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Fluids

津液 〔津液〕jīn yè

All normal bodily fluids, including the fluids of the stomach and intestines, the fluids of the orifices such as drool, spittle, tears, nasal mucus, and, in some contexts, excretions such as sweat and urine, as well as the general water content of the flesh. The Chinese term is a compound of two words, liquid and humor, referring to thin and thick fluids respectively.

The fluids of the body are yīn in nature and stand in complementary opposition to yáng qì. Hence, they are often referred to as yīn humor.

In modern texts, the production, distribution, and discharge of fluids from the body are often collectively referred to as water metabolism (metabolism is a biomedical concept).

Fluids in Physiology

Function of Fluids

The fluids moisten and nourish the body, constitute a major component of the blood, and also bear qì.

Moistening and Nourishment

The fluids moisten and nourish the bowels and viscera, their orifices, as well as the skin, flesh, sinews, and bones.

Transforming into Blood

The fluids seep into the blood vessels to form a major component of the blood.

Fluids Are Needed to Produce Qì

A healthy state of the fluids is required for the health of the bowels and viscera involved in the production of qì: lung, spleen-stomach, and kidney.

In pathology, loss of fluid as a result of profuse sweating or from excessive vomiting or diarrhea can lead to qì vacuity. This phenomenon is most pronounced in the case of summerheat disease, in which dual damage to qì and liquid is very common.

Regulating Yīn and Yáng

The fluids are important in that they help to regulate the balance of yīn and yáng. In hot weather, the interstices become loose and open, allowing increased sweating that helps to reduce the temperature of the body. When the weather is cold, the interstices tighten and close so that sweating decreases to preserve bodily warmth.

Bearing Qì

The fluids, like blood, facilitate the movement and activity of qì. Consequently, the state of the fluids can affect qì. Notably, it is said that while blood bears provisioning qì, the fluids bear defense qì.

The qì-bearing function of the fluids is reflected in pathology. When fluids are lost from the body through great vomiting, great diarrhea, and great sweating, qì can desert with them, giving rise to what is called qì deserting with liquid (气随津脱 qì suí jīn tuō). Also, when fluids fail to move and accumulate in the form of water-damp, phlegm, and rheum, this can also obstruct the movement of qì, giving rise to distension and fullness.

Classification of Fluids

A twofold distinction is made between liquid and humor, while a fivefold distinction is made between sweat, snivel, drool, tears, and spittle.

Liquid and Humor (津液 jīn yè)

Distinction is made between thin runny fluids called liquid (jīn 津) and thicker, viscous ones called humor (yè 液). The thinner fluids pervade the skin and flesh and moisten the orifices. The thicker ones moisten the joints, bowels and viscera, and the brain and marrow.

This distinction between liquid and humor is of greatest significance in the context of pathology. Damage to liquid refers to mild dehydration, while humor desertion, also called damage to yīn, refers to a more severe loss of internal bodily fluids essential to the functioning of the body and it notably characterized by emaciation.

Five Humors (五液 wǔ yè)

In addition to the differentiation into liquids and humors, we distinguish between five types of body fluids. The five humors (五液 wǔ yè) are tears, sweat, drool, snivel, and spittle, which are associated with the liver, heart, spleen, lung, and kidney respectively. Note that these are called humors, but are strictly speaking liquids according to the dual distinction explained above.

Sweat (汗 hàn) is the humor of the heart. When the interstices open, sweat flows; when the interstices close, sweating ceases.

Sweat is related to other bodily fluids. Excessive sweating can cause damage to liquid, giving rise to dry pharynx and mouth, thirst, and scant urine.

Sweat is also related to the blood. This is traditionally expressed as sweat and blood are of the same source (血汗同源 xuè hàn tóng yuán). The fluids are a major component of the blood, which is traditionally expressed as liquid and blood are of the same source. When excessive sweating damages liquid, the blood can be affected too. When blood and fluids are depleted, the source of sweat is insufficient, so sweating is reduced.

