Section one yin-yang theory

Yin-yang theory is an ancient philosophy that explores the basic concept of yin-yang and its law of motion, which is employed to interpret the occurrence, development and transformation of matters in the universe. It believes that the world is an integrate whole of things and that it is the result of the unity of opposites between yin and yang.The unity of opposites between yin and yang remains not only inside the things;the occurrences, development and transformation of the matters are also the result of the unity of opposites between yin and yang.

Traditional Chinese medicine employs yin-yang theory to analyze human tissue structure, to interpret its physiological function and pathological changes, and then to give guidance to clinical diagnosis as well as prevention and treatment of diseases.

I Basic concept of yin-yang

1.Defnition of yin-yang

Yin and yang originally referred to the things exposed to or in the shade of the sun. If exposed to the sun, it is yang;otherwise it is yin.Places faced to the sun are bright and warm;while places in the shade of the sun are dark and cold.Yin and yang are further introduced to refer to things and phenomena with relative properties, such as heaven and earth, up and down, the sun and the moon, day and night, fire and water, ascending and descending, dynamic and static, inside and outside, feminine and masculine, i.e.all things and phenomena in the nature are divided into two aspects-yin and yang.Now yin and yang have become abstract conceptions that generalize things and phenomena with relative properties.

Yin-yang is the generalization of the relative properties of interrelated things and phenomena in the universe. Yin and yang can both represent two different things or phenomena opposing to each other, and analyze two aspects in opposition to each other within one thing.For the former, take heaven and earth, day and night, fire and water, cold and hot as examples;for the latter, take qi and blood, zang and fu in human body, and warm and cool natures of Chinese medicines as examples.

2.Properties of yin-yang

The following special properties of yin and yang derive from the concept of yin-yang:

2.1　Universality

Universality means that yin and yang exist in all aspects of the universe. It refers to getting to know the nature and the society from the aspect of yin-yang theory and considering that the world is formed by yin and yang that are both united with and opposite to each other, which is the basic principle of the movements of all things in the universe.No matter the inside of one thing or two different things, only if they have some characteristics that are correlated with and opposite to each other, they can be analyzed and generalized with yin-yang theory, such as heaven and earth, fire and water, dynamic and static, ascendingand descending, etc..

2.2　Relativity

Relativity means that when exploring the world with yin-yang theory, there must be two different things or phenomena that are correlated with and opposite to each other. It is manifested as the following three aspects:

2.2.1　Separability of yin and yang

Separability of yin and yang means that the things with yin or yang property can also be further divided into yin and yang. Take day and night as an example.Day is of yang property, while night of yin property.The day with yang property can be divided into morning and afternoon, among which morning is yang within yang and afternoon is yin within yang;the night with yin property can also be further divided into yin and yang, i.e.before midnight it is yin within yin, while after midnight it is yang within yin.Another example is human body.The surface of the body is yang, while the inside of the body is yin;the six fu-organs inside the body are yang and the five zang-organs are yin.

2.2.2　Transformability of yin and yang

Under certain conditions, yin and yang can transform into each other, i. e.yang may transform into yin and yin into yang.Take qi and blood as the example.Qi is yang while blood is yin.The functional movement of qi can generate blood, the process of which is transforming from yang into yin;on the other hand, blood can supply nutrition to qi, which is the process of transforming from yin into yang.

2.2.3　Mobility of yin and yang

Yin and yang are not proper nouns. They are mobile pronouns.Since the opposite things or phenomena are different, the contents represented by yin and yang are also different.For example, the heaven is opposite to the earth:the heaven is yang and the earth is yin;six-fu is opposite to five-zang:six-fu isyang and five-zang is yin.If properties of five zang-organs are divided according to upper and lower locations, the heart and the liver are above the diaphragm and are of yang property, while the liver, the spleen and the kidney are below the diaphragm and are of yin property.Though yin and yang are mobile pronoun, the yin and yang properties should be divided in accordance with specific things or phenomena.

