Chapter VI: Book IV: Of Animals in general (1)

In the last BOOK, having survey’d the Earth it self in Particular, I shall next take a View of the Inhabitants thereof; or the several Kinds of Creatures[a], that have their Habitation, Growth, or Subsistence thereon.

These Creatures are either Sensitive, or Insensitive Creatures.

In speaking of those endow’d with Sense, I shall consider:

I. Some Things common to them all.

II. Things peculiar to their Tribes.

I. The Things in common, which I intend to take Notice of, are these Ten:

1. The five _Senses_, and their Organs.

2. The great Instrument of Vitality, _Respiration_.

3. The _Motion_, or Loco-motive Faculty of Animals.

4. The _Place_, in which they live and act.

5. The _Balance_ of their Numbers.

6. Their _Food_.

7. Their _Cloathing_.

8. Their _Houses_, _Nests_ or _Habitations_.

9. Their Methods of _Self-Preservation_.

10. Their _Generation_, and _Conservation_ of their Species by that Means.

FOOTNOTES:

[a]

_Principio cœlum, ac terras, camposque liquentes,_
_Lucentemque globum Lunæ, Titaniaque astra_
_Spiritus intùs alit, totamque infusa per artus_
_Mens agitat molem, & magno se corpore miscet._
_Inde hominem, pecudumque genus, vitæque volantum,_
_Et quæ marmoreo fert monstra sub æquore pontus._
_Igneus est illis vigor, & cœlestis origo_
_Seminibus._

Virgil. Æneid. L. 6. Carm. 724.

CHAP. I.

_Of the five Senses in general._

The first Thing to be consider’d, in common to all the Sensitive Creatures, is, their Faculty of _Seeing_, _Hearing_, _Smelling_, _Tasting_ and _Feeling_; and the _Organs_ ministring to there five _Senses_, together with the exact Accommodation of those Senses, and their Organs, to the State and Make of every Tribe of Animals[a]. The Consideration of which Particulars alone, were there no other Demonstrations of God, is abundantly sufficient to evince the infinite Wisdom, Power and Goodness, of the great Creator. For, Who can but stand amaz’d at the Glories of these Works! At the admirable Artifice of them! And at their noble Use and Performances! For suppose an Animal, as such, had Breath and Life, and could move it self hither and thither; yet how could it know whither to go, what it was about, where to find its Food, how to avoid thousands of Dangers[b], without Sight! How could Man, particularly, view the Glories of the Heavens, survey the Beauties of the Fields, and enjoy the Pleasure of beholding the noble Variety of diverting objects, that do, above us in the Heavens, and here in this lower World, present themselves to our View every where; how enjoy this, I say, without that admirable Sense of _Sight_[c]! How could also the Animal, without _Smell_ and _Taste_, distinguish its Food, and discern between wholsome and unwholsome; besides the Pleasures of delightful Odours, and relishing Gusto’s! How, without that other Sense of _Hearing_, could it discern many Dangers that are at a Distance, understand the Mind of others, perceive the harmonious Sounds of Musick, and be delighted with the Melodies of the winged Choir, and all the rest of the Harmonies the Creator hath provided for the Delight and Pleasure of his Creatures! And lastly, How could Man, or any other Creature distinguish Pleasure from Pain, Health from Sickness, and consequently be able to keep their Body sound and entire, without the Sense of _Feeling_! Here, therefore, we have a glorious Oeconomy in every Animal, that commandeth Admiration, and deserveth our Contemplation: As will better appear by coming to Particulars, and distinctly considering the Provision which the Creator hath made for each of these Senses.

FOOTNOTES:

[a] _Ex sensibus ante cætera Homini Tactus, deinde Gustatus: reliquis superatur à multis. Aquilæ clariùs cernunt: Vultures sagaciùs ordorantur, liquidiùs audiunt Talpæ obrutæ terrâ, tam denso atque surdo naturæ elemento._ Plin. Nat. Hist. l. 10. c. 69.

[b] _Subjacent Oculi, pars corporis pretiosissima, & qui lucis usu vitam distinguant à morte._ Plin. Nat. Hist. l. 11. c. 37.

[c] _Fœminæ aliquæ Megarenses solis oculis discernere valebant inter Ova quæ ex Gallinâ nigrâ, & quæ ex albâ nata sunt_, is what is affirmed (how truly I know not) by _Grimald. de Lumin. & Color. Pr._ 43. §. 60.

CHAP. II.

