In this article I explore certain modeling in Aristotle's zoological work. In particular, I am interested in the type of theoretical schemes in which Aristotle does not claim anatomical or physiological precision because they refer to more than one genus of animals or their parts or activities. On the one hand, I analyse the triaxial scheme of the faculties of animals in the De Incessu Animalium 4, in which the dimensions are defined not by their position but by a function. (...) On the other hand, I examine the diagram of the De Motu Animalium 9, in which Aristotle concludes that the material middle of the animal, the heart, cannot originate simultaneous movements, so there must be something that moves without being moved. I believe that this model also distinguishes its elements not by their positions but their functions. The geometric terms assigned in each case account for certain functions of animals, presenting a double value of the analogy: between the animal domain and the geometric one, and granting the necessary generality to capture the similarity between different genus within the animal domain itself. (shrink)