Sweat is the humor of the heart. Because of the close connection between sweat and blood and because blood is governed by the heart, there is a close connection between sweat and the heart. Healthy people sweat in hot environments, and also when they engage in strenuous exertion that causes the heart to race. Sweating can affect the heart and, conversely, heart disease can also manifest in sweating, as the following examples show.

Despite these connections between sweat and the heart, it must be remembered that sweating is associated with any heat condition, with yáng qì failing to contain sweat, and with disturbances of the exterior and the lung in external contractions.

Snivel (涕 tì), or nasal mucus, is the humor of the lung. The lung opens at the nose, and snivel is the fluid that moistens the nose. For this reason, snivel is classed as the humor of the nose. When wind-cold fetters the lung, it causes runny nose with clear snivel. When wind-heat invades the lung, it manifests in runny nose with turbid snivel. In lung dryness, the nose is dry with little or no snivel.

Drool (涎 xián) is a thin form of saliva that is related to the spleen. Drooling from the corners of the mouth during sleep is attributed to spleen vacuity or stomach heat.

Tears (泪 lèi) are the humor associated with the liver. Tear fluid keeps the eyes clean and moist. Insufficiency of liver yīn or liver blood can cause dry eyes. Patients suffering from red eyes due either to wind-fire eye (acute conjunctivitis) or to liver channel damp-heat may suffer from copious eye discharge and experience tearing on exposure to wind.

Spittle (唾 tuò) is a thicker form of saliva and is related to the kidney. It is believed to result from a transformation of kidney essence. The supposed connection between spittle and the kidney is reflected in the practice among qì-gōng masters of swallowing their spittle in order to nourish their kidney essence.

Sweat as the Humor of the Heart?
The Nèi Jīng asserts that sweat is the humor of the heart. The presumed reason for this is the connection between racing of the heart and sweating during physical exercise. It is important to understand, however, that sweating is not necessarily associated with morbidity of the heart. Spontaneous sweating, which is sweating during the daytime or sweating at the slightest physical exertion, is the result of qì vacuity or yáng vacuity. It is also observed when, in externally contracted disease, defense qì is vacuous and the interstices slacken or when heat evil causes the fluids of the body to steam outward. Night sweating (called thief sweating because it occurs unbeknown to the patient during sleep) is a sign of yīn vacuity in general and hence, in particular, kidney yīn vacuity, not merely heart yīn vacuity.

Production of Fluids

Fluids are derived from ingested food by the spleen, stomach, small intestine, and large intestine.

Spleen and Stomach

Food entering the stomach is ripened and rotted (preliminarily digested) by the stomach, and the spleen extracts the essence of grain and water from it. The spleen governs movement and transformation and the upbearing of the clear. It transports the essence of grain and water upward to the heart and lung for distribution throughout the whole body.

Small Intestine

Liquid and Humor in the Context of the Intestines
The distinction between liquid as governed by the large intestine and humor governed by the small intestine is made on the basis of usefulness. Humor refers here to nutritious fluids; liquid refers to excess water content.

The contents of the stomach are passed on to the small intestine, which is responsible for separation of the clear and turbid. Here, the clear refers to the essence of grain and water, i.e., the useful elements of food and drink; the turbid refers to waste fluids and solids. The small intestine, like the stomach, extracts essence of grain and water, which then, by the action of the spleen, is transported upward to the heart and lung, to be distributed around the whole body. As to the turbid elements remaining in the small intestine, much of the liquid part is drawn off and transported to the kidney and bladder, for discharge from the body in the form of urine, while the solid part is passed on to the large intestine. Because the small intestine extracts much useful fluid from food, it is said to govern humor.

Large Intestine

The contents of the small intestine pass to the large intestine, where excess fluid is removed from it so that it can form into solid stool, ready for discharge from the body via the anus. For this reason, it is said that the large intestine governs liquid.

