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. X. Of the vse of the Humours of the Eye and of the Sight.

HAuing declared the admirable wisedome, prouidence and goodnes of God our Creator in the conformation of this diuine member which wee call the Eie: although we haue spoken somewhat in the History of euery particular part concerning their vse, yet there remaine many things worthy our obser∣uation touching the humours, which being ioyned to that that hath bin sayd before will better absolue and accomplish this discourse of the vse of the eye and the true manner of sight. Which though I must confesse that they are more Philosophicall then Anatomicall, yet because they pertaine to the same subiect, I presume the Reader will not abhor from them.

That the Eyes are the instruments of the sight by which it perceiueth all visible things as well Proper as Common there is no man ignorant; Proper as all colours, Common as the figure, magnitude, number, motion and scite, which are sensible qualities common to all the Sences; so that it is truely sayed that the Eye seeth not a Man but those thinges which are visible in a Man, as colours together with the scite, figure, magnitude, number and motion of his partes, out of which afterward the Soule collecteth that that thing is a Man.

The Eie is framed of many parts, all which were created for the vse of the sight. But be∣cause in euery organ which is compounded of many parts, there is one similar particle vp∣pon which the action of that organ doth especially depend, it would be knowne what this particle is in the eye: we answere that it is the Chrystaline humour which is the authour of the action, because in it the species or formes of visible thinges are receiued and by it iud∣ged of.

Beside this, there are some particles without which the action cannot be; as the optick nerue which leadeth along the faculty vnto the christaline; some also by whose helpe the action •••• made more perfect, as the membranes and the muscles: and finally, some parti∣cles a•••• ordayned for the conseruation of all these, as the Eye-liddes and the partes about them.

Seeing therefore the faculty is deriued from the braine by the opticke nerues vnto the

eyes, which are set as scout-watches to take knowledge of the ariuall of outward thinges; that they may better apprehend the knowledge of such outward obiectes, it was necessary that whatsoeuer is to be perceiued should touch the nerue: for Aristotle sayeth in his third Booke de Anima, That euery action is made by contaction.

This contaction is here made by a medium or meane; for the Sences doe perceiue their obiects through a meane. Wherefore seeing the nerue is separated from the visible obiect, that there may bee sight it is necessary there should bee a contaction either of the nerue to the obiect or of the obiect to the nerue, or else that either of them should be mo∣ued in a certaine proportion to the other.

The two first wayes it cannot be, as euen Sense it selfe teacheth vs, and therfore it must be done the third way. If vision be made the third way, then either something must pro∣ceed from the nerue to the visible obiects, or on the contrary something must be sent from the obiects to the nerue, or else both must be: that is, Sight must bee made either by an e∣mission of spirites, or a reception of beames, or else by emission and reception both to∣gether.

Now the spirit is not carried from the nerue to the thing that is to bee seene, for then it would follow that the nerue alone by which the faculty yssueth can absolue and perfect the action of sight, and the iudgement should be made without the eye. Againe, neither is there any corporeall thing transported from the body which is sent vnto our eyes; for then the obiects by continuall diffusion would be diminished. Neither is Vision made the third way, so that a spirite or a beame or a light should yssue out of the Eie vnto the ob∣iect and againe something of the obiect should be moued vnto the spirite, that so the contaction might be made in the middle; for then the nerue alone would haue sufficed for the action, and the iudgement should haue beene made without the eie. VVhere∣fore we thinke with the Philosopher that this contaction is made by a medium, so that a certaine quality with some colour affecting and changing the ayre that is cleare and lu∣cid betwixt the eie and the obiect, doeth transferre from the things themselues the visi∣ble species by one right line from the obiect to the eyes, yea to the center of the chrysta∣line humour. So the ayre which is in the middest betwixt the eye and the obiect lea∣deth along that which is perceiued, and first of all the colour; for the ayre is altered by colours which it receiueth by contaction; for euen as the Sun attayning by the bright∣nes of his light vnto the Element of the ayre illustrateth the same; so coulours when they touch the ayre make a kinde of impression therein, for the ayre is alwayes capable of co∣lours when it is cleare, light and illustrated by the brightnes of the Sunne beames. Vi∣sion therefore or sight is made by the Reception of visible forms, when the light affected with those formes entreth into the eies through their translucid bodies; first of al with right beames, afterward diuersly refracted or broken and affecteth the chrystaline with some colour, which chrystaline as the primary instrument of sight doth in an instāt receiue those visible formes whereof refraction is made in the membranes, perfection in the con∣iunction of the Opticke nerues, and finally a perception in the braine. For the light is the proper obiect of the sight whereby it is moued and affected; Light I say stayned with the formes of colours and externall light, for the eie of a man hath not in it any In-bredlight, for then he might see in the darke by sending out a light from his eye. Albeit Suetonius re∣porteth that Tiberius Caesar had such an eye, and that excellent Philosopher and Physitian Cardan, as also Iohn Babtista Porta of Naples do affirme the same thing of themselues. Some creatures there are we know which see worse in the day time then in the night, and there∣fore they seeke their food in the night season.

