We consider, then, that we need not spend more time in inquiring in which of the vital members such a thing resides, when the energy of motion is shown to be here. But that the brain contributes to life in a special degree is shown clearly by the result of the opposite conditions: for if the tissue surrounding it receives any wound or lesion, death immediately follows the injury, nature being unable to endure the hurt even for a moment; just as, when a foundation is withdrawn, the whole building collapses with the part; and that member, from an injury to which the destruction of the whole living being clearly follows, may properly be acknowledged to contain the cause of life.

But as furthermore in those who have ceased to live, when the heat that is implanted in our nature is quenched, that which has become dead grows cold, we hence recognize the vital cause also in heat: for we must of necessity acknowledge that the living being subsists by the presence of that, which failing, the condition of death supervenes. And of such a force we understand the heart to be as it were the fountain-head and principle, as from it pipe-like passages, growing one from another in many ramifications, diffuse in the whole body the warm and fiery spirit.

And since some nourishment must needs also be provided by nature for the element of heat-for it is not possible that the fire should last by itself, without being nourished by its proper food-therefore the channels of the blood, issuing from the liver as from a fountainhead, accompany the warm spirit everywhere in its way throughout the body, that the one may not by isolation from the other become a disease and destroy the constitution. Let this instruct those who go beyond the bounds of fairness, as they learn from nature that covetousness is a disease that breeds destruction.

Οὐκέτι οὖν ἡγούμεθα δεῖν πολυπραγμονεῖν περί τε τῶν ζωτικῶν μορίων͵ τὸ τοιοῦτόν ἐστιν͵ ἐν τούτῳ δειχθείσης τῆς κινητικῆς ἐνεργείας. Ὅτι δὲ μέγιστόν τι συντελεῖ πρὸς τὴν ζωὴν ὁ ἐγκέφαλος͵ ἐναργῶς τὸ ἐξ ἐναντίου συμβαῖνον δηλοῖ. Εἰ γάρ τινα τρῶσιν ἢ ῥῆξιν ὁ περὶ αὐτὸν ὑμὴν πάθοι͵ εὐθὺς ἐπηκολούθησε τῷ πάθει ὁ θάνατος͵ οὐδὲ πρὸς τὸ ἀκαρὲς τῆς φύσεως ἀντισχούσης τῇ τρώσει͵ ὥσπερ θεμελίου τινὸς ὑποσπασθέντος ὅλον τὸ οἰκοδόμημα συγκατεσείσθη τῷ μέρει· οὗ τοίνυν παθόντος πρόδηλός ἐστιν ἡ τοῦ παντὸς ζώου διαφθορά͵ τοῦτο κυρίως ἂν τῆς ζωῆς τὴν αἰτίαν ἔχειν ὁμολογοῖτο.  

Ἐπειδὴ δὲ καὶ τῶν παυσαμένων τοῦ ζῇν κατασβεσθείσης τῆς ἐγκειμένης τῇ φύσει θερμότητος͵ τὸ νεκρωθὲν καταψύχεται͵ [245] διὰ τοῦτο καὶ ἐν τῷ θερμῷ τὴν ζωτικὴν αἰτίαν κατενοήσαμεν. Οὗ γὰρ ἐπιλελοιπότος ἡ νεκρότης ἐπηκολούθησεν͵ ἀνάγκη πᾶσα τῇ παρουσίᾳ τούτου συνεστάναι τὸ ζῶον ὁμολογεῖσθαι. Τῆς δὲ τοιαύτης δυνάμεως οἶον πηγήν τινα καὶ ἀρχὴν τὴν καρδίαν κατενοήσαμεν͵ ἀφ' ἧς αὐλοειδεῖς πόροι πολυσχιδῶς ἄλλος ἐξ ἄλλου διαφυόμενοι͵ παντὶ τῷ σώματι τὸ πυρῶδες καὶ θερμὸν διαχέουσι πνεῦμα.  

Ἐπεὶ δὲ πάντως καὶ τροφὴν ἔδει τινὰ τῷ θερμῷ συμπαρεῖναι παρὰ τῆς φύσεως - οὐ γὰρ ἐνδέχεται τὸ πῦρ ἐφ' ἑαυτοῦ μένειν͵ μὴ διὰ τοῦ καταλλήλου τρεφόμενον - διὰ τοῦτο οἱ τοῦ αἵματος ὀχετοί͵ καθάπερ ἐκ πηγῆς τινος τοῦ ἥπατος ἀφορμηθέντες τῷ θερμῷ πνεύματι πανταχῆ κατὰ τὸ σῶμα συμπαροδεύουσιν͵ ὡς ἂν μὴ μονωθὲν τοῦ ἑτέρου τὸ ἕτερον͵ διαφθείρῃ τὴν φύσιν πάθος γενόμενον. Παιδευέτω τοῦτο τοὺς ἀτακτοῦντας περὶ τὸ ἴσον͵ διδαχθέντας παρὰ τῆς φύσεως͵ ὅτι ἡ πλεονεξία φθοροποιόν τι πάθος ἐστίν.