脉乃血 ，气血之先，血之隧道，气息应焉。
水自源而分流曰 。合分起伏，道各井然。人身之血，犹夫水也。血中之脉，
犹夫 也。 通则水源活，脉通则气血行。气也，血也，其在于人身，浑沦条析，
非一非二。设经脉不先为流转，则潜行默运之机碍矣。 濡守使，又安望其各尽乃
职耶。（《难经》二十二难曰∶气主 之，血主濡之。《素问》阴阳应象论曰∶阴在内，阳之守；阳在外，
阴之使。）隧道，即经脉也。言其在血中，精密隐隧，自成一道。《灵枢》营气篇云∶营气之道，内谷
为宝。谷入于胃，乃传之肺。流溢于中，布散于外。精专者，行于经隧。（营出中焦之义
了然。）《灵枢》决气篇云∶中焦取汁，变化而赤，是谓血。壅遏营气，令无所避，是谓
脉。（壅遏犹言拥迫，使入隧道，而无别道可避也。）《灵枢》卫气篇云∶其精气之行于经者为营气。
《灵枢》营卫生会篇云∶中焦亦并胃中，出上焦之后。此所受气者，泌糟粕，蒸津液，
化其精微，上注于肺脉，乃化而为血。以奉生身，莫贵于此，故独得行于经隧。合
诸篇论观之，乃知血为总名，而脉则指营气流行不息之道耳。若与血二，实无有二。
然非呼吸，不能流行，故曰气息应焉。（仲景平脉篇云∶呼吸者，脉之头也。又《灵枢·动输篇》云∶其
行也，以息往来。）
脉是血的通道，是气血运行的先导，也是血液流动的隧道，其搏动与呼吸的节律相应。
水从源头分流而出称为河道。水流汇合、分散、起伏，其道各自井然有序。人身中的血液，就像水一样。血脉中的脉络，就像河道一样。河道通畅则水源活跃，脉络通畅则气血运行。气和血，存在于人体之中，既浑然一体又条理分明，既不是完全的一，也不是截然的二。假如经脉不先进行流转，那么潜行默运的机制就会受到阻碍。濡养和守卫的功能又如何能各自尽到职责呢？（《难经》二十二难说：气主煦之，血主濡之。《素问·阴阳应象大论》说：阴在内，为阳之守；阳在外，为阴之使。）隧道，就是经脉。说的是它在血中，精密隐蔽的通道，自成一道。（《灵枢·营卫生会》篇说：营气的运行之道，以内谷为宝。谷物进入胃中，然后传送给肺。流溢于体内，布散于体表。其中精纯专一的，运行于经隧之中。（营气出于中焦的意义就很清楚了。）《灵枢·决气》篇说：中焦摄取汁液，变化而变红，这就叫做血。壅遏营气，使其没有别的路可避，这就叫做脉。（壅遏犹言拥迫，使进入隧道，而没有其他道路可以躲避。）《灵枢·卫气》篇说：其精气在经脉中运行的叫做营气。《灵枢·营卫生会》篇说：中焦也在胃中，位于上焦之后。这里所接受的气，泌出糟粕，蒸化津液，化生精微，向上注入肺脉，于是化生为血。以奉养生命之身，没有比这更宝贵的了，所以唯独能在经隧中运行。综合各篇论述来看，就知道血是总称，而脉则是指营气流行不息的道路罢了。如果将脉与血看作两回事，实际上并没有两个。然而如果没有呼吸，就不能流行，所以说气息相应。（张仲景《平脉法》篇说：呼吸者，是脉动的开端。又《灵枢·动输》篇说：它的运行，随着气息的往来。）
The pulse is the vessel of blood, the precursor of qi and blood, and the tunnel through which blood flows; its pulsation corresponds to the rhythm of respiration.
Water flowing from its source in branches is called a river channel. The convergence, divergence, rising, and falling of water follow distinct and orderly paths. Blood in the human body is like water, and the vessels within the blood are like these channels. When the channels are unobstructed, the water source remains active; when the vessels are unobstructed, qi and blood circulate. Qi and blood, existing within the human body, are both a unified whole and distinctly organized; they are neither absolutely one nor absolutely two. If the meridians do not first undergo circulation, the mechanism of hidden movement and silent operation would be obstructed. How could the functions of nourishment and guarding then fulfill their respective duties? (Chapter 22 of *Nan Jing* states: "Qi primarily warms [Xu], while blood primarily nourishes [Ru]." *Su Wen · Yin Yang Ying Xiang Da Lun* states: "Yin resides within, serving as the guard for Yang; Yang resides outside, serving as the envoy for Yin.") The "tunnel" refers to the meridians. This describes how, within the blood, there are precise and concealed pathways that form their own distinct routes. (*Ling Shu · Ying Wei Hui Hui* chapter states: "The path of Ying Qi treasures the internal grain." Grain enters the stomach, is transmitted to the lungs, overflows internally, and spreads externally. The pure and concentrated portion travels through the meridian tunnels. [The meaning that Ying Qi originates from the Middle Jiao becomes clear.] *Ling Shu · Jue Qi* chapter states: "The Middle Jiao extracts juices, transforms them into redness, and this is called blood. It constrains Ying Qi, preventing it from deviating, and this is called the vessel." [To constrain here means to press or urge, forcing entry into the tunnel so that no other path is available for avoidance.] *Ling Shu · Wei Qi* chapter states: "Its essential qi circulating within the meridians is called Ying Qi." *Ling Shu · Ying Wei Hui Hui* chapter states: "The Middle Jiao also lies within the stomach, posterior to the Upper Jiao. The qi received here separates dregs, steams fluids, transforms essence and subtle substances, and directs them upward to the lung vessels, thereby transforming into blood. To nourish the living body, nothing is more precious than this; thus, it alone can travel through the meridian tunnels." Synthesizing these discussions, we understand that 'blood' is the general term, while 'vessel' refers specifically to the unceasing pathway of Ying Qi circulation. If one were to separate the vessel from the blood, in reality, there would be no distinction. However, without respiration, circulation cannot occur; hence it is said that it corresponds to breath. (Zhang Zhongjing's *Ping Mai Pian* states: "Respiration is the head of the pulse." Furthermore, *Ling Shu · Dong Shu* chapter states: "Its movement occurs with the coming and going of breath.")