CHAP. 53.—THE DIVERSITY OF THE COLOUR OF THE EYES.
The eyes vary in colour in the human race only; in all other animals they are of one uniform colour peculiar to the kind, though there are some horses that have eyes of an azure colour. But in man the varieties and diversities are most numerous; the eyes being either large, of middling size, remarkably small, or remarkably prominent. These last are generally supposed to be very weak, while those which are deep-seated are considered the best, as is the case also with those which in colour resemble the eyes of the goat.
CHAP. 54.—THE THEORY OF SIGHT—PERSONS WHO CAN SEE BY NIGHT.
In addition to this, there are some persons who can see to a very great distance, while there are others, again, who can only distinguish objects when brought quite close to them. The vision of many stands in need of the rays of the sun; such persons cannot see on a cloudy day, nor yet after the sun has set. Others, again, have bad sight in the day-time, but a sight superior to that of others by night. Of persons having double pupils, or the evil eye, we have already spoken[196] at sufficient length. Blue[197] eyes are the best for seeing in the dark.
It is said that Tiberius Cæsar, like no other human being, was so endowed by Nature, that on awaking in the night[198] he could for a few moments distinguish objects just as well as in the clearest daylight, but that by degrees he would find his sight again enveloped in darkness. The late Emperor Augustus had azure eyes like those of some horses, the white being larger than with other men; he used to be very angry if a person stared intently at them for this peculiarity. Claudius Cæsar had at the corners of the eyes a white fleshy substance, covered with veins, which would occasionally become suffused with blood; with the Emperor Caius[199] they had a fixed, steady gaze, while Nero could see nothing distinctly without winking, and having it brought close to his eyes. The Emperor Caius had twenty pairs of gladiators in his training-school, and of all these there were only two who did not wink the eyes when a menacing gesture was made close to them: hence it was that these men were invincible. So difficult a matter is it for a man to keep his eyes from winking: indeed, to wink is so natural to many, that they cannot desist from it; such persons we generally look upon as the most timid.
No persons have the eye all of one colour; that of the middle of the eye is always different from the white which surrounds it. In all animals there is no part in the whole body that is a stronger exponent of the feelings, and in man more especially, for it is from the expression of the eye that we detect clemency, moderation, compassion, hatred, love, sadness, and joy. From the eyes, too, the various characters of persons are judged of, according as they are ferocious, menacing, sparkling, sedate, leering, askance, downcast, or languishing. Beyond a doubt it is in the eyes that the mind has its abode: sometimes the look is ardent, sometimes fixed and steady, at other times the eyes are humid, and at others, again, half closed. From these it is that the tears of pity flow, and when we kiss them we seem to be touching the very soul. It is the eyes that weep, and from them proceed those streams that moisten our cheeks as they trickle down. And what is this liquid that is always so ready and in such abundance in our moments of grief, and where is it kept in reserve at other times? It is by the aid of the mind that we see, by the aid of the mind that we enjoy perception; while the eyes, like so many vessels, as it were, receive its visual faculties and transmit them. Hence it is that profound thought renders a man blind for the time, the powers of sight being withdrawn from external objects and thrown inward: so, too, in epilepsy, the mind is covered with darkness, while the eyes, though open, are able to see nothing. In addition to this, it is the fact that hares, as well as many human beings, can sleep with the eyes open, a thing which the Greeks express by the term κορυβαντιᾷν. Nature has composed the eye of numerous membranes of remarkable thinness, covering them with a thick coat to ensure their protection against heat and cold. This coat she purifies from time to time by the lachrymal humours, and she has made the surface lubricous and slippery, to protect the eye against the effects of a sudden shock.
CHAP. 55.—THE NATURE OF THE PUPIL—EYES WHICH DO NOT SHUT.
In the midst of the cornea of the eye Nature has formed a window in the pupil, the small dimensions of which do not permit the sight to wander at hazard and with uncertainty, but direct it as straight as though it were through a tube, and at the same time ensure its avoidance of all shocks communicated by foreign bodies. The pupils are surrounded by a black circle in some persons, while it is of a yellowish cast with others, and azure again with others. By this happy combination the light is received by the eye upon the white that lies around the pupil, and its reflection being thus tempered, it fails to impede or confuse the sight by its harshness. So complete a mirror, too, does the eye form, that the pupil, small as it is, is able to reflect the entire image of a man. This[200] is the reason why most birds, when held in the hand of a person, will more particularly peck at his eyes; for seeing their own likeness reflected in the pupils, they are attracted to it by what seem to be the objects of their natural affection.
It is only some few beasts of burden that are subject to maladies of the eyes towards the increase of the moon: but it is man alone that is rescued from blindness by the discharge of the humours[201] that have caused it. Many persons have had their sight restored after being blind for twenty years; while others, again, have been denied this blessing from their very birth, without there being any blemish in the eyes. Many persons, again, have suddenly lost their sight from no apparent cause, and without any preceding injury. The most learned authors say that there are veins which communicate from the eye to the brain, but I am inclined to think that the communication is with the stomach; for it is quite certain that a person never loses the eye without feeling sickness at the stomach. It is an important and sacred duty, of high sanction among the Romans, to close[202] the eyes of the dead, and then again to open them when the body is laid on the funeral pile, the usage having taken its rise in the notion of its being improper that the eyes of the dead should be beheld by man, while it is an equally great offence to hide them from the view of heaven. Man is the only living creature the eyes of which are subject to deformities, from which, in fact, arose the family names of “Strabo”[203] and “Pætus.”[204] The ancients used to call a man who was born with only one eye, “cocles,” and “ocella,” a person whose eyes were remarkably small. “Luscinus” was the surname given to one who happened to have lost one eye by an accident.
The eyes of animals that see at night in the dark, cats, for instance, are shining and radiant, so much so, that it is impossible to look upon them; those of the she-goat, too, and the wolf are resplendent, and emit a light like fire. The eyes of the sea-calf and the hyæna change successively to a thousand colours; and the eyes, when dried, of most of the fishes will give out light in the dark, just in the same way as the trunk of the oak when it has become rotten with extreme old age. We have already mentioned[205] the fact, that animals which turn, not the eyes but the head, for the purpose of looking round, are never known to wink. It is said,[206] too, that the chameleon is able to roll the eye-balls completely round. Crabs look sideways, and have the eyes enclosed beneath a thin crust. Those of craw-fish and shrimps are very hard and prominent, and lie in a great measure beneath a defence of a similar nature. Those animals, however, the eyes of which are hard, have worse sight than those of which the eyes are formed of a humid substance. It is said that if the eyes are taken away from the young of serpents and of the swallow,[207] they will grow again. In all insects and in animals covered with a shell, the eyes move just in the same way as the ears of quadrupeds do; those among them which have a brittle[208] covering have the eyes hard. All animals of this nature, as well as fishes and insects, are destitute of eye-lids, and their eyes have no covering; but in all there is a membrane that is transparent like glass, spread over them.