[Analysis on the concepts of qi, blood and meridians in Huangdi Neijing (Yellow Emperor's Canon of Internal Classic)].

Concepts of qi, blood, meridians and collaterals in Huangdi Neijing (Yellow Emperor's Canon of Internal Classic) were analyzed systematically based on their relationships described in the classic. With the assistant of the annotation of the later generations and the modern scientific knowledge, the unknown concepts were gradually replaced by the known concepts. It is found that meridians and collaterals are the grading concepts for vessels, boundaries between muscles, tendons, etc. Ying (nutrient) and Wei (defensive) are the concepts of site and level description of qi and blood. And qi has different names at different positions and conditions which is held as various states of body fluid. In this article, the concepts of meridians, qi and blood were demonstrated in the forms of tables and figures. It developed gradually into a conceptual system with clear levers which benefits people to understand Huangdi Neijing (Yellow Emperor's Canon of Internal Classic).