Mikrokosmographia a description of the body of man. Together vvith the controuersies thereto belonging. Collected and translated out of all the best authors of anatomy, especially out of Gasper Bauhinus and Andreas Laurentius. By Helkiah Crooke Doctor of Physicke, physitian to His Maiestie, and his Highnesse professor in anatomy and chyrurgerie. Published by the Kings Maiesties especiall direction and warrant according to the first integrity, as it was originally written by the author.

CHAP. VI. Of the Membranes of the Eyes.

HAuing declared the Muscles & the vessels of the eies & now remoued them away, the eye it selfe round like a bowl appeareth [Ta. 2. fig. 3 & 4. Ta. 1. fi. 2 & 3] which may be compared to the world & an egge, both for the figure & construction. To an Egge which consisteth of Membranes, the shel which is an indurated Membrane & a thin Membrane vnder it, & humors, the white & the yolke: So the globe of the eye hath membranes & hu∣mors. Membranes that being of a watery nature it might better be conteined in his positiō and the humors by them encompassed, which membranes had need to haue a more solid

substance; beside they are a great furtherance to the sight: Humours onely for the sight.

Concerning the number of the Membranes the authors are at great difference. Hip∣pocrates in his Booke De Locis in Homine acknowledgeth but three, the vppermost thick, the middlemost thinner, and the third thinnest of all which conteineth the humors; but in his booke De Carn. he saith they are manie. The later Grecians reckon four, Siluius fiue Vesalius sixe, Galen in the seuenth chapter of his tenth book De vsu part. seuen; vnto whō Fuchsius & Aquapendens do consent. We wil diuide them into two kinds, some are com∣mon to the whole eie, some are proper to the humors; the common Membranes are the Cornea and the Vuea the horny and the grapie coates. The proper Membranes are the Cristaline and the glassye. But whereas there are commonly reckoned seauen, Adnata, Cornea, Dura, Vuea, Choroides, Aranea, and Retina, whereto some haue added those which are called Vitrea and Innominata, we wil runne thorough them al after our Anato∣mical order.

The first is called Adnata which is the seauenth according to Galen in the second chap∣ter of his tenth booke De vsu partium, so called as it were Nata circa oculum, bred about the eye. Galen cals it 〈 in non-Latin alphabet 〉〈 in non-Latin alphabet 〉, because it cleaueth on the outside of the other mēbranes of the eye, whereupon it is also called Adherens or the cleauing Membrane. This is the vtmost. Aquapendens supposeth that it ariseth from the Periostium & tendons or chords of the Muscles. It first offereth itselfe before Dissection together with the transparant part of the horny Membrane lying vpon the white thereof.

The Periostium is alwayes next vnto the bone, vnlesse it be wher it produceth the cyclid, for hauing therto attained it maketh an angle & so is doubled, one part of which dupli∣cation compasseth the lid of the eye, the other part [Ta. 1. fig. 6, 7, 8, V] maketh this Ad∣nata or adhering Membrane, which becomming thinner in the fore-part only where the white of the eye appeareth, couereth the same and determineth or endeth in the greater circle of the Iris or Rain-bow, where it is continued with the hornie Membrane. [Tab. 1. fig. 7, 8. V. and Tab. 3. fig. 1 ^d]

It is said to be white from the colour, although saith Aquapendens it be not indeed white but onely appeareth so, because the Tendons of the Muscles lying vnder it do re∣present a kind of whitenesse. But Hippocrates in Coacis calleth it 〈 in non-Latin alphabet 〉〈 in non-Latin alphabet 〉, the white of the eye. It is a smooth Membrane, and by the interposition thereof the eye is fastned to the orb and to the inner bones, and it serueth instead of a Ligament to all the bones about the eye. Hence it is called commonly Coniunctiua a Coniungendo, because it ioyneth toge∣ther all the Membranes of the eye, thereby making it firmer and stronger, or rather be∣cause at the Iris or Raynbow it is ioyned to the rest of the Membranes.

