Chapter XVIII.—Concerning Sensation.

Sensation is that faculty of the soul whereby material objects can be apprehended or discriminated. And the sensoria are the organs or members through which sensations are conveyed. And the objects of sense are the things that come within the province of sensation. And lastly, the subject of sense is the living animal which possesses the faculty of sensation. Now there are five senses, and likewise five organs of sense.

The first sense is sight: and the sensoria or organs of sight are the nerves of the brain and the eyes. Now sight is primarily perception of colour, but along with the colour it discriminates the body that has colour, and its size and form, and locality, and the intervening space and the number429    Nemes., ch. 71.: also whether it is in motion or at rest, rough or smooth, even or uneven, sharp or blunt, and finally whether its composition is watery or earthy, that is, wet or dry.

The second sense is hearing, whereby voices and sounds are perceived. And it distinguishes these as sharp or deep, or smooth or loud. Its organs are the soft nerves of the brain, and the structure of the ears. Further, man and the ape are the only animals that do not move their ears.

The third sense is smell, which is caused by the nostrils transmitting the vapours to the brain: and it is bounded by the extreme limits of the anterior ventricle of the brain. It is the faculty by which vapours are perceived and apprehended. Now, the most generic distinction between vapours is whether they have a good or an evil odour, or form an intermediate class with neither a good nor an evil odour. A good odour is produced by the thorough digestion in the body of the humours. When they are only moderately digested the intermediate class is formed, and when the digestion is very imperfect or utterly wanting, an evil odour results.

The fourth sense is taste: it is the faculty whereby the humours are apprehended or perceived, and its organs of sense are the tongue, and more especially the lips, and the palate (which the Greeks call οὐρανίσκος ), and in these are nerves that come from the brain and are spread out, and convey to the dominant part of the soul the perception or sensation they have encountered430    Nemes., ch. 9.. The so-called gustatory qualities of the humours are these:—sweetness, pungency, bitterness, astringency, acerbity, sourness, saltness, fattiness, stickiness; for taste is capable of discriminating all these. But water has none of these qualities, and is therefore devoid of taste. Moreover, astringency is only a more intense and exaggerated form of acerbity.

The fifth sense is touch, which is common to all living things431    Ibid., ch. 8.. Its organs are nerves which come from the brain and ramify all through the body. Hence the body as a whole, including even the other organs of sense, possesses the sense of touch. Within its scope come heat and cold, softness and hardness, viscosity and brittleness432    ξηρόν is added in some mss. but wrongly: for it is what is perceived by touch alone that is here spoken of, whereas, below, we are told that dryness is recognised also by sight; so also in Nemesius., heaviness and lightness: for it is by touch alone that these qualities are discriminated. On the other hand, roughness and smoothness, dryness and wetness, thickness and thinness, up and down, place and size, whenever that is such as to be embraced in a single application of the sense of touch, are all common to touch and sight, as well as denseness and rareness, that is porosity, and rotundity if it is small, and some other shapes. In like manner also by the aid of memory and thought perception of the nearness of a body is possible, and similarly perception of number up to two or three, and such small and easily reckoned figures. But it is by sight rather than touch that these things are perceived.

The Creator, it is to be noted, fashioned all the other organs of sense in pairs, so that if one were destroyed, the other might fill its place. For there are two eyes, two ears, two orifices of the nose, and two tongues, which in some animals, such as snakes, are separate, but in others, like man, are united. But touch is spread over the whole body with the exception of bones, nerves, nails, horns, hairs, ligaments, and other such structures.

Further, it is to be observed that sight is possible only in straight lines, whereas smell and hearing are not limited to straight lines only, but act in all directions. Touch, again, and taste act neither in straight lines, nor in every direction, but only when each comes near to the sensible objects that are proper to it.

Περὶ αἰσθήσεως

Αἴσθησίς ἐστι δύναμις τῆς ψυχῆς ἀντιληπτικὴ τῶν ὑλῶν ἤγουν διαγνωστική: αἰσθητήρια δὲ τὰ ὄργανα ἤγουν τὰ μέλη, δι' ὧν αἰσθανόμεθα: αἰσθητὰ δὲ τὰ τῇ αἰσθήσει ὑποπίπτοντα: αἰσθητικὸν δὲ τὸ ζῷον τὸ ἔχον τὴν αἴσθησιν. Εἰσὶ δὲ αἰσθήσεις πέντε, ὁμοίως καὶ αἰσθητήρια πέντε.