2.3　Correlation

Correlation of yin and yang is also known as relevance of yin and yang, which means that objects analyzed with yin-yang should be the things or phenomena of the same category and at the same level. Only the correlated things or two aspects within the same things can be interpreted and analyzed with yin-yang.For example, up and down, heaven and earth which can indicate directions;cold and hot are at the same level which refer to temperature.It is forbidden to define up and cold or down and hot which are not of the same category with yin-yang.Things at different levels or of different categories are incomparable in their yin-yang properties and cannot be classified with yin-yang theory.

3.Yin-yang properties of things（or phenomena）

Classification of yin-yang properties of things:Generally speaking, all things that are dynamic, outwards, ascending, warm and hot, shapeless, bright and exciting are of yang property;while those that are static, inwards, descending, cold, shaped, dark and restrained are of yin property. Take heaven and earth as an example:that the heaven is yang and the earth is yin is because the heaven is in the upper and the earth in the lower.As for fire and water, the water is yin and the fire is yang is because the water is cold in nature and flows downward and the fire is hot in nature and flames upward.Take the motion and transformation of matters as an example:the transpiring process from tangible to intangible is of yang property, while the condensing process from intangible to tangible is of yin property.To introduce the relative yin-yang properties into medical field, the matters and functions that are motivating, nourishing and exciting pertain to yang, while those that are condensing, withering and restraining pertain to yin.

Because yin and yang have the properties of relativity and correlation, yinand yang properties are different for different things or phenomena at different levels, but they must be relative and correlative.

II Basic contents of yin-yang theory

1.Opposition and restriction of yin and yang

Yin-yang theory believes that most of the things and phenomena in the nature have two opposite aspects, i. e.yin and yang, whose properties and characteristics are in opposition to each other, such as, up and down, heaven and earth, dynamic and static, in and out, ascending and descending, day and night, bright and dark, fire and water, cold and hot and so on.

Restriction of yin and yang means that the opposite yin and yang are always restricting each other and trying to conquer each other with their own strength. Due to the opposition and restriction of yin and yang, all things are in constant motion and changes.The opposite yin and yang achieve unity and demonstrate dynamic balance in the process of restricting and competing with each other.Take changes of the seasons as the example:when winter solstice comes, yang rises and restricts yin, and the weather begins to turn warm and hot from cold;while when summer solstice comes, yin rises and restricts yang, and the weather begins to get cool and cold from hot.And so moving in circle, there are changes of four seasons-spring, summer, autumn and winter.

Two opposite aspects of human body under physiological conditions are also in restrictions to each other. Take the substances and functions that maintain human life activities as the example:the substances that form and maintain the life activities are yin essence, while all functional activities of human body are yang qi.The yin essence restricts yang qi and makes it move with cadence;yang qi restricts yin essence and gives it vigor of life.It is the opposition and restriction of yin essence and yang qi that maintains the normal life activities of human body.

Two opposite aspects of yin and yang do not coexist peacefully in a single entity. They are restricting each other constantly.The opposition and restriction between yin and yang is the intrinsic motivation for the motion and development of the things;however, if it is too strong or too weak, the dynamic balance of yin and yang would be broken, which is manifested in nature as abnormal changes ofthe climate and in human body as pathological changes.

2.Interdependence and mutual promotion between yin and yang

Interdependence between yin and yang means that yin and yang depend on each other and neither can exist in isolation. Take up and down as the example:up is yang and down is yin.Up cannot exist without down and down also cannot exist without up.Another example is cold and hot.Cold is yin and hot is yang.Hot cannot exist without cold and cold also cannot exist without hot.

Mutual promotion between yin and yang refers to the relationship of mutual generation and mutual promotion between yin and yang. Yin and yang not only oppose to and restrict each other, but also depend on and promote each other.Without interdependence and mutual promotion between them, yin or yang would wither away.That's why yin takes yang as its function and yang takes yin as its foundation.

Take the weather changes as an example:the process of the earth air（attributing to yin）going up and becoming the cloud is due to the evaporation with the hot air of the heaven;while the process of heaven air（attributing to yang）going down and becoming the rain is due to the agglomeration of the cold air of the earth. Thus it can be seen that the repeated circulation between the cloud and the rain, the heaven air and the earth air is the process of yin and yang promoting each other.

