Book IV. employed 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 ftand amazed, when we view its admirable Fabrick, and confider the prodigious exactness, and the exquifite Skill employed in every part ministering to this noble and neceffary Senfe. by affected, and the Soul thereby informed, c. but see more hereafter under Note 38, 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 rise in the Thalamus Nervorum Opticorum, and thence continued to both the Reine, which are made of them : And farther, that those Fibrilla have the fame Parallelism, 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 Oμ between the Retina, &c. he makes very probable from the enfuing of double Vifion upon the Interruption of the Parellelifm of the Eyes; as when one Eye is depreffed with the Finger, or their Symphony interrupted by Disease, Drunkenness, c. And laftly, that fimple Vision 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 otherwise than by a bare Contact, which is particularly manifeft in Fishes ; and in fome Inftances it hath been found, that they have been separated without any double Vision ensuing 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, Q. 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 same way with both Eyes, (as of Fishes and of the Chameleon) do not meet, if I am rightly informed. Newt. Opt. Q. 15. To To pafs by its Arteries and Veins and fuch other Parts common to the reft of the Body, let us caft our Eye on its Mufcles. Thefe we fhall find exactly and neatly placed for every Motion of the Eye. Let us view its Tunicks; and thefe we fhall find fo admirably feated, fo well adapted, and of fo firm a Texture, as to fit every place, to anfwer every occafion, and to be proof against all common Inconve niences, and Annoyances. Let us examine its three Humours and these we fhall find all of exquifite Clearness and Tranfparency, for an eafy Admillion 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 wandering Rays into a Point. And to name no more, let us look into its darkned Cell, where thofe curious Humours le, and into which the Glories of the Heavens and the Earth are brought, and exquifitely Pictured; and this Cell we thall 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 confuse, or difturb the beneficial Rays (16). 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 Meafure done by others, that have written of God's Works. Paffing over therefore what they 3 (16) Nigra eft [Uvea] ut radios (ab Oculi fundo ad anteriorem ejus partons reflectes) obumbret ne bi (ut ait clar. Cartefius) ad Oculi fundum retorti ibidem confussam vifionem efficerent. Alia forfan ratio hujus nigredinis ftatuatur, quod radii in vifione fuperflui, qui ab obje&tis lateralibus proveniunt hoc ritu absorbeantur. Ite enimè loco obfcuro interdiu objecta optimè intuemur, quia radii tune temporis circumfufo lumine non diluuntur. Brigg's Ophthal. c. 3. §. 5. Book IV. have obferved, I fhall under each principal Part take a tranfient Notice of fome Things they have omitted, or but flightly fpoken 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 Design, than the Muscles of the Eye, admirably adapted to move it any, and every way; upwards, downwards, to this fide, or that, or howfoever we please, or there is occafion for, fo as to always keep that Parallelifin of the Eye, which is neceffary to true Vifion. 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 (17); the Magnitude and Strength of the Attollent Mufcle, fomewhat exceeding that of its Antagonift; the peculiar Mufcle called the Seventh or Sufpenfory Mufcle (18), given to Brutes, by rea fon of the prone Pofture of their Bodies, and frequent Occa (17) 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 artificiofius Nilitandi Membrane dederit. Blaf. Anat. Animal p. 2. c. 4. ex Stenon. [Mufculum Trochlearem] per intermedium trochleam traduƐtum, nunquam intueor, quin admirabundus mecum, ‘O Otòs, exclamem, * μόνον ἀεὶ γεωμετρεί, ἀλλὰ καὶ ἀεὶ μηχανάται. I. C. Sturmii Exercit. Acad. 9. de Vif. Org, & Rat c. 3. §. 4. P. 446. (18) Obfervare eft quod Quadrupedes, qui oculos in terram pronos, ac pendulos gerunt, Mufculum peculiarem habent, que Oculi globus fufpenditur Hoe 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 alfo was Bartholine Anat. 1. 3. c. 8. and divers other eminent Anatomists, But 2 the , Occafions to hang down their Heads: and I might ment But Dr. Briggs is of Opinion that the Adnata, and the other Muscles The Mufculus Sufpenforius being in the Porpefs, as well as Brutes, (19) Mufculus obliquus inferior oritur à peculiari quodam for ami- (20) Befides thofe particular Motions which the Eye receives from the Oblique Mufcles, and I may add its Libration also in fome Measure, fome Anatomifts afcribe another no lefs confiderable Ufe to them; namely, to lengthen and fhorten the Eye (by fqueezing H 2 and 1 nent Mufcles. By this fo curious and exact a Libration, not only unfeemly Contortions, and incommodious Vagations of the Eye are prevented, but alfo it is able with great readiness, and exactness to apply it felf to every Object. As to the Tunicks of the Eye, many things might be taken notice of, the prodigious Fineness of the Arachnoides, the acute Senfe of the Retina, the delicate Tranfparency of the Cornea (21), and the firm and ftrong Texture of that, and the Sclerotica too; and each of them in thefe, and every other refpect in the moft accurate manner adapted to the place in which it is, and the Bufinefs it is there to perform. But for a Sample, I fhall only take notice of that part of the Uvea which makes the Pupil. It hath been obferved by others, particularly by our Honourable Founder (22), That as we are. forced to ufe various Apertures to our optick Glaffes, fo Nature hath made a far more compleat Provision in the Eyes of Animals, to fhut out too much, and to admit fufficient Light, by the Dilatation and Contraction of the Pupil (23). But it deferveth our efpecial Remark, that thefe Pupils are in divers Animals and compreffing 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 thinneft, and most liquid, eafily changeth its Figure, when either the Ligamentum Ciliare contracts, or both the Oblique Mafcies 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 22. (21) Quis verò opifex præter Naturam, quâ nihil poteft effe callidius, tantam folertiam perfequi potuiffet in Senfibus? que primum Oculos membranis tenuiffimis veftivit, & fepiit; quas primum perlucidas fecit, ut per eas cerni poffet: firmas autem, ut continerentur. Cic. de Nat. Deor. L. 2. c. 57. (22) Boyl of Final Causes. (23) It is easy to be obferved, that the Pupil openeth in dark Places; as alfo when we look at far diftant Objects, but contracts by |