《黄帝内经·灵枢·营卫生会》
岐伯回答说：营气和卫气都是源自水谷精气，血是神气的物质基础，也是水谷精气化生，因此血与营卫之气，只是不同名，却是同一类的物质。
何谓也？岐伯答曰：营卫者，精气也。血者，神气也。故血之与气，异名同类焉。
Qi Bo replied: The camp gas (nutrient gas) and Wei gas (defensive gas) both originate from the refined air of water and food grains, and blood is the material basis for spiritual gas, and is also the refined product of water and food grains. Therefore, blood and the camp-guard gas are just names, but they are of the same category of substances.