脉者，天地之元气也。人受天地之气以生，故一身之升降浮沉，即造化生生不息之机。其不息
者，脉也。按《内经·五常政大论篇》岐伯曰∶“根于中者，命曰神机，神去则机息。”顾其为字，
从肉从永，其命名为陌，谓脉脉不断，长永之道也，是斡旋一身而为之纲领。彼四时之脉体，有如
弦、钩、毛、石之谓者，无非迹阴阳浮沉升降消长而取义耳。至其营运之妙，有起伏隐见，可验于
一呼一吸之间。仲景曰∶“呼吸者，脉之头也。”是以有呼吸则有脉，无呼吸，则脉息气绝而物化
矣。此其天人一致之理，四时流行之机，微妙不易名状，必潜会默契，庶可得其真体。刘守真释名
为幕，余以为未然。《尔雅》谓膜，幕也；幕络一体也，非谓脉也。膜则有形，而脉则以神运，无形者
也。观天何言哉，四时行，百物生，可见矣。故见此者谓之知道，悟此者谓之知脉，脉何容易言哉。（
上释脉义。）
有以十二支问于生生子曰∶十二支属水火木金者
各二，土属有四者何也？生生子曰∶万物生于土，而归于土，土本四维，寄旺于四季之末，故土有四
也。土也者，在人以脾胃应之；四肢属脾，四肢犹四维也。脏腑皆藉脾胃以为养，犹万物皆藉于土也
。又问∶人之十二经，金木水土各二而已，火独有四者何也？生生子曰∶有令德之君，必有调元赞化
之臣，然后纲维立，教化行，而成无为之治。假令君非相以赞密勿，何能帅百执事，恪恭厥职。三焦
、包络，亦犹是也。包络有护持之功，三焦有承宣节制之效，何以见？盖荣卫出于三焦，而所以营于
中，卫于外，大气搏于胸中以行呼吸，使脏腑各司其职，而四肢百骸奠安者，孰非相火斡旋之功哉！
古人以药譬兵，以身譬国，良以此夫。丹溪曰∶“天非此火，不能生物；人非此火，不能以有生。”
信然。
Mai (Pulse), is the primordial Qi of Heaven and Earth. Humans receive the Qi of Heaven and Earth to generate life; thus, the ascending, descending, floating, and sinking of Qi throughout the body constitute the mechanism of endless generation in nature. That which ensures this endless generation is the Mai (Pulse). According to the "Wu Chang Zheng Da Lun" chapter of the *Huangdi Neijing* (Yellow Emperor's Inner Canon), Qibo stated: "Those rooted within are called Shen Ji (Spirit Mechanism); when Shen departs, the mechanism ceases." Regarding the character "Mai," it consists of the radical for flesh/meat and "Yong" (forever). Its naming implies a continuous path, signifying that the vessels flow without interruption, representing the long-lasting way that orchestrates the entire body as its guiding principle. The forms of pulses corresponding to the four seasons, described as Xian (String-like), Gou (Hook-like), Mao (Feather-like), and Shi (Stone-like), are merely metaphors derived from the floating/sinking, ascending/descending, waxing/waning of Yin and Yang. As for the subtlety of their operation, with fluctuations and appearances/disappearances, they can be verified within a single exhalation and inhalation. Zhang Zhongjing said: "Respiration is the head/source of the pulse." Therefore, where there is respiration, there is a pulse; without respiration, the pulse ceases, Qi exhausts, and transformation/death occurs. This illustrates the principle of consistency between Heaven and Humanity and the mechanism of seasonal Qi circulation. It is so subtle that it defies easy description; one must immerse oneself in understanding and achieve intuitive insight to grasp its true essence. Liu Shouzhen interpreted the name as "Mu" (Curtain/Screen), but I consider this incorrect. The *Erya* states that "Mo" (Membrane) is "Mu"; Mo and Luo (Network) form a unity, not referring to Mai. Mo has form, whereas Mai operates through Shen (Spirit/Mind) and is formless. Observe Heaven: does it speak? Yet the four seasons proceed, and all things grow. Thus, those who perceive this are said to understand Dao, and those who comprehend this are said to understand Mai. How easily can the meaning of Mai be explained! (Above explains the significance of the Pulse.)
Someone asked Sun Yikui (courtesy name Shengshengzi): "Among the Twelve Branches, Water, Fire, Wood, and Metal each correspond to two meridians, but Earth corresponds to four. Why is this?" Shengshengzi replied: "All things are born from Earth and return to Earth. Earth originally occupies the Four Dimensions (Four Corners) and thrives at the end of each season; therefore, Earth has four [meridians]. In the human body, Earth corresponds to the Pi Wei (Spleen and Stomach). The Si Zhi (Four Limbs) belong to the Spleen, and the four limbs are analogous to the four dimensions of Earth. All Zang Fu organs rely on the Pi Wei for nourishment, just as all things rely on Earth." He was then asked: "In the human body's Twelve Regular Meridians, Metal, Wood, Water, and Earth each have only two, but Fire has four. Why is this?" Shengshengzi replied: "A virtuous ruler must have ministers who regulate Yuan Qi and assist in transformation, so that governance is established, education is propagated, and non-action (Wu Wei) governs. If the ruler lacked a Chancellor to assist in secret deliberations, how could he lead the officials to diligently perform their duties? The San Jiao (Triple Burner) and Bao Luo (Pericardium) are similar. The Bao Luo has the function of protecting [the Heart], and the San Jiao has the effect of transmitting orders and exercising control. How do we know this? Generally, Ying Qi (Nutritive Qi) and Wei Qi (Defensive Qi) originate from the San Jiao; they nourish internally and defend externally. Da Qi (Great Qi) pulsates in the chest to facilitate respiration, enabling the Zang Fu organs to perform their respective functions and ensuring the stability of the four limbs and hundred bones. Are these not all the merits of the Xiang Huo (Ministerial Fire) orchestrating operations? Ancients compared herbs to soldiers and the body to a state, precisely for this reason. Zhu Danxi said: 'Without this Fire, Heaven cannot generate living things; without this Fire, humans cannot sustain life.' This is indeed true."