Nowe because the light thus affected with the images of visible thinges must passe through a refraction of his beames, it is necessary there should bee diuers translucide bo∣dies. First the ayre through which it attayneth to the eye, then water in the eye in which this refraction might be made. plato indeed (who thought that sight was made extramit∣tendo, or by an emission of light out of the eye) thought that the nature of the eie was fiery, yet not such a fire as would burne but onely illustrate; for, sayth he, there is a threefould fire: one shining and not burning, another shining and burning, and the third burning and not shining. But we are taught by Anatomy & by the whole composition of the eye, that the instrument of sight is watery, and therefore Hip. in his book de locis in homine, saith that the sight is nourished, that is increased by a moyst brayne. And hereto also may we adde rea∣son, for it is the property of water to receiue; wherefore seeing the formes and images of

outward obiects must be receiued it is necessary that there should be water in the eie.

But because these visible formes should not onely bee receiued, but also retained in the eie, it was necessary that the body of the eie should bee made not onely translucid but also dense and fastly compacted: wherefore Nature did not only make the eye watery that there might bee a refraction, but also that this refraction might bee manifould shee hath created translucid bodies of diuers consistences; for the watery humour is indeed translucid and admitteth the light yet the Diaphanum or transparancie thereof differs from the trans∣parancie of the horny membrane that there might bee also a different refraction; this re∣fraction is made from a perpendicular and is in the eie foure-foulde. The first is from the ayre into the horny membrane which is a faster Diaphanum. The second from the horny membrane into the watey humour which is a thinner Diaphanum; in this watery humour the light is vnited and made stronger, so that it is able to pierce through the third Diapha∣num which is the christaline humour, wherein as in a faster substance the light is yet more strongly vnited and so passeth on to the last refraction at the glassy humour of which wee shall speake by and by. And as in the eye naturally disposed there are foure refractions, so in the spectacles which make the obiect both larger and brighter there are sixe. For first of all the light entreth into the spectacle which is a thicker Diaphanum from the ayre which is a thinner, from the spectacle before it come to the eye it passeth through the ayre again which is a thinner Diaphanum into the horny membrane which is a thicker; from the horny membrane into the watery humour which is a thinner Diaphanum, from thence into the chrystaline which is a thicker, and finally into the glassy humour so that it proceedeth by course out of a thinner Diaphanum into a thicker.

Another vse of the watery humour is to fill vp the empty space betwixt the christaline and the forward membranes, as also to keepe the horny membrane streatcht or tentered & moyst least if it should grow dry it might be corrugated or wrinkled, and so become thic∣ker and hinder the reception of the visible formes.

Thirdly, the watery humour sayth Galen in the sixt Chapter of his tenth Booke de vsu partium, keepeth the horny membrane, the grapy membrane and the chrystaline from ex∣iccation: because the moysture thereof keepeth thē transparant without which there could be no vision at all, for we see that in compunctions or wounds of the eye; when this wate∣ry humour is let out and dryed vp, the horny membrane which before was turgide and full falleth into it selfe and becommeth darke and rugous.

The fourth vse of the watery humour is to be a defence vnto the chrystaline, least the horny membrane should touch the chrystaline through the Pupilla and offend it with his hardnesse.

The fift vse is to restraine the impetuous or violent occursion or confluence of externall colours vnto the chrystaline.

And finally to eleuate or lift vp the formes of visible things as spectales doe, that they might be more fully and directly perceiued by the sence. For when the images of exter∣nall thinges are ariued at the narrow hole of the Pupilla they are lifted vp and so exhibited in the watery humour, wherein they are made more perspicuous; and this indeede was the chiefe reason why Nature placed so pure and neate a humour before the christaline, which is the prime instrument of the sight.

