Section two Five Zang-organS

Five zang-organs refer to the heart, the liver, the spleen, the lung and the kidney, whose physiological functions, though different, have something in common, mainly manifested in the following two aspects:

First, five zang-organs have the physiological functions of transforming and generating and storing the essence;second, five zang-organs all relate to mental activities, such as,"heart storing spirit","lung storing corporeal soul","spleen storing thought","liver storing spiritual soul","kidney storing will"and so on.

I The heart

The heart is situated at the left of the chest, above the diaphragm, and is enveloped by pericardium externally. It is round and point in shape, just like an overhanging undeveloped lotus.

The heart, together with the small intestine, the vessel, the face and the tongue, constitutes the heart system. It attributes to fire in five elements and yang within yang in yin-yang of five zang-organs, and it corresponds to summer qi in the nature.Its main physiological functions are dominating blood and vessel and dominating spirit and consciousness, i.e.it has the function of governing life activities;therefore, it is also known as"the monarch organ","source of life",and"the major governor of five zang-organs and six fu-organs".

1.Physiological functions

1.1　The heart dominating blood and vessel

Blood refers to blood in the body;vessel refers to blood vessel, which is the passage for blood circulation. The heart dominating blood vessel means that the heart propels blood through the vessels to nourish and moisten the whole body.The heart dominating blood and vessel has two aspects, i.e.dominating blood and dominating vessel.

The heart dominating blood means that the heart propels blood circulation to transport nutrients to the body constituent, sense organs and orifices. The heart propels the blood to circulate in the vessels to transport the nutrient substances throughout the whole body so that all tissues and organs such as zang-fu organs, all the limbs, bones, muscles and skin can be fully nourished.In this way, normal physiological functions of the body can be maintained.

Another aspect of the heart dominating blood is that the heart has the function of generating blood, that is to say, the essence of food and water transformed by the spleen and the stomach is transported to the heart and the lung, and then it is transformed into blood after being warmed by heart yang.

The heart dominating vessel means that the vessels originate from the heart, i. e."the heart dominates the blood vessels of the body".The heart qi drives and adjusts the vessels so that the blood can flow unobstructed to nourish the whole body.Heart yang has the function of warming blood vessel and promoting blood circulation.

There are three most elementary preconditions of the heart dominating blood vessel:first, the heart yang is abundant;second, the blood is plentiful;third, the vessel is unobstructed. According to traditional Chinese medicine, it is believed that the functions of the heart depend mainly on the heart qi and heart yang.Only when the yang qi of the heart is abundant and plentiful can the blood circulate regularly and continuously in the vessels to nourish the whole body, which is manifested as signs of ruddy and lustrous complexion and moderate and strong pulse.If the heart qi is insufficient, the blood circulation would be weak and obstructed, and thus blood stasis would appear.Blood is the carrier that supplies nutrients to zang-fu organs and sense organs and orifices.Regular circulation of blood also depends on the abundance of blood itself.If the heart blood is insufficient, the blood vessel would be empty and the heart function sand regular circulation of the blood would also be affected.Besides, unobstructed vessel is also the rudimental condition for regular and unobstructed circulation of blood.Therefore, regular circulation of the blood should take abundant blood and unobstructed vessels as the most elementary preconditions.

If the physiological functions of the heart are in normal state, the complexion would be ruddy and lustrous, the pulse would be moderate and strong and the tongue is reddish. If the heart qi is insufficient, the blood is deficient and the vessels are obstructed, the blood circulation would be impeded, or the blood vessels are empty.Exterior symptoms such as dim complexion and thin and weak pulse would appear.If worse, blood stasis and obstructed blood vessels would be caused, and symptoms of pale complexion, purple lip and tongue, oppression and stabbing pain in precordium, as well as knotted, intermittent, hurried and choppy pulse would appear.

1.2　The heart dominating spirit and consciousness

The heart dominating spirit and consciousness, also known as heart dominating mental activity and heart storing spirit, refers that the heart has the functions of governing life and dominating consciousness, thoughts and mental activities.

In traditional Chinese medicine, spirit has distinctions in broad and narrow senses. Spirit in broad sense refers to the exterior manifestation of human life activities, i.e.the general image or"physical qualities"of the body, including complexion, expression, eyesight, verbal responses, consciousness and gestures.Spirit in narrow sense, i.e.the spirit governed by the heart, refers to the mental activities of human beings, including spirit, consciousness and mental activities.

There are two kinds of physiological functions of the heart dominating spirit and consciousness. The first is dominating"carrier things",among which carrier means to receive, to burden and to load, and things refer to the external objective things.The heart that dominates spirit and consciousness has the physiological functions of receiving the objective things or messages from the outside world and having spiritual, conscious and mental activities.So it is said that"The heart takes on the performance of activities".The second is dominating life activities.The spiritual, conscious and mental activities, as the most essential components of life activities, dominate all physiological activities of zang-fu organs of the body.The mind is normal, the functional activities of zang-fu organs would be governed and coordinate with each other, and then regular life activities can be carried on normally.Therefore, the ancients named the heart as"the major governor of five zang-organs and six fu-organs",and"the heart is the monarch organ, the source of spirit".

The theory of zang-fu manifestation believes that all the spirit, consciousness and mental activities of the body not only attribute to five zang-organs, but also are governed by the physiological functions of the heart. The theory has always been guiding the clinical practice of traditional Chinese medicine, with important scientific values and practical significances.

Based on holism concept, traditional Chinese medicine divides spirit into five aspects and attributes them to five zang-organs, i. e."heart storing spirit","lung storing corporeal soul","spleen storing thought","liver storing spiritual soul","kidney storing will".Though spirit, consciousness and mental activity attribute to five zang-organs respectively, they are dominated by the heart.The heart controls the functions of zang-fu organs by coordinating qi of zang-fu organs;therefore, it is called"the major governor of five zang-organs and six fu-organs",which also has close relations with its functions of dominating blood vessel, i.e.the functions of generating and transporting blood.Physiological function of all the organs and tissues, including metal activities, cannot leave alone without nourishment of the blood.Blood flowing through the vessels to the whole body is driven by heart qi.So only when the function of heart dominating blood vessels is at normal state, all tissues and organs can exert their normal physiological functions.However, if the heart's function of dominating blood and vessel is abnormal, the functional activities of the other zang-fu organs, body constituent and orifices, even the life would be affected.

The functions of heart's dominating spirit and consciousness and dominating blood and vessels are closely related to each other and interactive. On one hand, blood is the substantial basis of mental activities and the heart blood can nourish the spirit, so heart's dominating blood vessel is the substantial basis of heart's dominating spirit and consciousness.On the other hand, heart's dominating spirit and consciousness can control the functions of zang-fu organs and the regular blood circulation.

2.Physiological characteristics

Physiological characteristic of the heart is that the heart is a yang organ and dominates yang qi. The heart is situated in the middle of the diaphragm, attributes to fire, is taiyang within yang, and is used for its yang qi.Heart yang has the function of warming and promoting.It can warm the blood vessels throughout the body to make the blood circulate regularly and the spirit inspired.Its warming and promoting functions not only can help the heart and the vessels smooth and maintain the physiological functions of the heart itself, but also can warm and nourish the whole body to make man inspired, vigorous and quick-thinking.If heart yang is damaged, its function of warming would be lost.This would not only damage the physiological functions of the heart itself, resulting in such symptoms as palpitations and cold extremities, but also affect the normal physiological activities of other zang-fu organs, such as spleen and stomach digesting and transforming food and water, and kidney yang warming and transforming.

3.Relationships with constituent, orifice, emotion, fluid and seasons

3.1　The heart governing the vessels of the body with its outward manifestation in complexion

Constituent here refers to the body constituent;vessel referring to the blood vessels, vessel passages, also named"house of the blood",is one of five body constituents. The heart governing the vessels of the body refers that all blood vessels throughout the body are governed by the heart and coordinate with the heart to realize circulation of the blood.Luster which means glory and splendor refers that whether the essence of the heart is in excess or in deficiency and whether the physiological functions of the heart is normal can be seen from the luster of the face.From the expressions of the face, conditions of heart's dominating spirit and emotions can be reflected.Blood vessels in the head and the face are plentiful.All blood vessels of the whole body can reach the face, so if the face is red and with luster, the heart qi is in excess and the blood vessels are plentiful;otherwise, if the face is pale and dim, the heart qi is in deficiency.Complexion without luster shows blood deficiency;dark-purple complexion shows that the heart vessels are obstructed;pale and dim complexion shows collapse due to deficiency of heart yang, and etc.That's why Plain Questions·Generation of Five Zang-organs（Su Wen·Wu Zang Sheng Cheng）says"The tissue that connects with the heart is the vessel;its outward manifestation is complexion."

3.2　The heart opening into the tongue

The heart opening into the tongue is also known as"the tongue is the sprout of the heart". It refers that the tongue is the outward reflection of the heart, from the changes of which the excess or deficiency of the heart and its physiological functions can be reflected.The heart and the tongue connect with each other through the meridians.What's more, blood vessels of the tongue are plentiful, so the changes of the color of the tongue can reflect the physiological conditions of heart's dominating blood.Spiritual Pivot·Lengths of Meridians（Ling Shu·Mai Du）says,"Heart qi communicates with the tongue.If the heart is healthy, the tongue can taste five flavors".Spiritual Pivot·Worry about Mute and Hoarseness（Ling Shu·You Huan Wu Yan）says,"The tongue is the mechanism of the voice".Therefore, the main functions of the tongue are to govern the sense of taste and language expression.If the physiological functions of heart'dominating blood and vessel and heart's dominating spirit and consciousness are normal, the sense of taste and language expression of the tongue would be normal too;if pathological changes occur to the heart, corresponding pathological changes of the tongue would also occur, such as pale and thin tongue, red tongue with sores, purple tongue, or with ecchymosis, stiff tongue, dysphasia, or even loss of voice.In addition, the tongue also has connections with the spleen, the liver and the kidney, which corresponds to"the major governor of five zang-organs and six fu-organs".So observation of the tongue can help the diagnosis of the other zang-fu organs.

