In the early modern period, the reception of Galen’s treatise On the Formation of the Foetus drove the embryological study. One specific case arises. When in On Formative Power (De virtute formativa, 1506, 1524) Nicolò Leoniceno (1428-1524) reconstructs Galen’s view, a meaningful role is attributed to the comparison between the formation of the fetus and the formation of plants in Galen. The analogy between plants and animals took a specific bend. While blaming Aristotle on this issue, Galen’s uses of the animal-plant continuity importantly clarify the questions concerning embryology and the basic functions of life. Accordingly, in the beginning animals are plants: not just in the first stages of embryological life, but also as long as they perform vegetal operations through the organs of the abdomen. This original interpretation surfaces again in seventeenth century medicine, when physicians repeated the animal-plant continuity following Galenic interpretation. In this paper, after a rapid reconstruction of Galen’s tenet, I focus on a few examples of seventeenth century physicians who re-appropriated and reinterpreted Galen’s theory, ultimately revealing the flexibility of the latter’s medical science and its influence on the early moderns, but also the emergence of comparative anatomy in the later seventeenth century medicine.