As opposed to its function of dispersion, the lung governing depuration and decent means that the lung governs the depuration and descent of lung qi, i.e., the lung inhales fresh air, transports body fluids, qi, and blood downward, and depurates. This physiological function of the lung is manifested in four aspects. First, via the descent of lung qi, the lung inhales deeply the fresh air in nature. Second, through the descent of lung qi, inhaled fresh air, body fluids, and nutrients from food and drinks transported to the lung by the spleen are distributed downward and inward into the whole body, and metabolites and excessive body fluids are transported downward to the kidney and the urinary bladder and turned into urine for discharge. Third, the depuration function of lung qi rids the respiratory tract off foreign matters and keeps it clean. Fourth, with the inward movement of lung qi, the blood in the whole body flows to the lung along the blood vessels.