_Of the Eye._

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

1. The _Form_ of the Eye.

2. Its _Situation_ in the Body.

3. Its _Motions_.

4. Its _Size_.

5. Its _Number_.

6. Its _Parts_.

7. The _Guard_ and _Security_ Nature 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 the _Form_ of 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 the _Retina_, 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. The _Situation_ of 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, in the 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, the _Motions_ of 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 she hath 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 probably more 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, the _Mole_[m]. As the Habitation of that 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, its _Numbers_; 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 the Misfortune 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 manifest Sign 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 the _Parts_ and _Mechanism_ of 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 its _Muscles_. These we shall find exactly and neatly placed for every Motion of the Eye. Let us view its _Tunicks_, 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 common Inconveniences and Annoyances. Let us examine its three _Humours_, 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 the _Crystalline 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 the _Muscles_ of the Eye, and their Equilibration. Nothing can be more manifestly an act of Contrivance and Design, than the _Muscles_ of the Eye, admirably adapted to move it any, and every way; upwards, downwards, to this side or that, or howsoever we 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 the _Trochlearis_, and the Augmentation of its Power by the _Trochlea_[r]; the Magnitude and Strength of the _Attollent Muscle_, somewhat exceeding that of its Antagonist; the peculiar Muscle, called the _Seventh_, or _Suspensory Muscle_[s], given to Brutes, by reason of the prone Posture of their Bodies, and frequent Occasions to hang down their Heads: And I might speak also of the peculiar Origine and Insertion of the _lower 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 these _Opposite_ and _Antagonist Muscles_, affected partly by the Equality of the Strength; which is the Case of the _Adducent_ and _Abducent Muscles_; partly by their peculiar Origine, or the Addition of the _Trochlea_, which is the Case of the _Oblique Muscles_[u]: and partly by the natural Posture of the Body, and the Eye, which is the Case of the _Attollent_ and _Depriment Muscles_. By this so curious and exact a Libration, not only unseemly Contortions, and incommodious Vagations of the Eye are prevented, but also it is able with great Readiness and Exactness to apply it self to every Object.

As to the _Tunicks_ of the Eye, many Things might be taken notice of, the prodigious Fineness of the _Arachnoïdes_, the acute Sense of the _Retina_, the delicate Transparency of the _Cornea_[w], and the firm and strong Texture of that and the _Sclerotica_ too; 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 the _Uvea_ which makes the _Pupil_. 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 their peculiar 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 the _Tunicks_.

The next Thing I shall take notice of, will relate to the _Humours_ of the Eye, and that only concerning the Mechanism of the _Crystalline Humour_; not its incomparable Transparency; nor its exact lenticular Form; nor its curious araneous Membrane[cc], that constringeth and dilateth it, and so varieth its _Focus_, (if any such Variation there be, as some affirm with great Probability,) nor lastly, its admirable Approach to or from the _Retina_, by help of the _Ciliar Ligament_[dd], according as Objects 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], composed of 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, an _Optick 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 its _Nerves_. And here, among others, the admirable Make of the _Optick Nerves_ might deserve to be taken notice of in the first Place, their _Medullary_ Part[ff] terminating in the Brain it self, the Teguments propagated from the _Meninges_, 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 others obliquely 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 the _Third Pair_ of Nerves, called the _Motory 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

_Seventh_ and last Place, Let us consider what Provision this admirable Artist hath made for the _Guard_ and _Security_ of this so well formed Organ[ii]. And here 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, particularly Birds[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 withdrawing its 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 than GOD, 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 great GOD, 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 Alacrity and 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], and fill 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 of _Hearing_.

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_, whose _Ophthalmography_ I 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 Reason _Frier Bacon_ assigns 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. _Briggs_ saith, _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 the _Retina_, or back part flat for the Reception of the Images, as in _Fig. 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 the _Retina_ lying 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, (which _Sturmius_ calls his Artificial Eye, in his _Exercit. 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 of _Pliny_, no doubt our famous Romancer Sir _J. Mandevile_, had his Romnantick Stories related in his Travels.

[e] See _Book V. Chap. 2. Note (e)._

[f] _Galen_ deserves to be here consulted, who in his Book _De 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 in _Hares_ and _Conies_, 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 in _Dogs_, (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 of ~Spiders~, ~(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 her ~per saltum~, (as they do) without any Motion of the Head to discover her: Which Motion would have scared away so timorous an Insect._ _~Power~’s_ Micros. Observ. pag. 11.

_The Eyes of the ~Cameleon~ resemble 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. _Goddard_ in 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 the ~Pupilla~ under the Crest which makes the Eye-brow, and so far into the ~Canthi~, 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] _Snails_ send 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. _Power_ wordeth it. _Obs. 31. pag. 36._ So the ingenious Dr. _Lister_. _Exercit. Anat. Cochl. & Limac._

[l] _Vid._ _l. 8. c. 3. Note (a)._

[m] _Severinus_ is of _Aristotle_’s, _Pliny_’s, and _Alb. Magnus_’s Opinion, that the _Mole_ hath no Sight; _G. Seger_ denies any Humour to be therein, but thinks they may probably see, because Nature made nothing in vain. But _Borrichius_ saith, their Eyes have _appendiculam 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 the _Eyes_ of _Moles_, 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 the _Vitreous_ and _Crystalline_ Humours, yea, the _Ligamentum Ciliare_, and the atramentaceous _Mucus_. The _Pupil_ I could manifestly discern to be round, and the _Cornea_ copped, 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, (as _Snails_) yet more or less within the Hair, as they have more or less Occasion to use or guard their Eyes.

