§31.23Διὰ τί δάκρυα, ἐὰν μὲν κλαίοντες ἀφίωμεν, θερμά ἐστιν, ἐὰν δὲ πονοῦντες τοὺς ὀφθαλμοὺς δακρύωμεν, ψυχρά;
Why is it that, if we shed tears when crying, they are warm, but if we weep because our eyes are in pain, they are cold?
ἢ ὅτι τὸ μὲν ἄπεπτον ψυχρόν, τὸ δὲ πεπεμμένον θερμόν;
Is it because what is unconcocted is cold, while what is concocted is warm?
ἡ δὲ μαλακία ὅλως πᾶσά ἐστιν ἐξ ἀπεψίας, καὶ τῶν τοὺς ὀφθαλμοὺς πονούντων ἄπεπτόν ἐστι τὸ δάκρυον· διὸ ψυχρόν.
All weakness in general arises from lack of concoction, and the tears of those whose eyes are in pain are unconcocted; therefore they are cold.
διὰ τοῦτο καὶ οἱ ἰατροὶ οἴονται σημεῖον εἶναι μεγάλης νόσου τοὺς ψυχροὺς ἱδρῶτας, τοὺς δὲ θερμοὺς τοὐναντίον ἀπαλλακτικούς.
For this reason, physicians also consider cold sweats to be a sign of a major illness, while warm sweats, on the contrary, are signs of release from it.
ὅταν μὲν γὰρ ᾖ τὸ περίττωμα πολύ, οὐ δύνανται τὸ ἐντὸς θερμὸν πέττειν, ὥστε ἀνάγκη ψυχρὸν εἶναι· ὅταν δὲ ὀλίγον, κρατεῖ.
For when the residue is abundant, the internal heat cannot concoct it, so that it is necessarily cold; but when it is small, the heat prevails.
γίνονται δὲ ἐκ τῶν περιττωμάτων αἱ ἀρρωστίαι.
And illnesses arise from residues.
§31.24Διὰ τί ποτε εὐκινήτων ὄντων τῶν δεξιῶν μερῶν ὁ ὀφθαλμὸς ὁ ἀριστερὸς μᾶλλον τοῦ δεξιοῦ συνάγεται;
Why is it that, although the right-side parts are more agile, the left eye contracts more than the right?
ἢ ὅτι τὰ ἀριστερὰ πάντα ὑγρότερα τῶν δεξιῶν ἐστίν, τὰ δὲ ὑγρότερα μᾶλλον συνάγεσθαι πέφυκεν·
Is it because all the left parts are moister than the right, and moister things naturally contract more?
εἶτα εἰς τὸ δεξιὸν μᾶλλον ἀποτελεῖν δύναται, τοῦ ἀριστεροῦ δυναμένου καὶ καθ’ αὑτό.
Furthermore, [the right eye] is more able to achieve its effect towards the right, while the left is capable of doing so even by itself.
§31.25Διὰ τί ἀμφότεροι κατὰ ἀσθένειάν τινα τῶν ὀφθαλμῶν διακείμενοι, ὅ τε μύωψ καὶ ὁ πρεσβύτης, ὁ μὲν ἐγγὺς προσάγει, ἄν τι βούληται ἰδεῖν, ὁ δὲ πόρρω ἀπάγει;
Why is it that, although both suffer from some weakness of the eyes, the short-sighted person brings things close if he wants to see anything, while the presbyopic person moves them far away?
ἢ ὅτι οὐχ ὁμοία ἡ ἀσθένεια παρέπεται αὐτοῖς;
Is it because the weakness that accompanies them is not similar?
ὁ μὲν γὰρ πρεσβύτης αὐτὸ ἰδεῖν ἀδύνατός ἐστιν· οὗ δὴ συμπίπτει ἡ ὄψις αὐτῷ, ἀπάγει τὸ θεώμενον, ἅτε καὶ μάλιστα μέλλων ὄψεσθαι· πόρρω δὲ συμπίπτει.
For the presbyopic person is unable to see it [close by]; so, where his vision happens to meet, he withdraws the object of sight, as he is most likely to see it there; and [the meeting] happens far away.
ὁ δὲ αὐτὸ μὲν ὁρᾷ, ποῖα δὲ κοῖλα ἢ ποῖα ἐξέχοντα τοῦ ὁρωμένου οὐκέτι δύναται κρίνειν, ἀλλὰ περὶ ταῦτα ἀπατᾶται.
But the other sees the object itself, but can no longer judge which parts of what is seen are hollow and which are projecting, but is deceived about these.
τὰ δὲ κοῖλα ἢ τὰ ἐξέχοντα μάλιστα τῇ αὐγῇ κρίνεται.
And hollows and projections are judged chiefly by the light.