Πρώτη αἴσθησις ὅρασις. Αἰσθητήρια δὲ καὶ ὄργανα τῆς ὁράσεως τὰ ἐξ ἐγκεφάλου νεῦρα καὶ οἱ ὀφθαλμοί. Αἰσθάνεται δὲ ἡ ὄψις κατὰ πρῶτον μὲν λόγον τοῦ χρώματος, συνδιαγινώσκει δὲ τῷ χρώματι καὶ τὸ κεχρωσμένον σῶμα καὶ τὸ μέγεθος αὐτοῦ καὶ τὸ σχῆμα καὶ τὸν τόπον, ἔνθα ἐστί, καὶ τὸ διάστημα τὸ μεταξὺ καὶ τὸν ἀριθμὸν κίνησίν τε καὶ στάσιν καὶ τὸ τραχὺ καὶ λεῖον καὶ ὁμαλὸν καὶ ἀνώμαλον καὶ τὸ ὀξὺ καὶ τὸ ἀμβλὺ καὶ τὴν σύστασιν, εἴτε ὑδατώδης, εἴτε γεώδης ἤγουν ὑγρὰ ἢ ξηρά.

Δευτέρα αἴσθησίς ἐστιν ἀκοὴ τῶν φωνῶν καὶ τῶν ψόφων οὖσα αἰσθητική. Διαγινώσκει δὲ αὐτῶν τὴν ὀξύτητα καὶ τὴν βαρύτητα λειότητά τε καὶ τραχύτητα καὶ μέγεθος. Ὄργανα δὲ αὐτῆς τὰ νεῦρα τὰ ἐξ ἐγκεφάλου τὰ μαλακὰ καὶ τῶν ὤτων ἡ κατασκευή. Μόνος δὲ ἄνθρωπος καὶ πίθηκος οὐ κινοῦσι τὰ ὦτα.

Τρίτη αἴσθησις ὄσφρησις, ἥτις γίνεται μὲν διὰ τῶν ῥινῶν ἀναπεμπουσῶν τοὺς ἀτμοὺς ἐπὶ τὸν ἐγκέφαλον, περαίνεται δὲ εἰς τὰ πέρατα τῶν προσθίων κοιλιῶν τοῦ ἐγκεφάλου. Ἔστι δὲ αἰσθητικὴ καὶ ἀντιληπτικὴ τῶν ἀτμῶν. Τῶν δὲ ἀτμῶν ἡ γενικωτάτη διαφορά ἐστιν εὐωδία καὶ δυσωδία καὶ τὸ μέσον τούτων, ὃ μήτε εὐῶδές ἐστι μήτε δυσῶδες. Γίνεται δὲ εὐωδία τῶν ὑγρῶν τῶν ἐν τοῖς σώμασιν ἀκριβῶς πεφθέντων, μέσως δὲ μέση διάθεσις: καταδεέστερον δὲ ἢ μηδὲ ὅλως πεφθέντων ἡ δυσωδία γίνεται.

Τετάρτη αἴσθησις ἡ γεῦσις. Ἔστι δὲ τῶν χυμῶν ἀντιληπτικὴ ἤγουν αἰσθητική. Ὄργανα δὲ αὐτῆς ἡ γλῶσσα καὶ ταύτης πλέον τὸ ἄκρον καὶ ἡ ὑπερῴα, ἣν καλοῦσί τινες οὐρανίσκον: ἐν οἷς ἐστι τὰ ἐξ ἐγκεφάλου φερόμενα νεῦρα πεπλατυσμένα καὶ ἀπαγγέλλοντα τῷ ἡγεμονικῷ τὴν γενομένην ἀντίληψιν ἤγουν αἴσθησιν. Αἱ δὲ καλούμεναι γευστικαὶ ποιότητες τῶν χυμῶν εἰσιν αὗται: γλυκύτης, δριμύτης, ὀξύτης, στρυφνότης, αὐστηρότης, πικρότης, ἁλμυρότης, λιπαρότης, γλισχρότης: τούτων γάρ ἐστιν ἡ γεῦσις διαγνωστική. Τὸ δὲ ὕδωρ ἄποιόν ἐστι κατὰ ταύτας τὰς ποιότητας: οὐδεμίαν γὰρ αὐτῶν ἔχει. Ἡ δὲ στρυφνότης ἐπίτασις καὶ πλεονασμός ἐστι τῆς αὐστηρότητος.