The substances and functions that maintain the life activities of human body not only oppose to and restrict each other but also depend on and promote each other. The functional activities attributing to yin provide material guarantee to promote generation of yang;the function of yang can in turn generate yin.Both exist in a single entity through depending on and promoting each other.If such relation is destroyed, pathological changes of yin deficiency involving yang or yang deficiency involving yin would come up.

3.Inter-containing and interaction between yin and yang

Inter-containing between yin and yang means that the opposing yin and yang contain each other, i. e.there is yin within yang and yang within yin.Thingsin the universe have the components or forces with yin and yang properties.Things attributing to yang have components or forces attributing to yin, and vice versa.For example, the heaven is up and attributes to yang.The air in the heaven descends and descending is yin, i.e.there is yin within yang;the earth is down and attributes to yin.The air in the earth ascends and ascending is yang, i.e.there is yang within yin.

Interaction between yin and yang refers to the process of yin and yang inducing and copulating during their movement. It is the basic condition of generation of things in the universe.If yin and yang could not copulate with each other, new things and new individuals would not be generated.

In nature, yang of the heaven descends and yin of the earth ascends and they induce to form cloud, fog, thunder, rain and dew. Thus all things under the sun are generated.For human beings, male and female copulate and then new life is born, and thus mankind can multiply.If there were no inter-induction between yin and yang, there would be no life and no nature.Thus interaction is the basic condition of life.

Interaction happens in the motion of yin and yang. Without the movement of yin and yang, there would be no interaction of yin and yang.It can be said that the movement of yin and yang is the foundation of interaction of yin and yang, which in turn is a phase of yin-yang interaction in the movement and is the optimum state of the whole process.Such optimum state can only be achieved when yin and yang are in balance and harmony, which is known as the so called"harmonious"raised by Chinese ancient philosophers.

The theory of interaction between yin and yang tells us yin and yang are in constant movement, and that when they meet in a harmonious state they will interact with each. The interaction between yin and yang makes two opposing things or forces are unified in one entity, which generates the nature, the things and human beings and makes the nature in constant movement.

Inter-containing is the foundation of interdependence and promotion of yin and yang. When yin is within yang, yin is the source of generating yang;when yang is within yin, yang is the motivation of generating yin.If not, yin would be"solitary yin"and yang be"solitary yang".Interdependence and mutual promotion between them would also be destroyed.

4.Waxing and waning of yin and yang balance between yin and yang

Waxing and waning of yin and yang means that while opposing, restricting, depending on and promoting each other, yin and yang are in constant growth or decline to keep dynamic balance.

4.1　Waxing and waning of yin and yang

Waning means decreasing, weakening and declining;while waxing means increasing, strengthening and exciting.

Waxing and waning is a form of yin-yang motion, the causes of which lie in opposition and restriction of yin and yang as well as interdependence and mutual promotion between yin and yang. On the basis of the opposition and restriction of yin and yang, the growth process of"one aspect wanes, the other waxes"and"one aspect waxes, the other wanes"will be generated;while based on interdependence and mutual promotion between yin and yang, the growth process of"one aspect wanes, the other wanes"and"one aspect waxes, the other waxes"will come up.

4.1.1　Waxing and waning of yin or yang

In opposition and restriction of yin and yang, such changes may appear:when one rises, the other falls, or when one falls, the other rises, i. e.when yang rises, yin falls or when yin rises, yang falls.For example, climate changes from winter solstice to summer solstice is the process of yang rising and yin falling while form summer solstice to winter solstice is the process of yin rising and yang falling.As for the physiological activities of human body, during the day yang is exuberant, and yang of the body rises outwards, whose functional activities are mainly exciting, i.e.yang rises and yin falls;in the night yin is exuberant, and the body functional activities also turn to be restricted and yang falls inwards, i.e.yin rises and yang falls.