πόρρωθεν μὲν οὖν οὐ δύναται τῇ αὐγῇ καταμαθεῖν πῶς ἐπιβάλλει ἐπὶ τὸ ὁρατόν· ἐγγύθεν δὲ μᾶλλον καταφανής ἐστιν.
From far off, therefore, he cannot perceive by the light how it falls upon the object of sight; but from close by, it is more apparent.
§31.26Διὰ τί τῶν ζῴων ἄνθρωπος ἢ μόνον ἢ μάλιστα διαστρέφεται;
Why is it that of all animals man either alone or most of all becomes squint-eyed?
ἢ ὅτι ἢ μόνον ἢ μάλιστα ἐπίληπτον ἐν τῇ νεότητι γίνεται, ὅτε καὶ διαστρέφεσθαι συμβαίνει πᾶσιν;
Is it because he either alone or most of all is subject to epilepsy in youth, at which time it happens to all to squint?
§31.27Διὰ τί οἱ ἄνθρωποι μόνοι τῶν ἄλλων ζῴων τὰ ὄμματα διαστρέφονται;
Why is it that humans alone of the other animals have squinting eyes?
πότερον διὰ τὸ ἐλάχιστον διάστημα εἶναι τῶν ὀμμάτων, καὶ ἐπ’ εὐθείας, ὥστε εὔδηλον σφόδρα γίνεται τὸ μὴ κατωρθωμένον.
Is it because the distance between their eyes is very small and they are on a straight line, so that any failure to be straight becomes extremely obvious?
ἢ διότι τῶν ἄλλων μονόχροα τὰ ὄμματά ἐστι μᾶλλον·
Or is it because the eyes of other animals are more of a single color?
εἰ δ’ ἦν ἓν χρῶμά τι τοῦ ὄμματος, οὐκ ἦν διαστροφή.
If the eye were of one color, there would be no squinting.
ἢ διότι μόνοι ἐν τῷ γένει ἐπίληπτοι γίνονται τῶν ζῴων, ἡ δ’ ἐπίληψις διαστροφὴν ποιεῖ, ὅταν γένηται, ὥσπερ καὶ τῶν ἄλλων μορίων·
Or is it because they alone among the class of animals are subject to epilepsy, and epilepsy, when it occurs, produces distortion just as in the other parts?
ἀλλ’ ἐνίοις ὀψὲ παντελῶς γίνεται ἡ διαστροφή, ὅσοις τὸ ἀρρώστημα.
However, in some, the distortion occurs completely late, in as many as have the disease.
§31.28Διὰ τί πρὸς τὸν λύχνον καὶ πρὸς τὸν ἥλιον προστησάμενοι τὴν χεῖρα πρὸ τοῦ φωτὸς μᾶλλον ὁρῶμεν;
Why is it that, when we hold our hand up before the light against a lamp or the sun, we see better?
ἢ ὅτι τὸ ἀπὸ τοῦ ἡλίου καὶ λύχνου φῶς προσπῖπτον μὲν ἡμῶν πρὸς τὴν ὄψιν ἀσθενεστέραν ποιεῖ δι’ ὑπερβολήν;
Is it because the light from the sun and the lamp falling upon our sight makes it weaker because of its excess?
φθείρει γὰρ αὐτὰ καὶ τὰ συγγενῆ τῇ ὑπερβολῇ.
For excess destroys both sight itself and things related to it.
εἰρχθέντα δὲ ὑπὸ τῆς χειρὸς τὴν μὲν ὄψιν οὐ πημαίνει, τὸ δὲ ὁρώμενον ὁμοίως ἐστὶν ἐν φωτί.
But when the light is blocked by the hand, it does not harm the sight, while the object seen is equally in the light.
διὸ ἡ μὲν μᾶλλον δρᾷ, τὸ δὲ ὁρώμενον οὐδὲν ἧττον ὁρᾶται.
Therefore, the sight functions better, and the object seen is seen no less.
§31.29Διὰ τί χεὶρ μὲν καὶ ποὺς διαφορὰν ἔχει πρὸς [τὰ] δεξιὰ 〈καὶ〉 τὰ ἀριστερά, ὄμμα δὲ καὶ ἀκοὴ οὔ;
Why is it that, while the hand and foot differ in respect to the right and left, the eye and hearing do not?
ἢ ὅτι τὰ στοιχεῖα τὰ εἰλικρινῆ ἀδιάφορα, ἐν δὲ τοῖς ἐκ τῶν στοιχείων ἡ διαφορά;
Is it because the pure elements have no difference, whereas the difference is in those things made of elements?
αὗται δὲ αἱ αἰσθήσεις εἰσὶν ἐξ εἰλικρινῶν, ἡ μὲν ὄψις πυρός, ἡ δ’ ἀκοὴ ἀέρος.
And these senses consist of pure elements, sight of fire and hearing of air.