The vse of the chrystaline humour is to be the first and chiefe instrument of the Sight, as wherein it is perfected, and therefore some haue called it the Idol or image of the sight, and Aristotle calleth it Pupilla, haply because we see especially right before vs. That it is the chiefe instrument of sight may thus bee demonstrated. The Philosophers say, That whatsoeuer is made to receiue any thing must be vtterly free from the Nature of that which it is to receiue, because the same thing can neither worke vpon it selfe, nor suffer from it selfe. VVher∣fore that which is the proper Organ or instrument of Sight must haue in it no colour at al, because it is to receiue all colours. And indeed hereby may wee perceiue a thing to bee without colour, when if it bee placed against any colour it representeth the same, as it is in ayre, water, chrystall and such like: wherefore the instrument of sight must either bee ayrie or watery, or chrystaline.

Ayrie it might not be, because the colours that are receiued in the ayre do flow through it, making to mutation at all therein; but we know that the instrument doth only then per∣ceiue & apprehend the obiect when it so suffereth therefrom that it is made the very same; seeing therefore that the colours doe passe through the ayre and make no mutation there∣in,

it could not be that the instrument of Sight should be airy

In the second place it could not be watery, for though the species and formes of co∣lours make a deeper impression in the Water then they do in the Ayre: yet are not the colours therein so imprinted that a man may behold them in it, but they flow through it also. It remaineth therefore that the instrument of sight must be Cristalline, because that onely can receiue and retaine the visible formes. And this also may bee proued by Autopsie or ocular inspection, for if you take a beade of Cristall and set it opposite against a coloured body, which way soeuer you looke you shall see the colours in the cristall, as if the cristal were of the same colour, & did not receiue the impression thereof from those coloured bodyes. Wherefore in the cristalline humor colours are not onely receiued but also so retayned that the power thereof is changed into the colour which it receineth.

And the reason hereof is, because there is in the cristalline not onely a watery moysture, but also a glutinous or sl••my, which with his lentor and tenacity retaineth the images or formes of the colours.

The chiefe instrument therefore of Sight Nature hath placed within the eye, a round and glutinous humour most like vnto cristall to receiue and retayne the representations of all colours. This cristalline humour if you duely consider when it is taken out of the eye you shall perceiue it hath no colour in it, but will represent any colour layde neere it, as if it were of the same colour.

Moreouer, if you cut this cristalline humour in sunder, you shall finde that it is made of a glutinous and slymy moysture. And because sensation is a kind of reception, there∣fore was the Cristalline made round.

The action also of the Cristalline humour is assisted by the cobweb-like mēbrane which compasseth it about for if you take out the cristalline humour compassed with his Mem∣brane and lay it vpon a written paper, the letters vnder it will appeare much greater then indeed they are, from whence haply came the inuention of Spectacles, and indeed this hu∣mour is a very spectacle to the Opticke nerue, gathering the species which fall vpon it and representing them in a larger forme vnto the nerue.

Sight therefore is perfected and absolued, both by alteration & apprehention or dis∣cerning. The alteration is made in the Cristalline by reason of the transparencie therof; yet is this transparancie of another kind then that of the watery humour, that it might bee both altered and also changed by the light. For that the impression might be more firme, it is thicker then the watery humour, that in the superficies thereof the light might bee bro∣ken ad perpendiculum: for so the light is stronger vnited and corroborated when the beames are obliquely shed abroade and yet meete together againe into one be∣cause of their refraction; wherefore the Cristalline humour is thicker then the other translucide bodies that are in the eye, as the horny membrane, the watery and glassy hu∣mours; because it was made not onely to returne and giue way to light and colours, but also to deteine them, to suffer from them, and to receiue a sensation of visible things: for the thicknesse thereof prohibiteh the transition or vanishing away of the formes which are fixed in the superficies and body therof. For sense is not made without passion or suffring: now it could not suffer vnlesse the action of the Agent had bene receiued vnto it. Not∣withstanding, it is not so thicke or hard that the species or formes could not be imprinted therein, but soft like vnto waxe and viscid that they might cleaue faster thereto. Hence it commeth to passe, that when a strong light, as that of the Sunne; beateth vpon the Cri∣stalline it is pained and offended, because the image of the light maketh a kinde of abode therein. But naturally the image of visible things are no longer retained in the Cristal∣line then is necessary for their perception, but giue way to others: otherwise the sight wold be imperfect: for before the former images be vanished the succeeding cannot bee admit∣ted, because the alteration remaineth in the Cristalline vntill the representation acquir the place when: that is gone the alteration vanisheth together with it, and so there is way made for a new alteration.

