Of the Eyes.
WHY have you one nose and two eyes?
Because our light is more necessary for us than the smelling; and therefore it doth proceed from the goodness of Nature, that if we receive any hurt or loss of one eye, that yet the other should remain; unto the which the spirit with which we see, called Spiritus Visus, is directed when the other is out.
Why have children in their youth great eyes, and why do they become smaller and lesser in their age?
According to Aristotle de Generat, it proceedeth from the want of fire, and from the assembling and meeting together of light and humour, the eyes which are lightened by reason of the sun, which doth lighten the easy humour of the eye, and purge it, and in the absence of the sun those humours become dark and black, and therefore the sight not so good.
Why does the bluish-grey eye see badly in the day time and well at night?
Because, said Aristotle, greyness is light and shining of itself, and the spirits with which we see are weakened in the day time, and strengthened in the night.
Why be men's eyes of divers colours?
This proceedeth, saith Aristotle, by reason of the diversity of the humours; the eye therefore hath four coverings and three humours: the first covering is called consolidative, which is the uttermost, and strong and fat. The second is called a horny skin and covering to the likeness of a horn, and that is a clear covering. The third is called Uvea, of the likeness of a black grape. The fourth is called a cobweb. But according to the opinion of some, the eye doth consist of seven coverings or skins, and three humours. The first humour is called abungines, for the likeness unto the white of an egg. The second glarial, that is clear, like unto ice or crystalline. The third vitreous, that is clear as glass. And the diversity of humour causeth the diversities of the eye.
Why are men who have but one eye good archers? and why do good archers commonly shut one eye? and why do such as behold the stars look through a trunk with one eye?
This matter is handled in the perspective arts, and the Mason is, as it doth appear in the book of causes, because that every virtue and strength united knit together, is stronger than itself dispersed and scattered. Therefore all the force of seeing dispersed in two eyes, the one being shut, is gathered into the other, and so the light is fortified in him, and by the consequence he doth see better and more certainly with one eye being shut than two being open.
Why do such as drink much and laugh much shed much tears? Because that whilst they drink and laugh without measure, the air which is drawn in doth not pass out through the windpipe, and so with force is directed and sent to the eyes, and by their pores passing out doth expel the humours of the eyes, the which humour being so expelled do bring tears.
Why do such as weep much urine but little?
Because (saith Aristotle) the radical humidity of a tear and of urine is of one and the same nature; and therefore where weeping doth increase their urine doth diminish; and that they be of one nature is plain to the taste, because they are both salt.
Why do some that have clear eyes see nothing at all?
By reason of the oppilation and naughtiness of the sinews with which: we see; for the temples being destroyed, the strength of the light cannot be carried from the brain to the eye, as the philosopher doth teach, lib. de sen. and senatio.
Why is the eye clear and smooth like unto glass?
Because the things which may be seen are better beaten back from a smooth thing than otherwise, that thereby the sight should strengthen.
Secondly, I answer it is because the eye is very moist above all parts of the body, and of a waterish nature; and as the water is clear and smooth, so likewise is the eye.
Why do men who have their eyes deep in their heads see well afar off, and the like in beasts?
Because, saith Aristotle (2 de Gener. Animal), the force and power by which we see is dispersed in them, and doth go directly to the thing which is seen. And this is proved by a similitude, because that when a man doth stand in a deep ditch or well, he doth see in the day time, standing in those places, the stars of the firmament; as Aristotle doth teach in his treatise De Formula Specula; because that then the power of the sight and of the beams are not scattered.
Wherefore do those men that have their eyes far out and not deep in their head see but meanly, and not far distant?
Because, saith Aristotle, the beams of the sight which pass from the eye are scattered on every side, and go directly unto the thing that is seen, and therefore the sight is weakened.
Why are many beasts born blind, as lions' whelp. and dogs' whelps?
Because such beasts are not yet of perfect ripeness and maturity, and the course of nutriment doth not work in them. And this is proved by a similitude of the swallow, whose eyes, if they were taken out when they are little ones in the nest, would grow again; and this is plain in many other beasts, which are brought forth before their time as it were dead, as bear whelps. And this reason doth belong rather to the perspective than the natural philosopher.
Why do the eyes of a woman that hath her flowers stain a new glass, as Aristotle saith, de somno and vigil.; and this is the like problem, why doth a basilisk kill a man with his sight?
To the first I answer, that when the flowers do run from a woman, then a most venomous air is dissolved in them, which doth ascend unto the woman's head; and she having grief of her head, doth cover it with many veils and kerchiefs; and because the eyes are full of small insensible holes, which are called pores, there the air seeketh a passage, and so doth infect the eyes, which are full of blood. And their eyes do appear also dropping and full of tears, by reason of the evil vapour that is in them, and those vapours are incorporated and multiplied, until they come unto the glass before them; and by reason that such a glass is found, clear, and smooth, is doth easily receive that which is unclean.
To the second it is answered that the basilisk is a very venomous and infected beast, and that there pass from his eye venomous vapours, which are multiplied upon the thing which is seen by him, and even unto the eye of man; the which venomous vapours or humours entering into the body do infect him, and so in the end the man dieth. And this is also the reason why the basilisk, looking upon a shield perfectly well made with fast clammy pitch, or any hard smooth thing, doth kill himself, because the humours are beaten back from the smooth hard thing unto the basilisk, by which beating back he is killed. And the like is said of a woman when she hath her monthly disease, whereof it followeth that some old women do hurt themselves when they look upon glasses, or other firm and solid thing, in the time of their terms.
Why are not sparkling cats' and wolves' eyes seen in the light and not in the dark?
Because that the greater light doth darken the lesser, and therefore in a greater light the sparkling cannot be seen, but the greater the darkness the easier it is seen, and is made more strong and shining, because it is not then hindered by a greater external light, which might darken it.
Why doth a man beholding himself in a glass presently forget his own disposition?
Answer is made in lib. de forma speculi that the image seen by the glass doth represent it weakly and indirectly to the power of the sight; and because it is represented weakly, it is also weakly apprehend, and by consequence is not long retained.
Why is the sight recreated and refreshed by a green colour, as this verse showeth:
"Fens, speculum gramen oculis sunt aleviamen"?
Because the green colour doth meanly move the instrument of sight, and therefore doth comfort the sight; but this doth not black nor white colours, because the colours do vehemently stir and alter the organ and instrument of the light, and therefore make the greater violence, but by how much the more violent the thing is which is felt or seen, the more it doth destroy and weaken the sense, as Aristotle doth teach, lib. 2, do animal.