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On the Yin and Yang of Drug Properties

Drugs possess natures of cold, heat, warm, and cool; flavors of sour, bitter, pungent, salty, sweet, and bland; functional tendencies of ascending, descending, floating, and sinking; and applications of density, thinness, lightness, and heaviness. Some drugs share the same qi (vital energy/aroma) but differ in flavor, while others share the same flavor but differ in qi. Taken together, they must not be used interchangeably; taken separately, each has its specific efficacy. Those derived from heaven (qi) tend toward the upper part; those derived from earth (flavor) tend toward the lower part. Light and clear substances form images (functional aspects), while heavy and turbid substances form shapes (structural aspects). Clear yang disperses into the couli (interstices of skin and muscle), while turbid yin travels to the five zang organs. The clearest among the clear nourishes the spirit (shen); the most turbid among the turbid strengthens the bone marrow. Pungent and sweet flavors have a dispersing action and belong to yang; sour and bitter flavors have an inducing-vomiting and purgative action and belong to yin. Qi belongs to yang: dense qi is yang within yang, while thin qi is yin within yang. Thin qi causes exfoliation/dispersal, while dense qi generates heat. Flavor belongs to yin: dense flavor is yin within yin, while thin flavor is yang within yin. Thin flavor promotes unblocking/circulation, while dense flavor provides moistening/nourishment. Only when one clearly comprehends the distinctions among ascending, descending, floating, and sinking can one speak of medicine and assume responsibility for human life. People only know that the miraculous effect of drugs lies in the power of the drugs themselves. They do not realize that it actually lies in the power of how drugs are applied. People only know that distinguishing authenticity and identifying drugs is difficult; they do not realize that distinguishing yin and yang to guide drug application is even more difficult.

Those who apply drugs must understand the concepts of root (ben) and branch (biao). In terms of the body, the exterior is the branch, and the interior is the root; qi is the branch, and blood is the root; yang is the branch, and yin is the root; the six fu organs, belonging to yang, are the branch, and the five zang organs, belonging to yin, are the root. In terms of disease, the condition first contracted is the root, and subsequent transformations or transmissions are the branch. In treating any disease, one should first treat the root and then the branch. Even if multiple diseases exist, none will remain untreated. If one treats the branch first and the root later, the pathogenic factors will become more vigorous, and the disease will become more entrenched. However, if there is abdominal fullness (zhong man), regardless of root or branch, one must first treat the fullness because it is an urgent condition. If, following abdominal fullness, there is difficulty in urination or defecation, regardless of root or branch, one must first address the urinary or fecal obstruction, and then treat the abdominal fullness, as this is even more urgent. For example, if a patient first suffers from fever, followed by vomiting and diarrhea with inability to eat, one should first stop the vomiting, allow food intake, and then concurrently treat the diarrhea. Once the primordial qi (yuan qi) has slightly recovered, one may then attack the heat. This is what is meant by "treat the root when the condition is slow/stable, and treat the branch when the condition is urgent." Except for difficulties in urination/defecation, abdominal fullness, vomiting, and diarrhea, one should always treat the root first; this must not be ignored. Suppose the liver is affected by pathogenic fire from the heart; this is an excess pathogen coming from the preceding organ (Wood generating Fire, here implying the mother-son relationship where Heart is the son of Liver in some contexts, or specifically referring to the Five Elements generation sequence where Liver Wood generates Heart Fire, so Heart is the 'son' of Liver? Note: The text says "from front" which usually implies generation sequence. In Five Elements, Liver (Wood) generates Heart (Fire). So Heart is the son of Liver. If Liver is affected by Heart Fire, it's "coming from behind" in generation? Wait. Standard TCM theory: "From the one that generates me is deficiency pathogen (Xu Xie), from the one I generate is excess pathogen (Shi Xie)." The text says "Liver receives Heart Fire... from front... excess". Let's stick to the text's logic: "From front" = Excess. "Excess requires draining the son". Text says "drain its son". If Liver is the subject, and it receives Heart Fire, and it's treated by draining the son... wait. If Liver is the diseased organ, and it's an excess pattern caused by Heart, standard theory might differ. However, I must translate the text faithfully. Text: "Liver receives Heart Fire... from front... excess... drain the son". I will translate literally based on the provided text's internal logic.) ...this is an excess pathogen originating from the preceding stage. In excess patterns, one drains the "son" organ. However, this does not mean directly draining the fire, but rather using herbs entering the Liver meridian as guiding agents (yin jing yao). Using fire-draining herbs as the sovereign drug constitutes the treatment of excess pathogenic conditions. Suppose the liver is affected by pathogenic factors from the Kidney; this is a deficiency pathogen originating from the subsequent stage. In deficiency patterns, one tonifies the "mother" organ. Using herbs entering the Kidney meridian as guiding agents, and using liver-tonifying herbs as the sovereign drug, is the correct approach. When the root and branch are properly addressed, the pathogenic factors submit. There is no greater principle for the divine excellence of a physician than this.