§1515 Οἱ δʼ ὄρνιθες τὰ σκέλη καθάπερ τὰ τετράποδα κάμπτουσι.
15 Birds bend their legs in the same way as quadrupeds.
τρόπον γάρ τινα παραπλησίως ἡ φύσις αὐτῶν ἔχει· τοῖς γὰρ ὄρνισιν αἱ πτέρυγες ἀντὶ τῶν προσθίων σκελῶν εἰνοις.
For in a certain way their nature is similar; for in birds the wings are in place of the front legs.
διὸ καὶ κεκαμμέναι τὸν αὐτόν εἰσι τρόπον ὥσπερ ἐκείνοις τὰ πρόσθια σκέλη, ἐπεὶ τῆς ἐν τῇ πορείᾳ κινήσεως τούτοις ἀπὸ τῶν πτερύγων ἡ κατὰ φύσιν ἀρχὴ τῆς μεταβολῆς ἐστι· πτῆσις γάρ ἐστιν ἡ τούτων οἰκεία κίνησις.
Wherefore they are also bent in the same way as the front legs in those animals, since the natural beginning of the change in their walking movement is from the wings; for flight is their peculiar movement.
διόπερ ἀφαιρεθεισῶν τούτων οὔθʼ ἑστάναι οὔτε προϊέναι δύναιτʼ ἂν οὐθεὶς | ὄρνις.
Therefore, if these were removed, no bird would be able either to stand or to go forward.
ἔτι δίποδος ὄντος καὶ οὐκ ὀρθοῦ, καὶ τὰ ἔμπροσθεν μέρη τοῦ σώματος κουφότερα ἔχοντος, ἢ ἀναγκαῖον ἢ βέλτιον πρὸς τὸ ἑστάναι δύνασθαι τὸν μηρὸν οὕτως ὑποκείμενον ἔχειν ὡς νῦν ἔχει, λέγω δʼ ὅτι εἰς τὸ ὄπισθεν πεφυκότα.
Furthermore, since it is a biped and not erect, and has the front parts of its body lighter, it is either necessary or better, in order to be able to stand, to have the thigh placed underneath in the way it is now, I mean, being grown towards the rear.
ἀλλὰ μὴν εἰ δεῖ τοῦτον ἔχειν τὸν τρόπον, ἀνάγκη τὴν κάμψιν ἐπὶ τὸ κοῖλον γίνεσθαι τοῦ σκέλους, καθάπερ τοῖς τετράποσιν ἐπὶ τῶν ὀπισθίων, διὰ τὴν αὐτὴν αἰτίαν ἥνπερ εἴπομεν ἐπὶ τῶν τετραπόδων καὶ ζῳοτόκων.
But indeed, if it must be in this way, it is necessary for the bending of the leg to be towards the concave, just as in the hind legs of quadrupeds, for the same cause that we mentioned in the case of quadrupeds and viviparous animals.
ὅλως δὲ οἵ τε ὄρνιθες καὶ τὰ ὁλόπτερα τῶν πετομένων καὶ τὰ ἐν τῷ ὑγρῷ νευστικά, ὅσα αὐτῶν διʼ ὀργάνων τὴν ἐπὶ τοῦ ὑγροῦ ποιεῖται πορείαν, οὐ χαλεπὸν ἰδεῖν ὅτι βέλτιον ἐκ πλαγίου τὴν τῶν εἰρημένων μερῶν πρόσφυσιν ἔχειν, καθάπερ καὶ φαίνεται νῦν ὑπάρχειν αὐτοῖς ἐπί τε τῶν ὀρνίθων καὶ τῶν ὁλοπτέρων.
In general, as for birds, holopterous flying insects, and swimming creatures in the water, as many of them as make their progress through the water by means of organs, it is not difficult to see that it is better to have the attachment of the aforementioned parts from the side, just as indeed it appears to belong to them now in the case of birds and holoptera.
