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of others has been said before; but of movement according to choice we will now speak. 26 concerning the movement according to impulse or according to choice, which belongs to the appetitive faculty. The principle, then, of movement according to choice or according to impulse is the brain and the spinal marrow, which is itself also a part of the brain; and the instruments are the nerves that grow from these, and the ligaments and the muscles. The muscles are composed of flesh and of sinewy fibers and tendons, intertwined with the fibers of the nerves. Whence some have supposed them to be sensory, on account of the sensation produced by the nerves intertwined with them. A tendon, therefore, is a composite of ligament and fine nerves. A tendon differs from a nerve in that every nerve is sensory and round and softer and has its origin from the brain; but the tendon is both harder and from bone and insensitive in itself, and is sometimes flat. The hands are an instrument for grasping and most suitable for the arts. For if one takes away the hands, or only the fingers of the hands, he renders man most useless for almost all the arts. For which reason man alone, since he is rational and capable of arts, received hands from the Creator. The feet are an instrument for locomotion. For through these we make movement from place to place. Man alone sits down, needing no support. For he alone bends his legs at two right angles, both at the hip and at the back of the knee; the one inwards, the other outwards. Therefore, all things that are moved by means of nerves and muscles are both of the soul and are accomplished according to choice. And we have shown that the senses and the voice are of this kind. This, then, is the rational diagnosis of the works of both soul and nature. But the Creator, in His supreme providence, intertwined the things of the soul with the things of nature, and vice versa. For since the excretion of superfluities belongs to the secretive power, which is one of the natural powers, so that we might not behave unseemly without choice, releasing them where we ought not and when we ought not and in circumstances we ought not, He set certain gatekeepers, the muscles, over the excretions, and thus He made the works of nature to be of the soul. For this reason, then, we are able to hold back the excretions both often and for a long time. The sensory and soft nerves are sent down from the middle and from the anterior ventricles of the brain; but the harder and motor nerves from the posterior ventricle and the spinal marrow; and harder still are those from the spinal marrow, and of