Traditional Chinese Medicine : Basic Ying Yang

The Yin-Yang and Five Elements Theories

The theories of Yin-Yang and Five Elements were the creation and development of the ancient Chinese through their long and faithful tradition of observing nature's cycles and changes. They held that wood, fire, earth, metal, and water were the basic substances constituting the material world. These five basic substances were considered an indispensable part of daily life. They also noted that the material world is in a constant state of flux due to the dynamic movement and mutual antagonism of yin and yang factors.

The ancient Chinese applies these two theories in the medical field to explain the physiological activities and pathological changes of the human body, and to serve as a guide to the clinical treatment on the basis of syndrome differentiation. These theories have become in important component of traditional Chinese medicine.

The Theory of Yin-Yang

The Yin Yang theory holds that all phenomena consist of two opposite aspects, yin and yang, which are variously defined as: up and down, left and right, light and dark, hot and cold, stillness and movement, substance and function, etc. The movements and changes of yin and yang give impetus to the development of everything or in the words of the Suwen, "Yin and yang are the law of Heaven and Earth, the outline of everything, the parents of change, the origin of birth and destruction...."

Yin and yang represent two opposite aspects of every object and its implicit conflict and interdependence. Generally, anything that is moving, ascending, bright, progressing, hyperactive, including functional disease of the body, pertains to yang. The characteristics of stillness, descending, darkness, degeneration, hypoactivity, including organic disease, pertain to yin.

The nature of yin and yang is relative. According to Yin-Yang theory, everything in the universe can be divided into the two opposite but complementary aspects of yin and yang and so on ad infinitum. For example, day is yang and night is yin, but morning is understood as being yang within yang, afternoon is yin within yang, evening before midnight is yin within yin and the time after midnight is yang within yin. As the Suwen states, "Yin and yang could amount to ten in number, be extended to one hundred, to one thousand, to ten thousand and ever to the infinite."

1. The Basic Content of Yin-Yang Theory

The Opposition of Yin and Yang
The theory of Yin-Yang holds that every object in the universe consists of two opposite aspects which are in continual mutual restriction and interaction. The alternation of the four seasons is an example. The spring is warm and the summer hot. This is due to the rising of yang qi which restricts the autumn cool and the winter cold. Alternately, the coolness of autumn and cold of winter arise because of the ascendancy of yin that restricts the spring warmth and summer heat. According to Yin-Yang theory, the seasonal cycle is the outcome of the mutually restrictive and mutually consuming-increasing activities of yin and yang. Either side of the two opposites always restricts and acts on the other. This process of mutual restriction and interaction is the operation of yin and yang, without which change would not occur. Thus the two opposites of yin and yang do not exist as an entity in a still and unconcerned state. They constantly interact with each other, hence the alteration and development of an object.

Yin and Yang Interdependence
Yin and yang are at once in opposition and in interdependence. They rely on each other for existence, coexisting in a singe entity. Each of the two aspects is the condition for the other's existence and neither can exist in isolation. For example, daytime is yang, night in yin, without day there would be no night; upper is yang, lower is yin; left is yang, right is yin, etc., each pair exists in a state of mutual dependence, and without its opposite it could not exist. The interdependent relationship of yin and yang is described in the Suwen, "Yin is installed in the interior as the material foundation for yang, while yang remains on the exterior as the manifestation of the yin function." This is a traditional explanation of the interdependence of yin and yang.

The Mutual Consuming-Increasing Relationship of Yin and Yang
The yin and yang aspects within an object are not quiescent, but in a state of constant motion. They can be described as being in a state where the lessening of yin leads to an increase of yang, or vise versa. Taking the transformation of the seasons as an example, in terms of the Yin-Yang theory, the process of transition from winter cold through spring warmth into summer heat demonstrates the process of a lessening of yin leading into an increasing of yang. While the transition from the heat of summer to the cold of winter is the lessening of yang leading to an increasing of yin.

Regarding the human body's functional activities, which are considered yang, the consumption of nutrient substances, which are considered yin, results in the lessening of yin to the increase of yang. As the metabolism of nutrient substances (yin) exhausts the functional energy (yang) to a certain extent, this is understood as a lessening of yang to the increase of yin. Under normal conditions the mutual consuming and increasing of yin and yang maintain a relative balance. Under abnormal conditions there is an excess or insufficiency of either yin or yang which leads to the occurrence of disease.

Yin and Yang's Mutual Transforming Relationship
In certain circumstances and at a certain stage of development, each of the two aspects of yin and yang, within an object, will transform from yin into yang and from yang into yin. The mutual consuming-increasing of yin and yang is a process of quantitative change, and the mutual transformation of yin and yang is a process of qualitative change. The Suwen comments, "Extreme cold will bring about heat, and extreme heat will induce cold..."furthermore, "Excessive yin may cause yang syndromes or tend to be transformed into yang and vice versa." These are the features and conditions of the mutual transformation of yin and yang.

The mutual transformation of yin and yang is often seen during the development of a disease. For example, if a patient has a constant high fever, which is suddenly lowered, accompanied by a pale complexion, cold limbs, extremely feeble pulse (the danger symptoms of yin cold syndromes), we may say that the disease has transformed from a yang syndrome into a yin syndrome. Under these circumstances, proper emergency treatment should warm the limbs to make the pulse normal. The yang qi will recover, and the danger will be removed. Thus yin syndromes can change into yang syndromes. Clinical practice provides other examples of the mutual transformation of yin and yang. It is common in clinical practice to have exterior syndromes transform into interior syndromes or vice versa and shi (excess) syndromes may change into xu (deficiency) syndromes or vice versa.

