This book presents an edition of the Questiones super libro ?De Animalibus? Aristotelis, a work by one of the greatest philosophers and physicians of the 13th century, Peter of Spain. Preceding the critical edition, Navarro offers an introduction to Peter of Spain and a short analysis of the linguistics and form of the Questiones. She also analyses the sources on which Peter drew, Greco-Latin, Arabo-Jewish and, of course, late antique and medieval treatises, showing that the text was not exclusively zoological in nature, but discusses important medical and philosophical topics, illustrating his extensive knowledge of both the Aristotelian corpus and 13th-century medicine.