The Huang Di Nei Jing (The Yellow Emperor’s Classic of Medicine) was written by a number of physicians between 770 B.C. and 2 A.D. This book brought together all aspects of Traditional Chinese Medicine (TCM) and systemised them. It used the philosophical theories of the time when man was seen as a microcosm that reflected the macrocosm of the universe. The theory expounded in the Nei Jing has remained the dominating theory of Chinese medicine to the present day.

 

The book was written in two parts the Su Wen (Plain Questions) and Ling Shu (Classic on Acupuncture). The Huang Di Nei Jing, from here on referred to as the Nei Jing, is the most revered piece of Chinese medical literature often referred to as the bible of TCM. It brought many aspects of TCM together in an open way, providing the physician with a solid grounding in principals and methodology.

 

This article looks at one of the theories that is central to not only Chinese medicine but also to Chinese philosophy and that forms the very roots of TCM. This theory is the Yin Yang Theory.

 

 

The concept of yin and yang predates the Nei Jing by thousands of years, legend tells of the August One, Fu Xi, giving the eight trigrams to man in 3000 B.C. Although the legend may not be completely true ancient carvings on animal bone and tortoise shell have been found that date back thousands of years.

 

The eight trigrams are a series of symbols made up of three tiers of broken and unbroken lines; the broken line represented Yin (- -) and the unbroken line Yang ( -- ). These carvings were used for divination by being tossed into a fire and the ones that cracked would reveal a message. This system of divination was modified by the emperor Zhou Wen Wang and his son Zhou Gong, and the I Ching was born. The I Ching expressed the changes and movement of the universe using the theory of yin and yang.

 

The I Ching had a huge impact on Chinese thinking from that point onwards, not only in terms of philosophy and divination but it also laid the foundations for TCM philosophy. The great doctor Sun Si-Miao (581-682 A.D.) said, “if you do not know the I Ching, you cannot understand medicine at all.” This emphasises the importance of the principals laid out in the I Ching and also the central role that Yin and Yang play in TCM.

 

The Tao is the basis to all Chinese philosophical thought; it is seen as the ‘way’ or method of maintaining the harmony between all things in nature. Yin and Yang represent the two polar opposites that make up all that is in existence; they are the two supreme components of the Tao. The ancients saw that man must live in a way that emulated the course of the universe. If man did not live in harmony with his surroundings then illness would beget them. The first book of the Nei Jing starts by discussing this very subject in the chapter called ‘Treatise on the Natural Truth in Ancient Times’.

 

 

The ideograms for Yin and Yang can be translated in many ways but it is thought that they originally referred to the ‘shady side of the mountain’ and the ‘sunny side of the mountain’. From meaning shady, Yin also came to embody moon, earth, night, water, cold, darkness and female. Likewise Yang’s meaning developed from light into sun, heaven, day, fire, heat, and male. Yin and yang were never seen as static or separate entities; day always changes into night, summer follows spring just as winter will always follow autumn.

 

The Nei Jing tells us that “Heaven was created by an accumulation of Yang, the element of light. Earth was created by an accumulation of Yin, the element of darkness.” Man lived between heaven and earth and therefore was seen to be composed of both yin and yang. This exemplifies the Chinese viewpoint that all things in the universe are integrated and inseparable.

 

In medical theory this was developed in to a way of categorizing the relationship between certain parts of the body and even classification of disease (i.e. The Eight Principals). The Nei Jing states: “Yin is active within and acts as a guardian of yang; yang is active on the outside and acts as a regulator of yin.” 

 

Here it explains that Yin is internal whereas Yang is external. Therefore the organs are regarded Yin when compared to the channels which are Yang. This concept is purely comparative though; the channels can be seen as Yin when compared to the body surface which is Yang. This comparison can be used to show the progress of a disease, a disease is seen to worsen as it moves inwards starting by affecting the Yang channels and progressing inwards to the Yin channels.

 

The comparison also highlights another aspect of Yin and Yang; there is never a pure form of Yin or Yang, as the seed of its opposite will always be present within itself. This could has been seen in the example with the channels, depending in which way the channels were looked at revealed different aspect. Another example in would be; ‘Within Yin illness characterized by coldness, there maybe aspects of Yang such as sharp, forceful contractions.’ Yin and Yang depicted in the Tai Chi symbol always are shown to hold the seed of the other.

 

 

The Nei Jing discuses in great depth the subdivisions of Yin and Yang with reference to the body. In nature there were three divisions, namely Heaven, Earth and Man. These three regions were also recognized within the human body. The three regions were held to be composed of one part Yang and one part Yin, the names attributed to them are; Tai Yang, Shao Yang, Yang Ming, Tai Yin, Shao Yin and Jue Yin.

 

The Nei Jing gives a complete description of the organs that were present in each of these regions and the relationship with the other regions; this is the Zangfu Theory. The names of the regions also relate to the channels that run through them, these names have stayed the same since the writing of the Nei Jing, although the organs are no longer referred to in this manner.

 

Yin and Yang are an inseparable concept without one the other cannot exist; this emphasizes the holistic viewpoint of this theory. Lao Tzu says, “Indeed, the hidden and the manifest give birth to each other. Difficult and easy complement each other. Long and short exhibit each other.” This is another way in which TCM uses Yin and Yang to categorize various parts of the body, internal and external, front and back, upper and lower etc.