3.3　The heart corresponding to joy in the emotion

Emotion refers to the feeling or the emotions. The theory of zang-fu manifestation thinks that there are five human emotional changes to theoutside messages, i.e.joy, anger, worry, anxiety, and fear, which are called five emotions.These five emotions are generated by the physiological functions of five zang-organs.The heart corresponding to joy in the emotion means that the physiological functions of the heart relate to"joy"of the emotions.The joyful feeling can harmonize qi and the blood, nutrient qi and defense qi, which is helpful to physical and mental health, but excessive joy can also injure the heart and the mind.In addition, the heart controls the mental and emotional activities.Not only excessive joy can injure the heart, but excess of five emotions can also damage the heart and the mind.That is why Spiritual Pivot·Pathological Manifestations of Zang-fu organs（Ling Shu·Xie Qi Zang Fu Bing Xing）says,"Worry and fear can damage the heart".

3.4　The heart corresponding to sweat in fuid

The heart corresponding to sweat in fluid is also called sweat as the fluid of the heart. Sweat is the fluid that is dejected from Xuanfu（sweat pore）after the fluids being steamed by yang qi.Secretion and dejection of sweat can adjust the temperature, exclude the wastes and pathogenic qi, keep balance of yin fluid and yang qi, as well as nourish and moisten the skin.The generation and secretion of the sweat has close relations with the physiological functions of heart dominating blood and vessel and heart dominating spirit and consciousness.The heart dominates blood and vessel, so the blood and the fluid are homologous to each other and the fluid is the source of the sweat.This is why we say"sweat and blood sharing the same origin".If the blood in the heart is plentiful, the fluid would be plentiful, and the generation of the sweat has sources;if the sweat is secreted more, the fluid would be damaged, which in turn will damage heart blood and heart spirit.Besides, the generation and secretion of sweat is also controlled and adjusted by the heart.

3.5　The heart corresponding with summer

"To correspond with"means to communicate with each other. The heaven corresponds with human beings.Functional activities of five zang-organs and waxing and waning of four seasons in the nature relate with each other.The heart attributes to fire and summer in the nature is mainly hot;therefore the heart qi and summer qi correspond with each other.Yang qi of the heart is most excessive in summer and its function is the most powerful in summer.So, patients with heart yang deficiency usually have their diseases relieved in summer and their symptoms also decrease.Grasping the characteristic of the heart can help analyze the physiology and pathology of the heart, especially the relations between the pathological changes and seasonal climates.

Appendix:Pericardium

The pericardium, also known as the pericardium collateral, is a membrane surrounding the heart and is the peripheral tissue of the heart, just as Orthodox Medical Record（Yi Xue Zheng Zhuan）says,"The pericardium is actually the membrane surrounding the heart. It covers the heart.That's why it is named."In the theory of channels and collaterals, pericardium meridian of hand jueyin and triple energizer meridian of hand shaoyang are internally-externally related, so the pericardium belongs to zang-organs.

Physiologically, the pericardium has the function of protecting the heart and"making orders on behalf of the heart". Pathologically, it also has the function of"being affected by pathogenic factors instead of the heart".Spiritual Pivot·Pathogenesis（Ling Shu·Xie Ke）says,"The heart is the major governor of five zang-organs and six fu-organs, and the house of the spirit.If it is in healthy state, pathogenic factors could not be hosted.Otherwise, the heart would be damaged and the spirit would die away and one would die.Therefore, invasion of pathogenic factors to the heart is to the pericardium."If a person is attacked by fever externally and invaded by warm and heat pathogens internally, there would be abnormality of heart's dominating spirit and consciousness, such as high fever, coma and delirium.This is called"entering of heat into pericardium"."Clouding of pericardium by phlegm heat"refers that invasion of pericardium by phlegm can cause spirit or conscious abnormality such as coma and disturbance of consciousness.Actually, though pericardium has the function of"being affected by pathogenic factors instead of the heart",cases of pericardium are often treated by treating the heart.

II The lung

The lung, including two lobes, one on the left and right separately, is situated in the thorax. The lung is"empty as the beehives","floating with water".With the throat as its window and opening into the nose, the lung communicates directly with qi in the nature.Because of its uppermost position among all the zang-fu organs as a cover, it is named"the canopy".The lung lobes are delicate, and so the lung is easily attacked by pathogenic cold, heat, dryness and dampness;the lung connects with qi in the nature directly and is liable to be invaded by pathogenic factors, so it is known as"delicate zang-organ".

The lung, together with large intestine, skin and hair, and nose, forms the lung system. It attributes to metal in five elements and yin within yang in yin-yang of five zang-organs, and it corresponds to autumn qi in the nature.Its physiological functions mainly are:lung dominating qi, lung communicating with numerous vessels, lung governing dispersing and descending, lung dominating water movement and lung governing management and regulation.

1.Physiological functions

1.1　The lung dominating qi

The lung dominating qi is the term of lung dominating breathing qi and lung dominating qi of the whole body. Plain Questions·Generation of Five Zang-organs（Su Wen·Wu Zang Sheng Cheng）says,"All qi is governed by the lung".

1.1.1　The lung dominating respiring qi

The lung dominating respiring qi is also known as"lung dominating respiration",which refers that the lung inhales the clear qi in the nature and exhales the turbid qi to realize the exchange of interior and exterior qi so as to maintain life activities of the body. The lung is the place where respiration takes place.It has respiratory function and through continuous inhaling and exhaling it regulates lung movement of ascending, descending, exiting and entering andpromotes the generation of qi so as to maintain the normal metabolism of human body.If it is in an abnormal state, normal qi movement will be affected and various pathological changes would be caused.

1.1.2　The lung dominating qi of the whole body

The lung dominating qi of the whole body means that qi of the whole body all belongs to the lung and is governed by the lung, i. e.the lung has the function of dominating and regulating qi of all the zang-fu organs, which is mainly manifested in the following two aspects:

Generating qi:The lung involves in the generation of qi of the whole body, especially the generation of pectoral qi, which is acquired qi. It is generated by the clear qi inhaled from the nature and the essential qi of food and water transformed by the spleen and the stomach accumulating in the chest（qi sea）.The pectoral qi comes up out from the throat to promote the respiration of the lung, goes into the heart and vessels to promote blood circulation, and warms and nourishes all zang-fu organs to maintain their normal functional activities.It also goes down to dantian to notify the innate original qi.So we can say pectoral qi plays a significant role in life activities.In a word, normal respiratory function of the lung dominates not only the generation of pectoral qi, but also the rise and fall of qi of the whole body.

Regulating qi movement of the body:Qi movement refers to the movement of qi, with ascending, descending, exiting and entering as its basic forms. It regulates the ascending, descending, exiting and entering of qi of the whole body through rhythmical inhaling and exhaling of the lung.

To sum up, the lung dominating qi of the body and respiration actually depends on the respiratory function of the lung. Respiration is the elementary condition of qi generation and regulated qi movement.Abnormal respiratory function of the lung is sure to affect the generation and movement of qi.However, insufficient qi generation and abnormal qi movement, as well abnormal blood circulation and dysfunction of fluid distribution may also affect respiration of the lung, even cause abnormal respiratory function of the lung.

1.2　The lung communicating with numerous vessels

Communicating means to join in, to face. Numerous vessels refer to blood vessels of the whole body.Lung communicating with numerous vessels refers that the lung communicates with the vessels of the body through which all blood joins together in the lung, where the clear qi and the turbid qi are exchanged, and then the blood is distributed to the body by dispersing and descending of the lung.

Physiological function of lung communicating with numerous vessels is to assist the heart to circulate blood. The structural basis of lung assisting blood circulating blood is"lung communicating with numerous vessels".The lung dominates qi and the heart dominates blood.Heart qi is the motive force of blood circulation, which in turn depends on the distribution and regulation of qi.Blood of the body keeps accumulating in the lung and have clear qi and turbid qi exchanged there.The clear qi breathed in from the nature and the essential qi of food and water transformed by the spleen and the stomach combine and generate pectoral qi, which has the function of"going through the heart"to assist the heart to circulate blood.Real Mass of Medicine·Qi and Blood（Yi Xue Zhen Chuan·Qi Xue）says,"Human body is the circulation of qi and blood.Qi without blood cannot be harmonized, and blood without qi cannot circulate."Therefore, only when the lung qi is sufficient and pectoral qi is exuberant can blood circulate normally.On the contrary, if the lung qi were insufficient and could not assist the heart to circulate blood, the physiological function of heart dominating blood and vessel would be affected and blood circulation would be obstructed, resulting in the symptoms such as chest stuffiness, palpitation, and purple tongue.

1.3　The lung dominating water movement

The lung dominating water movement, also known as"lung regulating the water ways",means that the dispersing and descending of the lung dredges and regulates the distribution, movement and excretion of fluids in the body so as to adjust the metabolism of the fluids. That's why On Blood Syndromes（Xue Zheng Lun）says,"The lung is the source of the fluids.The lung qi moves, and the fluid circulates."

The lung dominating water movement is completed through the dispersing and descending of lung qi. Dispersing of lung qi can distribute the fluid to the body to perform its moistening and nourishing function.The waste and surplus water would be discharged out of the body through respiration and sweat pores.Descending of lung qi can distribute the fluids transmitted and transformed by the spleen downwards to nourish all zang-fu organs in the body.On the other hand, lung qi keeps transmitting the metabolized water down to the kidney and the bladder, by which the water is transformed into urine and discharged out of the body to keep the smooth urination.If dispersing and descending of the lung is abnormal, the water passage would be obstructed, distribution and excretion of the water would also be obstructed, and pathological changes such as edema and phlegm would appear.Therefore, the so called"uncover the lid of the jar"therapy（Tihu Jiegai Therapy）is to treat the edema syndrome caused by abnormal dispersing of lung qi with the method of ventilating the lung, inducing diuresis and diminishing swelling.