The above-mentioned relationships of mutual opposing, depending, consuming-increasing, and transforming of yin and yang are the basic content of Yin-Yang theory. Furthermore, these four relationships between yin and yang are not so isolated from each other but interconnect with and interact upon each other.(See Fig. 1)

2. The application of Yin-Yang Theory to the Field of Traditional Chinese Medicine

The Anatomical and Histological Structure of the Human Body
The Yin-Yang theory asserts that the human body is an organic whole, and there exists an organic connection between all tissues and structures. Yet, at the same time, each of them can be divided into the opposite aspects of yin and yang.

Viewing the body as a whole, the portion above the waist pertains to yang and that below belongs to yin; the exterior of the body is associated with yang, while the interior is associated with yin; the back is considered yang and the front, yin; the lateral aspect is yang and the medial, yin.

The zang-fu organs also have yin and yang aspects, the six fu organs are considered yang while the zang organs are yin. Each of the zang-fu organs itself can again be divided into yin or yang; for example, heart yin and heart yang or kidney yin and kidney yang. However complex, all human body structures and tissues can be generalized and explained by the yin-yang relationship. As the Suwen says, "Man has physical shape which is inseparable from yin and yang."

The Physiological Functions of the Human Body

The Yin-Yang theory considers the normal vital activities of the human body to be the result of the relative balance between yin and yang. In traditional Chinese medicine, the physiological functions of the organs and their substances are inseparably related to yin and yang. For example, the activities (yang) of a particular organ are based on that organ's substance (yin) and when either of these aspects is absent, the other cannot function. Thus the result of physiological activities is to constantly promote the transformation of yang into yin essence. If yin and yang cannot maintain relative balance and interaction, they will separate from each other ending the life that depends upon them. As the Suwen says, "When yin keeps balance with yang and both maintain a normal condition of qi, then health will be high-spirited. A separation of yin and yang will lead to the exhaustion of essential qi."

The Pathological Changes of the Human Body
The Yin-Yang theory holds that disease is a result of an imbalance between yin and yang which leads to the hyperactivity or hypoactivity of yin and yang. The occurrence and the development of a disease are also related to zheng qi (body resistance or antipathogenic factors) and xie qi (pathogenic factors). The Yin-Yang theory can be used to generalize the interacting relations between body resistance and antipathogenic factors. Pathogenic factors are divided into yang-natured pathogenic factors and yin-natured pathogenic factors, while zheng qi includes yin essence and yang qi. Yang pathogenic factors may bring about hypoactivity of bodily yang which leads to injury of yin; a heat syndrome results. If the disease is caused by yin pathogenic factors, it may give rise to hypoactivity of yin followed by the injury of yang; a cold syndrome will result. When yang is deficient it fails to restrict yin in the balanced relationship between the two giving rise to xu (deficiency) which is a cold syndrome. The xu heat symptoms complex, however, is caused by a yin deficiency and yang excess. Pathological changes of disease are varied, but can be generally explained in terms of yin-yang imbalance: yin excess causes cold syndromes, yang preponderance leads to heat syndromes, yang deficiency causes cold syndromes, and yin deficiency leads to heat syndromes.

Diagnosis of Diseases
The basic causative factor of disease is an imbalance between yin and yang. Therefore, no matter how intricate and volatile the clinical manifestations are, they can still be summarized into two categories: yin syndromes and yang syndromes. A correct diagnosis depends upon a clear classification of yin and yang syndromes or in the words of the Suwen, "If one is good at diagnosis, they should differentiate the yin from yang after the observation of color (of complexion, tongue, urine, stool, etc.) and feeling the pulse." The four diagnostic methods (inspection, auscultation and olfaction, inquiry, and palpation) also use yin and yang, for example: interior, xu (deficiency), and cold syndromes are considered yin; exterior, shi(excess), and heat syndromes are considered yang; bright color is yang, dim color is yin; a sonorous voice indicates yang, a low voice i yin; feeble and weak respiration is yin, coarse breathing is yang; superficial, rapid, and forceful pulses are yang, slow, deep feeble, and weak pulses are yin.

Applications in Clinical Treatment
Since imbalance and fluctuation of yin and yang are considered the basic causative factors of disease occurrence and development, treatment must readjust yin and yang to their basic state of relative balance. For example, if pathogenic heat, a yang disease causative factor, is overabundant, it consumes the yin fluid and affects the superabundant yang of the body. In this case, the cold methods for heat syndromes (for example, the use of herbs with a "cold" nature to cure "heat" illnesses) is the prescribed treatment. If pathogenic cold is in excess, it will damage the yang qi and exert influence on the body's remaining yin. In this case, the heat method for cold syndromes (for example, the use of herbs with a "hot" nature to cure "cold" illnesses) is sued. Conversely, in cases where yang excess if caused by insufficient yin fluid failing to restrict yang or where yin preponderance is due to yang qi deficiency being unable to control yin, then treatment should reinforce the insufficient yin or yang. The general principle is, "Treat yin for yang diseases, and treat yang for yin disorders."

In medical treatment, the theory of yin and yang is not only used to decide the principles of treatment. This theory is also generally applied to the properties, flavor and action of Chinese herbal medicine as a guide to the clinical administration of herbs. For example, drugs with cold, cool or moist properties are classified as yin and drugs with the opposite properties are classified as yang. Herbs with sour, bitter, or salty flavors are yin, while those with pungent, sweet, or insipid flavors are yang. Drugs with an astringent or descending action are yin and those with an ascending and dispersing action are yang. In clinical treatment, we should determine the principles of treatment based on an analysis of the yin and yang conditions present in terms of their difference yin-yang properties and actions. The goal of clinical treatment is to restore of healthy yin-yang properties and actions. The goal of clinical treatment is to restore a healthy yin-yang balance in the patient.