The general rule of the yin yang categorization of Zang Fu is that Zang (viscera) (to store) belong to yin and Fu (bowel) (a palace) belong to yang. However, the five Zang (belong to the yin) could be further categorized into yin and yang. In Ling Shu, Yin Yang Xi Re Yue (The Yin and Yang of Human Body relate to Moon and Sun) says “the parts above the loins are Heaven which is yang; the parts below the loins are earth which is yin”. In fact, the divider between yin and yang of the Zang is the diaphragm. The Zang in the chest are yang and those in the abdomen are yin. The chapter also says “In the five Zang, the heart is the Taiyang in yang, the lung is the Shaoyin in yang, the liver is the Shaoyang in yin, the spleen is the extreme yin in yin, and the kidney is the Taiyin in yin.” (The above quote is also seen in Ling Shu, Nine Needles and Twelve Yuan-origins). In Su Wen, Jin Gui Zhen Yen Lun (The Truth in the Collections of Books of Golden Chamber) says “the back is yang. The heart is the yang in yang; the lung is the yin in yang. The abdomen is yin. The kidney is the yin in yin and the liver is the yang in yin. The extreme yin in yin is the spleen.”
The heart and liver both are “yang viscera”. The heart is the Taiyang in yang because it is located in the chest. The liver is located in the abdomen and is the Shaoyang in yin. The lung, kidney, and spleen all are “yin viscera”. The lung is Shaoyin in yang because it is located in theS chest and back. The kidney is Taiyin in the yin because it is located in the loins. The spleen is located in the abdomen and is the extreme yin in the yin.
In the five elements, the wood and fire are light and going upward, hence they govern ascending. The earth, metal, and water are heavy and sinking and hence govern descending. The yin channels travel upward (the foot three yin channels travel from feet to the chest; while the hand three yin channels travel from the chest to the hands.). Hence, the beginning five-element of the five transport points of the yin channels start from wood and then fire. The yang channels travel downward and hence the beginning five-element of the five transport points of those channels start from metal and then water. The heart (fire) and liver (wood) channels are yin channels but yang viscera. Because they belong to wood and fire, their nature is to ascend. That is why in the yin channels, only the yang viscera, the heart and liver channels travel upward from their internal pathways to the head region (no points on those pathways though). Because both the liver and heart channels go to the head, the disorders of the heart and liver will influence the spirit and will (Shen Zhi). The hyperactivity of the liver yang (such as the cerebral hemorrhage in western medicine term) and the phlegm confusing the heart orifice (brain thrombus) both will cause stroke. To treat it, needle the Muhuo (wood fire) point and Linggu and Dabai (the wood fire nature points) of the Tung’s acupuncture. The effectiveness of the point combination is very high.