1.4　The lung governing management and regulation

Plain Questions·Linglan Secret Book（Su Wen·Ling Lan Mi Dian Lun）says,"The lung is the organ of prime minister which manages and regulates."The lung governing management and regulation refers that lung qi has the functions of managing and regulating respiration, and assisting the heart to manage the physiological functions of qi, blood, fluids and zang-fu organs of the body. The heart is the monarch organ, the major governor of five zang-organs and six fu-organs;the lung is the organ of prime minister, dominating management and regulation.

Lung dominating management and regulation is mainly manifested in the following four aspects:The first is to manage and regulate respiration. The lung inhales and exhales with rhythm, which plays the critical role in the exchange of the air inside and outside the body.The second is to regulate qi movement of the body.The lung regulates the ascending and descending of qi through respiration to keep qi movement of the body smooth.The third is to assist the heart to circulate blood.The lung assists the heart to promote and regulate blood movement through adjusting ascending and descending of qi and the function of lung communication with various vessels.The fourth is to manage and regulate distribution, transmission and excretion of fluids.The lung manages andregulates distribution, transmission and excretion of fluids through dispersing and descending of lung qi.In a word, lung dominating management and regulation is the generalization of the major physiological functions of the lung.

2.Physiological characteristics

2.1　The lung is the canopy

Canopy originally refers to the hood of vehicles for the emperors in ancient times. Canon of Medicine（Nei Jing）compares the lung to canopy.The lung is the canopy means that the lung is situated the highest among five zang-organs and six fu-organs, and is the guard of zang-fu organs, protecting all the organs and resisting invasion of pathogenic factors.The lung communicates directly with the outside world, so it is liable to be affected by"six excesses",among which pathogenic wind and cold invade the lung most easily, which may result in pathogenic changes of obstruction and disturbance of lung qi.The lung also corresponds with skin and hair, so at the outset stage, the exterior syndromes such as fever, aversion to cold, cough, and nasal congestion are mostly seen.

2.2　The lung is the delicate zang-organ

It is the generalization of physiological and pathological characteristics of the lung. Delicate means tender, referring to the characteristic of lung being clear and delicate and liable to be affected by pathogenic factors.The lung is clear and delicate and situated highest as the canopy of zang-fu organs, and communicates with various vessels.Pathologically, the lung is canopy and communicates with the outside directly.It can tolerate neither cold nor heat and is likely to be invaded by pathogenic factors.So, no matter external contraction, internal injury or other pathogenic changes of zang-fu organs can involve the lung in to cause lung diseases.That's why it is called"delicate zang-organ".

2.3　The lung dominating dispersing and descending

Dispersing refers to the upward dispersion and scattering towards thesurroundings of lung qi;descending refers to the downward movement of lung qi.

The physiological functions of lung dominating dispersing are mainly manifested in the following three aspects:first, to discharge turbid qi out of the body, i. e.to exhale the turbid qi through the mouth and the nose;second, to distribute the essence and the fluid, i.e.the lung distributes the essence and fluid generated by the spleen through dispersion of lung qi to the body and outwards to the skin and hair;third, to disperse defensive qi, i.e.the lung disperses defensive qi from essence of food and water generated by the spleen to regulate interstice closing and enlarging and to discharge the metabolized sweat out of the body.So, abnormal lung dispersion can cause pathological syndromes, such as poor respiration, oppression in chest, cough, dyspnea, as well as nasal congestion, sneezing and anhidrosis.

The physiological functions of lung dominating descending are mainly manifested in the following three aspects:first, to inhale clear qi, i. e.the lung exhales the turbid qi in the body and inhales clear qi in the nature and distributes it downwards, so inhaling the clear and exhaling the turbid of the body is completed.Second, to transmit and distribute fluid and essence, i.e.the lung distributes the essence of food and water transmitted and generated by the spleen and fluid to all zang-fu organs to maintain their normal physiological functions.In addition, the lung keeps transmitting water of the upper energizer to the bladder, which is transformed by kidney qi into urine and discharged out of the body.In this way, the lung regulates water metabolism of the body.So there is the saying"The lung is the upper source of water".If the lung fails in descending and promoting water, symptoms of edema and scanty urine will appear.Third, to clear and disperse, i.e.descending of the lung can clear unclean things from the lung and the respiratory tract so that lung qi can move without obstruction to maintain its normal physiological functions.If the lung fails in descending, syndromes of adverse rising of lung qi will be seen.

Dispersing and descending of the lung opposite and supplement each other. Physiologically, they depend on each other and restrict each other.Pathologically, they also affect each other.If dispersing and descending are normal, the airway is smooth, respiration is regular and exchange of the interior and exterior air will go smoothly.If dispersing and descending are in disorder, pathological changes of"obstruction of lung qi"and"failure of lung in descending"will come up, withsyndromes of cough, dyspnea and adverse rising of lung qi.

3.Relationships with physique, orifice, emotion, fluid and seasons

3.1　The heart governs the skin of the body, and has its outward manifestation in hair

Skin is the skin of the body, and hair refers to the fine hair on the body, which is the surface of the body. The skin covers the body in the surface, including fine hair and sweat pores.Depending on the nourishment and moist of defensive qi and fluids, it becomes the barrier of defending against pathogenic factors and has functions of regulating metabolism, adjusting temperature and assisting respiration.The so-called"lung governing the skin"means that the lung has close relations with the skin and the hair.The lung having its outward manifestation in hair refers that the rise and fall of lung functions can be seen from the hair.That's why Plain Questions·Generation of Five Zang-organs（Su Wen·Wu Zang Sheng Cheng）says"The lung governs the skin.Its outward manifestation is in hair".

The relations between the lung and skin and hair are mainly manifested in the following three aspects:First, the lung transmits essence to skin and hair by dispersing to nourish and moisten skin and hair, so as to warm fleshes and muscles, fertile interstice, govern closing and enlarging and defend invasion of pathogenic factors. Second, Xuanfu（sweat pores）in skin and hair can disperse lung qi to regulate respiration, so sweat pores are also called"qimen".Third, the lung regulates temperature and water metabolism by regulating closing and enlarging of sweat pores.

If physiological functions of the lung are in normal state, the skin and hair is nourished, the hair is shiny, and the ability of resisting invasion of pathogenic factors is strong;on the other hand, if lung qi is in deficiency, it would be weak in dispersing defensive qi and transmitting essence to skin and hair, and its defensive ability would be also weak, which is manifested as excessive sweating, spontaneous sweating, and susceptible to cold, or emaciation and haggardness. If pathogenic factors invade skin and hair, the pores would close and the symptoms such as anhidrosis would be seen.

3.2　Lung associated with nose in orifce

The nose is in the middle of the face and connects with the lung directly, as the pathway of respiration, so it is called the orifice of the lung. Lung associated with nose in orifice means that various physiological functions of the lung have close relations with the nose.And it is known that"Throat is the window of the lung",so ventilation and smell of the nose and articulation of the throat all depend on regular lung functions.Therefore, lung qi disperses smoothly, the nose would be unobstructed and breathe steadily, with sharp smell and normal articulation;if the lung fails to disperse, the nose would be obstructed, with poor breath and smell, and articulation of the throat would also be affected.In traditional Chinese medicine, there are sayings of"broken metal failing to sound"and"excessive metal failing to sound",which mean both the deficiency syndrome and excess syndrome of the lung may affect articulation of the throat respectively.In clinic, abnormal changes of the nose are often considered one of the bases of diagnosing lung diseases for treating symptoms of nasal congestion, nasal discharge and smell disorders mainly with therapy of releasing, dispelling and ventilating lung.

3.3　Lung associated with sorrow in emotions

Sorrow and grief are all the emotional activities of the lung. Though somewhat different, they have the same effects on the body.Sorrow and grief are all bad emotional stimuli, which consume continuously qi of the body, just as the saying in Plain Questions·On Pains（Su Wen·Ju Tong Lun）,"Sorrow decreases qi,……and the upper energizer is obstructed, nutritive qi and defensive qi cannot be dispersed and heat qi remains inside, so lung qi is eliminated."And the lung dominates qi, so sorrow and grief are easily to injure the lung to cause disorder of dispersing and descending of lung qi, which may induce deficiency of lung qi resulting in symptoms such as shortness of breath.Conversely, when the lung is in deficiency, tolerance of the exterior bad stimuli also decreases, which in turn causes emotional changes of sorrow and grief.

3.4　Lung associated with snivel in fuids

Snivel refers to nasal fluid, which is the fluid dispersed by the lung and secreted by the nose, with the function of moistening the nostril and defending against pathogenic factors for better respiration. Snivel is generated by lung fluid and the nose is the orifice of the lung, so it is said that lung is associated with snivel in fluids.Plain Questions·On Qi of Five Zang-organs（Su Wen·Xuan Ming Wu Qi）says,"Five zang-organs generate fluid.……The lung generates snivel."Whether the lung function is normal can be reflected in snivel changes.Normally, the snivel moistens the nostril without flowing out.If the lung is cold or lung qi is deficient, thin nasal discharge would flow out;if the lung is heat, the nasal discharge would be yellow and turbid;if the lung is dry, the nose would be dry.

