3. The Spleen and the Stomach
Both the spleen and stomach are located in the middle-jiao and are inter-connected by meridians, forming an exterior-interior relationship. Physiologically, they share the work and coordinate to maintain the normal digestive function, the relationship between the spleen and stomach is manifested in the following:

1) Coordination of Ingestion and Transportation and Transformation
The stomach has the function of taking and digesting food into chyme, and thus provides the material basis for transportation and transformation of the spleen. The spleen transports, transforms, and distributes the essential substance to the entire body, and this function adapts to the stomach's continuing capacity for food intake. As both organs function in close cooperation in performing digestive activity, they affect each other in pathology. For example, if the stomach's digestive function is impaired, the spleen is left with fewer raw materials from which to form qi and blood, giving rise to poor appetite and an unpleasant and hungry sensation in the stomach. Dysfunction of the spleen in transportation and transformation may attack the digestive function of the stomach, leading to abdominal distension after eating, loss of appetite, belching and loose stools, and so on.

2) Complementary of Ascending and Descending
The spleen dominates ascending, while the stomach dominates descending. The former distributes clear-yang and the essential substance of drink and food up to the heart and lung. The latter sends digesting food down to the small intestine, and in a broader sense, to down-flow throughout the whole of the digestive tract. Hence, the two organs work in harmony to guarantee a normal digestive function. The spleen is in charge of sending up the clear, while the stomach is in charge of sending the turbid downwards, which are opposing, yet complementing functions. Failure of the clear qi to send upward may impair the sending downward of the turbid qi. Similarly, failure of the turbid qi to send downward may affect the sending up of clear qi. Failure of the spleen in sending up the clear can lead to the fall of the middle-qi, characterized by abdominal distension, diarrhea, and prolapse of rectum. In this case, the stomach-qi goes upwards instead of downwards, and there may be nausea, vomiting, hiccups, and abdominal distension. Therapeutic efforts should aim at strengthening the spleen and harmonizing the stomach.

3) Adjustment of Dryness and Dampness
The spleen likes dryness and dislikes dampness. The stomach likes moistness and dislikes dryness. The spleen belongs to the yin organs, and transports and transforms water and dampness, which is particularly susceptible to invasion by the damp evil. When dampevil invades the spleen, it may impair the function of transportation and transformation, and in turn, it may easily produce phlegm-dampness, in which case the spleen is said to be encumbered by damp. The stomach, on the other hand, pertains to yang and has the function of ingestion and decomposition, which is vulnerable to dryness-heat evil. When dryness-heat evil invades the stomach, it consumes fluids in the stomach. Only when the spleen-dryness and the stomach-dampness are in coordination with each other can yin and yang of the spleen and stomach be kept in balance, ensuring a flourishing state of the digestive function. In summary, the spleen and the stomach are closely related, and the coordination of the stomach's reception and the spleen's transportation, the complementary nature of the spleen's ascending and the stomach's descending, and the adjustment of dryness and dampness all are of particular importance in the digestive process. Disruption of this balance constitutes a primary cause of digestive disturbances, and its restoration figures frequently in the treatment of spleen and stomach disorders.