4.1.2　Waxing or waning of both yin and yang

Due to inter-promotion of yin and yang, there are also the growing changes of one waxing and the other also waxing and one waning and the other also waning, i. e.when yin rises, yang also rises, or when yang falls, yin also falls, and vice versa.Temperature of the nature goes up from spring to summer and the rain also rises, i.e.when yang rises yin also rises;however the rain will reduce with the temperature goes lower from autumn to winter, i.e.when yin rises yang also rises.After eating, the strength of man will grow（yang rising）because of taking nutrients（yin rising）.For the same reason, when the functions of the stomach and the intestines are strengthened and the digestion will also be strengthened（yang rising）,there would be adequate nutrients to be transformed and stored（yin rising）.

Waxing and waning of yin and yang is the process of quantitative change, whose intrinsic motivation is opposition and restriction of yin and yang and interdependence and promotion between yin and yang.

Balance of yin and yang means that yin and yang remain in a harmonious and relative balanced state within certain limits. If waxing and waning of yin and yang were destroyed, there would be abnormal climate changes in the nature and corresponding pathological changes in human body, such as relative predominance or relative decline of yin or yang.

5.Transformation between yin and yang

Transformation between yin and yang means that under certain conditions, the opposed and interdependent yin and yang can transform to its opposite side, i. e.yin transforms to yang and yang to yin.It is the changes of the essential attributes of two parties within things when waxing and waning of yin and yang has developed to certain stages.

Canon of Medicine（Nei Jing）makes full description about this,"Extreme yin gives rise to yang, while extreme yang gives rise to yin;extreme cold brings on heat, while extreme heat brings on cold."（Plain Questions·On Yin and Yang Corresponding with Natural Phenomena）（Su Wen·Yin Yang Ying Xiang Da Lun）,which explains the transformation mechanism of yin and yang. Here,"extreme"is the internal factor and essential condition for transformation between yin andyang.When either of yin or yang develops to an extreme state, it will transform to the opposite direction or state, i.e.yin transforms into yang, and yang into yin.

Ways of transformation between yin and yang can be divided into two kinds-gradual change and sudden change. Gradual change refers to the slow changing process of yin into yang or yang into yin with waxing and waning of them.For example, the alternation of four seasons and the replacement between day and night, as well as transformation between the substances and functions of human body.Sudden change means that when waxing and waning develops to certain extends or if there are some inducing factors, yin and yang will make qualitative changes to the opposite side quickly.For example, in midsummer the extremely hot day may be extremely cold and it may also hail.

Transformation between yin and yang in illness is manifested by transformation between the exterior and interior syndromes, cold and heat syndromes, asthenia and sthenia syndromes and yin and yang syndromes under certain conditions. For example, evil heat obstructing lung syndrome is manifested as high fever, red face, cough, think breath, polydipsia, rapid and strong pulse, which is heat syndrome with sthenia interior.If evil heat is extremely excessive and injures healthy qi, pale face, cold limbs, sluggish spirit, feeble and impalpable pulse would appear, which is asthenia cold syndrome due to yang decline.Another example is cold fluid retention.It is a yin syndrome, but if cold fluid stays long or if drugs are taken, cold fluid can transform into heat and the syndrome would also transform into yang syndrome.Heavy toxic heat of the former case and long retention of cold fluid are the interior factors and conditions of transformation between yin and yang.

Waxing and waning of yin and yang is quantitative change of things, while transformation between yin and yang is qualitative change of things. Thus, waxing and waning of yin and yang has close relations with transformation between yin and yang.

6.Spontaneous harmonization of yin and yang

Spontaneous harmonization of yin and yang refers to yin and yang automatically maintaining and restoring their capability or tendency of coordinating the balanced state between them. For human body it is the capabilityof self-coordination in physiological state and the capability of self-recovery of balance coordination in pathological state.In nature, it is to maintain and restore ecological balance.

The intrinsic motivations of spontaneous harmonization of yin and yang are opposition and restriction, interdependence and mutual promotion, inter-containing and inter-induction, waxing and waning and transformation between yin and yang. Promoted by them, yin and yang can automatically incline to optimum state and keep developing forward.It is the comprehensive embodiment of the motion patterns of yin and yang and can be used to reveal the intrinsic mechanism of disease self-healing.