3.5　Lung corresponding with autumn qi

The lung is a clear and delicate organ, with clear and moistening nature, corresponding with brightness of autumn. The lung and autumn both attribute to metal of the five elements.So lung qi corresponds with autumn qi.Now the lung is powerful in restricting and astringing.But in mid-autumn, the weather is dry and the lung dislikes dryness, so dry pathogenesis is easily to injure lung fluid, causing dry cough, dry skin, dry mouth, dry nose and weather-shack skin.But when treating exterior syndromes caused by invasion of wind and cold pathogenic factors, pungent-dispersing superficies such as Mahuang and Guizhi are often used to conform to its astringing and descending nature, without excessively dispersing lung qi.

III The spleen

The spleen is located in the middle energizer, below the diaphragm, deep in the left flank and attaching to the top left of the back of the stomach. Plain Questions·On Taiyin and Yangming（Su Wen·Tai Yin Yang Ming Lun）says,"The spleen and the stomach connect with membrane."It"likes the dog tongue in shape and cockscomb in appearance".

The spleen together with the stomach, the flesh, the lips and the mouth constitutes the spleen system. It attributes to earth in five elements and zhiyin/taiyin within yin of five zang-organs, corresponding with long summer qi in the nature.The physiological functions of the spleen are dominating transportation and transformation, generating and governing blood, and sending up the clear.It is regarded as"the source of qi and blood".All zang-fu organs of the body are nourished by the essence of water and grain generated by the spleen, so it is also called"source of acquired constitution".

1.Physiological functions

1.1　The spleen dominating transportation and transformation

Transportation means to transport, to convey;transformation means to digest, to absorb. The spleen dominating transportation and transformation refers that the spleen has the physiological function of transforming water and grain（food）into the essence, and transporting the essence to the body.Digestion of the food and absorption and transportation of the nutrients is a complex physiological activity completed by the spleen, the stomach, the liver, the bladder, the small and large intestines together, among which the spleen plays the leading role.The spleen dominating transportation and transformation including transporting and transforming water and grain and transporting and transforming water fluid.

1.1.1　Transporting and transforming water and grain

Water and grain refer to various drinks and food. Transporting and transforming water and grain means that the spleen qi has the function of promoting digestion and absorption of food and transport the essence（grain essence）,which can be interpreted from the following two aspects:the first is"to transform".The food taken into the stomach is actually digested and absorbed in the stomach and the small intestine.However, it must rely on the function of the spleen to transform water and grain into essence, just as Classified Canon（Lei Jing）says,"The spleen dominates transportation and transformation, the stomach governs reception, both of which governs water and grain";the Second is"to transport".The"transformed"essence must rely on transportation of the spleen to be distributed to the body.On one hand, the essence absorbed by the spleen istransmitted upward to the heart and the lung;on the other hand, it is distributed to all zang-fu organs through distributing function of the spleen for the need of physiological activities of the organs.

Therefore, if the spleen's function of transporting and transforming water and grain essence is strong, it is usually called"spleen qi transporting normally". Only when the spleen qi transports normally, can essence, qi, blood and fluid be generated and can all tissues and organs be nourished fully to take normal physiological activities.Conversely, if the spleen's function of transportation and transformation declines, i.e."failure of spleen in transportation",on one hand, poor digestion would come up, which is manifested as abdominal distension, loose stool and loss of appetite;on the other hand, malabsorption would be been, which may result in deficiency of essence, with pathological changes as tiredness, emaciation and poor generation of qi and blood caused by poor generation of essence, qi, blood and fluid.

1.1.2　Transporting and transforming water and fuid

It refers to the spleen's function of absorbing, transporting and distributing water and fluid. It is manifested in the following two aspects:first, transporting water and fluid（fluid）absorbed by the organs up to the lung by transporting function of lung qi, and distributing it to the body by dispersing and descending function of the lung to function as nourishment;second, transporting the metabolized water, or waste water to the lung and the kidney timely, which is transformed into sweat and urine by dispersing and descending function of the lung and transforming function of the kidney respectively to be excreted out of the body."The lung is the upper source of the water","The kidney is the lower source of the water",and the spleen is situated in the middle energizer as the pivot of distributing the water, which ascending and descending of water must depend on.

To sum up, if spleen qi transports healthily, the function of spleen transforming water would be regular and all tissues and organs could be moistened and nourished. Conversely, if the spleen fails in transportation, water and fluid would stay in the body to produce pathological products as dampness, phlegm and retained fluid, even edema.So Plain Questions·On The Most Fundamental Theories（Su Wen·Zhi Zhen Yao Da Lun）says,"All dampness syndromes with swelling and fullness are ascribed to the spleen."This is the occurrence mechanism of the spleen generating phlegm and the syndrome of spleen insufficiency with swelling.In clinic, it is treated mostly with therapies of invigorating spleen to dry dampness and invigorating spleen to drain water.

Transporting and transforming water and grain and transporting and transforming water and fluid are two aspects of the spleen dominating transportation and transformation. They relate to and affect each other and take place simultaneously.The spleen dominating transportation and transformation is significant to both itself and the whole body.Without the spleen's transforming and transporting the essence, human life activities cannot be maintained, so it is called"spleen being source of acquired constitution"and"spleen being the source of qi and blood".The spleen and the stomach being"source of acquired constitution"play the significant role in disease prevention and health preservation."Excessive spleen in four seasons cannot be affected by pathogenic factors".This requires us to pay attention to protecting the spleen and stomach so that they can be full with healthy qi without being invaded by pathogenic factors.

1.2　The spleen governing blood

The spleen governing blood means that the spleen has the function of governing blood and making it circulate in the vessels in case it runs out of the vessels.

The spleen is the source of generating qi and blood. Qi is the commander of blood, i.e.qi dominates blood, so the spleen dominating blood is the securing function of the spleen.Shen Mingzong in Qing dynasty said,"The blood in five zang-organs and six fu-organs all depends on the governance of spleen qi".Moreover, the spleen governing blood is related with the spleen dominating transportation and transformation.The essence of water and grain transformed by the spleen is the source of qi and blood generation.Only sufficient qi and blood can circulate blood regularly.Besides, the spleen governing blood is also related with spleen yang.On Blood Stasis·Pathogenesis（Xue Zheng Lun·Zang Fu Bing Ji Lun）says,"Deficient spleen yang cannot govern blood."If spleen yang is in sufficiency and spleen transforms normally, generation of essence of water and grain is sufficient and so qi and blood is plentiful.Therefore, deficient spleenqi, deficient spleen yang, or disorder of spleen dominating transformation all can affect spleen governing blood, which may result in symptoms of bleeding, hematochezia, hematuria, as well as metrorrhagia and metrostaxis.

1.3　The spleen dominating ascending

"Ascending"here refers that the movement of spleen is characterized by ascending."The spleen dominating ascending"includes two aspects-ascending clear and raising. Ascending clear refers to ascending essence of water and grain and other nutrients.The spleen transports the generated nutrients up to the heart, the lung, the head and the eyes, which is transformed into qi and blood by the lung and the heart to nourish all tissues and organs of the body.Raising refers that the spleen maintains relative constant position of zang-fu organs in case they hang down.

If the spleen ascends the clear normally, the essence of water and grain can be regularly absorbed and distributed to maintain normal physiological activities of the body. If the spleen fails in ascending the clear, qi can blood cannot be generated, and symptoms such as dizziness, tiredness, loose stool and diarrhea would come up.If the spleen fails in ascending and sinks, it is known as sinking of middle qi or sinking of spleen qi, manifested in clinic as anal prolapse due to chronic diarrhea or visceral ptosis, which can be treated with the therapy of tonifying and replenishing spleen qi and raising therapy.

2.Physiological characteristics

2.1　The spleen qi ascends

Qi of five zang-organs ascends or descends respectively. Situated in the middle, with spleen qi dominating ascending and stomach qi dominating descending, the spleen and the stomach are the pivot of ascending and descending qi movement.Proper ascending and descending qi movements of zang-fu organs promote and restrict each other, so that qi movement of the body can be coordinated.Spleen qi dominates ascending.Only when the movement of spleen qi is characterized by ascending, can the physiological functions of thespleen be exerted regularly.

2.2　The spleen prefers dryness to dampness

The spleen is damp-earth organ attributing to taiyin, while the stomach is dry-earth organ attributing to yangming. The spleen likes dryness and hates dampness, while the stomach likes moist and hates dryness.Why the spleen likes dryness and hates dampness is closely related with its physiological function of transporting and transforming water and fluid.If the spleen is in deficiency and fails in transforming, it will be affected by dampness and becomes ill;contrarily, if pathogenic dampness in the body is excessive, it is most liable to disturb the spleen, which might in turn affect ascending and transforming of spleen qi.Besides, invasion of external pathogenic dampness is also liable to disturb the spleen, which may make the spleen qi fail in ascending and affect the physiological functions of the spleen itself.Therefore, the spleen is especially susceptible to pathogenic dampness and desires for dryness and salubriousness.That is why we say"The spleen likes dryness and hates dampness".

3.Relationships with physique, orifice, emotion, fluid and seasons

3.1　The spleen governs the muscles and four limbs

The spleen governs the flesh and limbs means that flesh and muscles of the body as well as four limbs depend on transportation and transformation of the spleen and the stomach to be nourished to make the muscles strong and the extremities move normally. Whether the muscles are strong and whether the extremities move normally all relate closely with transformation of the spleen and stomach and the spleen ascending the clear, and their abnormality may cause the flesh and extremities cannot be nourished and moistened by the essence of water and grain as well as the fluid, which may result in emaciation, weak limbs, and even paralysis.So atrophy-flaccidity syndrome is often treated with invigorating spleen and stomach to generate essence as the basic principle.Plain Questions·Atrophy-flaccidity（Su Wen·Wei Lun）says,"To treat atrophy-flaccidity, yangming is the only one to be treated."Besides, if muscle lesions can not be cured for a long time and are also affected by pathogenic factors, the spleen might be affected and have pathogenic changes.So proper movement of the extremities and muscles can promote transportation and transformation of the spleen and stimulate appetite.

