Aristotle opens the work with a detailed structural comparison of the human body, establishing a standard for examining animals. He details the external and internal parts, distinguishing between simple homogeneous components like flesh, bone, and veins, and compound structures like organs and limbs.
The inquiry progresses through distinct zoological classes, including viviparous quadrupeds, birds, fishes, and cephalopods. Each group is analyzed through its characteristic organs, from the respiratory systems of lung-bearing creatures to the branchia of fishes.
A significant portion of the text is dedicated to the mechanics of reproduction and generation. The author investigates spontaneous generation from mud and decaying matter, as well as sexual reproduction across species, describing physiological structures and mating behaviors.
The treatise then explores the sensory capacities, voice, and behavioral patterns of animals. The text examines how creatures navigate their environments, hunt, migrate, and interact socially, with particular attention to the complex hive structures of bees and wasps.
Throughout the work, the analysis relies on direct observation rather than theoretical abstraction. The concluding books synthesize these anatomical and behavioral insights into a coherent natural history, setting a standard for scientific inquiry that endured for centuries.
