A problem in Huangdi's Neijing

The sky is not enough in the northwest, and it is cloudy. People's eyes and ears on the right are not as smart as those on the left. The southeast of the land is insufficient, and the southeast belongs to the sun. People's left hand and feet are not as strong as their right hand. The Yellow Emperor said: Why is this? Qi Bo said: the east belongs to Yang, the left belongs to Yang, and the Yang dominates the ascent, and the essence of human beings also converges on the top, thus forming the deficiency of the upper solid. So the eyes and ears on the left are smart, and the hands and feet are not flexible. The west belongs to yin, and the yin dominates the descending, and the essence of the human body also gathers in the lower part, forming the deficiency of the upper part. So the eyes and ears on the right are not smart but handy.

Therefore, the invasion of evil spirits is heavier on the right side of the upper half and heavier on the left side of the lower half. This is because the ups and downs of Yin and Yang of the Qi of heaven and earth are incomplete, and people also have corresponding shortcomings. So when evil spirits invade the human body, they will take advantage of it and live there.

That's not beside the point This is its literal meaning. The left dominates the rise, so the essence fills the body, so the left eye and the left ear are good. The right is the main descending, which belongs to yin, and the essence is filled in the lower part, so the upper part is useless. Mainly the land where the essence gathers is rich in nutrition.