To sum up, opposition and restriction of yin and yang is the basic universal law of yin and yang, through which yin and yang within things can achieve equilibrium. Interdependence and mutual promotion between yin and yang emphasizes the relationship of interdependence and mutual promotion between yin and yang.Inter-containing is the premise of interdependence, mutual promotion, inter-deduction and transformation of yin and yang.When yin and yang intercourse in their motion and attain the optimum state, old things may die out and new things may come into existence.Waxing and waning of yin and yang is the form of movement of yin and yang, is the manifestation of opposition and restriction and interdependence and mutual promotion of yin and yang.Only when waxing and waning of yin and yang remains stable in certain ranges, can relative dynamic balance be achieved.Transformation between yin and yang is another basic form of movement of yin and yang.It is the result of waxing and waning of yin and yang.Movement of yin and yang is eternal, while balance of yin and yang is relative.Spontaneous harmonization of yin and yang is the capability and tendency of maintaining and restoring coordinating state between yin and yang.Balance of yin and yang is a relative dynamic balance, which is essential to the nature and to mankind.If the coordination balance is destroyed, abnormal phenomena in the nature will come up and pathological changes which will bring on diseases in human body will also appear.

III The application of yin-yang theory in TCM

Yin-yang theory is one of the philosophies in ancient China. It can reveal thegeneral rules of the development of things.Traditional Chinese medicine was also guided by yin-yang theory in its formation and development, therefore, yin-yang theory permeates into all levels of the theoretical system of TCM, analyzing tissue structures, physiological functions and pathological changes of human body and giving guidance to diagnosis and prevention of diseases.

1.Explaining tissue structure of human body

The human body is an integrated whole. Zang-fu, meridians and collaterals and the constituent that constitute human body can be divided into yin and yang at different levels according to the basic principles of yin-yang theory.

In terms of the anatomical locations, the upper part of the body is yang and the lower part is yin;the exterior is yang and the interior is yin;the back is yang and the abdomen is yin. In terms of the inner side and outer side of the limbs, the outer side of the extremities is yang and the inner side is yin.In terms of five zang-organs and six fu-organs, six fu-organs digests and transports food downward and it attributes to yang;five zang-organs produces and store essence inward and it attributes to yin.Among five zang-organs, the heart and the lung are located in upper energizer and attribute to yang, while the spleen, the liver and the kidney are located in middle energizer and lower energizer and attribute to yin.To be specific to each internal organs of the body, there are heart-yin, heart-yang, kidney-yin and kidney-yang and so on.

In conclusion, zang-fu organs and meridians and collaterals all can be generalized with yin and yang according to their locations（such as up and down, interior and exterior, surface and inside, front and back）and their functions to explain the unity of two opposites of tissue structures of human body.

2.Explaining the physiological functions of human body

The normal life activities of human body is the manifestation of the unity of opposites between yin and yang, therefore, the physiological functions of human body, no matter as a whole or partly, all can be described with yin and yang. The normal life functions of the body are the result of the balance of yin and yang.For example, in terms of the substances and functions of the body, the substances areyin and the functions are yang.With the substances as the basis, functions may take action, while the result of functions is the generation of substances.Both qi and blood are the basic substances that constitute human body and maintain life activities.But qi governs dynamic and attributes to yang, while blood governs static and attributes to yin.It is the opposition and restriction, interdependence and mutual promotion between them that maintain the balance between them.Movement of qi of the zang and fu-organs is anther embodiment of the unity of opposites between yin and yang.For example, lung qi descends and liver qi ascends;heart fire descends and kidney water ascends;spleen governs ascent of the clear, while stomach governs descent of the turbid.

3.Explaining the pathological changes of human body

Yin-yang theory is employed to analyze the occurrence, development and changes of diseases, i. e.imbalance of yin and yang, which is a series of pathological changes caused by pathogenic factors that destroy the coordination and balance of yin and yang.

According to their properties, pathogenic factors can also be divided into yin and yang. For example, in terms of six pathogenic qi-wind, cold, summer, dampness, dryness and fire, wind, summer, fire and dryness are yang pathogens, while cold and dampness are yin pathogens;for internal injuries due to diet, if it is caused by taking too much spicy and thick-taste food, it is yang pathogens;if it is caused by taking too much cold food, it is yin pathogens.Yang pathogen in human body will result in yang excess, while yin pathogen in human body will result in yin excess, both of which will cause a series of pathological changes.In the struggle between healthy qi and pathogenic factors, healthy qi will be consumed, which will develop into complex pathological changes such as yin or yang deficiency.