The conformation also of the Cristalline helpeth much to make the sight perfect, for example. It is smooth and polished, that the formes therein mightbe most like to the bo∣dyes from which they are diduced. It is round that the light and the perpendicular beames thereof might in it be better vnited, and againe, that the light might be gathered in his su∣perficies where the sensatiue facultie is the strongest, for so the formes euen of the greatest obiects are conuayed whole vnto the Organ. Notwithstanding on the foreside this

roundnesse is somewhat depressed, which depression helpeth much the reception of the formes. On the backeside it is rounder that the light beeing brought vnto the Cristalline might be vnited in it selfe and not disparkled but determine and subsist in the glassy hu∣mour.

The Cristalline humour also before and behind is at liberty or free from connexion, that the light which entereth alway directly, might haue free passage through all the trans∣lucide bodyes of the eyes; for by this meanes whatsoeuer is betwixt the Cristalline humor and the thing seene is continuated by a continuity of transparancy. Yet ought it not to be on euery side loose, because then any extraordinary motion might haue violated the frame of the eye. Nature therefore hath tyed it in his circuite to the neighbour partes, and scituated it in the middest, that it might receiue the seruice & ministery of all the rest.

The glassy humour is seated after the Cristalline, least if the light should haue pas∣sed on to the Net-like and Grapie Membranes which are coloured, it should haue retur∣ned againe to the Cristalline defiled with those colours, and so the sight haue bene for∣stalled by those inward colours which are neerest vnto it. Againe, at this Diaphanum of the glassy humor there is a new refraction made of the light, not such a refraction as is in the Cristalline wherby the light is more vnited, but because the substance of the glas∣sy humor is more rare and thin the light therein is dispersed and weakned, some say al∣so vanisheth, others that it reacheth from thence into the cauity of the Opticke Nerue where the sight is perfected; and surely the finenesse of the net-like Membrane is not a∣ble to returne the light that beateth against it, but rather giueth way thereto.

Another vse of the Glassy humour saith Galen is to nourish the Cristalline, which it doth per Diadosin or transumption; for he thought that the Cristalline humor could not be nourished by blood. But to saue Galens credit, we must heere distinguish, for al parts are nourished by blood; now the Cristalline is a part and therefore it is nourished with blood. We answere, that it is not immediately nourished with bloode but mediately, for because there are no Veines neither in the cristalline nor in the glassy humors (at lest that the sight of man is able to apprehend) blood cannot be conueyed vnto them; ney∣ther indeede ought it, least it should haue infected the Cristalline with a redde colour, which woulde haue bene a great hindrance to the sight; for it behoued aboue al things that the cristalline should be free from all colour, because it was to receiue all. Where∣fore it was necessary that his Aliment should be prepared and not conueyed vnto him before it were fitted for his vse.

The blood therefore conteined in the Veines of the Grapy Membrane in which it is thicke and blackish, is powred foorth into lesser branches running through the Net∣like Membrane, where it receiueth an alteration becomming very thin and of a cleare ruddinesse, which blood is receiued by the glassy humor therein prepared and made a fit Aliment both for itselfe and for the cristalline. Hence it is that Galen saith, The Glassy humor to the Cristalline is like the stomacke to the Liuer.

But because Anatomistes are of diuers opinions concerning the nourishment of the Cristalline humour, it shall not bee amisse to giue you a taste of euery mans appre∣hension in this matter, especially of those that are accounted Maisters in Anatomy.

Galen therefore in the first chapter of his tenth Booke De vsupartium sayth, that the Cristalline humour is nourished by the glassy, and the glassy by that bodye which com∣passeth it about, to wit, the Net-like Membrane, and that per Diadosin or Transumption of matter, because (saith he) the cristalline humor which is white, cleare and resplendent ought not to be nourished by blood, as whose qualities doe differ much one from the other, whereas the aliment should be familiar to that which is nourished thereby. Na∣ture therefore prepared for it a proportionable aliment, to witte, the glassye humour, which glassy humor by how much it is thicker and whiter then blood, by so much doth the cristalline humour exceede it in humidity and whitenesse, for this cristalline is ex∣quisitely white and moderately hard.

