470 b 25πάντα μᾶλλον δεῖται τῆς ἀναπνοῆς διὰ τὸ πλῆθος τῆς θερμότητος· τῶν δ᾿ ἄλλων ὅσα μὴ ἔχει πλεύμονα, οὐδὲν ἀναπνεῖ.
II. Δημόκριτος μὲν οὖν ὁ Ἀβδηρίτης καί τινες ἄλλοι τῶν περὶ ἀναπνοῆς εἰρηκότων οὐδὲν περὶ 30τῶν ἄλλων διωρίκασι ζῴων, ἐοίκασι μέντοι λέγειν ὡς πάντων ἀναπνεόντων· Ἀναξαγόρας δὲ καὶ Διογένης, πάντα φάσκοντες ἀναπνεῖν, περὶ τῶν ἰχθύων καὶ τῶν ὀστρείων λέγουσι τίνα τρόπον ἀναπνέουσιν. καί φησιν Ἀναξαγόρας μέν, ὅταν 471 aἀφῶσι τὸ ὕδωρ διὰ τῶν βραγχίων, τὸν ἐν τῷ στόματι γίνομενον ἀέρα ἕλκοντας ἀναπνεῖν τοὺς ἰχθῦς· οὐ γὰρ εἶναι κενὸν οὐδέν· Διογένης δ᾿ ὅταν ἀφῶσι τὸ ὕδωρ διὰ τῶν βραγχίων, ἐκ τοῦ περὶ τὸ στόμα περιεστῶτος ὕδατος ἕλκειν τῷ κενῷ τῷ 5ἐν τῷ στόματι τὸν ἀέρα, ὡς ἐνόντος ἐν τῷ ὕδατι ἀέρος. ταῦτα δ᾿ ἐστὶν ἀδύνατα. πρῶτον μὲν γὰρ τὸ ἥμισυ τοῦ πράγματος ἀφαιροῦσι, διὰ τὸ τὸ κοινὸν ἐπὶ θατέρου λέγεσθαι μόνον. ἀναπνοὴ γὰρ καλεῖται, ταύτης δὲ τὸ μὲν ἐκπνοή ἐστι τὸ δ᾿ εἰσπνοή· περὶ ἧς οὐθὲν λέγουσι, τίνα τρόπον 10ἐκπνέουσι τὰ τοιαῦτα τῶν ζῴων. οὐδ᾿ ἐνδέχεται αὐτοῖς εἰπεῖν· ὅταν γὰρ ἀναπνεύσωσι, ταύτῃ ᾗ ἀνέπνευσαν πάλιν δεῖ ἐκπνεῖν, καὶ τοῦτο ποιεῖν ἀεὶ παραλλάξ, ὥστε συμβαίνει ἅμα δέχεσθαι τὸ ὕδωρ κατὰ τὸ στόμα καὶ ἐκπνεῖν. ἀνάγκη δ᾿ ἀπαντῶντα ἐμποδίζειν θάτερον θατέρῳ. εἶτα ὅταν 15ἀφῶσι τὸ ὕδωρ, τότε ἐκπνέουσι κατὰ τὸ στόμα ἢ κατὰ τὰ βράγχια, ὥστε συμβαίνει ἅμα ἐκπνεῖν καὶ ἀναπνεῖν· τότε γάρ φασιν αὐτὸ ἀναπνεῖν. ἅμα δ᾿ ἀναπνεῖν καὶ ἐκπνεῖν ἀδύνατον. ὥστ᾿ εἰ ἀνάγκη
much blood depend more upon breathing because of the amount of their heat; but none of the other creatures which have no lung breathe at all.
II. Democritus of Abdera and certain others whoBreaking in fishes. have discussed breathing have not treated these other animals in detail, but appear to speak as if they all breathed; Anaxagoras and Diogenes, asserting that all creatures breathe, describe the way in which fishes and oysters breathe. Anaxagoras says that fishes breathe by drawing in the air which enters their mouth when they discharge water through their gills, for there can be no vacuum; Diogenes says that when they let out water through the gills by means of the vacuum in the mouth they draw in the air from the water surrounding the mouth; which implies that there is air in the water. But all this is impossible. First of all they leave out half the facts, by confining to one process a term which covers two. For what is called respiration includes exhalation as well as inhalation; but of the former they make no mention; how, that is, such animals exhale. Nor can they explain it; for when animals have respired, they must exhale again by the same way by which they respired, and so on alternately, so that it follows that they take in water by the mouth and exhale by it at the same time. But the one operation must clearly meet and obstruct the other. Again, when they discharge the water, they are at the same time exhaling by the mouth or by the gills, so that they must exhale and respire at the same time; for they say that this is the time at which they respire. But it is impossible to respire and exhale at the same time. The conclusion