§4.11.8τῶν μὲν οὖν ὀρνίθων ἔνιοι καὶ σκαρδαμύττουσιν 8 ὑμένι ἐκ τῶν κανθῶν, ταῦτα δὲ τὰ ζῷα οὐ σκαρδαμύττει· σκληροφθαλμότερα γάρ ἐστι τῶν ὀρνίθων.
Now, while some of the birds also blink with a membrane from the corners of their eyes, these animals do not blink; for they have harder eyes than birds.
αἴτιον δʼ ὅτι ἐκείνοις χρησιμωτέρα ἡ ὀξυωπία πτηνοῖς οὖσι πρὸς τὸν βίον, τούτοις δʼ ἧττον· τρωγλόδυτα γὰρ πάντα τὰ τοιαῦτά ἐστιν.
The cause is that keenness of sight is more useful to those, since they are flying creatures, for their life, but less so to these; for all such animals are hole-dwellers.
εἰς δύο δὲ διῃρημένης τῆς κεφαλῆς, τοῦ τε ἄνω μορίσυ καὶ τῆς σιαγόνος τῆς κάτω, ἄνθρωπος μὲν οὖν καὶ τὰ ζῳοτόκα τάν τετραπόδων καὶ ἄνω καὶ κάτω κινοῦσι τὰς σιαγόνας καὶ εἰς τὸ πλάγιον, οἱ δʼ ἰχθύες καὶ ὄρνιθες καὶ τὰ ᾠοτόκα τῶν τετραπόδων εἰς τὸ ἄνω καὶ κάτω μόνον.
And while the head is divided into two, namely the upper part and the lower jaw, man and the viviparous quadrupeds move their jaws both up and down and laterally, but fish, birds, and the oviparous quadrupeds move them only up and down.
§4.11.99 αἴτιον δʼ ὅτι ἡ μὲν τοιαύτη κίνησις χρήσιμος εἰς τὸ δακεῖν καὶ διελεῖν, ἡ δʼ εἰς τὸ πλάγιον ἐπὶ τὸ λεαίνειν.
9 And the cause is that such movement is useful for biting and dividing, whereas lateral movement is for grinding.
τοῖς μὲν οὖν ἔχουσι γομφίους χρήσιμος ἡ εἰς τὸ πλάγιον κίνησις, τοῖς δὲ μὴ ἔχουσιν οὐδὲν χρήσιμος, διόπερ ἀφῄρηται πάντων τῶν τειούτων· οὐδὲν γὰρ ποιεῖ περίεργον ἡ φύσις.
Thus, for those that have molars, lateral movement is useful, but for those that do not have them, it is of no use at all; wherefore it has been withheld from all such animals; for nature does nothing in vain.
§4.11.1010 τὰ μὲν οὖν ἄλλα πάντα κινεῖ τὴν σιαγόνα τὴν κάτω, ὁ δὲ ποτάμιος κροκόδειλος μόνος τὴν ἄνω.
10 So, all other animals move the lower jaw, but the river crocodile alone moves the upper one.
τούτου δʼ αἴτιον ὅτι πρὸς τὸ λαβεῖν καὶ κατασχεῖν ἀχρήστους ἔχει τοὺς πόδας· μικροὶ γάρ εἰσι πάμπαν.
The cause of this is that they have feet useless for seizing and holding; for they are entirely small.
πρὸς οὖν ταύτας τὰς χρείας ἀντὶ ποδῶν τὸ στόμα ἡ φύσις χρήσιμον αὐτῷ ἐποίησεν.
Therefore, for these needs, nature made his mouth useful instead of feet.
§4.11.1111 πρὸς δὲ τὸ κατασχεῖν ἢ λαβεῖν, ὁποτέρωθεν ἂν ᾖ ἡ πληγὴ ἰσχυρστέρα, ταύτῃ χρηδιμωτέρα κινουμένη ἐστίν· ἡ δὲ πληγὴ ἰσχυροτέρα ἀεὶ ἄνωθεν ἢ κάτωθεν·
11 And for holding or seizing, from whichever side the blow may be stronger, in that direction the moving part is more useful; and a blow is always stronger from above than from below.
ἐπεὶ οὖν ἀμφοτέρων μὲν διὰ τοῦ στόματος ἡ χρῆσις, καὶ τοῦ λαβεῖν καὶ τοῦ δακεῖν, ἀναγκαιοτέρα δʼ ἡ τοῦ κατασχεῖν μήτε χεῖρας ἔχοντι μήτε πόδας εὐφυεῖς, χρησιμώτερον τὴν ἄνωθεν κινεῖν σιαγόνα ἢ τὴν κάτωθεν αὐτοῖς.
Since, therefore, the use of the mouth is for both, namely seizing and biting, and the need for holding is more necessary for one who has neither hands nor well-adapted feet, it is more useful for them to move the jaw from above than the one from below.
§4.11.12διὰ τὸ αὐτὸ δὲ καὶ οἱ καρκίνοι τὸ ἄνωθεν 12 τῆς χηλῆς κινοῦσι μόριον, ἀλλʼ οὐ τὸ κάτωθεν· ἀντὶ χειρὸς γὰρ ἔχουσι τὰς χηλάς, ὥστε πρὸς τὸ λαβεῖν ἀλλʼ οὐ πρὸς τὸ διελεῖν χρήσιμον δεῖ εἶναι τὴν χηλήν.
12 And for the same reason, crabs also move the upper part of their claw, but not the lower part; for they have claws instead of hands, so that the claw must be useful for seizing, but not for dividing.
τὸ δὲ διελεῖν καὶ δακεῖν ὀδόντων ἔργον ἐστίν.
But dividing and biting is the work of teeth.
τοῖς μὲν οὖν καρκίνοις καὶ τοῖς ἄλλοις ὅσκς ἐνδέχεται σχολαίως ποιεῖσθαι τὴν λῆψιν διὰ τὸ μὴ ἐν ὑγρῷ εἶναι τὴν χρῆσιν τοῦ στόματος, διῄρηται, καὶ λαμβάνουσι μὲν χερσὶν ποσί, διαιροῦσι δὲ τῷ στόματι καὶ δάκνουσιν· §4.11.13τοῖς δὲ κροκοδείλοις ἐπʼ ἀμφότερα 13 χρήθιμον τὸ στόμα πεποίηκεν ἡ φύσις, κινουμένων οὕτω τῶν σιαγόνων.
Therefore, for crabs and all other animals for whom it is possible to make their capture leisurely because the use of their mouth is not in a liquid, there is a division of labor, and they seize with hands and feet, but divide and bite with their mouth; 13 but for crocodiles, nature has made the mouth useful for both purposes, with the jaws moving in this way.
ἔχουσι δὲ καὶ αὐχένα πάντα τὰ τοιαῦτα διὰ τὸ πλεύμονα ἔχειν· δέχονται γὰρ τὸ πνεῦμα διὰ τῆς ἀρτηρίας μῆκος ἐχούσης.
And all such animals also have a neck because they have a lung; for they receive breath through a windpipe that has some length.