Explain in detail how Galen, a physician during the Middle Ages, expanded on Hippocrates’ theory of the four humors and explain what he believed each humor represented.

Hippocrates developed the theory of the four humors, consisting of the following: blood=air, phlegm=water, black bile=Earth, yellow bile=fire. He linked an imbalance of these liquids to mean a display of illness within the body. While studying the anatomy of apes, Galen was able to expand on this theory; he believed that there exists a connection  between these bodily humors and human emotion/temperament. Galen believed that blood represented optimism, phlegm represented calmness, black bile represented a sense of sadness or melancholy, and finally, yellow bile represented anger issues or a shortness in temper. 

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