Determination of Qi

The Yellow Emperor said: I have heard that the human body has essence, qi, fluid, humor, blood, and vessels. I originally thought these were but one qi, yet now they are distinguished into six names, and I do not understand the principle behind this.

Qi Bo said: When two kinds of spirit qi intermingle and fuse to form a physical body, that which exists before the body is generated is called essence.

What is called qi? Qi Bo said: The upper burner opens and spreads forth, diffusing the refined and subtle flavors of the five grains, warming the skin, nourishing the body, and moistening the hair, like the irrigation of mist and dew—this is called qi.

What is called fluid? Qi Bo said: When the interstices discharge and sweat issues forth abundantly, this is called fluid.

What is called humor? Qi Bo said: When grains enter the stomach, the essence qi becomes abundant, and the thick, slippery liquid pours into the bones. The bone joints thereby can flex and extend. The discharged essence supplements the brain and marrow, and the skin becomes moistened—this is called humor.

What is called blood? Qi Bo said: The middle burner receives the essence qi of water and grains, absorbs the liquid therein, and transforms it into a red color—this is called blood.

What is called vessel? Qi Bo said: That which constrains the nutrient qi so that it has nowhere to escape is called a vessel.

The Yellow Emperor said: These six qi have conditions of excess and deficiency. The abundance or scarcity of qi, the emptiness or fullness of the brain and marrow, the clarity or turbidity of blood and vessels—how can these be known?

Qi Bo said: When essence is exhausted, there will be deafness. When qi is exhausted, vision will be unclear. When fluid is exhausted, the interstices open and sweat issues forth excessively. When humor is exhausted, the bone joints cannot flex and extend properly, the complexion becomes withered, the brain and marrow diminish, the lower legs ache, and the ears often ring. When blood is exhausted, the complexion becomes pale, withered, and without luster, and the vessel passages become empty. These are their signs.

The Yellow Emperor said: Among these six qi, what are their noble and base qualities?

Qi Bo said: These six qi each have their governing domain. Their noble and base qualities, whether good or bad, can serve as fixed masters. However, the five grains and the stomach are their great sea.