Lung yin, the yin fluid of the lung, as opposed to lung yang, performs the functions of inhibiting, nourishing, moistening, calming, and keeping essence in the interior. Its physiological functions are threefold. First, it nourishes the lung and inhibits lung yang so that the lung can properly perform its functions of dispersion and descent. Second, it helps lung qi to depurate and descend and regulates qi movement to guarantee the depuration and decent functions of the lung. Third, connected with kidney yin, lung yin helps the kidney to receive qi from the lung and transports essence to the kidney to replenish kidney yin. Because the lung governs respiration, the inhaled fresh air is sent downward to the kidney and finally stored in the kidney with the help of kidney yin.