3.1　Yin or yang excess

Yin or yang excess refers to the pathological changes when yin or yang is excessive and over the normal levels.

3.1.1　Yang excess

Yang excess refers to"excess of yang leading to heat syndrome",which means that with the action of pathogenic yang, the functions of the organs may be excited and produce excessive heat. In clinic it is manifested by a series of excessive heat syndromes.

"Yang in excess leading to yin disease"refers to the pathological state that yang excess restrict yin too much that yin is weakened. This is the process of"yang waxes and yin wanes".Diseases are lack of yin fluid caused by excess of yang heat damaging yin fluid."Disease"here refers to decreasing due to injuries.

When warm-heat pathogens invade the body, excessive heat syndromes may appear, such as high fever, dysphoria, red face and rapid pulse, which are called"excess of yang leading to heat syndrome". Excess of yang is naturally to consume yin of the organs, which may result in moist shortage and dryness, such as thirst, scanty urine, red tongue and less fluid, etc.,which is called"yang in excess leading to yin disease".

3.1.2　Yin excess

Yin excess refers to"excess of yin leading to cold syndrome",which means that with the invasion of yin pathogen, functions of the body is blocked and yang is restricted. In clinic it is manifested by a series of excessive cold syndromes.

"Yin in excess leading to yang disease"refers to the pathological state that yin excess restricts yang too much that yang is weakened. This is the process of"yin waxes and yang wanes".Diseases are lack of yang caused by excess of yin cold damaging yang.

When cold pathogen invades Taiyin, excessive cold syndromes may appear, such as pale, cold, pain and coldness in stomach, clear and thin diarrhea, light-colored tongue with white coating, delay sunken pulse or tense sunken pulse, etc.,which is called"excess of yin leading to cold syndrome". Since yin can restrict yang, excess of yin is naturally to consume and restrict yang of the organs, which will result in deficiency of yang.Therefore, with the development of the disease, syndromes of cold limb, shrinkage, slow sunken pulse or thin pulse may appear.This is"yin in excess leading to yang disease".

3.2　Yin or yang defciency

Yin or yang deficiency refers to the pathological changes when yin or yang is lower than the normal levels. If yin or yang is insufficient, one can not restrict the opposite one, so the opposite one becomes excessive.

3.2.1　Yang defciency

Yang deficiency refers to the pathological state of excess of yin caused by reduction of yang restriction to yin, which results from the deduction of the functions of warming and promoting due to the deficiency of yang-qi. In clinic, it is manifested as deficiency-cold syndromes, i.e."yang deficiency resulting in cold syndrome".

For example, yang deficiency of the body may cause deficiency-cold syndromes of"yang deficiency resulting in cold syndrome",such as pale complexion, cold limbs, tiredness and shrinkage, spontaneous perspiration and feeble pulse.

3.2.2　Yin defciency

Yin deficiency refers to the pathological state of excess of yang caused by reduction of yin restriction to yang, which results from the deduction of the functions of moistening and restricting due to the deficiency of yin fluid. In clinic, it is manifested as deficiency-heat syndromes, i.e."yin deficiency resulting in heat syndrome".

Deficiency of yin caused by long illness may result in deficiency heat syndrome of"yin deficiency resulting in heat syndrome",such as tidal fever, night sweating, feverish sensation in chest, palms and soles and thin rapid pulse.

Either cold syndrome or heat syndrome caused by yin or yang excess attributes to sthenia syndrome, while cold syndrome or heat syndrome caused by yin or yang deficiency attributes to asthenia syndrome.

3.3　Mutual consumption of yin and yang

Mutual consumption of yin and yang refers to the pathological changes caused by consumption of yin or yang causing deficiency of the other. Its theoretical basis is interdependence and mutual promotion of yin and yang, therefore, when either yin or yang is deficient, pathological changes of"consumption of yang affecting yin"due to"waning of yang causing waning of yin",and"consumption of yin affecting yang"due to"waning of yin causing waning of yang"may occur.