3.2　The spleen associated with mouth in orifices and having its outward manifestation in the lips

Mouth cavity, situated at the top of the digestive tract, is the entrance of taking in food. The spleen associated with mouth includes appetite and taste.If spleen qi transforms well, the appetite and the taste are normal;if the spleen fails in transforming, abnormal sensations would be felt, such as lack of appetite, tastelessness in mouth, sweet taste in mouth, slimy sensation in mouth and bitter taste in mouth.

The spleen having its outward manifestation in the lips means that color of the lips can reflect the excessiveness and deficiency of the spleen function. Since lips are nourished by qi and blood generated by the spleen-transformed essence, whether the lips are ruddy can reflect not only the general qi and blood conditions of the body, but the state of the spleen and the stomach transforming essence of water and grain.If the spleen transforms well and qi and blood is plentiful, the lips would be ruddy and lustrous;otherwise, if the spleen fails in transforming, qi and blood would be in deficiency and the lips would be pale and matte.

3.3　The spleen associated with contemplation in emotions

Contemplation, one of five emotions, is a state of human mental activities. The spleen associated with contemplation means that physiological function of the spleen is related with contemplation.Though contemplation is the emotion of spleen, it is also related to heart dominating spirit and consciousness, so there is saying of"contemplation derives from the heart and corresponds with the spleen".If the spleen transforms well and qi and blood are plentiful, one can think things thoroughly and correctly.Normal thinking has no harmful effect on the organs, but excessive contemplation or emotional depression can affect normal qi movement, which may result in qi stagnation and affect qi movement of the spleen and stomach, with symptoms of poor appetite, epigastric and abdominal distending fullness and dizziness.That's why it is said"anxiety makes qi depressed".

3.4　The spleen associated with saliva in its secretion

Saliva is the fluid in the mouth, which is the sticky part with less froth（i. e.the thin fluid）of the spittle.The spleen meridians"connect with the tongue and are scattered under the tongue".Spleen essence goes up to the mouth and generates saliva, so it is said"the spleen associated with saliva in its secretion".Saliva can moisten the mouth, as well as help swallowing and digesting, so there is the saying"saliva is generated from the spleen and comes out from the stomach".Under normal circumstances, saliva goes up to the mouth, but not out of the mouth.If the spleen and stomach do not harmonize, or if spleen qi fails in dominating, the saliva would increase and comes out from the mouth;if spleen yin is in deficiency, saliva excreted would be less, and the mouth would be parched and the tongue would be scorched.

3.5　The spleen corresponding with long summer qi

Long summer refers to June in the lunar calendar, and it is hot, rainy and damp, brewing generation and transformation, corresponding to earth generating everything. And the spleen dominates transforming, spleen qi primarily ascending, and spleen is the source of generation of qi and blood, so the spleen corresponds with long summer qi.Therefore, spleen yang is most excessive in long summer, so is its physiological function.

Though dampness of long summer dominates generation and transformation, excessive dampness can invade the body easily. Dampness encumbering spleen yang may result in epigastric oppression, less appetite, tiredness, sloppy diarrhea, sweat taste and full of saliva in mouth, slippery and greasy tongue coating.Besides, during the hot summer, when encountering with pathogenic heat, dampness is liable to cause diseases, which is manifested as unsurfaced fever, limited motion, epigastric oppression, anorexia, diarrhea and other symptoms of mixed damp and heat, which should be treated according to the circumstances.When dampness is eliminated, heat would decease.

IV The liver

The liver is situated below the diaphragm in the abdomen. Elaboration of the Fourteen Meridians（Shi Si Jing Fa Hui）says,"The liver is at the right hypochondriac region before the right kidney.Together with the stomach, it goes through the ninth vertebra".

The liver, together with gallbladder, eyes, tendon and fingernails forms the liver system. It attributes to wood in five elements and yang within yin in zang-fu organs, and corresponds with spring.Physiological functions of the liver are dominating free flow and storing blood.It likes smoothness and hates depression, so it is said"liver being the resolute zang-fu organs".The liver,"being yin in substance and yang in function",is"the general organ, from which contemplation comes".

In traditional Chinese medicine, there is saying"left liver, right lung". It originated from Canon of Medicine（Nei Jing）,"The liver is at the left, and the lung hides in the right".This is not based on the anatomic position, but on their physiological functions.According to traditional Chinese medicine, the pathway of yin and yang is at the left and the right.Yang rises from the left and yin falls at the right.The liver, attributing to wood, corresponding to spring qi, and situated in the east, is the source of yang and dominates generation and ascending;the lung, attributing to metal, corresponding to autumn qi, situated in the west, is the initiation of yin and dominates killing and descending.On the left yang ascends and on the right yin descends.Liver qi ascends from the left;while lung qi descends at the right.The liver is yang within yin and dominates ascending, while the lung is yin within yang and dominates descending.

1.Physiological functions

1.1　The liver dominating free fow

Dominating free flow refers to the liver's physiological functions of dredging, smoothing, dispersing, circulating and excreting. The ancient physicians compared liver dominating free flow to the growing characteristic of woods in the nature.The woods sprout in spring.Assisted by spring qi, they grow smoothly and freely.Liver qi is like wood in spring, free and smooth, full of vitality.The liver dominating free flow involves a wide rang.On one hand, it represents the soft and smooth physiological state of liver itself;one the other hand, it involves regulating smoothness of qi movement.Various complex substance metabolisms of human body are completed in the process of qi"ascending, descending, exiting and entering".If liver dominates free flow normally, qi movement will be free, qi and blood harmonize, the meridians smooth, functions of zang-fu organs coordinate, various nutrients are continuously generated, and water and wastes are discharged smoothly.If liver fails dominating free flow, there are various pathological changes such as liver depression, liver fire and liver wind.Main functions of liver dominating free flow in physiological activities of human body are illustrated as the follows:

1.1.1　Regulating spirit and emotions

According to the theory of traditional Chinese medicine, besides being dominated by the heart, emotional activities also have close relation with liver dominating free flow. Only when the liver dominates free flow regularly and qi movement is smooth can the spirit be optimistic, the mood cheerful, qi and blood harmonious and five zang-organs coordinated.Conversely, if the liver fails in dominating free flow and qi movement is in disorder, abnormal mental and emotional activities would be caused, which are manifested in the following two aspects:First, failure of liver dominating free flow would result in stagnation of qi movement, accompanied with pathological phenomena such as distending and oppressive pain in the chest and breast, depression, and suspiciousness.This is called"liver depression",or"stagnation of liver qi".Second, excess of liver dominating free flow may cause excited emotions, accompanied with symptoms of headache, red face and eyes, hot-tempered, even sleeplessness.This is call"adverse flow of liver qi".

1.1.2　Promoting transformation and absorption of spleen and stomach

Whether the transforming and absorbing functions of spleen and stomachare normal relates not only to coordination between spleen ascending the clear and stomach descending the turbid, but also to liver dominating free flow. Since liver dominating free flow and regulating qi movement is the essential condition for maintaining coordination of stomach ascending and descending so as to promote transformation of the spleen and stomach.The liver attributes to wood and the spleen and the stomach attribute to earth.Plain Questions·Preservation of Precious Life（Su Wen·Bao Ming Quan Xing Lun）says,"Getting earth, wood grows".If the liver dominates free flow normally, the spleen and stomach would ascend and descend properly, and the bile would be secreted and excreted regularly and orderly, which is beneficial for digesting and absorbing functions of the spleen and stomach.If the liver fails in dominating free flow, syndrome of"excessive wood over-restricting earth"（Earth refers to spleen and stomach）would be resulted in.Invading the spleen is manifested at the upper as dizziness, and at the lower as lienteric diarrhea;invading the stomach is manifested at the upper as vomiting and belching, in the middle as distending pain in the chest and breast, and at the lower as constipation.On the other hand, liver dominating free flow is helpful for spleen and stomach transformation and absorption, as well as secretion and excretion of bile.The bile, generated by abundant liver qi, is the"essence"involved in digesting and absorbing food.Its secretion and excretion is affected by liver dominating free flow.If liver qi stagnates and the bile cannot be secreted and excreted normally, digesting and absorbing functions of the spleen and the stomach would be affected, manifested in clinic as distension under the flank, pain, bitter taste in mouth, dyspepsia, and even jaundice.

1.1.3　Regulating water metabolism

Water metabolism is completed by the lung, the spleen and the kidney together, but also depends on liver dominating free flow. Liver dominating free flow can regulate qi movement.Only when qi movement is regulated and the triple energizers are smooth can the spleen transport and transform water, the lung transmit fluid and the kidney disperse water normally to regulate water metabolism.Collection of Medical Classics（Yi Jing Su Hui Ji）says,"Water is son of qi, and qi is mother of water.Qi moves and water moves;qi stagnates and water stagnates".Abnormality of liver dominating free flow may result in obstruction offluid distribution metabolism, which can cause pathological products as phlegm, retained fluid and edema, or phlegm nodule due to phlegm obstructing meridians, or swelling due to water stagnation.

1.1.4　Regulating reproductive function

Female ovulation and menstruation and male sperm generation all have close relations with liver dominating free flow.

Liver dominating free flow makes qi movement smooth. Conception vessel would be smooth, thoroughfare vessel would be in excess and menstruation would appear regularly.However, if liver fails in dominating free flow, conception vessel and thorough vessel would be in disorder, and qi and blood cannot be harmonized, which may cause female diseases of menstruation, leucorrhea, pregnancy and labor, or sexual dysfunction and sterility.