Πέμπτη αἴσθησίς ἐστιν ἡ ἁφή, ἥτις κοινή ἐστι πάντων τῶν ζῴων: ἥτις γίνεται ἐκ τοῦ ἐγκεφάλου πεμπομένων νεύρων εἰς ὅλον τὸ σῶμα. Διὸ καὶ ὅλον τὸ σῶμα, ἀλλὰ καὶ τὰ ἄλλα αἰσθητήρια τὴν τῆς ἁφῆς ἔχουσιν αἴσθησιν. Ὑπόκειται δὲ τῇ ἁφῇ τὸ ψυχρὸν καὶ θερμόν, τό τε μαλακὸν καὶ σκληρὸν καὶ γλίσχρον καὶ κραῦρον, βαρύ τε καὶ κοῦφον: διὰ μόνης γὰρ ἁφῆς ταῦτα γνωρίζεται. Κοινὰ δὲ ἁφῆς καὶ ὄψεως τό τε τραχὺ καὶ λεῖον, τό τε ξηρὸν καὶ ὑγρόν, παχύ τε καὶ λεπτόν, ἄνω τε καὶ κάτω καὶ ὁ τόπος καὶ τὸ μέγεθος, ὅταν εἴη τοιοῦτο ὡς κατὰ μίαν προσβολὴν τῆς ἁφῆς περιλαμβάνεσθαι, καὶ τὸ πυκνόν τε καὶ μανὸν ἤγουν ἀραιὸν καὶ τὸ στρογγύλον, ὅταν εἴη μικρόν, καὶ ἄλλα τινὰ σχήματα. Ὁμοίως δὲ καὶ τοῦ πλησιάζοντος σώματος αἰσθάνεται, σὺν τῇ μνήμῃ δὲ καὶ τῇ διανοίᾳ, ὡσαύτως δὲ καὶ ἀριθμοῦ μέχρι δύο ἢ τριῶν καὶ τούτων μικρῶν καὶ ῥᾳδίως περιλαμβανομένων. Τούτων δὲ μᾶλλον τῆς ἁφῆς ἡ ὅρασις ἀντιλαμβάνεται.

Χρὴ γινώσκειν, ὡς ἕκαστον τῶν ἄλλων αἰσθητηρίων διπλοῦν ὁ δημιουργὸς κατεσκεύασεν, ἵνα τοῦ ἑνὸς βλαπτομένου τὸ ἕτερον ἀναπληροῖ τὴν χρείαν: δύο γὰρ ὀφθαλμοὺς καὶ δύο ὦτα καὶ δύο πόρους τῆς ῥινὸς καὶ δύο γλώσσας, ἀλλ' ἐν τοῖς μὲν τῶν ζῴων διῃρημένας ὡς ἐν τοῖς ὄφεσιν, ἐν τοῖς δὲ ἡνωμένας ὡς ἐν τῷ ἀνθρώπῳ: τὴν δὲ ἁφὴν ἐν ὅλῳ τῷ σώματι πλὴν ὀστέων καὶ νεύρων ὀνύχων τε καὶ κεράτων καὶ τριχῶν καὶ συνδέσμων καὶ ἄλλων τινῶν τοιούτων.

Χρὴ γινώσκειν, ὅτι ἡ μὲν ὄψις κατ' εὐθείας γραμμὰς ὁρᾷ, ἡ δὲ ὄσφρησις καὶ ἡ ἀκοὴ οὐ κατ' εὐθεῖαν μόνον, ἀλλὰ πανταχόθεν. Ἡ δὲ ἁφὴ καὶ ἡ

γεῦσις οὐδὲ κατ' εὐθεῖαν οὐδὲ πανταχόθεν γνωρίζουσιν, ἀλλὰ τότε μόνον, ὅταν αὐτοῖς πλησιάσωσι τοῖς ἰδίοις αἰσθητοῖς.