_Galen_ saith, _Moles_ have Eyes, the _Crystalline_ and _Vitreous_ Humours, encompassed with _Tunicks_. _De Us. Part. l. 14. c. 6._ So accurate an Anatomist was he for his Time.

[n] _Pliny_ tells us of a sort of _Heron_ with 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 the _Nigræ_ that 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. This _Galen_, and others after him, generally thought to be from a Coalition or Decussation of the Optick Nerves, behind the _Os Sphenoïdes_. But whether they decussate, coalesce, or only touch one another, they do not well agree. The _Bartholines_ expressly assert they are united, _non per simplicem contactum vel intersectionem in homine, sed totalem substantiæ confusionem_, Anat. l. 3. c. 2. And whereas _Vesalius_, 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, they _are 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 Monsieur _Cartes_ is of Opinion, that the _Fibrillæ_ constituting the medullary Part of those Nerves, being spread in the _Retina_ of each Eye, have each of them corresponding Parts in the Brain; so that when any of those _Fibrillæ_ are 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 under _Note (oo)_, from _Cartes_ himself.

Somewhat like this is the Notion of our judicious Dr. _Briggs_, who thinks the Optick Nerves of each Eye consist of _Homologous Fibres_, having their rise in the _Thalamus Nervorum Opticorum_, and thence continued to both the _Retinæ_, which are made of them; And farther, that those _Fibrillæ_ have the same Parallelism, Tension, _&c._ in both Eyes; and consequently when an Image is painted on the same corresponding, sympathizing Parts of each _Retina_, the same Effects are produced, the same Notice or Information is carried to the _Thalamus_, and so imparted to the Soul, or judging Faculty. That there is such an Ὁμοιοπάθεια between the _Retina_, &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. and _Nov. Vis. Theor._ _passim_.

What the Opinion of our justly eminent Sir _Isaac Newton_ is, may be seen in his _Opticks_, 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 was _Bartholine Anat._ l. 3. c. 8. and divers other eminent Anatomists.

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

The _Musculus Suspensorius_ being in the _Porpess_, as well as Brutes, Dr. _Tyson_ thinks the Use of it is not to suspend the Bulk of the Eye; but rather by its equal Contraction of the _Sclerotis_, 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 the _Oblique Muscles_. Brigg’s _Nova Vis. Theor._ p. 11. _meo libro_.

[u] Besides those particular Motions which the Eye receives from the _Oblique 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 the ~Ligamentum Ciliate~ contracts, or both the ~Oblique Muscles~ squeeze 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._ See _Note (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] _Boyl_ of _Final Causes._

[y] It is easy to be observed, that the _Pupil_ openeth 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 the _Pupil_ some say, is effected by the circular and strait Fibres of the _Uvea_, and some attribute it to the _Ligamentum Ciliare_. Yet I have no great doubt but that they both concur in that Action, and that the _Ligamentum Ciliare_ doth, at the same time the Pupil opens or shuts, dilate or compress the _Crystalline_, and bring it nigher unto, or carry it farther off the _Retina_. For the Structure of the _Ligamentum 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.~_ Willis _de Anim. Brut._ p. 1. c. 15.

[aa] Thus _Cats_ (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. _Willis_ thus; _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 the _Tapetum_, in the Bottom of the Eye, or the shining of the _Retina_, round the optick Nerve.

Besides which, he saith, the _Iris_ hath 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, _Pliny_ tells us, was reported of _Tiberius 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] The _Tunica Aranea_ is taken notice of by _Frier 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 the _Cornea_ (as the Skin is of old Persons) he thinks is the Cause of the Obscurity of the Sight in such Persons. _Bacon_ Ib. par. 2. cap. 2. But this _Tunick_ some deny, and others allow of: Dr. _A. M._ of _Trinity-College, Dublin_, (in his _Relat. of Anat. Obs._ in the Eyes of Animals, in a Letter to Mr. _Boyl_, _Ann. 1682._ annexed to his _Anat. Account of the Elephant burnt in ~Dublin~_, p. 57.) affirms the _Tunica Aranea_, and saith, _I have often seen it before ’twas exposed to the Air one Minute, notwithstanding what Dr. ~Briggs~ saith to the contrary, ~&c.~_ But Dr. _Briggs_ his 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._

The _Crystalline Humour_ being 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 the _Ligamentum Ciliare_; Dr. _Grew_ doth, upon these Accounts, not doubt to ascribe to the _Ligamentum Ciliare_, a Power of making the _Crystalline_ more Convex, as well as of moving it to, or from the _Retina_. See _Grew_’s _Cosmolog. 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 the _Crystalline Humour_ should be made more Convex, or more flat; or else an Elongation, or shortning of the Eye, or of the Distance between the _Crystalline Humour_ and the _Retina_.