In like manner it tieth the eie to eie-liddes and to the head, and in a worde it de∣fendeth the eie from the hardnesse of the bones. it ioyneth it with the bones, the liddes, and the rest of the coats, whereby it is so established that in violent motions it doth not fall out of his orbe, but is freely mooued; and besides it couereth the Muscles which mooue the eie and keepeth them in their proper seates but because it hath rather the vse of a Ligament then of a Membrane, we thinke it approacheth nearer to the nature of a Ligament.

This coate or Membrane or Ligament whither you list to cal it, is sprinkled with ma∣nie smal Veines [Tab. 1. fig. 6. 7. 8. V] and Arteries, which commonly when the eie is in perfect health do not appeare. Sometimes they grow verie red and being ful of bloode they strut therewith and so become more conspicuous as in the inflammation of the eie. For as Hippocrates hath it, sometime this white groweth red or blackish, or is ful of black Veines; this Membrane or coat it is which communicateth to the eie the sense of Tou∣ching, because neyther without nor within it hath any sense at al, and therefore the pain which proceedeth from the eye-liddes molesteth the Eye onely by reason of this Mem∣brane.

The second Coate of the Eye is called Innominata by some, as if it had bene but new∣ly found out, whereas Galen knew it wel enough, and in the second chapter of his Tenth booke De vsu partium reckons it for the sixte Membrane. It ariseth from the Neruous Tendons or Chords of the Muscles and determineth neere the Iris vnder the Adnata or Coniunctiue Membrane: and these Tendons do encrease the whitenesse of the eye, be∣cause they haue a bright Candor or whitenesse. But being nothing lesse then the Chords

[illustration]

Table 3. Figure 1. sheweth the Membranes and humors of the eye by lines drawne after the manner of a true eye.

[illustration]

Figure 2. Sheweth the horny coate with a portion of the Optick Nerue.

[illustration]

Figure 3. sheweth the same diuided by a transuerse section.

[illustration]

Figure 4. sheweth the Vuea or Grapy coate with a portion of the Opticke Nerue.

[illustration]

Figure 5. The Grapie coate of a man.

[illustration]

Figure 6. The Horny, Grapie, and the Choroides.

[illustration]

Figure 7. The interior superficies of the Grapie coate.

[illustration]

Figure 8. The Posterior part of the horny coate together with the saide Net separated from the Eye.

[illustration]

Fig. 9. The coat of the vitreous or glassy humor cald Hyaloides.

[illustration]

Figure 10. Three humors ioyned together.

[illustration]

Figure 11. The forward part of the Cristalline.

[illustration]

Figure 12. The Cristalline humor couered yet with his Coate.

[illustration]

Figure 13. The Cristalline bared on the sides.

[illustration]

Figure 14. The Cristalline of a man.

[illustration]

Figure 15. His Coate.

[illustration]

Fig. 16. The watery, disposed vpon the Cristaline round about.

[illustration]

Fig. 17. The hairy processes beaminglie sprinkled through the foreside of the coate of the glassy humor.

[illustration]

Figure 18. The foreside of the glassy humour.

[illustration]

Figure 19. The place of the watery humour.

[illustration]

Figu. 20. The glassy humour conteining or comprehending the Cristalline.

[illustration]

TABVLA. III.

[illustration]

FIG. 1.

[illustration]

II.

[illustration]

III.

[illustration]

IV.

[illustration]

V.

[illustration]

VI.

[illustration]

VII.

[illustration]

VIII.

[illustration]

IX.

[illustration]

X.

[illustration]

XI.

[illustration]

XII.

[illustration]

XIII.

[illustration]

XIV.

[illustration]

XVII.

[illustration]

XIIX.

[illustration]

XIX.

[illustration]

XX.

