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。
脉，是天地间的元气。人禀受天地的精气而生成生命，所以全身气机的升降浮沉，就是大自然生生不息的机理。那生生不息的根本，就在于脉。查阅《黄帝内经·素问·五常政大论篇》，岐伯说：“根源于体内的，叫做神机，神气离去则生机停止。”看“脉”这个字，由“肉”和“永”组成，它的命名意为陌（田间小路），意指血脉流通不断，是长久延续的道路，这是斡旋全身气机并作为纲领的关键。那些四季变化的脉象形态，被称为弦、钩、毛、石等，无非是根据阴阳的浮沉、升降、消长来取象比喻罢了。至于其运行营运的精妙之处，有起伏隐现的变化，可以在一呼一吸之间验证。张仲景说：“呼吸，是脉搏的源头。”因此有呼吸就有脉搏，没有呼吸，脉搏就会停止，气息断绝，生命也就终结了。这是天人相应的道理，四季气机流行的机理，微妙得难以用语言形容，必须潜心领会、心领神会，才能掌握其真实本体。刘完素将脉解释为“幕”，我认为这不恰当。《尔雅》中说膜就是幕；幕与络是一体的，并不是指脉。膜是有形的，而脉则是依靠神气运行的，是无形的。看上天说了什么吗？四季照样运行，百物照样生长，由此可以明白了。所以能看见这一点的人叫做懂道，领悟这一点的人叫做懂脉，脉的道理哪里是轻易能说清楚的呢。（以上解释脉的含义。）
有人向孙一奎（号生生子）问道：“十二地支中，属于水、火、木、金的各对应两条经脉，唯独土对应四条经脉，这是为什么呢？”孙一奎回答说：“万物生于土，最终也归于土，土原本位于四维（四个角落/方位），寄旺于四季的最后一个月，所以土有四条经脉。土，在人体中对应脾胃；四肢归属于脾，四肢就像土的四个维度一样。脏腑都依赖脾胃来提供营养，就像万物都依赖土地一样。”又问道：“人的十二正经，金、木、水、土各只有两条，唯独火有四条，这是为什么呢？”孙一奎回答说：“有具备美德的君主，必然有调理元气、辅助教化的臣子，然后纲纪确立，教化推行，从而达成无为而治的理想境界。假如君主没有宰相来协助谋划，怎么能统领百官，恭敬地履行各自的职责呢？三焦和心包络也是这个道理。心包络有护卫心脏的功能，三焦有传达命令、节制调控的作用，怎么证明这一点呢？大概营气和卫气都出自三焦，它们在体内营养脏腑，在体表护卫肌表，宗气搏动于胸中以推动呼吸，使脏腑各司其职，四肢百骸安稳有序，这些难道不是相火斡旋运作的功劳吗！古人把药物比作士兵，把身体比作国家，确实是因为这个道理。朱丹溪说：‘上天如果没有这把火，就不能化生万物；人如果没有这把火，就不能维持生命。’确实是这样的。”
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."