Mutual consumption of yin and yang includes two kinds of pathogenesis, i. e."consumption of yang affecting yin"and"consumption of yin affecting yang".

3.3.1　Consumption of yang affecting yin

Consumption of yang affecting yin means that when yang deficiency reaches certain extent, generation of yin reduces, which may cause the pathological process of yin deficiency. In clinic, it is manifested as asthenia syndrome of both yin and yang with yang deficiency as the main.

3.3.2　Consumption of yin affecting yang

Consumption of yin affecting yang means that when yin deficiency reaches certain extent, it cannot nourish yang, which may cause the pathological process of poor generation of yang. In clinic, it is manifested as asthenia syndrome of both yin and yang with yin deficiency as the main.

To sum up, though pathological changes of diseases are complicated, they can be explained with imbalance between yin and yang（excess or deficiency）;therefore, imbalance between yin and yang is the basic pathogenesis of the occurrence and development of diseases.

4.Serving as the guide to diagnosis of diseases

To diagnose diseases with yin-yang theory is to explain the disease location, nature and properties of various syndromes with yin and yang, which can be used as the guiding principle of syndrome differentiation.

4.1　Analyzing the information collected with four diagnostic methods

Yin-yang theory can be used to analyze the information collected with four diagnostic methods-observation, listening, interrogation and pulse-taking, explaining the yin-yang property of the signs and symptoms related to the disease.

In terms of inspection, brightness and luster attribute to yang, while dimness and darkness attribute to yin;yellow and red attribute to yang, while blue, white and black attribute to yin. In terms of listening, loud and strong voice attributes to yang, while low and weak voice attributes to yin;strong and loud breath attributes to yang, while weak and low breath attributes to yin.In terms of interrogation, hot feeling attributes to yang, while cold feeling attributes to yin;dry mouth and thirst attributes to yang, moist mouth attributes to yin.In terms of pulse-taking, to differentiate yin or yang of the pulse:in terms of location, cun pulse is yang and chi pulse is yin;in terms of frequency, rapid pulse is yang, late pulse is yin;in terms of shape, floating, full and slippery pulse is yang, while sunken, rough and thin pulse is yin.To take pulse of the parts, those hurt when pressing attribute to yang and those feeling good when pressing attribute to yin.

4.2　Summarizing the symptoms of diseases

In differentiating syndromes, yin, yang, exterior, interior, cold, heat, deficiency and excess are regarded as eight principles, among which, yin and yang are the general principles, i. e.exterior, heat and excess attribute to yang, while interior, cold and deficiency attribute to yin.

In clinical syndrome differentiation, no matter what symptoms, signs, or syndromes, it is required to differentiate yin and yang so as to grasp the nature of the disease.

5.Employed for disease prevention and treatment

Regulating yin and yang, i. e.to take all measures to keep and restore the balance of yin and yang, is the basic principle of preventing and treating disease.

5.1　To instruct health-preserving

Health-preserving means to keep healthy. It aims at keeping healthy and preventing diseases.The basic principle of health-preserving is to follow the changing rules of yin and yang in the nature, to be in coordination with the changes of yin and yang, so as to keep fit and prevent the occurrence of diseases.For example, in spring and summer yang qi is in excess, while in autumn and winter yin qi is in excess, so from the aspect of living and food taboos, in spring and summer, yang of the body should be protected to prevent yang qi being damaged, while in autumn and winter yin of the body should be protected to prevent yin fluid being damaged.In this way we can gain the aim of preventing diseases and prolonging life.

5.2　To determine treating methods and principles

Since imbalance between yin and yang is the basic pathogenesis of the development of diseases, to adjust yin and yang is the basic principle of disease treatment, i. e.to grasp further the state of imbalance between yin and yang and to adjust the excess or deficiency of yin and yang and to restore balance between yin and yang with drugs, acupuncture and moxibustion or other therapies.