• ...The explication of the first Figure by it selfe.
• a. The Cristalline humour.
• b. The Glassy humour.
• c. The watery humour.
• d. The vtmost coate called Adnata.
• e. the dark part of the horny Tunicle which is not transparant.
• f, the Grapy coate called Vuea.
• g, the Net-like coate called Retiformis.
• h. the coat of the glassy humor cald Hyaloi∣des.
• i, the coate of the Cristalline.
• kk, the hairy processes cald Processus-ciliares
• l, the impression of the Grapy coate where it departeth from the thick coate.
• m, the horny coate, a part of the thick coate
• nn, the fat betwixt the Muscles,
• o, the Optick Nerue,
• p, the Dura Meninx.
• q, the Pia Mater or thin Meninx.
• rr, The Muscles, The explication of the other 19. figures togither
• a, 2, 4, 8. The Optick Nerue,
• b, 2, 4. The thin Meninx clothing the nerue
• c, 2, 3. the thick meninx clothing the Nerue.
• d 8, the posterior part of the horny Coate.
• e 8, the coate called Ret na gathered toge∣ther on an heapt.
• f, 2, 3, the Raynbow of the eye.
• g, 2, 3, the lesser circle of the eie or the pupilla
• h, 2, 3. Vessels dispersed through the Dura Meninx.
• i, 3, 6. the Grapy coat, but i in the 3. Figure sheweth how the vessels doe ioyne the hard membrane with the Grapie coate.
• k, 6. the horny or hard membran turnd ouer
• ll, 3, 4. Certaine fibres & strings of vessels, wherby the grapy coat is tied to the horny.
• mm, 4, 5. the impression of the Grapie coate where it recedeth or departeth from the horny coate.
• nn, 4, 5, 6, 7, the pupilla or Apple of the eye.
• oo, 7, The Ciliar or hairy processes.
• p, 7. The beginning of the grapy coat made of a thin membrane dilated, but p in the 17. figure sheweth the Ciliar processes sprinckled through the fore-part of the glassy humour.
• r 9, the bosom or depression of the glassye humor receiuing the Cristaline.
• s, 12, 15, the bredth of the coat of the crista∣line
• t, 12. 13, 14, 16, the posterior part of the cri∣staline humor which is spherical or round.
• u, 11, 14, 20, the fore-part of the same Cri∣stalline depressed.
• x, 10, 20, the amplitude of the glassy humor
• y, 10, 16. 19, the amplit. of the watry humor
• z, 10, the place where the glassy humour is distinguished from the watry by the in∣terposition of the Hyaloides or coate of the glassy humor.
• α, 10, 16, the place where the gropie Coate swimmeth in the watrie humour.
• β, 18, The Cauity or depression of the glas∣sy humor which remaineth in the Cristal∣line is exempted or taken from it.
• ♌, 19. The cauity or depressiō of the watry humor made by the same meanes.

of the muscles, it cannot bee properly called a membrane but a part of the muscles, which together with them must needs be demonstrated, notwithstanding if any man list to stand vpon it and call it a membrane we will not gainsay him.

The vse of it is, that by the interposition thereof the muscles might bee more fitly inser∣ted into the horny membrane [tab. 2. fig. 5. sheweth the same.

The third coate of the eie is called Cornea, which is the first according to Hippocrates, and may well be called the thicke and hard coate both in respect of his substance and of his ori∣ginall, because it is produced from the hard Meninxe or the Dura mater which inuesteth the opticke nerue. And here we may take knowledge of the admirable wisedome of our Creator, who (as Galen hath excellently obserued in the 2. Chapter of his tenth Booke de vsu partium) whereas in no other place hee hath separated the Meninges from any Nerue which are produced with them, but hath led them along with the nerue that they might be nourished & couered; only in this place after the nerue is inserted into the eie, hath separa∣ted both the thicke and the thinne from the nerue it selfe; yea made them thicker and har∣der then they were when they encompassed the braine. For when this membrane is im∣planted into the backpart of the eye [Table 3. figure 3. c] it is dilated and maketh an orbi∣cular or round membrane [Table 3. figu. 2 and 3. exhibite it] which compasseth the whole eie, although it bee not in euery place alike, neither haue one and the same name; for the forepart is translucid but the backepart is not so; wherfore some immitating the Arabians of this membrane how made two. For because the sight did stand in need of transparen∣cie, this membrane, when it hath attayned vnto the middle of the forepart of the eie iusta∣gainst the Cristaline humor, it is so condensed that it degenerateth into a horny substance, which forepart [Table 3. fig. 1. ^cm] is called 〈 in non-Latin alphabet 〉〈 in non-Latin alphabet 〉 Cornicularis that is Horny, because in the middle as farre as the extent of the Rainebowe it is like a thinne and pollished home of a Lanthorn, not only in transparencie by which meanes it receiueth the light, but also in his substance, because it may be sliuen or deuided into diuers flawes. And that was the rea∣son why Fallopius in his obseruations could not perswade himselfe that it was a part of the hard membrane because, saith he, it differeth from the Dura meninx of the braine, not one∣ly in substance but also in thicknes and in figure. For by it selfe alone it maketh another spherical cauity arising beyond the superficies of the hard membrane, and both within and without is free from any connexion.

