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Chapter 4 asks: There is a method for distinguishing Yin and Yang in the pulse; what does this mean?

The response states: During exhalation, Qi emerges from the Heart and Lungs; during inhalation, Qi returns to the Kidneys and Liver. Between breaths, the Spleen receives the essence of grain, and its pulse is located in the middle.

This passage indicates that although the Yin and Yang of the pulse are manifested in the Cun (inch) and Chi (cubit) positions, the Qi of Yin and Yang is further distinguished by floating (Fu, 浮) and sinking (Chen, 沉). For instance, the Heart and Lungs reside above the diaphragm, which is Yang; thus, exhalation necessarily proceeds through them. The Kidneys and Liver reside below the diaphragm, which is Yin; thus, inhalation necessarily returns to them. The Spleen receives the essence of food and drink, serving as the source of pulse generation, located in the middle jiao. Since both exhalation and inhalation depend on it, the method of pulse diagnosis involves light palpation (floating) to assess the Heart and Lungs, heavy palpation (sinking) to assess the Kidneys and Liver, and moderate palpation to assess the Spleen and Stomach.

Commentary: The scripture's statement "exhalation" does not mean that Qi exits directly from the Heart and Lungs to the outside. Rather, because the Kidneys and Liver are below the diaphragm, their Qi rises with exhalation to reach the Heart and Lungs; hence, it is said that "exhalation comes from the Heart and Lungs." The Heart and Lungs are above the diaphragm, and their Qi descends with inhalation to reach the Kidneys and Liver; hence, it is said that "inhalation returns to the Kidneys and Liver." Exhalation involves the outward movement of Yin, while inhalation involves the inward movement of Yang. The Yin and Yang of respiration follow each other up and down, passing through the five Zang organs. This is nourished by the Spleen and Stomach receiving谷物 (grain/food) Qi. Therefore, it is stated that the pulse is in the middle. When reading this section, one must not rigidly interpret it to mean that exhaled Qi is purely Yang and inhaled Qi is purely Yin.

A floating pulse belongs to Yang, and a sinking pulse belongs to Yin; thus, they are called Yin and Yang.

When light pressure feels insufficient but heavy pressure feels excessive, it is called Floating (Fu, 浮). Floating is Yang, resembling fire which flares upward. When heavy pressure feels excessive but light pressure feels insufficient, it is called Sinking (Chen, 沉). Sinking is Yin, resembling water which moistens downward.

Both the Heart and Lung pulses float; how can they be distinguished?

The response states: A pulse that is floating, large, and scattered belongs to the Heart; a pulse that is floating, short, and choppy (Se, 涩) belongs to the Lung. Both the Kidney and Liver pulses sink; how can they be distinguished?

The response states: A pulse that is firm (Lao, 牢) and long belongs to the Liver; a pulse that feels soft upon heavy pressure but becomes solid when the finger is lifted belongs to the Kidney. The Spleen resides in the central region (Zhongzhou), so its pulse is located in the middle. This is the method of distinguishing Yin and Yang.

Supplementary explanation: A pulse that is floating, large, and forceless, feeling scattered and seemingly departing upon heavy pressure, is named Scattered (San, 散). A pulse that is floating, fine, and slow, moving with difficulty and stagnation without advancing, is named Choppy (Se, 涩). A pulse that is deep, forceful, solid, large, wiry, and strong, feeling extremely hard and immovable upon heavy pressure, is named Firm (Lao, 牢). A pulse that is large and long, slightly wiry, feeling solid under the finger upon heavy pressure, and forceful in both moderate and deep palpation, is named Solid (Shi, 实). How to distinguish the floating pulses of the Heart and Lung? Since the Heart belongs to Fire, its pulse image is floating, large, and scattered. Since the Lung belongs to Metal, its pulse image is floating, short, and choppy. How to distinguish the sinking pulses of the Kidney and Liver? Since the Liver belongs to Wood, its pulse image is firm and long. Since the Kidney belongs to Water, its pulse image feels solid upon lifting the finger and pressing, reflecting the nature of water being soft on the outside and hard on the inside. The Spleen belongs to Earth, residing in the center, flourishing in the four seasons, and nourishing the four other Zang organs. Its pulse comes leisurely and harmonious, neither sinking nor floating, hence it is said that its pulse is in the middle.

There are pulses with one Yin and one Yang, one Yin and two Yangs, one Yin and three Yangs; there are also pulses with one Yang and one Yin, one Yang and two Yins, one Yang and three Yins. Does this statement imply that all six pulse positions at the Cun Kou move simultaneously?

The response states: This statement does not refer to all six pulses moving simultaneously. It refers to the characteristics of Floating (Fu, 浮), Sinking (Chen, 沉), Long (Chang, 长), Short (Duan, 短), Slippery (Hua, 滑), and Choppy (Se, 涩). Floating is Yang, Slippery is Yang, Long is Yang; Sinking is Yin, Short is Yin, Choppy is Yin. "One Yin and one Yang" means the pulse comes Sinking and Slippery. "One Yin and two Yangs" means the pulse comes Sinking, Slippery, and Long. "One Yin and three Yangs" means the pulse comes Floating, Slippery, and Long, occasionally presenting a Sinking quality. "One Yang and one Yin" means the pulse comes Floating and Choppy. "One Yang and two Yins" means the pulse comes Long, Sinking, and Choppy. "One Yang and three Yins" means the pulse comes Sinking, Choppy, and Short, occasionally presenting a Floating quality. Based on the meridian where these pulses are found, one determines the disease's favorable or unfavorable course (Ni Shun, 逆顺).

Extending beyond the normal position is called Long (Chang, 长); failing to reach the normal position is called Short (Duan, 短). Moving smoothly and continuously upon pressure is called Slippery (Hua, 滑). The previous section cited the five Zang pulses to correspond with the Five Elements; this section cites the Three Yin and Three Yang pulses to correspond with the Six Qi. Floating, Slippery, and Long belong to the Three Yang; Sinking, Short, and Choppy belong to the Three Yin. By observing these six pulse qualities within the three positions (Cun, Guan, Chi), one can understand the mechanism of Yin and Yang excess and deficiency. Generally, Yin and Yang pulses do not appear alone. Precisely because they do not appear alone, these six pulse qualities appear combined. Precisely because they combine, there are variations such as one Yin one Yang or one Yang one Yin. This is the method for distinguishing Yin/Yang and Deficiency/Excess. Further considering the changes of Spring, Summer, Autumn, and Winter, and observing the variations of the six pulses, one can generally ascertain the favorable or unfavorable nature of the disease.

Commentary: Xu states: This section describes the phenomenon of the six pulses appearing in mutual interweaving. This is merely an example given, showing mutual complexity, not a fixed rule. The "meridians" refer to the Hand and Foot Three Yin and Three Yang meridians. "Favorable or unfavorable" (Ni Shun, 逆顺): for example, if the Heart pulse should be Floating and the Kidney pulse should be Sinking, this is Favorable (Shun); if the Heart pulse is instead Sinking and the Kidney pulse is instead Floating, this is Unfavorable (Ni). This again shows that pulses have no fixed form; favorability or unfavorability is determined according to the specific meridian. However, it should be understood that while Floating and Sinking may coexist, Slippery, Choppy, Long, and Short cannot appear simultaneously.