Distribution of Fluids

The spleen, lung, kidney, liver, heart, and triple burner all play a role in the distribution of fluids. The functions of the spleen, lung, and kidney are considered paramount.

Fluids and the Spleen

The spleen moves the fluids of the stomach. It churns them so that they exude their essential qì (游溢精气 yóu yì jīng qì). The movement and transformation function of the spleen sends fluids up to the lung, to be distributed around the whole body with the help of the lung’s diffusion and depurative downbearing actions. The upbearing action of the spleen also conjugates with the small intestine’s function of separating the clear and the turbid, bearing the clear upward.

Fluids and the Lung

The lung governs movement of water. It has an important role in the distribution of fluids. Lung qì has two actions: an upward and outward movement called diffusion and a downward action called depurative downbearing. By diffusion, fluids are carried outward and around the whole body to moisten the skin, flesh, orifices, and bowels and viscera. By depurative downbearing, fluids are carried down to the kidney and bladder. The aspect of these two actions that involves the fluids is called governing the regulation of the waterways.

Natural Loss of Fluids
Fluids are continually excreted from the body through sweat, breath, urine, and stool. The lung, spleen, and kidney play the most important roles in this process. Sweating occurs when the interstices are open; the opening and closing of the interstices is controlled by defense qì, which is closely related to the diffusing action of lung qì. About 2/3 of our fluid intake leaves the body in the form of urine, which is produced by the kidney. Some fluid is discharged from the body through the breath exhaled from the lung. Some fluid is also lost from the body in the stool.

Fluids and the Kidney

The kidney plays a major role in fluid metabolism. It produces urine and passes it down to the bladder, where it is stored temporarily for periodic discharge from the body.

The role of the kidney is conceived in a very dynamic fashion. The kidney is the basis of the yīn and yáng balance in the whole body. The yáng qì of the kidney powers the spleen’s function of distributing essence, the lung’s diffusion and depurative downbearing action, and the small intestine’s function of separating the clear and turbid. Kidney yáng also has the specific action of steaming or distilling the fluids: This means that fluids descending to the kidney are heated by kidney yáng so that the clear part steams upward to be used again by the body, while the turbid part becomes urine and is passed down to the bladder. The term qì transformation often refers specifically to this action of the kidney.

The liver and the triple burner also play a minor role in fluid metabolism. The free coursing action of the liver, for example, helps to keep fluids moving.

Fluids in Pathology

These include damage to fluids (fluid loss) and fluid accumulations.

Fluid Depletion

Fluid depletion (津液亏损 jīn yè kuī sǔn), also called damage to fluids, can be caused by high fever, vomiting, excessive sweating, excessive urination, or diarrhea. It is characterized by dry mouth, dry throat, and reddish urine.

Damage to fluids includes a mild form, damage to liquid (伤津 shāng jīn) and a more severe form called humor desertion (脱液 shāng jīn). Humor desertion refers to severe loss of fluids, characterized by sunken eyes and severe emaciation.

Fluid Accumulation

Fluid accumulations (津液过多 jīn yè guò duō) arise when the viscera involved in producing, distributing, and discharging fluids, namely the spleen, lung, and kidney, fail in their functions and allow water-damp, i.e., unwanted water and dampness, to accumulate.

Fluid accumulations include water swelling (edema), which mostly affects the extremities (e.g., the feet and ankles) and local accumulations called phlegm-rheum.

Water swelling (水腫 shuǐ zhǒng): This is an accumulation of water under the skin in the region of the head, face, limbs, or the whole body.

Water swelling is due essentially to impairment of the lung’s function of governing the waterways, the spleen’s function of moving and transforming water-damp, and the kidney’s qì transformation action.

A broad division can be made between two locations: above and below the waist. Water swelling below the waist, usually affecting the feet, ankles, and legs stems from disturbances of the lung, spleen, and or kidney. Water swelling in the upper part of the body, usually of rapid onset, is mostly the result of external wind (wind-heat or wind-cold) assailing the exterior and obstructing the lung diffusion so that it fails to drain excess fluid away from the fleshy exterior.