This horny membrane is round, circular, hard, fast, thin, streatched, transparant, bright, pollished and smooth. Round and circular in a man (for in Oxen it is of an ouall figure) bunching or bearing out in the middle of the eye: not onely that it might bee freer from being offended: but especially that the eie might discerne things greater then it selfe; that is, that it might receiue the Ideas or formes of great obiects and those whole & vnbroken, as also that the light which entreth in might be better vnited and contracted, and so attaine through the Pupilla or Apple vnto the Chrystaline humour. That this benefit commeth by the roundnesse and prominence of this membrane may be demonstrated by a Looking glasse, for if we desire to see our faces in a long fragment of a Looking glasse we cannot see them whole, because the figure is playne, and in a plain figure the perpendicular beames of the light are not vnited: whereas in a round figure they concutre and meete together into a poynt: for Galen sayth in the twelfth Chapter of his 10. Booke de vsu partium, that Visi∣on or Sight is made by a Pyramis, and therefore let the glasse bee neuer so small, yet if it bee round wee may see our whole face therein: hence it appeareth that if this part had any fi∣gure sauing a circular, the images or formes of great obiects could not bee admitted into the eie at all.

It is hard and in some Fishes sayth Aquapendens exactly carrieth the hardnesse and rigi∣dity of a horne it selfe. This hardnes secureth not only the membrane but also the Chri∣staline humour from outward iniuries: beside that, it resisteth any light occurrent vio∣lence.

Fast and thight it is, not onely for resistance, but also for the better conseruation of the watery and glassie humours that they sweat not out, and that the thinne spirites might not penetrate through it and so exhale. VVherefore in a liuing creature because of the aboun∣dance of spirites, it is notably streatched and shineth very cleare especially in the forepart. But when the creature is dead and the spirits extinguished, it falleth presently and growes loose and corrugated.

Hence it followeth that sight cannot be by an emission or eiaculation of spirites out of

the eies, because the tention or streatching of a liuing eie proceedeth from no other cause but from the aboundance of spirits concluded and contayned within this membrane. And although it be the first and next part of the eie which is exposed to all iniuries of cold, heat and whatsoeuer else might fall vppon or bruise the eye; yet by the wisedome of Nature it is defended by the lids, by the haires, by the bones and by the skinne. Moreouer it is not a simple or single membrane but made as it were of many shels or scales, vpon which sayth Ruffus in the first Chapter of his first book, there is a cuticle or curtaine spread which is far thinner then the rest of the scales, that if haply one of them should be gnawne asunder, the rest might suffice to contayne and defend the Chrystaline humour. Auicen maketh it four∣sould.

It is very thinne, for, sayth Galen in the third Chapter of his tenth book de vsu partium, if it had been thicke it might indeede haue beene a defence vnto the eie, but it would haue cast a perpetuall darke shadow vpon it, and would haue hindered the passage of the light; whereas now being thinne it transmitteth any light or brightnes freely and without delay so that the chrystaline humour may discern the true purtraitures and representations of all visible obiects; wherefore also it is transparant, cleare and bright because it should be more fit for the transmission of illumination, for so we see that the thinner a horne is the better doth the light extend it selfe through it.

