Chinese medical theory describes what fills and animates the body in five terms: qi, blood, the body fluids called jin and ye, essence (jing) and spirit (shen). The WHO’s International Standard Terminologies on Traditional Medicine in the Western Pacific Region (2007) files them together in a section headed “Essence, Spirit, Qi, Blood, Fluid and Humor”, and the definitions quoted on this page are the WHO’s unless another source is named. The five are terms of the theory, and each section below reports what the theory says the substance is, where it comes from and what it does. Where research has tested the theory, the last section reports what it found.
Qi
Qi was a term of cosmology before it was a term of medicine. Britannica’s entry describes it as “the psychophysical energies that permeate the universe”, and notes that early Daoist philosophers and alchemists regarded it as a vital force inhering in the breath and bodily fluids. Robin Wang’s entry on yinyang in the Internet Encyclopedia of Philosophy cites the Zuozhuan naming six heavenly qi: yin, yang, wind, rain, obscurity and brightness. The WHO terminology keeps both senses. Qi is “the basic element that constitutes the cosmos”, and in medicine it refers “both to the refined nutritive substance that flows within the human body as well as to its functional activities”.
The theory gives qi two origins. Innate qi “exists from birth and is stored in the kidney”; acquired qi is formed after birth “from the food in combination with the fresh air inhaled in the lung”. Its movement has four basic forms: ascending, descending, exiting and entering. Every organ has a qi of its own, which the WHO defines in each case as “the physical substrata and dynamic force” of that organ’s activity, so that spleen qi drives the spleen’s work and liver qi the liver’s. Among the further kinds the WHO names, four are defined by where they arise or where they travel.
| Kind | Chinese | What the WHO says it is and does |
|---|---|---|
| Source qi (yuan qi), also original qi | 原氣; 元氣 | the combination of innate and acquired qi, “the most fundamental qi of the human body” |
| Ancestral qi (zong qi), also pectoral qi | 宗氣 | the essential qi of food combined with inhaled air, stored in the chest; the dynamic force of blood circulation, breathing, voice and bodily movement |
| Nutrient qi (ying qi) | 營氣 | moves within the vessels and nourishes all the organs and tissues |
| Defence qi (wei qi) | 衛氣 | moves outside the vessels, protects the body surface and wards off external pathogens |
A shortfall or a blockage of qi is a pattern. AcuiQ’s index carries qi deficiency, qi stagnation and liver qi stagnation as search terms because published prescriptions name them; Patterns, symptoms and what you can look up explains how such terms differ from symptoms.
Blood
The WHO terminology defines blood (xue) as “the red fluid circulating through the blood vessels, and nourishing and moistening the whole body”. In the theory it does not move by itself. Ancestral qi is the force of its circulation, the heart “controls blood circulation”, the liver “stores blood”, and the spleen keeps it “flowing within the vessels”. Nutrient qi travels with it, and the WHO gives “nutrient and blood” as a single term. Blood shares its origin with essence: the WHO records that the two have “a common source, the essential qi of food”. The commentator Li Zhongzi, in Richard Bertschinger’s translation of Suwen chapter 5, writes that food entering the mouth “creates blood and builds up the physical form”, and that blood “is entirely dependent on qi”.
The Neijing says that the blood “flows continuously in a circle and never stops”, and the line has been read as an anticipation of the English physician William Harvey’s account of the circulation. Britannica’s history of medicine calls the evidence for that claim insubstantial. Weakness of blood is a pattern too: AcuiQ’s index carries blood deficiency and blood stasis.
Fluids: jin and ye
Jin-ye is the WHO’s “fluid and humor”, “a general term for all kinds of normal fluid in the body, except the blood”. Jin-ye divides by consistency. Jin is the thin fluid, “the liquid substance that circulates with qi and blood”; ye is the thick fluid “stored in body cavities such as bowels, viscera, articular and cranial cavities”. Fluid shares its source with blood in the same way essence does, and the WHO names the pair the “homogeny of fluid and blood”. The terminology also assigns five secretions to the five zang as their humors: sweat to the heart, tears to the liver, thin saliva to the spleen, nasal mucus to the lung and thick saliva to the kidney.
Essence: jing
The WHO terminology defines essence as “the fundamental substance that builds up the physical structure and maintains body function”, and in a second sense as the “reproductive essence stored in the kidney”. Essence too has two sources. Innate essence, also called prenatal essence, is “the original substance responsible for construction of the body and generation of offspring”; acquired essence is drawn from food after digestion and maintains the body’s activity from day to day. The kidney stores essence and, in the WHO’s definition of the organ, promotes “growth, development, reproduction, and urinary function”. When kidney essence is abundant it gives rise to tiangui, “that upon which development of the reproductive organs and maintenance of reproductive function depends”.
Suwen chapter 5 sets essence and qi in a loop. In Bertschinger’s translation, “the qi goes back to the jing”, “the jing feeds off the qi”, and “the jing transforms into qi”. AcuiQ’s index carries kidney jing deficiency as a search term.
Spirit: shen
The WHO terminology gives shen three senses: “mental activities, referring to mentality, consciousness, thinking and feeling”; spiritual activities; and the “manifestations of vital functioning” that a practitioner judges by inspecting a patient’s consciousness, facial expression, speech and responses. The heart governs shen, as the “bright spirit” that covers “all the human life activities including mind, will, mood and thinking”. The terminology names four further aspects of mind alongside shen: the ethereal soul (hun), “the moral and spiritual part of the human being”; the corporeal soul (po), “the animating part of one’s mind”; ideation (yi), the power of thinking and forming ideas; and will (zhi), the mental power by which a person directs thoughts and actions.
What research has found
Ted Kaptchuk’s 2002 review in Annals of Internal Medicine groups qi with yin-yang, dampness and wind as East Asian conceptual frameworks that rest on ordinary human sensory awareness. It notes that many physicians who practise acupuncture reject such prescientific notions, and reports that basic-science research has begun to offer plausible mechanisms for acupuncture’s presumed physiological effects, among them the activation of the body’s own opioid systems.
One claim about qi has been measured directly. The theory holds that meridian qi flows through the channels, and a long-standing claim in the field is that points and channels conduct electricity better than the skin around them. A 2008 systematic review by Ahn and colleagues found 18 studies that measured the claim in people. Five of 9 studies of points found lower electrical resistance or impedance at the point, and 7 of 9 studies of channels found lower impedance or higher capacitance along the channel. The studies were generally of poor quality, small and open to multiple confounders, and the reviewers concluded that the evidence does not conclusively support the claim that points or channels are electrically distinguishable, while calling the findings suggestive enough to direct further research.
What these definitions cannot tell you
The WHO terminology fixed one English definition for each term in 2007. The Neijing and the commentaries after it use several of these words in more than one way, as the WHO’s own entries show where they give a term two or three senses. A pattern name in AcuiQ’s index, such as qi deficiency or blood deficiency, records what a study’s authors called the condition they treated; AcuiQ does not check the differentiation behind it, as What AcuiQ does not do sets out.