This Chapter from The Yellow Emperor’s Classic of Internal Medicine explains the concept of the "fifty circulations" (五十营, wǔshí yíng) of qi within the human body. It describes the daily cyclical movement of qi through 28 meridians, correlating this internal process to the celestial movements of the 28 constellations. The text details the precise calculations of qi's movement based on breath cycles and their relationship to time measurements using a water clock. Ultimately, the unobstructed completion of these fifty circulations is presented as essential for achieving a full lifespan. The text emphasizes the harmonious correspondence between the microcosm of the human body and the macrocosm of the heavens.