It is also streatched, for if it had beene corrugated or wrinkled and so vnequall, it must needes haue lost his roundnes, smoothnes and transparancie; and so the sight would haue beene much hindered. An experience whereof wee haue in old men in whome this mem∣brane is sometimes so rugous and loose, that either they can see nothing at al or very con∣fusedly, for, sayth Aquapendens, when one plight or fold falleth vpon another and the coat thereupon is duplicated, the membrane becomes thicker & the Apple contracteth it selfe because it is not distended by a sufficent afluence of spirits.

It is transparant that it might giue way to all visible formes and representations, and also admit the light which beateth vpon it. But we must consider that this transparancie or lucidity of the membrane differeth much from the lucidity of the aire, that so there might insue a refraction or breaking of the light. But howe the light passeth vnto the eye and how it is refracted, because it belongeth rather to the opticke Art then to Anatomy; him that listeth to be further satisfied therein, we wil send vnto the writers of the Opticks, such as are Vitellius and Alharen. Aquapendens also the Anatomist hath elegantly written of these things of the eie: but we proceed.

This membrane is pollished and smooth that in it the formes of thinges might better shine and more fitly be receiued, and images represented to the chrystaline humour most like to the outward obiectes. For if it had beene rough and full of eminencies and caui∣ties, the light would not haue equally attained vnto it; for where cauities are there doe the representations passe through more easily and brighter; where there is any eminencie ther doe they passe through with more difficulty, and beside are very obscure. Moreouer such an asperity or roughnesse would haue beene troublesome to the eie-lid, as wee see it hap∣neth when any small substance falleth betwixt the eye and the lid. But being fast, hard & thinne, it could not receiue any veines into it, neither yet arteries nor nerues: neither if it could had it beene behoofefull, for they would haue hindred the sight, & although it might haue defended the chrystaline humour from outward offences, yet it would haue been of∣sensiue to the sight with his hardnesse: and finally it would haue abated the visible faculty communicated vnto the eies from aboue, and haue dimmed or dulled their brightnes. For that the eyes are offended with a bright and vehement light, euery man hath sufficient ex∣perience in himselfe. Beside, we read in histories that Zenophons souldiours were almost blinded by trauelling through the snow. And Dionisius that Tyrant of Cicilia aboue his pri∣son built a very lightsome and bright chamber which he whitened ouer with lime, & when he had a long time detained his prisoners in a darke dungeon, hee suddenly brought them into this light and bright place, where they instantly became blinde because their eies were not able to beare so sudden a change.

In like manner those that doe labour of the ophthalmia or inflamation of the eye are offended with the light: but duskish or greene colours they are able to behold without of∣fence.

Hence it is that if in a bright light a man would looke on any thing that is a far off, he will hould his handes or some other thing ouer his browes to shadow his eies that they

be not dazled. So also it hath bene obserued, that those that haue fixed their eyes vpon the Sunne to behold the Eclipses of the same, haue vtterly lost their sight. And this commeth to passe, euen as we see a torch or candle lighted and set in a bright Sun is instantly extin∣guished: In like maner if you light a candle and set it by a great flame, the candle will pre∣sently go out, because the lesse light is ouercome and dissipated by the greater.

After the same manner in the eye, not onely the spendor of the Cristalline humour, but with it also the brightnesse of the glassie humour is dissipated: wherefore the wise and prouident Creator, saith Galen in the third chapter of his tenth booke de vsu partium, hath interposed the coat called Choroides, which in many parts is black and duskish, and in oxen green; which coate nourisheth the horny coate that is next vnto it where they touch one another, and hindereth it also from falling vpon the Cristalline humour, although that inconuenience is in part preuented by the roundnesse and prominence of the saide horny coate.

Moreouer, the blacke colour of the Choroides in men, and the green colour in Oxen, is a medicinable curtaine or shadow for the ill affected eye; and this is the reason that e∣uery man by a naturall instinct, when he is offended with the brightnesse of the light, will suddenly close his eye-lids, making haste thereby vnto the remedy which Nature hath pre∣pared, euen within the eye. And this may be further exemplified by the custome of Pain∣ters, who when they paint vpon white tables would soone haue their eyes offended if they did not prepare against it, wherefore they place at their elbowes greene and duskish co∣lours, vpon which euer and anon they turne their sight, whereby their eyes are recreated and refreshed.

