Πάλιν δ’ ἐπὶ τὴν πρώτην τοῦ ζῴου σύστασιν ἐπανάγωμεν τὸν λόγον· καὶ ὅπως γε ἡμῖν εὔτακτός τε ἅμα καὶ σαφὴς γίγνοιτο, διελώμεθα τέτταρσι χρόνοις τὴν σύμπασαν τῶν κυουμένων δημιουργίαν. πρῶτος μέν, ἐν ᾧ κατὰ τὰς ἀμβλώσεις τε καὶ κατὰ τὰς ἀνατομὰς ἡ τοῦ σπέρματος ἰδέα κρατεῖ. κατὰ τοῦτον τὸν χρόνον οὐδ’ Ἱπποκράτης ὁ πάντα θαυμάσιος ἤδη που κύημα καλεῖ τὴν τοῦ ζῴου σύστασιν, ἀλλ’, ὡς ἀρτίως ἠκούσαμεν ἐπὶ τῆς ἑκταίας ἐκπεσούσης, ἔτι γονήν. ἐπειδὰν δὲ πληρωθῇ μὲν τοῦ αἵματος, ἡ καρδία δὲ καὶ ὁ ἐγκέφαλος καὶ τὸ ἧπαρ ἀδιάρθρωτα μὲν ᾖ καὶ ἀμόρφωτα, πῆξιν δ’ ἠδη τινὰ καὶ μέγεθος ἀξιόλογον ἕχῃ, δεύτερος μὲν οὗτος ὁ χρόνος ἐστί, σαρκοειδὴς δὲ καὶ οὐκέτι γονοειδής ἐστιν ἡ οὐσία τοῦ κυήματος. οὐκοῦν οὐδὲ γονὴν ἔτι προσαγορεύοντα τὸν Ἱπποκράτην τοιαύτην ἰδέαν εὕροις ἄν, ἀλλ’, ὡς εἴρηται, κύημα. τρίτος ἐπὶ τῷδε χρόνος, ἡνίκα, ὡς εἴρηται, τὰς μὲν τρεῖς ἀρχὰς ἔστιν ἰδεῖν ἐναργῶς, ὑπογραφὴν δὲ τινα καὶ οἷον σκιαγραφίαν ἁπάντων τῶν ἄλλων μορίων. ἐναργεστέραν μὲν γὰρ ὄψει τὴν περὶ τὰς τρεῖς ἀρχὰς διάπλασιν, ἀμυδροτέραν δὲ τὴν τῶν κατὰ τὴν γαστέρα μορίων, καὶ πολὺ δὴ τούτων ἔτι τὴν κατὰ τὰ κῶλα. ταῦτα γάρ ὕστερον, ὡς Ἱπποκράτης ὠνόμαζεν, ὀζοῦται, τὴν πρὸς τοὺς κλάδους ἀναλογίαν ἐνδεικνύμενος τῇ προσηγορίᾳ. τέταρτος δ’ οὗτός ἐστι καὶ τελευταῖος χρόνος, ἡνίκα ἤδη τά τ’ ἐν τοῖς κώλοις ἅπαντα διήρθρωται, καὶ οὐδ’ ἔμβρυον ἐτι μόνον, ἀλλ’ ἤδη καὶ παιδίον ὀνομάζει τὸ κυούμενον ὁ θαυμάσιος Ἱπποκράτης, ὅτε καὶ ἀσκαρίζειν καὶ κινεῖσθαί φησιν, ὡς ζῷον ἤδη τέλειον.
(Galen, De semine 1.8.9)
But let us take the account back again to the first conformation of the animal, and in order to make our account orderly and clear, let us divide the creation of the foetus overall into four periods of time. The first is that in which, as is seen both in abortions and in dissection, the form of the semen prevails. At this time, Hippocrates too, the all-marvelous,does not yet call the conformation of the animal a foetus; as we heard just now in the case of semen voided in the sixth day, he still calls it semen. But when it has been filled with blood, and heart, brain and liver are still unarticulated and unshaped yet have by now a certain solidarity and considerable size, this is the second period; the substance of the foetus has the form of flesh and no longer the form of semen. Accordingly you would find that Hippocrates, too no longer calls such a form semen but, as was said, foetus. The third period follows on this, when, as was said, it is possible to see the three ruling parts clearly and a kind of outline, a silhouette, as it were, of all the other parts. You will see the conformation of the three ruling parts more clearly, that of the parts of the stomach more dimly, and much more still, that of the limbs. Later on they form “twigs”, as Hippocrates expressed it, indicating by the term their similarity to branches. The fourth and final period is at the stage when all the parts in the limbs have been differentiated; and at this part Hippocrates the marvellous no longer calls the foetus an embryo only, but already a child, too, when he says that it jerks and moves as an animal now fully formed. (tr. Phillip de Lacy)