Aristotle thought that the brain was a radiator:
Great description of the blood brain barrier, it’s role and its challenges, and the involvement of those “other brain” cells, astrocytes. Interesting pondering on the origins of common saying such as “keeping a cool head”. Neuroscience meets ancient philosophy meets cartoon in this fantastic short post on the Scientific American blog.
Could it also be part of the reason we feel someone’s forehead to “check their temperature”?