Chinese Medicinal Herbs are categorized according
to their channels :
Herbs are also categorized according to their
selective therapeutic effects on particular
organs, and the meridians with which they
are connected. Some may act on one channel,
or several channels, and yet have no effect
on others. This is called channel tropism.
Certain heat-clearing herbs, for example,
will act on the lung channel, and will be
just as effective in treating diseases connected
with the liver channel or the heart channel.
Tonic herbs may be useful in strengthening
the lung, yet have no effect on the spleen
or the kidney.
Channel tropism
Channel tropism refers to a drug's selective therapeutic effects on a certain part of the body. A drug may exert obvious or specific therapeutic action on the pathological changes in a certain channel (including some viscera thereof) or several channels, but with little effects on the others. For instance, among the heat-clearing drugs, some only clear the heat either in the lung channel or in the liver channel or in the heart channel, etc. Again, among the tonics, some strengthen the lung while others strengthen the spleen or the kidney.
Channel tropism is based on the theory of viscera, the theory of channels and collaterals, and is summed up according to the curing particular diseases for which a drug is effective. The human body is an organic whole in which the channels and collaterals link up with the interior and exterior and all parts of the body. A pathological change in the exterior may affect the viscera while diseases in the viscera may, in turn, find expressions in the exterior of the body. For this reason, the symptoms and signs of diseases occurring in different parts of the body can be understood systematically according to the theory of channels and collaterals. For instance, the flaring up of stomach-fire may result in swollen gum; and whenever there is stagnation of liver-qi, pain in the hypochondriac region will be present. Since the swelling and pain of the gum disappear when gypsum is administered, and hypochondriac pain relieved with the use of bupleurum root, we may infer that gypsum acts on disorders of the stomach channel and bupleurum, the liver channel. The above examples show that the theory of channel tropism is summed up through clinical practice.
The channel tropism theory should be associated with the theories of the four properties and five flavors, and actions of lifting, lowering, floating and sinking of drugs. Different drugs acting on the same channel have different effects owing to their different properties, flavors and actions of lifting, lowering, floating and sinking. For example, scutellaria root, dried ginger, lily bulb, and lepidium seed all act on the lung channel, but scutellaria root can clear lung-heat, dried ginger can warm lung-cold, lily bulb can be used to make up for lung deficiency, and lepidium seed is used to soothe excess syndrome of the lung. Therefore, only when attention is paid to the different aspects of a drug, can its actions be comprehensively analyzed and the drug correctly employed. Besides, according to the theory that viscera as well as channels and collaterals are physiologically related to one another, and pathologically affect one another, when there is pathological change in one channel, drugs acting on other channels should be used in addition to the prescription for the diseased channel itself. For in stance, for abnormalities in the lung channel, drugs for strengthening the spleen channel should be added, and in case of hyperactivity of the liver-yang, drugs for nourishing the kidney-yin should be used at the same time.
