The foundation of the body is the heart, which is the residence of essence... By assembling essence in its residence, it will by and by enter into the blood ...
董仲舒 Han Dynasty Chinese scholar, 179 BC - 104 BC
Chunqui Fanlu 春秋繁露
Explanations of the Spring and Autumn Annals
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This description of essence as being first assembled in the heart and then passed on into the body allows the concrete understanding of the blood as energy and of the mind as energy in ancient Chinese thought. The mind is consequently thought of as fluid residing in one or the other organ and circulating freely around the body—carried, perhaps, by the energy of the blood.
Body and Mind: The Chinese Perspective