these even more so are those from the lower parts of the spinal marrow. For the further the spinal marrow recedes from the brain, the harder both it itself becomes and the nerves that grow from it. And just as we received the senses twofold, so also we have the outgrowths of the nerves twofold. For each vertebra of the spine sends out a pair of nerves, of which one goes to the right parts of the body, and the other to the left. For almost our whole body is divided into two, into right and left. So too the feet and hands and each of the other parts, as also of the sensory organs. 27 concerning respiration And respiration is also among the works of the soul. For there are muscles that expand the thorax, the most important organ of respiration, and sudden and sighing respiration, which occurs in great griefs, shows its activity to be of the soul; and the changes in respiration according to need are also up to us. For when we feel pain in any of the respiratory parts or those that move with them, such as the diaphragm or the liver or spleen or the stomach and the small intestines and the colon, we breathe shallowly and rapidly; shallowly, so that we may not strike the painful part more violently, and rapidly, so that the frequency may make up for what is lacking in volume. For also when we have pain in the leg, we extend it only for a short time while walking, for the same reason as with respiration. Therefore, just as walking is of the soul, so also is that of respiration. But while resting and not walking, for a very long time to live

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ἄλλων ἔμπροσθεν εἴρηται· τῆς δὲ κατὰ προαίρεσιν κινήσεως νῦν ἐροῦμεν. 26 περὶ τῆς καθ' ὁρμὴν ἢ κατὰ προαίρεσιν κινήσεως, ἥτις ἐστὶ τοῦ ὀρεκτικοῦ Ἔστιν οὖν τῆς κατὰ προαίρεσιν ἢ καθ' ὁρμὴν κινήσεως ἀρχὴ μὲν ὁ ἐγκέφαλος καὶ ὁ νωτιαῖος μυελός, ἐγκεφάλου μέρος ὢν καὶ αὐτός· ὄργανα δὲ τὰ ἐκ τούτων πεφυκότα νεῦρα καὶ οἱ σύνδεσμοι καὶ οἱ μύες. οἱ δὲ μύες συνεστήκασιν ἔκ τε σαρκῶν καὶ νευρωδῶν ἰνῶν καὶ τενόντων, συμπεπλεγμένων ταῖς τῶν νεύρων ἴνεσιν. ὅθεν τινὲς ᾠήθησαν αὐτοὺς αἰσθητικοὺς εἶναι, διὰ τὴν γινομένην ἐκ τῶν συμπεπλεγμένων αὐτοῖς νεύρων αἴσθησιν. ἔστιν οὖν ὁ τένων σύνθετος ἔκ τε συνδέσμου καὶ νεύρων λεπτῶν. διαφέρει δὲ νεύρου τένων ὅτι πᾶν μὲν νεῦρον αἰσθητικόν ἐστι καὶ στρογγύλον καὶ ἁπαλώτερον καὶ ἀπ' ἐγκεφάλου τὴν ἀρχὴν ἔχει· ὁ δὲ τένων καὶ σκληρότερος καὶ ἐξ ὀστέου καὶ ἀναίσθητος καθ' ἑαυτόν, καὶ ἔσθ' ὅτε πλατύς. εἰσὶ δὲ αἱ μὲν χεῖρες ἀντιληπτικὸν ὄργανον καὶ πρὸς τὰς τέχνας ἐπιτηδειότατον. ἐὰν γάρ τις ἀφέλῃ τὰς χεῖρας, ἢ τῶν χειρῶν μόνους τοὺς δακτύλους, εἰς πάσας σχεδὸν τὰς τέχνας ἀχρηστότατον ποιεῖ τὸν ἄνθρωπον. διὸ καὶ μόνος ἄνθρωπος, ἐπειδὴ λογικός ἐστι καὶ τεχνῶν δεκτικός, χεῖρας ἔσχε παρὰ τοῦ δημιουργοῦ. οἱ δὲ πόδες μεταβατικὸν ὄργανον. τὴν γὰρ κατὰ τόπον κίνησιν διὰ τούτων ποιούμεθα. μόνος δὲ ἄνθρωπος καθέζεται, μηδενὸς ἐρείσματος δεόμενος. μόνος γὰρ πρὸς δύο γωνίας ὀρθὰς κάμπτει τὰ σκέλη, κατά τε τὸ ἰσχίον καὶ τὴν ἰγνύν· τὴν μὲν ἐπὶ τὰ ἔνδον, τὴν δὲ ἐπὶ τὰ ἔξω. ὅσα τοίνυν διὰ νεύρων καὶ μυῶν κινεῖται, ταῦτα πάντα ψυχικά τε ἐστὶ καὶ κατὰ προαίρεσιν ἀποτελεῖται. τούτων δὲ καὶ τὰς αἰσθήσεις καὶ τὴν φωνὴν ἐδείξαμεν εἶναι. αὕτη μὲν οὖν ἐστιν ἡ κατὰ λόγον τῶν τε ψυχικῶν καὶ φυσικῶν ἔργων διάγνωσις. ὁ δὲ δημιουργὸς κατὰ τὴν ἄκραν ἑαυτοῦ προμήθειαν συνέπλεξε τοῖς φυσικοῖς τὰ ψυχικὰ καὶ ἀνάπαλιν. ἐπειδὴ γὰρ ἡ ἔκκρισις τῶν περιττωμάτων τῆς ἀποκριτικῆς ἐστι δυνάμεως, ἥτις μία τῶν φυσικῶν ἐστι δυνάμεων, ἵνα μὴ ἀπροαιρέτως ἀσχημονῶμεν, ἔνθα οὐ δεῖ καὶ ὅτε οὐ δεῖ καὶ ἐφ' ὧν οὐ δεῖ προϊέμενοι, πυλωρούς τινας ἐπέστησε ταῖς ἐκκρίσεσι τοὺς μῦς, καὶ οὕτως ἐποίησε τὰ τῆς φύσεως ἔργα ψυχικά. τὰς γοῦν ἐκκρίσεις ἐπέχειν διὰ τοῦτο δυνάμεθα καὶ πολλάκις καὶ ἐπὶ πολύ. καταπέμπεται δὲ τὰ μὲν αἰσθητικὰ καὶ μαλακὰ νεῦρα ἀπό τε τῆς μέσης καὶ τῶν ἔμπροσθεν κοιλιῶν τοῦ ἐγκεφάλου· τὰ δὲ σκληρότερα καὶ κινητικὰ ἀπὸ τῆς ὄπισθεν κοιλίας καὶ τοῦ νωτιαίου μυελοῦ· σκληρότερα δὲ μᾶλλόν ἐστι τὰ ἐκ τοῦ νωτιαίου, καὶ τούτων δὲ ἔτι μᾶλλον τὰ ἐκ τῶν κάτωθεν μερῶν τοῦ νωτιαίου. ὅσῳ γὰρ πλέον ἀποχωρεῖ τοῦ ἐγκεφάλου ὁ νωτιαῖος, τοσούτῳ πλέον αὐτός τε σκληρότερος γίνεται καὶ τὰ νεῦρα τὰ ἐξ αὐτοῦ φυόμενα. ὥσπερ δὲ τὰς αἰσθήσεις διπλᾶς ἐλάβομεν, οὕτω καὶ τὰς ἐκφύσεις τῶν νεύρων διπλᾶς ἔχομεν. ἕκαστος γὰρ σφόνδυλος τοῦ νωτιαίου συζυγίαν ἐκπέμπει νεύρων, ἧς τὸ μὲν ἐπὶ τὰ δεξιὰ μέρη τοῦ σώματος χωρεῖ, θάτερον δὲ ἐπὶ τὰ ἀριστερά. σχεδὸν γὰρ ὅλον ἡμῶν τὸ σῶμα εἰς δύο μεμέρισται, εἰς δεξιὰ καὶ ἀριστερά. οὕτω καὶ πόδες καὶ χεῖρες καὶ τῶν ἄλλων ἕκαστον, ὡς καὶ τῶν αἰσθητηρίων. 27 περὶ ἀναπνοῆσ Καὶ ἡ ἀναπνοὴ δὲ τῶν ψυχικῶν ἐστιν ἔργων. καὶ γὰρ μύες εἰσὶν οἱ διαστέλλοντες τὸν θώρακα, τὸ κυριώτατον τῆς ἀναπνοῆς ὄργανον, καὶ ἡ ἀθρόα καὶ στεναγματώδης ἀναπνοή, ἐπὶ ταῖς μεγάλαις λύπαις γινομένη, ψυχικὴν δείκνυσι τὴν ἐνέργειαν· ἐφ' ἡμῖν δὲ καὶ αἱ κατὰ τὴν χρείαν τῆς ἀναπνοῆς μεταβολαί. ἀλγοῦντες γάρ τι τῶν ἀναπνευστικῶν μορίων ἢ τῶν συγκινουμένων αὐτοῖς, οἷον τοῦ διαφράγματος ἢ τοῦ ἥπατος ἢ σπληνὸς ἢ τῆς κοιλίας καὶ τῶν λεπτῶν ἐντέρων καὶ τοῦ κόλου, μικρὸν καὶ πυκνὸν ἀναπνέομεν· μικρὸν μὲν ἵνα μὴ σφοδρότερον πλήττωμεν τὸ ἀλγοῦν μόριον, πυκνὸν δὲ ἵνα τὸ λεῖψαν κατὰ τὸ μέγεθος ἡ πυκνότης ἀναπληρώσῃ. καὶ γὰρ ὅταν ἀλγῶμεν τὸ σκέλος ἐπ' ὀλίγον ἐκτείνομεν αὐτὸ βαδίζοντες, διὰ τὴν αὐτὴν αἰτίαν δι' ἣν καὶ τὴν ἀναπνοήν. ὥσπερ οὖν καὶ τὸ βαδίζειν ψυ χικόν, οὕτω καὶ τὸ τῆς ἀναπνοῆς. ἀλλ' ἡσυχάζοντες μὲν καὶ μὴ βαδίζοντες ἐπὶ πλεῖστον χρόνον ζῆν