The meridian and collateral theory is a great finding of TCM and is also an important component of TCM theory. The world famous acupuncture moxibustion therapy is developed based on this theory. The use of herbs is also guided by it.
The meridian system includes twelve main meridians corresponding to the viscera, extra meridians and eight collaterals not subordinate to the viscera and channel divergence, channel sinew and skin region subordinate to the twelve main meridians. As branches of meridians, collaterals mainly play the role of connecting different meridians.
In normal circumstances, the system of meridians and collaterals transport qi and blood and balance yin and yang of the whole body. At the same time, it “supplies the inner viscera with water and keeps the outer interstices moist”. Moistening and nourishing the inner viscera and outer five sense organs, nine orifices, skin, flesh, muscles and bones, the system, interconnected tightly like a net, maintains the relative balance and coordination of the body. Therefore, any problems of the body can be nursed and treated through the meridian and collateral system.