But although Dr. _Briggs_ (so good a Judge) denies the _Tunica 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 the _French Anatomists_, of the _Crystalline_ of the Eye, of the _Gemp_ or _Chamois_, 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 the _Ligamentum Ciliare_ on one side, and Dilatation on the other] _would make us think that these Fibres of the ~Ligamentum 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 the ~Crystallinus~, 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 a _Bear_, 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 the _Membrana 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 the _Crystalline_. But if the _Cornea_ and _Uvea_ be taken off before, or the _vitreous Humour_ behind it, and the out-side of the _Crystalline_ be gently cut, the _Arachnoïdes_ may be seen to open, and the _Crystalline_ will easily leap out, and part from the _Ligamentum Ciliare_; which otherwise it would not do: For it is by the _Arachnoïdes_ braced to the _Ligamentum 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 the _Tunica 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 the _Choroeides_, and thereby to lengthen and shorten the Eye: For the helping in which Service, I imagine it is that the _Choroeides_, and _Sclerotica_, are in a great Measure parted, that the _Choroeides_ may have the greater Liberty of acting upon the Humours within.

But in Birds, I have my self found, that although the _Choroeides_ be parted from the _Sclerotica_; yet the _Choroeides_ hath no Muscle, but instead thereof, a curious pectinated Work, seated on the optick Nerve, represented in _Fig. 2._ In which _c.a.e.b.d._ represents the _Choroeides_ and _Sclerotica_: _a.b._ the Part of the _optick Nerve_, that is within the Eye: _v.v.v._ the _vitreous Humour_: _a.f.g.b._ the _Pecten_: _h.i._ the _Crystalline_. For the Reception of this _Pecten_, the _optick Nerve_ comes farther within the Eye, than in other Creatures. The Structure of this _Pecten_, is very like that of the _Ligamentum Ciliare_; and in the Eye of a _Magpy_, and some others, I could perceive it to be musculous towards the Bottom. This _Pecten_ is so firmly fixed unto, or embodied in the _vitreous Humour_, that the _vitreous Humour_ hangs firmly to it, and is not so easily parted from it. By which Means all the Motions of the _Pecten_ are easily communicated to the _vitreous Humour_, and indeed to all contained in the _Choroeides_. And forasmuch as the _Crystalline_ is connected to the _vitreous Humour_, therefore also the Alterations in the _vitreous Humour_ affect also the _Crystalline_; and the _Crystalline_ is hereby brought nearer unto, or farther from the _Retina_, as occasion is. Besides all which Observables in the _Choroeides_, and inner Eye, I have also found this farther remarkable in the _Sclerotica_, and outer-part of the Eye of Birds, _viz._ That the fore-part of the _Sclerotica_ is horny and hard, the middle-part thin and flexible, and _Braces_ intervene between the fore and hind-part, running between the _Choroeides_ and _Sclerotica_; by which Means the _Cornea_, 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 curious _Apparatus_ in 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 their _Medium_. 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 in _Phil. 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_’s _Exp._ pag. 175, _&c._

Besides this Conformity in general, between the Eyes of Birds and Fishes, _Du Hamel_ tells us of a singular Conformity in the _Cormorant_’s Eye, and that is, that the _Crystalline_ is globous, as in Fishes, to enable it to see and pursue its Prey under Water: Which _J. Faber_, in Mr. _Willoughby_ saith, they do _with wonderful Swiftness, and for a long Time_. Will. Ornithol. p. 329.

[ee] The _Crystalline Humour_, when dry’d, doth manifestly enough appear to be made up of many very thin spherical _Laminæ_, or Scales lying one upon another. Mr. _Lewenhock_ reckons there may be 2000 of them in one _Crystalline_, 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. In _Oxen_, _Sheep_, _Hogs_, _Dogs_ and _Cats_, the Thread spreads into three several Courses, and makes as many Centers: In _Whales_ five; but in _Hares_ and _Rabbets_ only two. In the whole Surface of an _Ox_’s _Crystalline_, 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 in _Philos. 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. Malpighi_ observed the Middle of the _optick Nerve_ of the _Sword-Fish_, to be nothing else but a large Membrane, folded according to its Length in many Doubles, almost like a Fan, and invested by the _Dura 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. Ita _Willis 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._ So _Bartholine Anat._ Libellus 3. c. 2.