The meaning of the back for the yang and the abdomen for the yin has three layers, respectively, is the division of yin and yang of the human body, meridian circulation and yin and yang veins convergence place.
1. In the division of yin and yang in the human body, according to the ancients work on the ground, back facing up to face the sun, and the abdomen facing down and the earth, so the side facing the sun as the yang side, the back of the side of the sun positioning the yin side.
2. Twelve of the human body’s meridians circulating in the abdomen of the three yin meridians, so the abdomen for the yin, and the foot solar bladder meridian two lateral lines in the back, the foot Shaoyang meridian line in the coercive ribs, so the back of the yang.
3. Because the human body for the sea of yang veins, is the convergence of all the yang, and the direct line in the middle of the back for the yang, Ren vein line in the middle of the abdomen, and for the sea of yin veins, so the abdomen for the yin.