Zhong qi
Zhong qi is found mainly in the chest. It nourishes the structures and functions of the xin-heart and fei-lung.

Nourishing qi
Nourishing qi circulates in the channels and collaterals, mainly in the viscera

Defensive qi
Defensive qi is in the muscles and skin. It circulates outside the channels, in the subcutaneous tissues, and it defends the body against invasion by pathogens.

The original qi is nourished and maintained by qi derived after birth. These combine to form genuine qi, i.e. the total sum of qi in the healthy body. This contrasts with pathogenic factors that are known as pathogenic qi.

Blood
The nutrients from food are digested by the pi-spleen and stomach and they are then transported to the xin-heart and fei-lung and turned into red (oxygenated) blood by qi. The essence of shen-kidney produces bone marrow, and bone marrow uses the digested food to produce blood.
Qi of shen-kidney promotes digestion by pi-spleen, which in turn strengthens the xin-heart and fei-lung. This interaction therefore promotes haemopoesis.

There is a close relationship between qi and blood. The formation and circulation of blood depends on qi, whereas the formation and distribution of qi, as well as the health of the various organs of the body, is dependent on adequate nourishment from the blood. If the flow of blood ‘stagnates’ the circulation of qi is ‘retarded’ and, conversely, if the circulation of qi is ‘retarded’ then the blood flow ‘stagnates’.

Body Fluid
Body fluid is formed from food and drink. It exists in the blood, the tissues, and all the body openings and cavities.

V. The Pathogenesis of Disease
In traditional Chinese Medicine various elements and other factors cause disease. These are known as pathogenic factors or pathogens. Normally the human body is able to resist pathogens and maintain a healthy balance between the body and the environment. This ability is a function of normal qi, especially the defensive qi.

Disease develops because normal qi is unable to resist the onslaught of the pathogenic qi; if pathogenic qi overwhelms normal qi then a functional disturbance of the body results. The major principle of treating a disease in Chinese medicine is to strengthen and protect normal qi and maintain a healthy body. In ancient China a physician was only paid while his patient was healthy, not while his patient was ill!

Pathogenic Factors
These are divided into three main groups, exogenous pathogens, mental pathogens and various miscellaneous pathogens. ‘Phlegm and humour’ and ‘stagnant blood’ are pathological products; once they are formed new pathological changes will ensue so they are considered to be secondary pathogens.

Pathological factors serve as a generalization of clinical symptoms and signs, reflecting the struggle of normal qi and pathogenic qi. By differentiating the clinical symptoms and signs the cause of the disease can be traced, and then treatment can be determined. In order to do this the diseased organs must be defined and the pathogen causing that disease must also be diagnosed. This is called the ‘determination of treatment on the basis of the differentiation of a syndrome’, and it is the basis of diagnosis and treatment in Chinese medicine.

The Exogenous Pathogens
These refer to six relatively abnormal meteorological conditions; wind, cold, summer heat, damp, dryness and heat (fire, warmth). The diseases caused by these pathogens include most viral, bacterial and protozoal diseases and some ‘allergic’ conditions such as urticaria.

cold and damp normal qi of
invade pi spleen pi-spleen is
impairing its function       overpowered

symptoms of disease- impairment of the
anorexia. abdominal distention, function of pi-spleen
pain, diarrhoca, cold extremities,
greasy white tongue, deep thready pulse

Wind
This pathogen is characterized by movability (of symptoms) and changeability. The clinical manifestations are abnormal limb motion, such as spasm or twitching, and a wandering symptomatic site as in urticaria or arthralgia. The symptoms may vary in intensity and they usually include a dislike of wind, fever, sweating, headache and an itchy throat.

Cold
Invasion of cold will consume the yang causing a contraction of the channels and the blood vessels, and therefore a poor circulation of qi and blood. The symptoms are those of a slight fever, a dislike of cold, hypohydrosis, headache, muscular pain and spasm, and occasionally a dark blue and painful area in the local muscles and skin; a frozen shoulder is a good example of the pathogen cold.

Summer heat
This only occurs in the summer; it damages the yin and may progress to affect the level of consciousness. The symptoms are excessive body heat, profuse sweating, thirst, a dry mouth, dry red skin and, in severe cases, delirium (this is known as heat exhaustion in Chinese medicine). Summer heat may combine with wind and cause convulsions. Summer heat often combines with damp to produce dizziness, nausea, a stuffy sensation in the chest and general malaise.

Damp
Diseases caused by damp are sticky, muddy, greasy and stagnant. Damp causes a generalized heavy feeling associated with distension, dizziness and a heavy head, general malaise and a stuffy sensation in the chest. The patient may also complain of abdominal swelling and an exudative and prolonged skin disease.

Dryness
Dryness consumes yin fluid. There may be a dry sore feeling in the nose, mouth and throat, a coarseness of the skin, or a cough with scanty sputum and possibly haemoptysis. Tuberculosis is an example of the pathogen dryness.

Heat (fire, warmth)
All these represent the same pathogen, but at different intensities. Fire is the most severe and warmth the mildest. As with summer heat the yin may be damaged and this will affect the level of consciousness. The main difference is that summer heat only occurs in the summer and is generally less severe than fire. Diseases that are caused by heat are generally of abrupt onset and rapid change, they are nearly always acute infections. Initially the patient may complain of a high fever, chill, thirst, restlessness, irritability and profuse sweating. In severe cases the patient may be in coma with convulsions.

Mental Pathogens
These are overjoy, anger, anxiety, overthinking, grief, fear and fright.

Excessive fear and fright, or overjoy, injures the xin-heart. This causes palpitations, insomnia, irritability, anxiety and mental abnormality.

Excessive anger causes dysfunction of the gan-liver. This impairs the function of freeing, and causes pain and distention in the costal and hypochondriac region, abnormal menstruation, depression and irritability. If the function of storing blood is disturbed then menorrhagia and hemorrhage can result.

Excessive grief, anxiety and overthinking cause dysfunction of the pi-spleen and stomach. This causes anorexia and a feeling of fullness or distension after meals.

Excessive grief, anxiety and anger cause poor circulation of qi and blood. If there is retardation of qi and stagnation of blood then this can cause a tumor.

Miscellaneous Pathogens
Irregular feeding
Overeating, or eating too much uncooked or cold food, impairs the function of pi-spleen and stomach and causes nausea, vomiting, heartburn, sour regurgitation and diarrhea, for example dyspepsia, gastritis and enteritis.

Over-indulgence in alcohol and an excess of fatty or hot, pungent food produces damp and heat, or phlegm and heat, in the pi-spleen and stomach. Initially dyspepsia results but in more severe cases hypertension, enteritis, gastritis, cirrhosis, cancer or ischaemic heart disease can result. All these are related to nutritional habits.

Too little food intake, or lack of some essential material in food may cause malnutrition. This results in a deficiency of qi and blood which causes emaciation, lassitude, palpitations and sometimes coma.

The intake of contaminated food may impair the function of pi-spleen and stomach, and cause intestinal infections and various parasitic diseases.

Too little or excessive physical labor
Excessive physical labor results in feebleness, emaciation, palpitations and dizziness.

Too little physical exercise causes a poor circulation, limp muscles, soft bones and obesity. This lowers the resistance of the body to disease.