Issuing thence again, certain twin channels, each enclosing its own current like a pipe, disperse air and blood (that the liquid substance may have free course when accompanied and lightened by the motion of the heated substance) in divers directions over the whole body, breaking at every part into countless branching channels; while as the two principles of the vital powers mingle together (that alike which disperses heat, and that which supplies moisture to all parts of the body), they make, as it were, a sort of compulsory contribution from the substance with which they deal to the supreme force in the vital economy. Now this force is that which is considered as residing in the cerebral membranes and the brain, from which it comes that every movement of a joint, every contraction of the muscles, every spontaneous influence that is exerted upon the individual members, renders our earthen statue active and mobile as though by some mechanism. For the most pure form of heat and the most subtle form of liquid, being united by their respective forces through a process of mixture and combination, nourish and sustain by their moisture the brain, and hence in turn, being rarefied to the most pure condition, the exhalation that proceeds from that organ anoints the membrane which encloses the brain, which, reaching from above downwards like a pipe, extending through the successive vertebrae, is (itself and the marrow which is contained in it) conterminous with the base of the spine, itself giving like a charioteer the impulse and power to all the meeting-points of bones and joints, and to the branches of the muscles, for the motion or rest of the particular parts.

Εἶτα ἐκεῖθεν ἀφορμηθέντες δίδυμοί τινες ὀχετοί͵ τὸ οἰκεῖον ἑκάτερος σωληνοειδῶς περιέχοντες πνεῦμά τε καὶ αἷμα͵ ὡς ἂν εὐπόρευτον εἴη͵ τὸ ὑγρόν τε τοῦ θερμοῦ κινήσει συμπαροδεῦον καὶ κουφιζόμενον͵ ἐφ' ἅπαν τὸ σῶμα πολυσχιδῶς κατασπείρονται͵ εἰς μυρίας ὀχετῶν ἀρχάς τε καὶ διαφύσεις κατὰ πᾶν μέρος διασχιζόμενοι. Μιχθεῖσαι δὲ πρὸς ἀλλήλας τῶν ζωτικῶν δυνάμεων αἱ δύο ἀρχαί͵ ἥ τε τὸ θερμὸν πανταχῆ κατὰ τὸ σῶμα καὶ ἡ τὸ ὑγρὸν ἐπιπέμπουσα͵ καθάπερ τινὰ δανεισμὸν ἀναγκαῖον ἐκ τῶν οἰκείων τῇ ἀρχηγικωτέρᾳ τῆς ζωτικῆς οἰκονομίας δυνάμει δωροφοροῦσιν. Ἔστι δ' αὕτη ἡ κατὰ τὰς μήνιγγας καὶ τὸν ἐγκέφαλον θεωρουμένη͵ ἀφ' ἧς πᾶσα μὲν ἄρθρου κίνησις͵ πᾶσα δὲ μυῶν συνολκή͵ πᾶν δὲ προαιρετικὸν πνεῦμα καὶ τοῖς καθέκαστον μορίοις ἐπιπεμπόμενον͵ ἐνεργόν τε καὶ κινούμενον τὸν γήϊνον ἡμῶν ἀνδριάντα͵ καθάπερ ἐκ μηχανῆς τινος ἀποδείκνυσι. Τοῦ τε γὰρ θερμοῦ τὸ καθαρώτατον καὶ τοῦ ὑγροῦ τὸ λεπτότατον παρ' ἑκατέρας δυνάμεως διά τινος μίξεώς τε καὶ ἀνακράσεως ἑνωθέντα͵ τρέφει τε καὶ συνίστησι διὰ τῶν ἀτμῶν τὸν ἐγκέφαλον. Ἀφ' οὗ πάλιν ἐπὶ καθαρώτατον ἐκλεπτυνομένη ἡ ἀπ' ἐκείνου ἀνάδοσις ὑπαλείφει τὸν περιεκτικὸν τοῦ ἐγκεφάλου ὑμένα͵ ὃς ἄνωθεν ἐπὶ τὸ βάθος αὐλοειδῶς διήκων διὰ τῶν καθεξῆς σπονδύλων͵ ἑαυτὸν δὲ καὶ τὸν ἐγκείμενον αὐτῷ μυελὸν διεξάγων͵ τῇ βάσει συναπολήγει τῆς ῥάχεως, πάσαις ὀστέων τε καὶ ἁρμονιῶν συμβολαῖς καὶ μυῶν ἀρχαῖς οἷόν τις ἡνίοχος αὐτὸς ἐνδιδοὺς τῆς καθέκαστον κινήσεώς τε καὶ στάσεως τὴν ὁρμὴν καὶ τὴν δύναμιν.