Bigu, also known as "broken valley", "broken valley", "broken valley", "stopped valley" and "broken valley", means not to eat whole grains, and alchemists and Taoists regard it as a method of cultivating immortality. Taoism believes that when people eat whole grains, feces will accumulate in their intestines, which will produce foul smell and hinder the road to longevity. "Huang Ting Neijing" says: "The land of the hundred valleys eats fine food, evil spirits smell from the outside, and the sacred things of God are zero. So, how can we return to the baby from the old one? " At the same time, there are three worms (three corpses) in the human body, which depend on this kind of grain gas to survive. With its existence, people have evil desires and cannot become immortals. Therefore, if you want to clear the dirty gas in the intestine and get rid of the three corpse worms, you must break the valley. Therefore, Taoism imitates the immortal behavior described in "Zhuangzi Xiaoyao Tour", hoping to achieve the goal of becoming immortal.