"In the 'Discourse on the Correspondence with Phenomena of Yin and Yang' from the 'Inner Canon of the Yellow Emperor', it is recorded: 'The heavens are insufficient in the northwest, hence the northwest direction is yin, causing the right ear and eye of a person to be less perceptive than the left. The earth is incomplete in the southeast, so the southeast is yang, making the left hand and foot of a person less strong than the right.'"
"The northwest is associated with yin; insufficient heavenly qi affects the body, making the right ear and eye less perceptive. The southeast is associated with yang; insufficient earthly qi affects the body, making the left hand and foot less strong."
"This is the influence of heavenly and earthly qi on the human body, also known as qi interaction."
