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The Cun Kou pulse (Cun Kou Pulse, the radial artery at the wrist) is the master of Ying and Wei (Nutritive and Defensive Qi) throughout the body. Without Stomach Qi (Wei Qi, digestive energy), how can fluids be transported upward and distributed to Ying and Wei? Fu Yang (Fu Yang, a pulse position on the dorsum of the foot) belongs to the Zheng Yang (Correct Yang) channel, situated in the Central Earth, which is the mother of the Five Elements. Therefore, pulse diagnosis must take Stomach Qi as its foundation. Shao Yin (Shao Yin, the Kidney channel) belongs to the Kidney, which is an organ of Water. It combines with the San Jiao (Triple Burner) to form one Qi. The True Water and True Fire of the human body are rooted here. Water relies on Earth to control it; thus, Shao Yin must be subdued by Fu Yang before it can interact with the San Jiao, steaming and distributing fluids. The Classics state: "When Shao Yin is weaker than Fu Yang, it is favorable."

Fu Yang is used to observe Stomach Qi and serves as the master of the Middle Jiao (Middle Burner); Shao Yin is used to observe Kidney Qi and serves as the master of the Lower Jiao (Lower Burner). This essentially corresponds to the distribution of the Cun Kou pulse into the Upper, Middle, and Lower three positions. According to Wang Shuhe's *Mai Jue* (Pulse Classic), the Chong Yang point is located five cun above the dorsum of the foot, in the arterial pulse between the bones, three cun away from the Xian Gu point, and this is considered the diagnostic site for Fu Yang. However, pulse methods lack explicit text prescribing the palpation of the foot pulse. Moreover, the original treatise clearly states that there are three pulse positions (Cun, Guan, Chi), where Yin and Yang interact. If only Cun Kou is mentioned without referring to the Guan and Chi positions, it indicates that the two Guan positions govern the Middle Jiao, managed by the Spleen and Stomach, which corresponds to the Fu Yang diagnosis; the two Chi positions govern the Lower Jiao, managed by the Kidneys, which corresponds to the Shao Yin diagnosis. The Fu Yang diagnosis is at the Guan position, with the Right pulse governing the Left; the Shao Yin diagnosis is at the Chi position, with the Left pulse governing the Right. This is similar to how the Cun Kou pulse specifically governs the Hand Taiyin Lung channel. To understand the diagnoses of Fu Yang and Shao Yin, one must deduce them within the framework of the three positions (Cun, Guan, Chi).

A disciple asked: Zhang Zhongjing said, "Those with Yin diseases presenting Yang pulses survive; those with Yang diseases presenting Yin pulses die." The world consequently believes that Zhang Zhongjing's book focuses solely on supporting Yang and suppressing Yin. I replied: The terms "Yin" and "Yang" here should only be understood in terms of Exterior/Interior and Deficiency/Excess. When pathogenic factors invade the body, being in the Exterior is mild, while being in the Interior is severe; exiting the Exterior is favorable, while entering the Interior is adverse. If a Yin disease presents a Yang pulse, it indicates that interior pathogens have the potential to emerge to the exterior, hence survival is indicated. If a Yang disease presents a Yin pulse, it indicates that exterior pathogens have the tendency to sink into the interior, hence death is indicated. Floating, Surging, Large, Rapid, and Slippery pulses are Yang pulses; Yang pulses indicate Exterior and Excess conditions. If a Yin disease presents a Yang pulse, it means righteous Qi recovers and pathogens retreat naturally; even if the illness is severe, recovery is possible. Deep, Choppy, Weak, String-taut, and Fine pulses are Yin pulses; Yin pulses indicate Interior and Deficiency conditions. If a Yang disease presents a Yin pulse, it means righteous Qi declines and pathogens are unopposed; even if the illness is mild, death may occur. Yang diseases inherently indicate survival, but if Yin pulses appear, death lurks within survival; Yin diseases inherently indicate death, but if Yang pulses appear (Note: Text implies a nuance or potential typo in source logic regarding 'Yin seeing Yin', usually Yin seeing Yang is life, but translating strictly: if [condition] appears, life exists within death), life exists within death. These two instances of "seeing" reflect the meaning in the *Doctrine of the Mean*: "Nothing is more visible than what is hidden; nothing more manifest than what is subtle." Physicians facing clinical cases must not fail to be vigilant and cautious. As for supporting Yang and suppressing Yin, this is a derogatory theory inherited since the Yuan and Ming dynasties. The *I Ching* says: "One Yin and one Yang is called the Dao." Yang commands Yin, yet excessive Yang leads to regret; Yin follows Yang, yet excessive Yin leads to conflict. Thus, the Classics state: "When Yin is balanced and Yang is firm, spirit and vitality are regulated." All diseases arise from the imbalance of Yin and Yang. Zhang Zhongjing's various treatment methods merely address the excess of Yin or Yang, balancing the deviation so that the disease resolves itself. Sometimes, when Yang is extremely hyperactive, only pure Yin formulas are used, without any Yang herbs; this is not bias toward Yin, but nourishing Yin to balance Yang. Sometimes, when Yin is extremely abundant, only pure Yang formulas are used, without any Yin herbs; this is not bias toward Yang, but supporting Yang to balance Yin. In cases where Yin and Yang Qi are biased but not extreme, small amounts of Yin herbs are added to Yang formulas to preserve fluids, and small amounts of Yang herbs are added to Yin formulas to transform Qi. Although sometimes cold and hot herbs are combined, and tonification and purgation are advanced simultaneously, seemingly making prescriptions very complex, this is actually based on the principle of the mutual root of Yin and Yang, balancing the excess to harmonize with the Center. Humans are born from Central Qi; the Way of the Sages lies in the Middle Path. Later generations failed to clarify the Sage's Way, deviating into distorted theories. Therefore, Zhu Danxi proposed the theory that "Yin is often insufficient and Yang is often excessive." Zhang Jingyue refuted Danxi but proposed the opposite theory that "Yang is often insufficient and Yin is often excessive," causing students to have no direction and become increasingly confused. The *Nei Jing · Sheng Qi Tong Tian Lun* explicitly states that the Qi of life originates from Yin and Yang. In discussing the methods of treating climatic influences and overcoming excess/reversal, it simply says: "Treat cold with heat, heat with cold, warmth with cooling, coolness with warming," regardless of frequency, aiming for balance. This clearly states that Yin and Yang must be kept in equilibrium. Zhang Zhongjing's learning directly inherits from Xuanyuan (Yellow Emperor) and Qibo. The way passed down through sages does not exceed the concept of "Zhong" (Center/Middle). Bias toward Yin or Yang is always heterodox. When reading Zhang Zhongjing's books, one should focus on the character "Zhong" (Center).