ταὐτὸ δὲ τοῦτο καὶ ἐπὶ τῶν ἰχθύων· τοῖς μὲν γὰρ ὄρνισιν αἱ πτέρυγες, τοῖς δʼ ἐνύδροις τὰ πτερύγια.
And this same thing holds also in the case of fish; for to birds the wings, and to aquatic creatures the fins [are corresponding].
οὕτω γὰρ ἂν τάχιστα καὶ ἰσχυρότατα συστέλλοντα καὶ διαστέλλοντα τὰ μὲν τὸν ἀέρα τὰ δὲ τὸ | ὑγρὸν ποιοῖτο τὴν κίνησιν· εἰς γὰρ τὸ ἔμπροσ θεν καὶ τὰ | ὄπισθεν μόρια τοῦ σώματος ἐπακολουθοίη ἂν ὑπείκοντι φερόμενα τὰ μὲν ἐν τῷ ὑγρῷ τὰ δʼ ἐν τῷ ἀέρι.
For in this way they would make their movement by contracting and expanding, the ones the air and the others the water, most quickly and strongly; for the front and rear parts of the body would follow, being carried into the yielding medium, the ones in the water and the ones in the air.
τὰ δὲ τρωγλόδυτα τῶν τετραπόδων καὶ ᾠοτόκων, οἷον οἵ τε κροκόδειλοι καὶ σαῦροι καὶ ἀσκαλαβῶται καὶ ἑμύδες τε καὶ χελῶναι, πάντα ἐκ τοῦ πλαγίου προσπεφυκότα τὰ σκέλη ἔχει καὶ ἐπὶ τῇ γῇ κατατεταμένα, καὶ κάμπτει εἰς τὸ πλάγιον, διὰ τὸ οὕτω χρήσιμα εἶναι πρὸς τὴν τῆς ὑποδύσεως ῥᾳστώνην καὶ πρὸς τὴν ἐπὶ τοῖς ᾠοῖς ἐφεδρείαν καὶ φυλακήν.
Those of quadrupeds and oviparous animals that are hole-dwellers, such as crocodiles, lizards, geckos, pond turtles, and tortoises, all have their legs attached from the side and extended on the ground, and bend them to the side, because this is useful for the ease of creeping under, and for sitting upon and guarding their eggs.
ἔξω δʼ ὄντων αὐτῶν, ἀναγκαῖον τοὺς μηροὺς προσστέλλοντα καὶ ὑποτιθέμενα ὑφʼ αὑτὰ τὸν μετεωρισμὸν τοῦ ὅλου σώματος ποιεῖσθαι.
And since they are on the outside, it is necessary to make the elevation of the whole body by drawing in the thighs and placing them under themselves.
τούτου δὲ γινομένου κάμπτειν αὐτὰ οὐχ οἷόν τε ἄλλως ἢ ἔξω.
And when this happens, it is impossible to bend them in any other way than outwards.
§1616 Τὸ δʼ ἄναιμα τῶν ὑποπόδων ὅτι μὲν πολύποδά ἐστι καὶ οὐθὲν αὐτῶν τετράπουν, πρότερον ἡμῖν εἴρηται· διότι δʼ αὐτῶν ἀναγκαῖον ἦν τὰ σκέλη πλὴν τῶν ἐσχάτων ἔκ τε τοῦ πλαγίου προσπεφυκέναι καὶ εἰς τὸ ἄνω τὰς καμπὰς ἔχειν, καὶ αὐτὰ ὑπόβλαισα εἶναι εἰς τὸ ὄπισθεν, φανερόν.
16 That bloodless animals with feet are polypods and none of them is quadruped has been said by us before; but why it was necessary for their legs, except the extreme ones, to be attached from the side and to have their bendings upwards, and to be themselves somewhat crooked towards the rear, is clear.
ἀπάντων γὰρ τῶν τοιούτων ἀναγκαῖόν ἐστι τὰ μέσα τῶν σκελῶν καὶ ἡγούμενα εἶναι καὶ ἑπόμενα.
