Misfortune of the Lofs of one of these noble, and neceffary Organs of its Body.

But then befides all this, there is another Thing confiderable 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 feen with two or more Eyes (p). A manifeft

(p) The moft celebrated Anatomifts differ greatly about the Reafon why we fee not double with two Eyes. This Galen, and others after him, generally thought to be from a Coalition or Decuffation of the Optick Nerves, behind the Os Sphenoides. But whether they decuffate, coalefce, or only touch one another, they do not well agree. The Bartholines expreffly affert they are united, non per fimplicem contatium vel interfectionem in homine, fed totalem fubftantia confufionem, Anat. 1. 3. c. 2. And whereas Vefalius, and fome others had found fome Inftances of their being difunited; they fay, fed in plerifque ordinariè confunditur interior fubftantia, ut accuratâ difquifitione deprehendi.

But our Learned Dr. Gibfon, (Anat. l. 3. c. 10.) faith, they are united by the closest Conjunction, but not Confufion of their Fibres.

But others think the Reafon is not from any Coalefcence, Contact, or croffing of the Optick Nerves, but from a Sympathy between them. Thus Monfieur Cartes is of Opinion, that the Fibrilla conftituting the medullary Part of those Nerves, being spread in the Retina of each Eye, have each of them correfponding Parts in the Brain; fo that when any of thofe Fibrilla are ftruck by any part of an Image, the correfponding Parts of the Brain are thereby affected, and the Soul thereby informed, &c. but fee more hereafter under Note (00), from Cartes himself.

Somewhat like this is the Notion of our judicious Dr. Briggs, who thinks the Optick Nerves of each Eye confift of Homologous Fibres, having their rife in the Thalamus Nervorum Opticorum, and thence continued to both the Retina, which are made of them; And farther, that those Fibrilla have the fame Parallelifm, Tenfion, &c in both Eyes; and confequently when an Image is painted on the fame correfponding, fympathizing Parts of each Retina, the fame Effects are produced, the fame Notice or Information is carried to the Thalamus, and fo imparted to the Soul, or judging Faculty. That there is fuch an 'Omosomalea between the

nifeft Sign of the infinite Skill of the Contriver of this fo noble a Part, and of the exquifite Art heemployed in the Formation thereof. But the Defign and Skill of the infinite Workman, will beft be fet 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 confider the prodigious Exactness, and the exquifite Skill employed in every part miniftring to this noble and neceffary Senfe. To pafs by its Arteries and Veins, and fuch other Parts common to the rest of the Body, let us caft our Eye on its Mufcles. These we fhall find exactly and neatly placed for every Motion of the Eye. Let us view its Tunicks, and these we fhall find fo admirably feated, fo well adapted, and of fo firm a Texture, as to fit every Place, to answer every Occafion, and to be Proof against all common

Retina, &c. he makes very probable from the enfuing of double Vifion upon the Interruption of the Parallelifm of the Eyes; as when one Eye is depreffed with the Finger, or their Symphony interrupted by Difeafe, Drunkenness, &c. And lastly, That fimple Vifion is not made in the former way, viz. by a Decuffation or Conjunction of the Optick Nerves, he proves, because thofe Nerves are but in few Subjects decuffated, and in none conjoined otherwife than by a bare Contact, which is particularly manifeft in Fifhes; and in fome Inftances it hath been found, that they have been separated without any double Vifion enfuing thereupon. Vid. Brig. Ophthalmogr. cap. 11. & 5. and Nov. Vif. Theor. paffim.

What the Opinion of our juftly eminent Sir Ifaac Newton is, may be seen in his Opticks, Qu. 15. Are not the Species of Objects feen with both Eyes, united where the Optick Nerves meet before they come into the Brain, the Fibres on the right fide of both Nerves uniting there, &c. For the Optick Nerves of fuch Animals as look the fame way with both Eyes, (as of Men, Dogs, Sheep, Oxen, &c.) meet before they come into the Brain; but the Optick Nerves of fuch Animals as do not look the fame way with both Eyes, (as of Fishes and of the Cameleon) do not meet, if I am rightly informed. Newt. Opt. Q. 15.

Inconve

Inconveniences and Annoyances. Let us examine its three Humours, and thefe we fhall find all of exquifite Clearnefs and Tranfparency, for an eaty Admiffion of the Rays; well placed for the refracting of them, and formed (particularly the Crystalline Humour) by the niceft Laws of Opticks, to collect the wandring Rays into a Point. And to name no more, let us look into its darkned Cell, where thofe curious Humours lie, and into which the Glories of the Heavens and the Earth are brought, and exquifitely pictured; and this Cell we fhall find, without, well prepared by Means of its Texture, Aperture, and Colour, to fence off all the ufelefs or noxious Rays; and within, as well coated with a dark Tegument, that it may not reflect, diffipate, or any way confufe or difturb the beneficial Rays (9).

But to defcend to Particulars, although it would. be a great Demonftration of the Glory of God, yet would take up too much Time, and hath been in fome Measure done by others that have written of God's Works. Paffing over therefore what they have obferved, I fhall under each principal Part take a tranfient Notice of fome Things they have omitted, or but flightly spoken of.

And my firft Remark fhall be concerning the Mufcles of the Eye, and their Equilibration. Nothing can be more manifeftly an act of Contrivance and Defign, than the Mufcles of the Eye, admirably adapted to move it any, and every way; upwards, downwards, to this fide or that, or how

rent.

