The theory of traditional Chinese medicine（TCM） meridians originated from the experience of the diagnosis and treatment of distant acupoints under the concept of "diagnosis-therapy integration". The initial interpretation of this empirical fact has formed a theory of one acupoint and one meridian. With the rich understanding of the same function diagnosis and treatment of acupoints

people try to link the nodes of the same function and give certain names

but the initial naming has no unified rules

lacking internal logic

which can be described as the initial period of meridian theory. Later

under the control of the concept of "harmony of man with nature"

the yin and yang rules were used to divide the meridians

and the meridians were standardized for formation. The three parts of Plain Conversation

Discussion on Treatment of Lumbago with Acupuncture（《素问·刺腰痛篇》） fully reflect the process of the occurrence and evolution of the meridian theory. It is a typical text to understand the occurrence and evolution of the meridian theory.