§3.8.18 Κύστιν δʼ οὐ πάντʼ ἔχει τὰ ζῷα, ἀλλʼ ἔοικεν ἡ φύσις βουλομένῃ ἀποδιδόναι τοῖς ἔχουσι τὸν πλεύμονα ἔναιμον μόνον, τούτοις δʼ εὐλόγως.
8 But not all animals have a bladder, rather nature seems to wish to bestow it only on those that have a sanguineous lung, and to these with good reason.
διὰ γὰρ τὴν ὑπεροχὴν τῆς φύσεως, ἣν ἔχουσιν ἐν τῷ μορίῳ τούτῳ, διψητικά τε ταῦτʼ ἐστὶ μάλιστα τῶν ζῴων, καὶ δεῖται τροφῆς οὐ μόνον τῆς ξηρᾶς ἀλλὰ καὶ τῆς ὑγρᾶς πλείονος, ὥστʼ ἐξ ἀνάγκης καὶ περίττωμα γίνεσθαι πλεῖον καὶ μὴ τοσοῦτον μιόνον ὅσον ὑπὸ τῆς κοιλίας πέττεσθαι καὶ ἐκκρίνεσθαι μετὰ τού ταύτης περιττῴματος.
For because of the excess of nature which they have in this part, these are the most thirsty of animals, and require not only dry food but also more of liquid food, so that of necessity more residue also is produced, and not only so much as to be concocted by the stomach and excreted with its residue.
ἀνάγκη τοίνυν εἶναί τι δεκτικὸν καὶ τούτου τού περιττώματος.
It is necessary, therefore, that there should be some receptacle for this residue as well.
§3.8.22 διόπερ ὅσα πλεύμονα ἔχει τοιοῦτον, ἅπαντʼ ἔχει κύστιν· ὅσα δὲ μὴ τοιοῦτον, ἀλλʼ ἢ ὀλιγόποτά ἐστι διὰ τὸ πλεύμονα ἔχειν σομφόν, ἢ ὅλως τὸ ὑγρὸν προσφέρεται οὐ ποτοῦ χάριν ἀλλὰ τροφῆς, οἷον τὰ ἔντομα καὶ οἱ ἰχθύες, ἔτι δὲ πτερωτά ἐστιν ἢ λεπιδωτὰ ἢ φολιδωτά, ταύτα διʼ ὀλιγότητά τε τῆς τοῦ ὑγροῦ προσφορᾶς καὶ διὰ τὸ τρέπεσθαι εἰς ταῦτα τὸ περιγινὸμενον τού περίττώματος οὐδὲν ἔχει τούτων κύστιν, πλὴν αἱ χελῶναι τῶν φολιδωτῶν.
2 Wherefore, all that have such a lung have a bladder; but those that do not have such a lung, but either drink little because they have a spongy lung, or on the whole take in liquid not for the sake of drink but of food, such as insects and fishes, and furthermore those that are winged or have fine scales or horny scales—these, because of the smallness of their intake of liquid and because the remaining residue is diverted into these parts, none of them has a bladder, except for the turtles among the animals with horny scales.
καὶ ἐνταῦθʼ ἡ φύσις κεκολόβωται μόνον.
And in this respect alone has nature been curtailed.
αἴτιον δʼ ὅτι αἱ μὲν θαλαττίαι σαρκώδη καὶ ἔναιμον ἔχουσι τὸν πλεύμονα καὶ ὅμοιον τῷ βοείῳ, αἱ δὲ χερσαῖαι μείζω ἢ κατὰ λόγον.
The cause is that the sea turtles have a fleshy and sanguineous lung, similar to that of cattle, while the land turtles have one larger than proportion warrants.
ἔτι δὲ διὰ τὸ ὀστρακῶδες καὶ πυκνὸν εἶναι τὸ περιέχον οὐ διαπνέοντος τού ὑγροῦ διὰ μανῶν τῶν σαρκῶν, οἷον τοῖς ὄρνισι καὶ τοῖς ὄφεσι καὶ τοῖς ἄλλοις τοῖς φολιδωτοῖς, ὑπόστασις γίνεται τοσαύτη ὥστε δεῖσθαι τὴν φύσιν αὐτῶν ἔχειν τι μόριον δεκτικὸν καὶ ἀγγειῶδες.
Moreover, because their covering is bony and dense, and the moisture does not transpire through the porous flesh, as it does in birds, snakes, and other animals with horny scales, so much sediment is produced that their nature requires them to have some receptive and vessel-like part.
κύστιν μὲν οὖν ταῦτα μόνον τῶν τοιούτων ἔχει διὰ ταύτην τὴν αἰτίαν, ἡ μὲν θαλαττία μεγάλην, αἱ δὲ χερσαῖαι μικρὰν πάμπαν.
It is for this cause, then, that these alone of such animals have a bladder, the sea turtle a large one, and the land turtles an altogether small one.