5.2.1　To treat excess of yin and yang

The common characteristic of syndromes caused by excess of yin or yang is that they are manifested as excess syndromes caused by pathogenic qi;therefore, to reduce the excess, i. e."treating excess with purgation"is the principle of the treatment.For excess-heat syndromes caused by excess of yang, it is better to use cool and cold drugs to restrict the excessive yang and to remove the heat, which is the method of"treating heat with cold drug";for excess-cold syndromes caused by excess of yin, it is better to used warm and heat drugs to remove the excessive yin and to clear the cold, which is the method of"treating cold with hot drugs".

5.2.2　To treat defciency of yin and yang

The common characteristic of syndromes caused by deficiency of yin oryang is that they are manifested as deficiency syndromes caused by insufficiency of healthy qi;therefore, to make up the excess, i. e."treating deficiency with tonification"is the principle of the treatment.For deficiency-cold syndromes caused by deficiency of yang, it is better to use yang-invigorating drugs to nourish yang and to restrict the excessive yin;for deficiency-heat syndromes caused by deficiency of yin, it is better to use yin-nourishing drugs to tonify the deficient yin and to restrict the excessive yang.

For deficiency syndromes of yin and yang, the treatment method can also be determined based on the theories of interdependence and mutual promotion of yin and yang as well as waxing and waning of yin and yang, i. e.reinforcing yang from yin and reinforcing yin from yang.Reinforcing yang from yin means that when treating deficiency-cold syndromes caused by yang deficiency, one or two yin-nourishing drugs should be added to promote the generation of yang;reinforcing yin from yang means that when treating deficiency-heat syndromes caused by yin deficiency, it is better to add one or two yang-invigorating drugs to facilitate the generation of yin.

5.2.3　To treat mutual consumption of yin and yang

The key of treating asthenia syndrome of both yin and yang caused by mutual consumption of yin and yang is to differentiate whether it is consumption of yang affecting yin or consumption of yin affecting yang. For asthenia syndrome of both yin and yang caused by consumption of yin affecting yang, it is better to nourish yin with warming yang as supplementation;for asthenia syndrome of both yin and yang caused by consumption of yang affecting yin, it is better to warm yang with nourishing yin as supplementation.

5.3　To analyze and generalize the medicine performance

Yin-yang theory can be used to treat diseases, and also can be used to summarize the performance of medicines, which is the guideline for clinical medication.

Medicine performance depends on the property, taste and ascending, descending, floating and sinking of medicines, which in turn can be summarizedand explained with yin and yang.

Property of medicines refers to"four properties"of medicines i. e.cold, hot, warm and cool, among which cold and cool attribute to yin and warm and hot attribute to yang.Medicines with cold or cool properties can remove heat and relieve fire, which can be used for heat syndrome to reduce and eliminate heat of the organs;medicines with hot or warm properties can scatter cold and warm the interior, which can be used for cold syndrome to reduce or eliminate cold of the organs.

Five tastes are sour, bitter, sweet, pungent and salty tastes. Some medicine may have flat or astringent tastes.According to their actions, five tastes can also be divided into yin or yang, among which pungent, sweet and flat tastes attribute to yang, and sour, bitter and salty tastes attribute to yin.For example, pungent and sweet tastes are dispersing and attribute to yang;while sour, bitter and salty tastes are emetic and purging and attribute to yin.

Ascending, descending, floating and sinking refer to the functional trends of medicines in human body. Ascending is to go up;floating is to float outward to the surface.Ascending and floating medicines are most ascending and dispersing in nature, therefore, they attribute to yang.For example, Chaihu and duckweed are herbs with ascending and floating functional trend.Descending is to go down;sinking is to sink inward to the interior.Descending and sinking medicines are most converging, purging and tranquilizing, therefore, they attribute to yin.For example, Chenxiang and lodestone are medicinals with sinking and descending functional trend.

In conclusion, yin-yang theory plays significant role in guiding prevention and treatment of diseases. To preserve health and prevent diseases should adjust the dietary regimen in line with the changes of yin and yang of four seasons.To treat diseases should determine the treating principle according to the excess or deficiency of yin and yang of the syndromes and select corresponding medicines according to the yin-yang properties of the medicine, so as to adjust the imbalance of yin and yang, restore them to an equilibrium state and achieve the aim of curing disease.