Varolius enclineth to Galens opinion, his wordes are these or at least to this pur∣pose. Euery thing is nourished by such a substaunce as determineth nearest vnto that which it should nourish; and therefore the glassy humour is immediately placed behinde the cristaline, and is of a softer and a thinner consistence. Also because so noble a part which needeth such abundance of spirits by reason of their continual expense shold not at any time be defranded of nourishment▪ Nature made so great a quantitie of the

glassy humour, in which nutrition the Chrystaline turneth into his owne nature the thic∣ker parts of the glassy humour because it is farre thicker and faster then it. But the thinner part of the glassy humour she separateth as an vnprofitable excrement from the Chrysta∣line, and thereof maketh the watery humour. Thus far Varolius.

But sayth Archangelus (who thinketh that the Chrystaline is so nourished with the glas∣sie humour as a bone is nourished with the marrow) if the chrystaline and glassy humours be parts of the body then one part shall nourish another? But it may bee answered, that there is a surplussage of the nourishment of the glassye humour which is a conuenient Ali∣ment for the chrystaline. Another question may be asked, sayth he, how Galen sayth that in the glassy humour there is no veine? It is answered that there is no veine conspicuous, but yet there are very many which are so slender that the eye cannot discerne them, and hence it is that the glassy humour is not so white as the chrystaline, because it is sprinkled with many blinde veines. In like manner in the white of the eie which is called Tunica Ad∣nata, there appeare no veins at al, but if the eye be inflamed then many veines which before lay hid doe rise vp and become conspicuous. If the braine of a man bee dissected, there appeare no veines therin, but if it be inflamed then, sayth Archangelus, may an infinite mul∣titude be perceiued to run through his substance.

Laurentius conceiueth that the glassy humour is nourished by bloud, and receiueth small veines from the Ciliar or hayry crown; and that the glassy humour prepares the bloud for the chrystaline, which bloud it changeth least the purity of the chrystaline should be in∣fected, but he doth not thinke that the substance of the glassy humour is conuerted into the chrystaline and assimilated thereto.

Aquapendens his opinion is, that the christaline is nourished by bloud, and that as bones and membranes which are very white and farre remooued from the Nature of bloud by a propriety of their temperament doe change the bloud into their substance: so it com∣meth to passe in the chrystaline humour; and that the bloud is conuayed out of the veines of the grapy into the net-like coate and there depurated that it might better be conuerted into the nitid and pure substance of these bodies. The thicker part is thrust downe into the grapy coate and there collected. The thinner part maketh the watery humour. Nei∣ther doth he thinke it possble the Chrystaline should be nourished by the glassy humour, per Diadosin or Transumption, because the cobweb like membrane commeth betweene the two humours, which Galen was ignorant of, who thought that the forepart only of the Chrystaline was couered, and from that mistaking fell into that errour of nourishment by Transumption. And so much concerning the nourishment of the humours.

Two other vses there remaine of the glassy humour, the one to retaine the spirites for the illustration of the Chrystaline; the other to defend it from the hardnesse of the mem∣branes, and to make it a seat wherein it might securely rest it selfe.

Notes

• A philosophi∣call discourse of the vse of the eie.
• The proper obiects of the sight, Common.
• Particular v∣ses of the parts.
• All sense is by contaction.
• How many wales contac∣tion is made,
• How sight is made.
• Whether in mans eie ther be an ingenit light.
• Tiberius Caesar Cardanus. Ioh. ••ap. Porta.
• Plato thought the eie was firie.
• A threefold fire.
• How the formes are re¦tained.
• That there are 4. refrac∣tions of the light in the eie.
• 6. in a paire of spectacles,
• Another vse of the watery humour,
• A third,
• A fourth.
• A fift.
• A sixt.
• The vse of the christa∣line humour.
• An axiome in philosophy.
• Nor watery.
• But cristalline
• The cristal∣line humour is a spectacle to the nerue.
• How sight is perfected,
• Why the cri∣stalline is thicke.
• Why soft:
• The reason of the confor∣mation of the cristalline.
• The reason of his conne∣xion.
• The vse of the the glassy hu∣mour.
• Galens credit redeemed by a distinction.
• How the cri∣stalline is nourished.
• Diuers opini∣ons concer∣ning the nou∣rishment of the Cristalline humour. Galens opi∣nion.
• Varolius.
• Archangelus.
• Laurentius.
• Aquapendens.
• Other vses of the glassy hu∣mour,