Essence chamber is where male stores sperms. On Deduction and Exploration·On Exuberant Yang and Deficient Yin（Ge Zhi Yu Lun·Yang You Yu Yin Bu Zu Lun）says,"It is the kidney that dominates storing;it is the liver that dominates free flow."This shows that male seminal fluid is stored by the kidney and discharged by the liver.Only when kidney storing and liver discharging coordinate in balance can the essence chamber open and close reasonably and can the seminal fluid be discharged moderately, so that male sexual function and reproductive function can be in normal state.If the liver fails in dominating free flow, symptoms of spermatemphraxis, sexual hypoesthesia, impotence, and infertility would appear;if the liver dominates free flow excessively, symptoms of sexual hyperesthesia and nocturnal emission would appear.

1.2　The liver storing blood

The liver has functions of storing blood, regulating blood volume and preventing bleeding, so it is known as dominating"blood sea",which can be understood in the following three aspects:

1.2.1　Storing blood

The liver storing blood means that the liver stores certain volume of blood in the liver and thoroughfare vessel for the need of tissues and organs, which has great physiological significance for the liver itself and the whole body. On one hand, liver storing blood can restrict its own yang to prevent it from being excessive so as to maintain the balance of liver yin and liver yang;on the other hand, Spiritual Pivot·On Spirit Origin（Ling Shu·Ben Shen）says,"The liver stores blood and blood houses the spirit".The activity of the spirit takes blood as its material foundation.Only when liver blood is plentiful can the spirit be housed.If the liver fails in storing blood, symptoms of hyperactivity of liver yang may appear, such as dizziness, distending pain in the head and eyes, red face or eyes;lack of liver blood can also cause symptoms of failing in housing spirit, such as dream-disturbed sleep, uneasy sleep, sleep walking, sleep talking and delusion, etc..

1.2.2　Regulating blood volume

The function of liver regulating blood volume takes liver storing blood as the precondition and can be completed in coordination with the function of liver dominating free flow. Under normal condition, blood volume of each organ of the body is relatively invariable.When the organs are in static state, abundant blood around would be stored in the liver for use, just as Plain Questions·Generation of Five Zang-organs（Su Wen·Wu Zang Sheng Cheng）says,"When one lies down, the blood returns to the liver";when physical activities increase, emotions agitates and exterior climate changes, the liver would transport the stored blood to all zang-fu organs for use, which is completed through the functions of liver storing blood and liver dominating free flow.However, abnormal regulation of blood volume can cause malnutrition of zang-fu organs and tissues, for example, if the eyes can not be nourished, the eyes would be dry and dizzy, or night blind;if the tendons can not be nourished, the tendons would be contracted, the limbs would be numb and the joints would be impaired.

Liver regulating blood volume also plays a significant role in female menstruation and pregnancy. Blood is the base of female physiological activities.Only when the womb is nourished by liver blood can menstruation be regular;during pregnancy, blood nourishes fetus;and giving birth will cause bleeding.All these are related to liver.The liver stores blood and is named blood sea.Thethoroughfare vessel originates from the uterus and communicates with the liver, also known as"blood sea",which has close relation with women.If liver blood is insufficient, scanty menstruation, even amenorrhea would be seen.

The liver dominates free flow and qi movement, as well as stores blood, among which storing blood is the substantial base for dominating free flow and qi movement, and dominating free flow and qi movement is the specific manifestation of storing blood. They depend on and promote each other and relate closely with each other.They affect one another physiologically and pathologically.

2.Physiological characteristics

2.1　The liver likes spreading out freely and hates being stagnated

The liver likes spreading out freely and hates being stagnated means to maintain its free and smooth characteristic and avoid being restricted and stagnated. The liver attributes to wood in five elements and corresponds to spring qi in the nature, which should be soft, smooth, uprising.Only when the liver qi is not stagnated and not activated can the liver maintains its normal function of dominating free flow.Violent rages can result in hyperactivity of liver yang with symptoms such as red face and eyes, head fullness and headache, while depression can result in liver qi stagnation, which may be transformed into pathogenic fire and heat after a long time and thus cause the pathologic changes such as liver fire and live wind.

2.2　The liver being yin in substance and yang in function

Substance refers to the liver itself;function refers to the functional characteristic of the liver.

The liver"being yin in substance"has two meanings:first, the liver is the organ that stores blood, which attributes to yin;second, the liver is a zang-organ situated at the lower part and attributes to yin. The physiological functions of the liver can remain normal on the basis of the nourishment of liver blood.The liver is the resolute organ, and can function normally only when being nourished well

The liver"being yang in function"also has two meanings:first, physiologically, the liver stores fire, and is the organ attributing to wind and wood, dominating ascending and moving, which is yang;second, pathologically, liver yin and liver blood are easily to be in deficiency and liver yang is easily to be in excess. When the liver is diseased, there would be the symptoms of adverse and excessive yang and stirring of liver wind, such as dizziness, hypertonic tendon, contraction, even convulsion.Besides, liver failing in dominating free flow may also cause qi stagnation and blood stasis.Liver qi stagnation long for a long time can generate fire, which may injure liver yin and liver blood.Excessive consumption of liver yin and liver blood can also result in hyperactivity of liver yang.Therefore, in clinic, the therapy of nourishing yin and blood to tonify liver or the therapy of cooling liver and purging liver is often used to treat excessive ascending and stirring of liver qi and liver yang.

2.3　Liver being the resolute organ

"Resolute"means to be strong, unyielding and testily impatient. The ancients compared the liver to"a general",describing its physiological characteristics with the tough and impatient character of generals.It mainly refers that liver qi dominates ascending and stirring, and with tough character, it is liable to be in adverse and excessiveness.So it is called"resolute organ",or"general organ".The liver being a tough organ is determined by its characteristic of being yin in substance and yang in function.The liver itself is gentle and its function is tough, harmonization and coordination of which make it function normally.

3.Relationships with physique, orifice, emotion, fluid and seasons

3.1　The liver corresponding with tendons in the body, with its outward manifestation in the nails

Tendon, including sinews and ligaments, is a kind of tissues connecting the joints and muscles. It restricts and protects joints, muscles and other moving tissues.The liver corresponds with tendons in the body, and this is also known asthe liver governing tendons, which refers to the function of liver's governing all tendon movements of the body."Liver governing tendons"in Spiritual Pivot·On Nine Needles（Ling Shu·Jiu Zhen Lun）and"liver governing tendons and ligaments"in Plain Questions·Atrophy-flaccidity（Su Wen·Wei Lun）all mean that tendons depend on the nourishment of liver blood.If liver blood is sufficient, the tendons can be nourished, and then they are forceful and move normally to endure tiredness and to dissolve fatigue.If liver qi and liver blood are in deficiency, the tendons can not be nourished, which may result in weak tendons, inflexible movement, even limb numbness, hands and feet shaking.In heat diseases, if pathogenic heat injures fluid and blood, the tendons can not be nourished, which may cause clonic convulsions, opisthotonus, and stiff neck.This is called"stirring of liver wind"in traditional Chinese medicine.So Plain Questions·On The Most Fundamental Theories（Su Wen·Zhi Zhen Yao Da Lun）says,"All wind with vertigo and shaking is ascribed to the liver"and"All sudden muscular spasm and rigidity is ascribed to wind".

Nails include fingernails and toenails. According to traditional Chinese medicine, nails are the extension of tendons to the surface of the body, so there is the saying,"The nails are the surplus of the tendons".The liver's outward manifestation is in the nails refers that liver blood nourishes the nails, whose color and luster can reveal the excessiveness and deficiency of liver blood.Plain Questions·Generation of Five Zang-organs（Su Wen·Wuzang Shengcheng）says,"The liver corresponds with tendons in the body, and its outward manifestation is in the nails".If liver blood is in deficiency, the nails are soft and thin, pale and even deformed and brittle.Through observing color and shape of the nails, the excessiveness or deficiency of liver qi and liver blood can be deduced, so the pathological changes of nails are often differentiated from syndromes of the liver.

3.2　The liver opens into the eyes

Eye is also called"jingming". The liver opens into the eyes means that the normal physiological function of the eyes depends mainly on the liver and that the pathological changes of the liver can be seen from the eyes.Spiritual Pivot·Meridians（Ling Shu·Jing Mai）says,"The foot jueyin meridian of liver connects with the eyes".Though the eye relates with all zang-fu organs, it relatesmost closely with the liver.If yin blood of the liver is insufficient, there will be symptoms of dry eyes, blurred vision or night blindness;in upflaming of liver fire, there will be symptoms of redness, swelling and pain in the eyes;in hyperactivity of liver yang, there will be dizziness;in internal stirring of liver wind, there will be the symptom of deviation or upward movement of the eyeballs;in damp-heat in liver and gallbladder, there will be the symptom of yellow white of eye.Thus, liver diseases are often reflected in the eyes, so"The eye is the exterior manifestation of the liver".

3.3　The liver corresponds with anger in emotions

Anger is a kind of bad emotional stimuli. The liver corresponds with anger in emotions refers that anger takes the blood stored by the liver as its substantial basis.It relates closely with liver dominating dispersing and ascending and liver dominating free flow.If physiological functions of the liver are normal, one would not be excessively angry;if the liver is ill and liver yang disperses excessively, one would be changeable in emotions and get furious once irritated.Besides,"anger injures liver".Big fury may result in the symptoms of adverse flow of liver qi, such as red face and eyes, even hematemesis and syncope;depressed anger may cause the symptoms of stagnation of liver qi, such as hypochondriac distending pain, distension of breast and lower abdomen.

3.4　Liver associated with tear in fuids

Tears, with the function of moistening the eyes, are generated by liver yin. The liver opens into the eyes and the tears run out from the eyes and are governed by liver qi, so tears are fluid of the liver.When the liver functions are normal, enough tears are secreted to moisten the eyes without running down.If the liver is ill, secretion of the tears would be abnormal.For example, if liver blood is insufficient, secretion of tears would decrease with the symptom of dry eyes;if the liver meridian is attacked by dampness and heat, there would be the symptom of increased eye secretion;if the liver meridian is attacked by wind and heat, epiphora induced by wind could be seen.

