Like the other Greek physicians, he believed health and disease were controlled by the balance or imbalance of these humors.
Although the university in Alexandria and its massive library was destroyed by bands of conquerors, later Arabic physicians made the efforts to preserve some of the writings.
Praxagoras studied Aristotle's (384–322 BC) anatomy and improved it by distinguishing between artery and veins.
He saw arteries as air tubes, similar to the trachea and bronchi, which carried pneuma, the mystic force of life.
Also, he believed that arteries were the channels through which voluntary motion was given to the body, and that the cause of epilepsy was the blocking of the aorta by this same accumulation of phlegm.
Aristotle, Diocles, and Praxogoras insisted that the heart was the central organ of intelligence and the seat of thought.
Praxagoras differed with the others in that he believed the purpose of respiration was to provide nourishment for the psychic pneuma, rather than to cool the inner heat.
However, he speculated about the role of movement and was satisfied that he had found the answer of the center of vitality and energy.