Furthermore, the opposite affection, that, I mean, of mirth and laughter, contributes to establish the argument; for the pores of the body, in the case of those who are dissolved in mirth by hearing something pleasant, are also somehow dissolved and relaxed. Just as in the former case the slight and insensible exhalations of the pores are checked by grief, and, as they compress the internal arrangement of the higher viscera, drive up towards the head and the cerebral membrane the humid vapour which, being retained in excess by the cavities of the brain, is driven out by the pores at its base , while the closing of the eyelids expels the moisture in the form of drops (and the drop is called a tear), so I would have you think that when the pores, as a result of the contrary condition, are unusually widened, some air is drawn in through them into the interior, and thence again expelled by nature through the passage of the mouth, while all the viscera (and especially, as they say, the liver) join in expelling this air by a certain agitation and throbbing motion; whence it comes that nature, contriving to give facility for the exit of the air, widens the passage of the mouth, extending the cheeks on either side round about the breath; and the result is called laughter.

Ἀλλὰ καὶ τὸ ἐξ ἐναντίου γινόμενον πάθος͵ τὸ κατὰ τὴν εὐφροσύνην φημὶ καὶ τὸν γέλωτα͵ μᾶλλον τὸν λόγον συνίστησι. Διαχέονται γάρ πως καὶ διαλύονται δι' ἡδονῆς οἱ τοῦ σώματος πόροι τῶν ἔκ τινος ἀκοῆς ἡδείας διαχεθέντων. Ὡς γὰρ ἐκεῖ διὰ τῆς λύπης μύουσιν αἱ λεπταί τε καὶ ἄδηλοι τῶν πόρων διαπνοαὶ͵ καὶ διασφίγξασαι τὴν ἔνδοθεν τῶν σπλάγχνων διάθεσιν͵ ἐπὶ τὴν κεφαλὴν καὶ τὰς μήνιγγας τὸν νοτερὸν ἀτμὸν ἀναθλίβουσιν͵ ὃς πολὺς ἐναποληφθεὶς ταῖς τοῦ ἐγκεφάλου κοιλότησι͵ διὰ τῶν κατὰ τὴν βάσιν πόρων ἐπὶ τοὺς ὀφθαλμοὺς ἐξωθεῖται͵ τῆς τῶν ὀφρύων συμπτώσεως ἐξελκομένης διὰ σταγόνων τὴν ὑγρασίαν (ἡ δὲ σταγὼν δάκρυον λέγεται), οὕτω μοι νόησον͵ ἐκ τῆς ἐναντίας διαθέσεως πλέον τοῦ συνήθους εὐρυνομένων τῶν πόρων͵ εἰσέλκεσθαί τι πνεῦμα δι' αὐτῶν ἐπὶ τὸ βάθος͵ κἀκεῖθεν πάλιν ἐξωθεῖσθαι παρὰ τῆς φύσεως διὰ τοῦ κατὰ τὸ στόμα πόρου͵ πάντων τῶν σπλάγχνων καὶ μάλιστά γε τοῦ ἥπατος͵ ὥς φασι͵ διά τινος κλόνου καὶ βρασμώδους κινήσεως τὸ τοιοῦτον πνεῦμα συνεξωθούντων. Ὅθεν εὐκολίαν τινὰ τῇ διεξόδῳ τοῦ πνεύματος μηχανωμένη ἡ φύσις͵ ἀνευρύνει τὸν περὶ τὸ στόμα πόρον͵ ἑκατέρωθεν περὶ τὸ ἆσθμα τὰς παρειὰς διαστέλλουσα. Ὄνομα δὲ τῷ γινομένῳ γέλως ἐστίν.