It underlies everything in creation. In order to treat and cure diseases one must search for their origins. The pure and lucid element of light is manifested in the upper orifices, and the turbid element of darkness is manifested in the lower orifices. Yang, the element of light, originates in the pores. Yin, the element of darkness, moves within the five viscera.
Water is an embodiment of Yang.
Yang creates the air, while Yin creates the senses, which belong to the physical body. When the physical body dies, the spirit is restored to the air, its natural environment. If Yang is overly powerful then Yin may be too weak. If Yin is particularly strong, then Yang is apt to be defective. If the male force is overwhelming, then there will be excessive heat.