OW every one can see whence diseases arise. There are four natures out of which the body is compacted, earth and fire and water and air, and the unnatural excess or defect of these, or the change of any of them from its own natural place into another, or-since there are more kinds than one of fire and of the other elements-the assumption by any of these of a wrong kind, or any similar irregularity, produces disorders and diseases; for when any of them is produced or changed in a manner contrary to nature, the parts which were previously cool grow warm, and those which were dry become moist, and the light become heavy, and the heavy light; all sorts of changes occur. For, as we affirm, a thing can only remain the same with itself, whole and sound, when the same is added to it, or subtracted from it, in the same respect and in the same manner and in due proportion; and whatever comes or goes away in violation of these laws causes all manner of changes and infinite diseases and corruptions. Now there is a second class of structures which are also natural, and this affords a second opportunity of observing diseases to him who would understand them. For whereas marrow and bone and flesh and sinews are composed of the four elements, and the blood, though after another manner, is likewise formed out of them, most diseases originate in the way which I have described; but the worst of all owe their severity to the fact that the generation of these substances stances in a wrong order; they are then destroyed. For the natural order is that the flesh and sinews should be made of blood, the sinews out of the fibres to which they are akin, and the flesh out of the dots which are formed when the fibres are separated. And the glutinous and rich matter which comes away from the sinews and the flesh, not only glues the flesh to the bones, but nourishes and imparts growth to the bone which surrounds the marrow; and by reason of the solidity of the bones, that which filters through consists of the purest and smoothest and oiliest sort of triangles, dropping like dew from the bones and watering the marrow.

νόσοι τοῦ σώματος

Τὸ δὲ τῶν νόσων ὅθεν συνίσταται͵ δῆλόν που καὶ παντί. [82a] τεττάρων γὰρ ὄντων γενῶν ἐξ ὧν συμπέπηγεν τὸ σῶμα͵ γῆς πυρὸς ὕδατός τε καὶ ἀέρος͵ τούτων ἡ παρὰ φύσιν πλεονεξία καὶ ἔνδεια καὶ τῆς χώρας μετάστασις ἐξ οἰκείας ἐπ΄ ἀλλοτρίαν γιγνομένη͵ πυρός τε αὖ καὶ τῶν ἑτέρων ἐπειδὴ γένη πλείονα ἑνὸς ὄντα τυγχάνει͵ τὸ μὴ προσῆκον ἕκαστον ἑαυτῷ προσλαμβάνειν͵ καὶ πάνθ΄ ὅσα τοιαῦτα͵ στάσεις καὶ νόσους παρέχει· παρὰ φύσιν γὰρ ἑκάστου γιγνομένου καὶ μεθισταμένου θερμαίνεται μὲν ὅσα ἂν πρότερον ψύχηται͵ [82b] ξηρὰ δὲ ὄντα εἰς ὕστερον γίγνεται νοτερά͵ καὶ κοῦφα δὴ καὶ βαρέα͵ καὶ πάσας πάντῃ μεταβολὰς δέχεται. μόνως γὰρ δή͵ φαμέν͵ ταὐτὸν ταὐτῷ κατὰ ταὐτὸν καὶ ὡσαύτως καὶ ἀνὰ λόγον προσγιγνόμενον καὶ ἀπογιγνόμενον ἐάσει ταὐτὸν ὂν αὑτῷ σῶν καὶ ὑγιὲς μένειν· ὃ δ΄ ἂν πλημμελήσῃ τι τούτων ἐκτὸς ἀπιὸν ἢ προσιόν͵ ἀλλοιότητας παμποικίλας καὶ νόσους φθοράς τε ἀπείρους παρέξεται. Δευτέρων δὴ συστάσεων αὖ κατὰ φύσιν συνεστηκυιῶν͵ [82c] δευτέρα κατανόησις νοσημάτων τῷ βουλομένῳ γίγνεται συννοῆσαι. μυελοῦ γὰρ ἐξ ἐκείνων ὀστοῦ τε καὶ σαρκὸς καὶ νεύρου συμπαγέντος͵ ἔτι τε αἵματος ἄλλον μὲν τρόπον͵ ἐκ δὲ τῶν αὐτῶν γεγονότος͵ τῶν μὲν ἄλλων τὰ πλεῖστα ᾗπερ τὰ πρόσθεν͵ τὰ δὲ μέγιστα τῶν νοσημάτων τῇδε χαλεπὰ συμπέπτωκεν· ὅταν ἀνάπαλιν ἡ γένεσις τούτων πορεύηται͵ τότε ταῦτα διαφθείρεται. κατὰ φύσιν γὰρ σάρκες μὲν καὶ νεῦρα ἐξ αἵματος γίγνεται͵ νεῦρον μὲν ἐξ ἰνῶν διὰ τὴν συγγένειαν͵ [82d] σάρκες δὲ ἀπὸ τοῦ παγέντος ὃ πήγνυται χωριζόμενον ἰνῶν· τὸ δὲ ἀπὸ τῶν νεύρων καὶ σαρκῶν ἀπιὸν αὖ γλίσχρον καὶ λιπαρὸν ἅμα μὲν τὴν σάρκα κολλᾷ πρὸς τὴν τῶν ὀστῶν φύσιν αὐτό τε τὸ περὶ τὸν μυελὸν ὀστοῦν τρέφον αὔξει͵ τὸ δ΄ αὖ διὰ τὴν πυκνότητα τῶν ὀστῶν διηθούμενον καθαρώτατον γένος τῶν τριγώνων λειότατόν τε καὶ λιπαρώτατον͵ λειβόμενον ἀπὸ τῶν ὀστῶν καὶ στάζον͵ ἄρδει τὸν μυελόν.