(q) Nigra eft [Uvea] ut radios (ab Oculi fundo ad anteriorem ejus partem reflexos) obumbret; nè hi (ut ait clar. Cartefius) ad oculi fundum retorti ibidem confufam vifionem efficeAlia forfan ratio hujus nigredinis ftatuatur, quòd radii in vifione fuperflui, qui ab objectis lateralibus proveniunt hoc ritu abforbeantur. Ita enim è loco obfcuro interdiu objecta optimè intuemur, quia radii tunc temporis circumfufo lumine non diluuntur. Brigg's Ophthal. c. 3. §. 5.

foever we pleafe, or there is occafion for, fo as to always keep that Parallelifm of the Eye, which is neceffary to true Vision. For the Performance of which Service, the Form, the Pofition, and the due Strength of each Mufcle is admirable. And here I might Inftance 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, fomewhat exceeding that of its Antagonist; the peculiar Muscle, called the Seventh, or Sufpenfory Muscle (f), given to Brutes, by reafon of the prone Pofture of their

(r) Admirandum Dei artificium ex diverforum animalium comparatione indies evadit manifeftiùs. Mirantur omnes Trochlearem in oculis Hominum & Quadrupedum, & quidem jure : fed admirationem omnem fuperat, quòd fine Trochlea oculum movens in Avibus novum genus Trochlea longè artificiofiùs Nictitandi Membrana dederit. Blaf. Anat. Animal. p. 2. c. 4. ex Stenon.

[Mufculum Trochlearem] per intermedium trochleam traductum, nunquam intueor, quin admirabundus mecum, O EOS, exclamem, & μόνον ἀπ' γεωμετρε, ἀλλὰ καὶ ἀεὶ μηχανάς. I. C. Sturmii Exercit. Acad. 9. de Vif. Org. & Rat. c. 3. §. P. 446.

4.

(S) Obfervare eft quod Quadrupedes, qui oculos in terram pronos, ac pendulos gerunt, Mufculum peculiarem habent, quo Oculi globus fufpenditur Hoc Mufculo Bos, Equus, Ovis, Lepus, Porcus, &c. praditi funt: hoc etiam Canis inftruitur, fed alio modo conformatum habet. Willis de An. Brut. p 1. c. 15. Of this Opinion also was Bartholine Anat. 1. 3. c. 8. and divers other eminent Anatomists.

But Dr. Briggs is of Opinion that the Adnata, and the other Mufcles fufficiently answer all thofe Ends afcribed to that Mufcle by former Anatomifts, and thinks Probabiliùs itaque effe bunc Mufculum nervi Optici affionem (per vices) confirmare, nè à prono Brutorum inceffu & copiofo affluxu humorum debilitetur, Ophthal. c. 2. §. 2.

The Mufculus Sufpenforius being in the Porpefs, as well as Brutes, Dr. Tyson thinks the Ufe of it is not to fufpend the Bulk of the Eye; but rather by its equal Contraction of the Sclerotis, to render the Ball of the Eye more or lefs Spheri- . cal, and fo fitter for Vilion. Tyson's Anat. of the Porpefs, P. 39.

Bodies, and frequent Occafions to hang down their Heads: And I might fpeak alfo of the peculiar Origine and Infertion of the lower Oblique Mufcle (t), which is very notable, and many other Things relating to thefe Parts; but it would be tedious to defcend too much to thofe admirable Particulars. And therefore to close up these Remarks, all I fhall farther take Notice of, fhall be only the exquifite Equilibration of all these Oppofite and Antagonist Mufcles, affected partly by the Equality of the Strength; which is the Cafe of the Adducent and Abducent Mufcles; partly by their peculiar Origine, or the Addition of the Trochlea, which is the Cafe of the Oblique Mufcles (u): and partly by the natural Pofture of the Body, and the Eye, which is the Cafe of the Attollent and Depriment Mufcles. By this fo curious and exact a Libration, not only unfeemly Contortions, and incommodious Vagations of the

(t) Mufculus obliquus inferior oritur à peculiari quodam foramine in latere Orbita ocularis facto, (contra quàm in cateris, &c.) quo fit ut ex una parte à Mufculo trochleari, ex altera verò ab hujus Mufculi commodiffima pofitione, Oculus in aquilibrio quodam conftitutus, irretorto obtutu verfus objecta feratur, nec plus jufto accedat verfus internum externumve canthum; qua quidem Libratio omnino nulla fuiffet, abfque hujus Mufculi peculiari originatione (cujus ratio omnes hucufque Anatomicos latuit). And fo this curious Anatomift goes on to fhew farther the ftupendous Artifice of the great Creator in this Pofition of the Oblique Mufcles. Brigg's Nova Vif. Theor. p. 11. meo libro.

(u) Befides thofe particular Motions which the Eye receives from the Oblique Mufcles, and I may add its Libration alfo in fome Measure, fome Anatomifts afcribe another no lefs confiderable Ufe to them; namely, to lengthen and fhorten the Eye (by fqueezing and compreffing it) to make it correfpond 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, eafily changeth its Figure, when either the Ligamentum Ciliare contracts, or both the Oblique Mufcles fqueeze 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).

Eye