《黄帝内经·灵枢·胀论》
岐伯说：卫气在体内运行，总是依傍着经脉而循行于分肉之间，它的运行有逆顺的不同，营气、卫气在脉内、脉外相互伴随，与自然界阴阳变化的规律相合，五脏之气的交替运行，就像四季变化一样有固定的次序，饮食物也可以正常地化生精微营养周身。
岐伯曰：卫气之在身也，常然并脉，循分肉，行有逆顺，阴阳相随，乃得天和，五脏更始，四时循序，五谷乃化。
Qibo said: The Qi of Defense circulates in the body, always following the meridians and circulating between the muscles and bones. Its movement is inversely proportional, and the Qi of Nourishment and the Qi of Defense accompany each other inside and outside the pulse, and coincide with the law of the changes of yin and yang in nature. The alternate movement of the Qi of the five internal organs, like the change of the four seasons, has a fixed order, and the food and drink can also be transformed into fine and subtle nutrients throughout the body.