The posteror or backeward part of this coate which couereth the back part of the eye and the forepart also vnto the circle, [Tab. 1. fig. 7. 8. ^f] is hard, thicke, darke, or ob∣scure; differing as much from the colour or clearenesse of the horny membrane, as the white of an Egge when it is boyled differeth from the same white when it is raw. It is hard and thicke by reason of his originall, although it neither imitate the exterior coate of the nerue in thinnesse, nor the dura meninx or thicke membrane of the braine from which that ariseth in thickenesse; as being fourefold thicker then it, for when it formeth the coate of the eye it is thickened and hardned, for it was requisite it should be very hard and very thicke for more strength, because it maketh the whole globe and cauity of the eye where∣in the humours are contained; for this membrane it is which fashioneth the figure of the eye into a globous roundnesse, and in that figure conserueth it: it is also made whole, for this coate aboue compasseth the whole eye so that nothing can issue therout.

Add hereto that it receiueth the insertions of all the muscles & sustaineth their weight, as also the weight of the fat and is a Basis or foundation of the veines and arteries [Tab. 3 fig. 3. ^{h h}.] which neare the nerue behinde the glassie humour attaine vnto this membrane and afterward run forward till they be distributed through the coate called Choroides. By the mediation of these vessels, as also by smalties, as it were by ligaments this membrane cleaueth so fast to the Choroides, that they hang one vpon another. [Tab. 3. fig. 3. h i.] The profit of which connexion is, lest this coate alone should be mooued when the other parts of the eye are at rest, as we see a cloth wrapped about a smooth bowle will easily slippe, though the bowle be not moued.

This membrane is also thicke and darke or obscure, that the species or formes of things which are receiued might shine more brightly, as we see in a looking glasse if it be leaded on the backe side we my easily see our faces therein, but not so if the lead be remo∣ued. This part is white, and neither in nature nor in colour like vnto the forepart, and therefore some of the late writers as Fuchsius and Aquapendens haue distinguished it from the forpart, and say, that the limits and edges therof are continuated with the horny mem∣brane. It is scituated vnder the Coniunctiue and Tendons of the muscles, and is generated out of the dura meninx which compasseth the Optick nerue, for with it it is continuall, as may be perceiued if you separate the coate of the nerue with a sharpe knife through his length whilest you come vnto this membrane. It is called by some 〈 in non-Latin alphabet 〉〈 in non-Latin alphabet 〉 & 〈 in non-Latin alphabet 〉〈 in non-Latin alphabet 〉 the hard membrane, Ruffus calleth it candida or the white membrane, although common∣ly that name be giuen to the Adnata or Coniunctiue coate.

By the helpe of this membrane is the eye established, as also the next mem∣brane vnto it defended, which is sufficient indeed to defend that which is vnder it, but not to defend it selfe: this also is it which containeth the humors according to their due dispo∣sition;

and whereby the Cristalline humour it selfe is preserued from the cold and heate of the Ambient aire.

Notes

• The eie com∣pared to an Egge.
• The Mem∣branes of the eie.
• Their number verie diuerse according to authors,
• First Adnata.
• Whence com¦meth the white of the eie.
• Coniunctiua.
• The vse of the Adnata.
• The vessels of this coate.
• The 2. Coate Innominata.
• The vse of it,
• The 3, coate Cornea.
• How it is spred ouer the eie.
• Why it is com¦pared to a horne of a Lanthorne. Fallopius his opinion.
• The forme & disposition thereof. Why round & circular,
• Why hard.
• Why fast.
• Why thin.
• Why stret∣ched.
• Why transpa∣rant.
• Why polished and smooth.
• That much light is an eni¦my to the sight.
• Dyonisius his cruelty.
• The greater light extin¦guisheth the lesse.
• The wisedom of our Crea∣tor acknow∣ledged by Galen.
• The backe∣part of the horny coate.
• Why it is so thicke.
• Why it is thicke and darke.
• Fuschius. Aquapendens.
• Ruffus. The vse of this third membrane.