They bée called lyghts, for they receiue light without, and conuey it and ſend it forth. The eyes bée the inſtrumentes of ſight, as Conſtantine ſaith. And they bée two, leaſt if by happe the one were diſeaſed, that other might ſupplye the lacke thereof. And for the eie is in ſteede of a waite, or a ſpie, kinde ſetteth them in the higheſt place of the bodye. The eye is made of tenne things: Of ſeauen ſmal curtils, and thrée humours. Among the humours, the firſt is Whitiſh, the ſecond Criſtaline, the thirde Glaſſie. The ſeauen curtills bée ſeauen ſkinnes, either webbes, that beclippe the foreſayde humours, and diuideth them a ſunder. And in the middle of theſe humours the ſight is formed. And they be of kinde ſo ordinate: togethers, that foure bée in the formoſt parte. Of the which the firſt is called Tela Aranea, as it were the webbe of a Spider. The ſecond Vuea Grapie: The third Cornea, Hornie: The fourth Coniunctiua, Able to ioyne. And thrée bée in the inner part, the which three bée called Rethina, Sederina, and Sclirotica, that is, hard, as it ſhall bée ſhewed héereafter. But among all theſe, one alone is the inſtrument of ſight, that is the humour Criſtalline. And hath that name of Criſtall: for it is lyke Chriſtall in coulour. This humour Chriſtallinus, as Conſtāntine ſayth, is white, bright, cléere and plaine without: and is ſet in the middle of all the other, that all the other ſhoulde ſerue it euenly. It is paſſable, cléere, and bright, that it may the ſooner bée chaunged into coulours oppoſite, and haue & take lykeneſſe of all coulours indifferently. Alſo it is round in ſhape and ſubſtaunce, that it bée not lightly hurt and grieued. And alſo that no ſuperfluitie be gathered in ye corners thereof: by the which ſuperfluitie, it might happely bée grieued. And becauſe it ſhoulde not be too much moueable by too much roundneſſe, it is ſomewhat plaine, to be of meaſurable ſwiftneſſe. For euery thing that is all round (hurt) in the ſides is vnſtable, and vnſteadfaſt, as Conſtantine ſaith. And that by this humour the ſight is made, it is thus proued. For it ought to bée cloſed betweene this humour and the ſpirite of sight, as ſome humour or other thing: the working and the dooing of ſight is away and faileth. For the ſpirite of ſight may not pearce, and come therto ſor the let that is betwéene. This humour ſpringeth of the ouermoſt parts of the braine, that be pure, thinne, and bright, that letteth not paſſing of light. And properly to ſpeake, this is the blacke of the eie: and is called the middle of the eye, or the point of the eie, & therin is porperly the vertue of ſight, & of ſeeing. Wherin vnto vs beholding néere, appeare certeine Images, as it were in a mirrour: but thereof we ſhall ſpeake heereafter. This humour is ſet in the middle of the other two, betwéene the glaſſe and the white. The glaſſie humor is cleane, pure, & bright as glaſſe, ſo yt we may ſee there through, and is called Gelados in ye language of Arabia, & helpeth in two manners. Firſt & principally it taketh bloud to nouriſh the humour Criſtalline, & maketh it white and able to turne ſoone into the ſubſtance of the humour Criſtalline. It is not conuenient that ſo cleane & pure a humour ſhould receiue vnpure feeding: the which it ſhould doe, if ye red bloud not defied, not whited, not made ſubtill, were by any occaſion medled wt the humor Criſtalline. The ſecond wiſe it helpeth & defendeth & kéepeth the humour chriſtalline frō touching & ſharpneſſe of tunicles: the which in reſpect thereof be hard & more boiſtous. Likewiſe the humour that is called Albugineus, the which by another name is called Euagaidos, is in ye further part: & helpeth the Criſtalline in two manners: for it ſaueth him from hurting & grieuing, & by his moiſture tempereth the Chriſtalline, for the humour Albugineus in the eyen is more moiſt, & the Chriſtalline yt is called alſo Chriſtallidos is more drie. Alſo this humour Albugineus by his thickneſſe gathereth togethers & comforteth the ſpirit of ſight. Theſe thrée parts of ye eie, though they be called humours, yet they be not properly humors: for they be not ſoft & fléeting as humours be, but they haue much more thicknes in themſelues
