Interpretation of 'Tri-jiao' presented in ${\ulcorner}\;SuWen\;\cdot\;Linglanbidianlun\;{\lrcorner}$

There are wide variations in the definition and functions of tri-jiao among investigators in the area of Chinese medicine. Given a wide spectrum of views, it is difficult to identify uniform opinions about the definition and functions of tri-jiao. This paper is intended to clarify the meaning of the tri-jiao, which was presented as 'it builds a waterway and serves as the passage for the flow of Shuidao' in ${\ulcorner}\;SuWen\;\cdot\;Linglanbidianlun\;{\lrcorner}$ a classic text of traditional Chinese medicine. Investigators have been divided in their opinions in interpreting this reference; some claim that tri-jiao regulates fluid metabolism in the entire body while others assert that the role of tri-jiao is limited to lower-jiao that controls urination function. However, this does not appear convincing given the description in other texts of ${\ulcorner}\;SuWen\;\cdot\;Linglanbidianlun\;{\lrcorner}$, in which functions of 12 organs were explained in a summarized manner. The assumption that the role of tri-jiao is closely linked with lower-jiao seems to have deviated from the meaning of the original texts. Besides, fluid metabolism involves the entire body, and any pathological changes caused by disorders of fluid metabolism can affect any part of the body, not only the lower area of the body cavity. The phrase, 'passage for the flow of Shuidao,' expressed in the texts of ${\ulcorner}\;SuWen\;\cdot\;Linglanbidianlun\;{\lrcorner}$ is likely to mean that body fluid is also distributed and transported to the whole body along with primordial-Qi via tri-jiao. The phrase, 'passage for the flow of Shuidao' means that tri-jiao is involved in regulating body fluid metabolism and that it plays an important role in fluid distribution.