Qi in the body is a kind of very active and refined substance that is in constant movement. The moving styles of qi, though differing from organ to organ, can be classified into four kinds, namely ascending, descending, coming in and going out. These four styles can be synthesized into two major categories, namely ascending and descending, coming in and going out.
Upward movement of qi means ascending while downward movement of qi means descending. Though ascending and descending are opposite, they can be transformed into each other. When qi ascends to the supreme point, it begins to descend. Such a transformation is known as "extreme ascending changes into descending". When qi descends to the lowest point, it begins to ascend. Such a transformation is known as "extreme descending turns into ascending". This is the upward and downward movement of qi under normal conditions.
Coming in and going out, two opposite moving styles of qi, take place alternately. When qi disperses outward (going out) to a certain degree, it begins to restrain itself inward (coming in). When qi restrains itself inward (coming in) to a certain degree, it begins to disperse outward (going out). This is the external and internal movement of qi under normal conditions.
Ascending and descending, coming in and going out are two types of the motion of yin and yang, which coordinate with each other. For example, the activities of ascending and going out pertain to yang; the activities of descending and coming in pertain to yin. So ascending coordinates with going out while descending coordinates with coming in.
The ascending, descending, coming in and going out activities of qi are accomplished by the viscera and meridians. Each zang-organ or fu-organ may differ from others in the moving style of qi. For example, liver-qi is ascending, lung-qi is descending, spleen-qi is ascending and stomach-qi is descending, etc. The zang-organs and the fu-organs, though different from each other in the moving styles of qi, coordinate with each other and form a special system for regulating qi activity. For example, the liver and the lung restrict but coordinate with each other in ascending and descending; the spleen and the stomach associate and cooperate with each other in ascending and descending, etc.
The meridians and collaterals are the important routes for qi to flow. With the different running directions of the meridians, the ascending and descending activities of qi also become different. The meridians of the viscera run from the internal to the external, qi in these meridians flows outward accordingly. If the meridians run from the external to the internal of the body, qi in these meridians will flow from the external to the internal. If the meridians run from the head to the lower part of the body, qi in these meridians will accordingly flow from the upper to the lower. If the meridians run from the feet upward, qi in these meridians will certainly flow upward.
The ascending, descending, coming in and going out activities of qi are very important to life. If these activities of qi are normal, the functions of the viscera and the meridians will be normal. If these activities are abnormal, the functions of the viscera and meridians will be in disorder. If these activities of qi stop, death will occur.