For in all such animals it is necessary for the middle legs to be both leading and following.
εἰ οὖν ὑπʼ αὐτοῖς ἦν, ἔδει αὐτὰ καὶ εἰς τὸ ἔμπροσθεν καὶ εἰς τὸ ὄπισθεν τὴν καμθος ἔχειν, διὰ μὲν τὸ ἡγεῖσθαι εἰς τὸ ἔμπροσθεν, διὰ δὲ τὸ ἀκολουθεῖν εἰς τὸ ὄπισθεν.
If then they were under them, they would have to have their bendings both to the front and to the rear, because of leading to the front, and because of following to the rear.
ἐπεὶ δʼ ἀμφότερα συμβαίνειν ἀναγκαῖον αὐτοῖς, διὰ τοῦτο βεβλαίσωταί τε καὶ εἰς τὸ πλάγιον ἔχει τὰς καμπάς, πλὴν τῶν ἐσχάτων· ταῦτα δʼ ὥσπερ πέφυκε μᾶλλον, τὰ μὲν ὡς ἑπόμενα τὰ δʼ ὡς ἡγούμενα.
But since it is necessary for both to happen to them, for this reason they are crooked and have their bendings to the side, except the extreme ones; and these are rather grown as they are naturally, the ones as following and the others as leading.
ἔτι δὲ κέκαμπται τὸν τρόπον τοῦτον καὶ διὰ τὸ πλῆθος τῶν σκελῶν· ἧττον γὰρ ἂν οὕτως ἐν τῇ πορείᾳ ἐμπόδιά τε αὐτὰ αὐτοῖς εἴη καὶ προσκόπτοι.
Furthermore, they are bent in this way also because of the multitude of the legs; for in this way they would be less of a hindrance to themselves in walking and would clash less.
ἡ δὲ βλαισότης αὐτοῖς ἐστι διὰ τὸ τρωγλοδυτικὰ εἶναι πάντα ἢ τὰ πλεῖστα· οὐ γὰρ οἷόν τε ὑψηλὰ εἶναι τὰ ζῶντα τὸν τρόπον τοῦτον.
And their crookedness is because they are all or most of them hole-dwellers; for it is not possible for those living in this way to be high.
οἱ δὲ καρκίνοι τῶν πολυπόδων περιττότατα πεφύκασιν· οὔτε γὰρ εἰς τὸ | πρόσθεν ποιοῦνται τὴν πορείαν πλὴν ὥσπερ εἴρηται πρότερον, | πολλούς τε τοὺς ἡγουμένους πόδας ἔχουσι μόνοι τῶν ζῴων.
Crabs are the most extraordinary in nature of the polypods; for they do not make their progress to the front except as has been said before, and alone of animals they have many leading feet.
τούτου δʼ αἴτιον ἡ σκληρότης τῶν ποδῶν, καὶ ὅτι οὐ χρῶνται νεύσεως χάριν αὐτοῖς ἀλλὰ πορείας· πεζεύοντα γὰρ διατελοῦσι.
And the cause of this is the hardness of their feet, and because they do not use them for the sake of swimming but of walking; for they continue to go on land.
πάντων μὲν οὖν τῶν πολυπόδων εἰς τὸ πλάγιον αἱ καμπαί, ὥσπερ καὶ τῶν τετραπόδων ὅσα τρωγλόδυτα· τοιαῦτα δʼ ἐστὶν οἷον σαῦραι καὶ κροκόδειλοι καὶ τὰ πολλὰ τῶν ᾠοτοκούντων.
For all polypods, then, the bendings are to the side, just as also for those of quadrupeds that are hole-dwellers; such as lizards, crocodiles, and most oviparous animals.
αἴτιον δʼ ὅτι τρωγλοδυτεῖ τὰ μὲν τοῖς τόκοις, τὰ δὲ καὶ τῷ βίῳ παντί.
And the cause is that some dwell in holes for their offspring, and others also for their whole life.