Glossary

The Mo Yuan is first mentioned in the Su Wen ch. 39 where it is described as above the Stomach and Intestines but without any function given. 膜 (Mo) comprises of the usual ⺼ radical for "flesh" relating to a part of the body and 莫 representing the sun sinking into some bushes at dusk. Its definition of a membrane may come from the setting of the sun dividing the day from the night, and therefore as something in the body, as thin as the last sliver of light at dusk, that separates things. Some later authors took this to mean the diaphragm, while others associated it with the peritoneum, greater omentum and pleura.

It has always been associated with difficult to treat disorders. It was most developed by the Warm Disease School where it was said that some epidemics, after entering by the nose and mouth, are able to lurk at the "membrane source." Xue Shengbai said that "The Mo Yuan connects with the muscles and flesh on the exterior and with the yin and yang organs on the interior. It is the gate of the San Jiao. In fact, it is the entire body's half-exterior and half-interior." It is therefore closely associated with Shaoyang patterns and the San Jiao in particular. Wu Youke expanded this discipline further identifying it as the place where Pestilential Qi could lurk in the body making them difficult to treat by normal means.

This connection to the San Jiao is supported by several facts. The San Jiao divides the body into the upper, middle and lower Jiao which would imply a permeable division that would be located above the Stomach (separating upper and middle) and intestines (separating middle and lower). It is also said in Su Wen ch. 8 that The San Jiao is the official functioning as opener of channels. The paths of water originate in it." Belonging to the Ministerial Fire element and being the "paths of water," it has an intimate connection with Fire and Water, making its obvious pathology that of Damp-Heat, commonly seen in Warm Epidemic Diseases. Lastly, it was often associated with the Gaohuang, "Vital Regions," related to difficult to treat diseases, and is mentioned in the point's name Gaohuang Bl-43 which lies on the outer Bladder line to Jueyinshu Bl-14. The outer aspect of the Jueyin is Shaoyang and in the upper body particularly, these relate to the Pericardium and hence San Jiao.