The source of postnatal qi has two aspects: the lung controls breathing, clearing the qi aspect, which is governed by the lung; the spleen governs transportation and transformation, and the grain qi transformation originates from the spleen. Therefore, Suwen·five zang-organs generation chapter states: "All harmonious qi belongs to the lung"; Lingshu-Yingwei Shenghui chapter states: "Humans receive qi from grain, grain enters the stomach, and is transmitted to the lung, five zang and six fu-organs, all receive qi." The clearing qi aspect of the lung and the grain qi of the spleen are infused into the heart vessels to circulate through the five zang and six fu-organs, becoming the material basis for the functional activities of the zang-fu organs. Therefore, both the lung and spleen are sources of postnatal qi, physiologically they have a synergistic and mutually nourishing role, and pathologically they influence each other. If the lung is diseased, not only is the inhalation of clearing qi aspect insufficient, but the distribution of grain qi is also affected, this is known as "disorder of child-organ affecting mother-organ," which over time leads to deficiency in both the lung and spleen. Or if the spleen's generation and transformation function is weak, the source of generation and transformation is insufficient, and the lung metal loses its nourishment, leading to lung-spleen qi deficiency, this is known as "earth failing to generate metal." The pathological changes are mainly reflected in the insufficiency of clearing qi aspect and grain qi, thus manifesting as a dull complexion, fatigue, poor appetite, and other symptoms.