3.5　The liver corresponding with spring qi

Spring is the beginning of the year, when yang qi starts growing and woods begin to grow up freely. The liver dominates free flow, hates depression and likes growing freely, and attributes to wood in five elements, so the liver corresponds with spring qi.Therefore, in spring one should behave in accordance with spring qi, keeping smooth and moderate emotions and away from fury and depression, keeping early hours, hat off and hair hanging loose, clothes loosed and the body stretched so as to free liver qi and to benefit health care.Since liver qi is most excessive in spring and reacts severely, liver diseases are very common in spring.Especially, liver dominating free flow relates to spirit and emotional activities of human beings, so mental illnesses are liable to occur in spring.

V The kidney

The kidneys are situated in the lumbar zone, one on either side of the spinal column, oval-shaped and curved like cowpeas. Plain Questions·Precision and Subtleness of Pulse（Su Wen·Mai Yao Jing Wei Lun）says,"The lumbar is the house of the kidney".

The kidney, together with bladder, bones, marrow, hair and ears, constitutes the kidney system. It attributes to water in five elements and yin within yin in five zang-organs, and corresponds with winter in nature.Physiological functions of the kidney are:storing essence, regulating water metabolism and receiving qi.It is the basis of yin and yang of the body and source of life, so it is considered as the"foundation of prenatal life".

1.Physiological functions

1.1　The kidney stores the essence and governs the growth, development and reproduction

The essence is the most elementary substance that constitutes the body and maintains life activities. According to the theory of traditional Chinese medicine, essence has its broad sense and narrow sense.Essence in broad sense is thegeneral term of essence that constitutes human body and maintains the growth, development and reproduction, as well as the functional activities of zang-fu organs, including the innate essence inherited from parents and the acquired essence transformed by the spleen and the stomach, i.e.the essence of grain and water.Essence in narrow sense refers to the essence with reproductive function which is inherited from parents and stored in the kidney, i.e.the essence of reproduction.

The essences stored by the kidney include"innate essence"and"acquired essence". Innate essence originates from the essence of reproduction of the parents.It is inborn and stored in the kidney.It is the primordial substance that constitutes embryonic development.After one is born, the innate essence is nourished continuously by the acquired essence and becomes the material basis for the growth, development and reproduction of human body, so it is called"the essence of reproduction".Spiritual Pivot·On Spirit Origin（Ling Shu·Ben Shen）says,"The essence that is inborn is the innate essence".That is why"Kidney is the innate foundation".The acquired essence refers to various essences generated from grain and water.Since it is generated by the spleen and the stomach after one is born, it is called"acquired essence".It is the nutrients that maintain life activities, distributed to five fu-organs, six zang-organs and the skin and tendons to exert its function of nourishment.For example, it can be transported to the kidney and be part of kidney essence.

Though innate essence and acquired essence are from different origins, they are stored in the kidney and depend on and promote each other. Innate essence depends on acquired essence to nourish and foster it so that it can become exuberant gradually and exert fully its physiological functions;while continuous generation of acquired essence also depends on active endowment of innate essence.So there is the saying"Innate essence generates acquired essence and acquired essence fosters innate essence".Innate essence and acquired essence supplement each other and combine in the kidney to be the essential qi of kidney, whose physiological functions, i.e.functional manifestations of kidney's storing essence, can be understood from the following aspects.

Plain Questions·On Ancient Theory of Essence and Qi（Su Wen·Shang Gu Tian Zhen Lun）says,"When a female is seven years old, kidney qi is exuberant and her teeth begin to change and her hair begins to grow;till fourteen, sex-stimulating essence is generated, her conception vessel is through and taichong vessel is exuberant, and the menstruation appears and she is equipped with fertility;till twenty-one, kidney qi is moderate, and the dermal teeth grow mature;till twenty-eight, her tendons and bones are strong, her hair grows fair and her body is robust;till thirty-five, her yangming vessel begins to decline, her face begins to be emaciated and her hair starts to fall;till forty-two, three yang vessels（taiyang, shaoyang and yangming）begin to grow weak, her face is emaciated and her hair begins to grow pale;till forty-nine, her conception vessel is in deficiency, taichong vessel is becoming deficient, sex-stimulating essence is over and she loses the ability of being pregnant. When a male is eight years old, kidney qi is in sufficiency and his teeth begin to change and his hair starts to grow;till sixteen, his kidney qi is exuberant, sex-stimulating essence is generated, essence is overflow and he is equipped with fertility;till twenty-four, kidney qi is moderate, his tendons and bones are robust and his dermal teeth grow mature;till thirty-two, his tendons and bones are strongest and his muscles are robust;till forty, kidney qi declines, his hair begins to fall and his teeth start to be withered;till forty-eight, yang qi begins to be deficient, his face is emaciated and his hair begins to grow pale;till fifty-six, liver qi is deficient, her tendons are hard to move, sex-stimulating essence is consumed over, the essence is less, his kidney is declined and his body is weak;till sixty-four, his hair and teeth are all gone".The above statement tells the process of kidney essence growing from insufficiency to exuberance, and declining from exuberance to null, pointing out the close relations of kidney essence with the birth, growth and death of human beings.

The growth and development of human beings can be divided into childhood, adolescence, post-adolescence and old age. After one is born, since"innate essence"is nourished continuously by"acquired essence",kidney essence becomes exuberant gradually, which results in the physiological phenomena of teeth changing and hair growing in childhood.With the continuous exuberance of kidney essence, the adolescence essence that can promote maturity of reproduction and maintain function of reproduction is generated, i.e."sex-stimulating essence".Once sex-stimulating essence is generated, female menstruation will appear and male seminal fluid is generated.With the maturity of sexual function, man has acquired the ability of reproduction.Till post-adolescence kidney essence has been so exuberant that the tendons and bonesare strong, the body is robust, the energy is vigorous, and the reproductive function is also at its full blast.And then with the decrease of kidney essence, the organs are also gradually declining, accompanied with physiological phenomena of gaunt complexion, hair loss and withered teeth.Now generation of sex-stimulating essence gradually decreases and reproductive ability also decreases till null.

Exuberance and deficiency of kidney essence determines the growth and development of human body. Deficiency of kidney essence always causes abnormality in growth and development.For example, in childhood, deficiency of kidney essence may result in delayed growth and development, mental retardation, or"five lates"（standing late, walking late, teeth growing late, speaking late and hair growing late）,"five softs"（hands and feet soft, head soft, neck soft, muscle softy and mouth soft）;in adulthood, deficiency of kidney essence may cause prematurely senile, which is manifested as hair loss and loose teeth, dizziness, tinnitus, impaired memory and sexual dysfunction.Therefore, in clinic, the therapy of supplementing kidney essence is often adopted.

1.2　The kidney regulates water metabolism

Water, referring to fluid, is the general term for all normal fluids in the body. The kidney regulates water metabolism means that kidney qi plays a significant regulating role in distributing and discharging fluids of the body and in maintaining the balance of fluid metabolism.That's why Plain Questions·On Imbalance（Su Wen·Ni Tiao Lun）says,"The kidney, the zang-organ of water, governs fluids".Regulation of water metabolism, though relating with several zang-fu organs including the lung, the spleen, the liver and the kidney, is governed mainly by the kidney, whose action goes through the whole process of water metabolism.

The kidney regulating water metabolism is realized through transformation of kidney qi. The so-called"qi transformation"refers to the steaming of yang qi in the kidney.Kidney yang can steam water, make water steamed and can also make qi accumulated into water to facilitate water ascending, descending, exiting and entering in the body, and to be distributed and discharged to maintain normal water metabolism.To be specific, kidney regulating water metabolism is manifested in the following three aspects:Firstly, it is the promotion of kidney qi for water metabolism.Kidney yin and kidney yang are the basis of yin andyang of zang-fu organs.Qi of zang-fu organs must be under balance coordination of yin and yang so as to be involved in water metabolism;secondly, it is urine transformation of kidney qi.Water metabolized by zang-fu organs enters the kidney or bladder through the triple energizers and is discharged out of the body after qi transformation of the kidney;thirdly, it is through the promotion, regulation and coordination of kidney qi that the bladder can open and close regularly and excrete the urine properly to maintain the balance of water metabolism.If the kidney fails in regulating water metabolism, water metabolism of the body would be abnormal and the bladder would fail in closing, with the symptoms of urine metabolic disorders such as scanty urine and swelling, or kidney qi fails in transforming water, with pathological phenomena of clear abundant urine and hydrouria.

1.3　The kidney receiving qi

The kidney receiving qi means that the kidney has the function of receiving and controlling the clear qi inhaled by the lung, preventing hypopnea and ensuring normal exchange of interior and exterior air. Though respiration of human body is governed by the lung, it must rely on the function of kidney's receiving qi.Specifically, only when the clear qi inhaled by the lung goes down to the kidney and is received by the kidney can deep and steady respiration be maintained so as to guarantee normal exchange of interior and exterior air.Classified Treatment·Dyspnea（Lei Zheng Zhi Cai·Chuan Zheng）says,"The lung is the dominator of qi and the kidney is the foundation of qi.The lung governs respiring and the kidney dominates receiving qi.Yin and yang corresponds with each other and respiration can be harmonized.If respiring and receiving are in disorder, dyspnea occurs".The kidney's receiving qi is actually the specific expression of the encapsulation function of kidney qi in respiration.If kidney qi is exuberant, respiration of the lung is moderate and regulated, and the respiratory tract is unobstructed.If kidney qi is in deficiency and fails in receiving qi, the kidney would fail in receiving the clear qi inhaled, which may cause pathogenic manifestation of"failure of kidney to receive qi",such as hypopnea, or exhaling more and inhaling less and dyspnea at moving.So, regular respiration is the result of coordination of the lung and the kidney.

