Aristotle and Diogenes - The Principle of Air

The greek word for breath is pnuma, which is where we get words like pneumatic. A long testimony in aristotle explains that, according to empedocles, there's of interplay between breath and blood. There are passages through the flesh of our bodies which fill with blood and then with air. Many later, thinkers will go further and say that the soul itself is made of some kind of breath, which pervades the body and perhaps even circulates through what we now know as blood vessels or nerves.