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[1] at sufficient length. Blue[2] 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[3] 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[4] 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, me- nacing, sparkling, sedate, leering, askance, downcast, or lan- guishing. 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 xorubantia=|n. 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.