Library

The ancients used "mao" (hair) as a metaphor for lightness. In the *Book of Songs* (*Shijing*), Great Odes, it says "virtue is like hair," indicating lightness; in *Mencius*, a single feather is contrasted with a hundred jun (a unit of weight), and it is also stated that metal is heavier than feathers; in the *Book of Han*, some are heavier than Mount Tai, while others are lighter than goose down: all these refer to lightness. The pulse is named "mao" because it disappears upon heavy pressure but can be felt with light pressure.

In *Suwen: Yuji Zhenzang Lun* (Treatise on the Jade Machine and True Visceral Pulse), it states that the autumnal lung pulse comes lightly, void, and floating, arriving swiftly and dispersing quickly, hence it is called "floating" (Fu). The *Mai Jing* (Classic of Pulse Diagnosis) describes the lung pulse as coming "fanfan" (interpreted in *Shuowen Jiezi*: "Fu" means "Fan"; thus "fanfan" implies floating) and light, like a gentle breeze blowing the feathers on a bird's back. Therefore, the pulse that is light upon superficial palpation and vanishes upon deep pressure is the standard "mao" pulse. Those that are light but not significantly floating, or those that are light upon superficial palpation but exhibit other characteristics upon deep palpation, can only be termed "qing" (light) and not "mao." When discussing hematemesis and epistaxis, the *Mai Jing* states "the pulse comes lightly within the muscle layer." This indicates lightness at the middle level, hence it is not called "mao." When discussing pregnancy in women, it states "upon pressing it is slippery, upon floating it is light." Because there are other characteristics at the deep level, it is also not called "mao." Saying "light" is insufficient to encompass "floating," and saying "floating" is insufficient to encompass "light," therefore the *Shanghan Lun* (Treatise on Cold Damage) repeatedly refers to it as "mao fu" (light floating).

Ancient texts present several interpretations of the "dai" (intermittent/replacing) pulse. *Suwen: Xuanming Wuqi* states that the spleen pulse is dai, with annotations explaining it as soft and weak. Analysis shows that softness and weakness imply that qi flow is not fully smooth, suggesting irregularities in rate (now rapid, now slow). This aligns with *Ling Shu: Xieqi Zangfu Bingxing*, which states that patients with jaundice have a dai pulse, both referring to the normal pulse of the spleen. Cross-referencing with the *Mai Jing*, which describes the normal spleen pulse as long and weak, arriving slowly and departing rapidly, confirms that the "dai" mentioned here essentially means irregularity in rate (alternating between rapid and slow). Since there are periods of rapidity and slowness, the qi is not uniform, resembling mutual replacement, hence it is called "dai." Consequently, the ancients referred to irregular pulses as "dai." The *Records of the Grand Historian* (*Shiji*) in the biography of Cang Gong states: "He" (harmonious) corresponds to disease in the meridians, while "dai" corresponds to pathology in the collaterals. Contrasting "dai" with "he" reveals that "dai" signifies irregularity. *Suwen: Sanbu Jiuhou* states that death occurs if the central pulse is alternately rapid and slow, and disease in the collaterals is indicated by a dai pulse with a hook-like quality. This again defines "dai" as irregular. Following the previous statement about alternating rapidity and slowness, the meaning is that meridian dai leads to death, while terminal dai indicates disease. Summer qi resides in the collaterals, and the same logic applies to late summer; thus, the spleen considers the dai pulse as its normal state. This aligns with Cang Gong's view, taking the dai pulse of the normal spleen, whereas non-seasonal appearances of dai pulse indicate specific pathological conditions. The reason it is called "dai" is to evoke the concept of constant change, analogous to the succession of four seasons, the alternation of sun and moon, the transmission from father to son, and the shift between prosperity and decline. *Shuowen Jiezi* states: "Dai" means to replace/alternate, which is correct. The original meaning of "dai" does not imply stopping; rather, pure softness and weakness may hinder movement, while irregularities create intervals. An interval is a stop. Inability to move is also a stop. Thus, the ancients also referred to pulses with pauses as "dai." For example, classics mention "rapid movement with one pause" or "fifty movements with one pause," which are extended meanings of the character "dai." The reason "dai" was extended to mean stopping is that observing stops through movement appears rapid, and observing movement through stops also appears rapid, retaining the sense of alternating rapidity and slowness. However, it still generally refers to a single pause as "dai." It was not until Zhang Zhongjing that "dai" was distinguished from "jie" (knotted), beginning to define "dai" specifically as a pause during movement that cannot self-correct. It was not until Li Shizhen that "dai" was distinguished from "cu" (hasty) and "jie," beginning to define "dai" specifically by pauses occurring at regular intervals. This illustrates the evolution of terminology from ancient to modern times.