Today, it sounds silly to say that the human mind is related to the flow of fluid across empty spaces inside the brain. But in those days, the practice of medicine was all about fluids inside the body and the balance between them. Doctors considered human health as a result of balance among different kinds of fluids inside the body. They were thinking in terms of fluids because the leading science at the time was about the practice of moving water from its source to a target, namely to a dry town or farm. There were no machines or computers to build a dam, but there were plenty of man-made channels and bridges to bring water from one location to another. Do a Google search on "aqueducts" and you will see amazing pictures of those water channels and bridges! In Egypt and nearby Middle East and Greece, they did not have a lot of rain. So, they had to think very hard about fluids and how they could move fluids from one place to another.

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