The meridian-collateral system of traditional Chinese medicine refers to the regulating system composed of the known loose connective tissue

liquid-Qi of tissue

energy substances

nerves

blood vessels

lymph

etc.existing in the fascia space between the skin

muscles and bone and some associated unknown synthetic functions.This hypothesis of meridian-collateral

Qi-passage

and fascia space composed of multiple substances is probably able to unify different viewpoints about that the meridian-collateral system is in fact an integrated substance of nerves

body fluid and energy.In the present paper

the authors introduce their viewpoints about the essence of meridian-collaterals from nerves

humor and energy

and unknown function of the known anatomical structure.