Phlegm-rheum (痰飲 tán yǐn): Phlegm is a thick pathological fluid that accumulates in the lung, but in Chinese medicine it is also said to reach other places; rheum is a thinner pathological fluid that can accumulate in various locations.

Phlegm and rheum arise when the spleen’s movement and transformation function and the lung’s regulation of the waterways break down and allow fluid to accumulate and thicken. Qì stagnation may also be a factor in this. Furthermore, heat can boil the fluids to create phlegm.

Phlegm may be associated with either heat (phlegm-heat) or cold (cold phlegm), whereas rheum can only be associated with cold.

Phlegm-rheum takes tangible and intangible forms. The tangible forms are phlegm that accumulates in the lung and can be coughed up, rheum that accumulates in or around the lung and stomach. The intangible form can move to other parts of the body to cause a variety of different signs. In all their different manifestations, phlegm and rheum are characterized by a thick, slimy tongue fur and a slippery, sometimes stringlike pulse.

The broad scheme of phlegm-rheum conditions is as follows:

Fluids’ Relationships

Fluids and Qì

Qì is intangible and moves; it is yáng. The fluids are tangible and still; they are yīn. Qì engenders fluids, moves them, and contains them. The fluids bear qì.

Qì engenders the fluids: The fluids are derived from grain and water by the action of spleen and stomach qì. Hence when qì is weak, liquid is scant. In clinical practice, boosting qì can help to increase fluid production.

Qì moves liquid: The distribution and elimination of fluids is reliant on the power of the qì of the spleen, lung, kidney, and triple burner. Qì vacuity involving loss of propelling power or qì stagnation can cause abnormalities in the distribution and elimination of fluids, causing water-damp and phlegm-rheum to arise internally.

Qì contains liquid: Qì holds the fluids in the body and prevents excessive loss of them. Lung and defense qì control sweating, the kidney and bladder qì control the formation and elimination of urine, while spleen and stomach qì control the flow of drool and intestinal humor. When the retentive power of qì fails to contain fluids, the signs are profuse sweating, copious urine, frequent urination, enuresis, urinary incontinence, or drooling from the corners of the mouth. The treatment of such conditions frequently involves supplementing qì.

Liquid bears qì: The qì that flows outside the vessels is borne by the fluids. This is reflected in two pathologies.

Fluids and Blood

Blood and fluids are both liquid in form; they both nourish and moisten the body. By contrast to qì, they possess form and are still, and thus are yīn in nature. Fluids and blood are interdependent.

The relationship between fluids and blood is often described as liquid and blood are of the same source (津血同源 jīn xuè tóng yuán). This has two meanings:

Blood and fluid pathologies are interrelated. When there is excessive loss of blood, fluid seeps into the vessels to compensate for the loss, giving rise to depletion of fluids outside the vessels that manifests in dry mouth, dry pharynx, scant urine and dry skin. Conversely, loss of fluids as through great vomiting, great diarrhea, or great sweating can cause fluid to seep out of the blood to compensate for the loss. For this reason, the Líng Shū states, When blood is despoliated, there is no sweat; when sweat is despoliated, there is no blood (夺血者无汗, 夺汗者无血 duó xuè zhě wú hàn, duó hàn zhě wú xuè). In either case, blood is reduced in volume and becomes thicker. This gives rise to desiccated liquid and blood dryness (津枯血燥 jīn kū xuè zào) or liquid depletion and blood stasis (津亏血瘀 jīn kuī xuè yū). As a result, in massive bleeding, it is inappropriate to use the sweating method of treatment. In liquid depletion, it is inappropriate to use bloodletting or to use powerful stasis-dispelling medicinals.

Fluids in Relation to the Bowels and Viscera

The spleen, lung, large and small intestines, kidney, bladder, and liver are all intimately related to the fluids.

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