2.Physiological characteristics

2.1　Kidney dominating storage

Kidney dominating storage is the main physiological characteristic of the kidney. As the highly summarized physiological function of the kidney, it refers that the kidney has the function of storing essence of five fu-organs and six zang-organs.Kidney storing essence, regulating water metabolism and receiving qi are all the specific manifestations of kidney's dominating storage.So Plain Questions·Six-Section Theory of Zang-fu Manifestation（Su Wen·Liu Jie Zang Xiang Lun）says,"The kidney is the basis of storage and the house of essence".The kidney qi stores and the essence is exuberant, and so life activities are vigorous and the normal physiological functions of the organs can be maintained.

2.2　Kidney dominating yin and yang of the body

Kidney dominating yin and yang refers that the kidney has the functions of governing and regulating yin and yang of the body and maintaining dynamic balance of yin and yang of the organs. Kidney yin and kidney yang are both generated by the essence in the kidney, among which kidney yin is the foundation of yin fluid of the body and has the functions of moistening and nourishing body tissues and organs, while kidney yang is the foundation of yang qi of the body and has the function of warming and promoting body tissues and organs.Kidney yin is also known as original yin, genuine yin, genuine water and water of life gate;kidney yang is also known as original yang, genuine yang, genuine fire and fire of life gate.Kidney yin and kidney yang are the foundation of yin and yang of zang-fu organs.They restrict, depend on and promote each other.Exuberance of yin of zang-fu organs depends on exuberance of kidney yin, and exuberance of yang of zang-fu organs also depends on exuberance of kidney yang.That is why kidney dominates yin and yang of the body.

Imbalance of kidney yin and kidney yang may result in imbalance of yin and yang of the whole body, with symptoms of yin failing in restricting yang or yang failing in restricting yin. Kidney yin and kidney yang can also impair each other.Impairment of kidney yin to some extend can injure kidney yang, and deficiency ofkidney yang may also affect kidney yin, resulting in the pathological phenomenon of mutual impairment of yin or yang.

3.Relationships with physique, orifice, emotion, fluid and seasons

3.1　The kidney corresponding with bones in the body, with its outward manifestation in the hair

The kidney corresponding with bones means that the kidney stores essence and essence generates marrows, which are in the bones and nourish bones. If kidney essence is exuberant, marrows have sources to be generated and the bones are nourished to develop vigorously, being compact, solid and powerful.Conversely, if kidney yin is in deficiency, symptom of five late can be seen in children, while the aged people are easily to have their bones broken, or uneasy to be healed after being broken."Teeth are the surplus of bones".Kidney essence deficiency may also cause the teeth to loosen or even fall out.

The kidney's outward manifestation is in the hair refers that the exuberance of kidney essence can be revealed in the hair, i. e.hair is the exterior manifestation of the kidney.Growth and loss, glory and withering of the hair, relate not only to exuberance of kidney essence, but also to the nourishment of the blood.So, there is the saying"the hair is the surplus of the blood".But growth of the hair is rooted in the kidney, because the kidney stores essence and essence can transform blood to nourish the hair.Therefore, changes of the hair from glorious to withered, black to white vary with changes of kidney essence from sufficiency to deficiency.

3.2　The kidney opens into the ears and two orifces

Ears are the hearing organ. Whether the hearing is keen or not is related closely with the exuberance and deficiency of kidney essence.Spiritual Pivot·Lengths of Meridians（Ling Shu·Mai Du）says,"The kidney qi corresponds with the ears.The kidney is harmonious, and the ears can hear five sounds".If kidney essence is exuberant and the marrow sea（the brain）is nourished, the hearing is keen with high resolution.Conversely, symptoms of dysacusis, tinnitusand even deafness would come up.

The two orifices refer to the anterior orifice and the posterior orifice. The anterior orifice is the passage of urine discharge, male ejaculation, female menstruation and intrapartum fetal;the posterior orifice, i.e.,the anus, is the passage of discharging excrement.The discharging and reproductive functions of the two orifices are closely related to kidney essence.If kidney essence is in deficiency and fails in transforming and governing, abnormal urination and defecation would come up;as for reproduction, male impotence, premature ejaculation, oligospermia, involuntary emission, spermatorrhea, and sterility, and female dreaming of intercourse, abnormal menstruation and infertility would be seen.

3.3　The kidney corresponding with terror in emotions

Terror, meaning being frightened or afraid, is a kind of mental state of human beings'being afraid of things. The kidney corresponding with terror in emotions refers that the emotional activities of terror has close relation with the kidney.Plain Questions·On Pains（Su Weu·Ju Tong Lun）says,"Terror makes qi going down and fright makes qi perplexed"."Terror makes qi going down"refers that terror makes qi go down so that kidney qi cannot be distributed upward, but downward to the lower energizer;"fright makes qi perplexed"means that once the normal physiological activities of the organs are disturbed, phenomena of being absent-minded and restless may appear."Terror injures the kidney",i.e.,if one is in extreme terror, he may have symptoms of seminal emission, habitual abortion or urinary and fecal incontinence;however, if kidney essence is insufficient, once stimulated little, one would be horrified or flaccid paralyzed due to leg weakness.

3.4　The kidney corresponding with thick saliva in fuids

Thick saliva, one of five fluids, the thicker part of saliva, forms the mouth fluid together with thin saliva. Thick saliva is generated by kidney essence.Pushed by kidney qi, it is excreted going through Jinjin point and Yuye point under the tongue along kidney meridian of foot shaoyin.So it is said the kidney corresponds with thick saliva in fluids.Plain Questions·On Qi of Five Zang-organs（Su Wen·XuanMing Wu Qi Pian）says,"Five zang-organs generate fluids, among which the kidney generates thick saliva".Generated by kidney essence, if swallowed, it can nourish kidney essence;but if spitted out long and more, it may consume kidney essence.That is why the ancient physicians suggested one push the tongue against palate till fluid filling the mouth full and then swallow it down to nourish kidney essence.Such therapy is called"drinking jade pulp".

Thick saliva and thin saliva, though remain in the mouth together, have some differences. Thick saliva is generated by kidney essence, out from the tongue, thick in texture;while thin saliva is generated by spleen essence, out from cheeks, and thin in texture.So, in clinic, slobbering is often treated by treating the spleen, while frequent thick saliva is often treated by treating the kidney.

3.5　The kidney corresponding with winter qi

Among five zang-organs, the kidney attributes to yin within yin, and winter is the coldest season in a year, when cold water is in season and things are stored. As the foundation of storage, attributing to water in five elements, the kidney is water organ with characteristic of moistening and flowing downward.Water is cold in climate and refers to the kidney in zang-organs, so kidney qi corresponds with winter qi.In winter, kidney qi is most exuberant and its storing function is most powerful.Therefore, in winter one should take diet that can supplement yin and subdue yang in accordance with storage of winter, so as to facilitate storing yang and saving yin;meanwhile, one should also sleep early and get up late, and reduce outdoor exercises to preserve one's health.Patients with yang deficiency are easily to be invaded in winter.

Appendix:Gate of life

Gate of life means it is the foundation and key of life. It was first seen in Spiritual Pivot·On Position of Starting and Ending of Meridians（Ling Shu·Gen Jie）,which states clearly,"Gate of life is the eyes".Gate of life as the internal organ was first seen in Classic of Difficult Issues（Nan Jing）,"The left kidney corresponds with the right gate of life".Since then gate of life, as the content of the theory of zang-fu organs, has been considered and studied by later physicians, but many of them have disputes about the location and physiological functions of gate of life and presented their own opinions.The followings are the summarization of location of gate of life for reference:

1.The left is the kidney and the right is gate of life

Classic of Difficult Issues·The Thirty-ninth（Nan Jing·San Shi Jiu Nan）says,"The left is the kidney;the right is gate of life, which is the house of various spirits. Male gate of life stores essence and female gate of life fastens uterus.It corresponds with the kidney".The statement summarizes the location and functions of gate of life and tells that it corresponds with the kidney.

2.Both kidneys are gate of life

Hua Shou in Yuan Dynasty initiated this theory that"Gate of life corresponds with the kidney". Orthodox Medical Record（Yi Xue Zheng Zhuan）also points it out clearly,"Both kidneys are together gate of life".Though interpreting gate of life as this:for female it is gate of birth and for male it is gate of essence, Zhang Jingyue confirmed that"both kidneys are gate of life".

3.Gate of life is between the kidneys

Zhao Xianke said in The Key Link of Medicine·On Twelve Internal Organs（Yi Guan·Nei Jing Shi Er Guan Lun）,"Gate of life is located against the navel and close to the back bone, which is the fourteenth vertebra from the top and the seventh from the bottom. Canon of Medicine（Nei Jing）says,‘Near the seventh vertebra, there is gate of life'.Here is where the kidneys are located, among which the left kidney attributes to yin water and the right attributes to yang water.Between them is the house of gate of life……"He considered that gate of life governs yang qi of the body and are"intangible".His theory greatly influences the later generations.

4.Gate of life is the dynamic qi in the kidney

Though the theory confirms that gate of life is in between the kidneys, Sun Yikui of Ming Dynasty said in Ponders on Medical Aims（Yi Zhi Xu Yu）,"Gate of life and the dynamic qi between the kidneys is neither fire nor water. It is the pivot of generation and the root of yin and yang, i.e.the innate taiji.

Almost all physicians agreed on the physiological functions of gate of life, regarding it closely linked with kidney functions, which emphasized the important role kidney yin and kidney yang played in life activities of human body.