The whole work is roughly a study in animal anatomy and physiology; it aims to provide a scientific understanding of the parts (organs, tissues, fluids, etc.)
Here, he proposed the methodology to study organisms, and emphasized the importance of the final cause, design or purpose seeking a teleological explanation in the life sciences.
He criticized the dichotomous taxonomy practiced in Plato's Academy, since much of the time, it is superfluous and “pointless.”[2] He concludes by defending the study of animals as a science as important as that of celestial bodies.
First they start from the combination of the fundamental elements of nature (earth, water, air and fire) forming tissues and these organs.
In the rest of the books, Aristotle studies the internal and external parts of the blood and non-blood animals, comparing them with human beings, showing the common and the specific.