and consequently be directed to conclude it the Representation of the top? Hereof we may be satisfied, by supposing a Man standing on his Head. For here, though the upper Parts of Objects are painted on the upper Parts of the Eye, yet the Objects are judged to be erect. What is said of Erect and Reverse, may be understood of Sinister and Dexter.Molyneux’s Dioptr. Nov. Part I. Prop. 28.

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