 

Yin and Yang are in a continually dynamic state that continues to shift. They oppose each other and yet rely on each other for existence. Therefore all things in nature exhibit this continual struggle. At midday Yang is strongest but as the day progresses Yang fades as Yin grows stronger. By midnight Yin is at its strongest and Yang at its weakest, as dawn approaches Yang again grows stronger and Yin’s power fades until Yang reaches its strongest once again at midday. This cycle is never ending and exhibits perfect balance; it can be seen again in the rotation of the seasons and in the body’s fight against disease.

 

When Yin or Yang reach their extreme states they will transform into their opposite. This is often seen clinically with very severe cases. For example ‘the patient runs a high fever, has a red complexion, feels irritable and restless and exhibits rapid and strong pulse. However, all of a sudden, he feels listless, his temperature becomes lower, his face turns pale, and his pulse condition becomes so fine that the pulse is almost cut off.’ (Zhang 1990, p44)

 

The Nei Jing saw that health and long life were in the hand of man. For man knew the ways of the Tao as a means of maintaining perfect balance of Yin and Yang. The first chapter of the Nei Jing deals with the balance of Yin and Yang and their role in aging. It states “those who have the true wisdom remain strong, while those who have no wisdom grow old and feeble”. Aging was perceived to be due to the decline of Yin. Yin is substantial and represents the body fluids and secretions. The Nei Jing states ‘when at this stage (old age), the five viscera are dry, the muscles and bones decay…’ The sustenance of Yin is no longer able to fuel the functional activities of Yang and the body grows old. If man followed the Tao, Yin and Yang would stay in balance and life would be prolonged.

 

The Nei Jing brought together the ideas of Yin and Yang and successfully applied them to TCM in such a way, later generations were able to expand upon the knowledge to further explain health and disease.

 

Zhang Zhong Jing wrote another classic of TCM called the Shang Han Za Bing Lun (Treatise on Febrile Diseases Caused by Cold and Miscellaneous Disease). By using the workings of Yin and Yang as set up in the Nei Jing, he was able to explain the progress of pathogens through the Yin and Yang channels of the body. The book also contains many formulas, by using the principals of Yin and Yang to treat disease, he was able to cure disease so effectively that these formulas are still used today, some 1,700 years later.

 

By using the yin and yang to define diseases by their nature, location and relative deficient or excess condition of the body, the Nei Jing set up the structure for the Eight Principals of Diagnosis. Using this method Zhang wrote formulas that treated disease of excess and heat syndrome (Yang) with herbs of cold nature (Yin), and disease of deficiency and cold syndrome (Yin) with herbs of warm nature (Yang). By using the simple interplay of Yin and Yang, balance is restored and disease is cured.

 

The principals of Yin and Yang can also been seen in modern western medicine. The term homeostasis refers to the internal systems of the body ability to adapt and maintain balance in spite of external changes. Maintaining the balance of Yin and Yang was seen as of the utmost importance in the Nei Jing. It was the key to health and long life, Chinese physicians say "Yin ping Yang mi, jing shen nai zhi" (If yin and yang are balanced in form, our essence and spirit will be good).

 

Balance is just as important now in western medicine, ‘Homeostasis is absolutely vital; a failure to maintain it soon leads to illness or even death.’ (Martini 2001, p12)

 

An example of homeostasis in western terms is the control of body temperature. As the temperature outside of the body rises so does the body temperature (normal balance is disturbed). Sensors trigger a controlled reaction from the hypothalamus that causes stimulation of the blood vessels supplying the skin and the sweat glands. The blood vessels enlarge allowing a greater amount of blood to pass near the skin and heat is lost to the environment. Sweat glands secrete fluid onto the skin which speeds evaporation again increasing the amount of heat lost. As the body temperature lowers, the stimulation of the blood vessels and sweat glands ceases and normal body temperature is restored (balance is regained).

 

Many reactions occur all the time in the body to maintain balance of the internal systems. The ancient Chinese saw these reactions and attributed them to the interplay of Yin and Yang.

 

 

The Nei Jing compiled and systemized the theories of Yin and Yang so that generation after generation could build upon them. Now Yin-Yang theory is applied to all areas of TCM.

 

It provides a system for classification of the tissues and structures of the human body. With the many facets associated to Yin and Yang they can classify the difference between the zang and the fu organ. They can also be used to differentiate between function and substance of the organs, which in turn explains the physiological functioning of the body. ‘Physiological function is based on substance. Without substance (essence of life, blood, constructive energy and body fluid) there would be no source for functions. But the metabolism of substance must depend on the performance of function.’ (Zhang 1990, p48)

 

One cannot survive without the other. If imbalance between the two forces occurs then the theory can be applied to describe the pathological syndromes that occur. This includes syndromes of excess, heat and hyperfunction (Yang) and syndromes of deficiency, cold and hypofunction (Yin). The two factors are so strongly connected that if one dominates for too long it will eventually damage itself due to that fact that it relies on its opposite.

 

The theory can be utilised in diagnosis. By use of the Eight Principals the doctor can accurately diagnose disease. Strength of voice, demeanor, colour of face and tongue, and type of pulse are all subject to interpretation by Yin and Yang. Finally disease once diagnosed accurately can be treated by restoration of the balance between yin and yang, heat is cooled, hyperactivity slowed and deficiency tonified.

 

The Nei Jing sums up perfectly the importance of yin and yang by saying:

 

“The principle of Yin and Yang is the basis of the entire universe. It is the principle of everything in creation. It brings about the transformation to parenthood; it is the root and source of life and death…”

 

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