Born in Pergamum (Asia Minor) and educated in Alexandria, Galen became well known as a physician and writer. A Greek subject to the Roman Empire, he studied healing (medicine) in Smyna, traveled widely, and finally moved to Rome at the age of 32.
Although Galen believed that the liver was responsible for blood flow, his knowledge of anatomy and physiology was so authoritative that it actually discouraged others from questioning his findings for nearly 1400 years.
Using dissection and experimentation, Galen showed that the speech is controlled by the brain, and that arteries carry blood (in contrast to the previous view that arteries carried air). He distinguished between sensory and motor nerves, and held that the mind was located in the brain. Galen also believed that people are basically cheerful (full of blood) but they can get out of balance.