体象 疾为疾急，数之至极；七至八至，脉流薄疾。
六至以上，脉有两称，或名曰疾，或名曰极。总是急速之形，数之甚者也。
主病 疾为阳极，阴气欲竭。脉号离经，虚魂将绝。渐进渐疾，旦夕殒灭。毋论寸尺，短期已决。
阴阳相等，脉至停均。若脉来过数而至于疾，有阳无阴，其何以生！是惟伤寒热极，方见此脉，非他疾所
恒有也。若痨瘵虚惫之人，亦或见之，则阴髓下竭，阳光上亢，可与之决短期矣。阴阳易病者，脉常七八
至，号为离经，是已登鬼 者也。至夫孕妇将产，亦得离经之脉，此又非以七八至得名。如昨浮今沉，昨
大今小，昨迟今数，昨滑今涩，但离于平素经常之脉，即名为离经矣。心肺诸证，总之真阴消竭之兆。譬
如繁弦急管，乐作将终，烈焰腾空，薪传欲尽。夫一息四至，则一昼一夜约一万三千五百息，通计之当
五十周于身，而脉行八百一十丈，此人身经脉流行之常度也。若一息八至，则一日一夜周于一身者，
当一百营，而脉遂行一千六百余丈矣，必至喘促声嘶，仅呼吸于胸中数寸之间，而不能达于根蒂，真
阴极于下，孤阳亢于上，而气之短已极矣。夫人之生死由于气，气之聚散由乎血，凡残喘之尚延者，只
凭此一线之气未绝耳。一息八至之候，则气已欲脱，而犹冀以草木生之，何怪其不相及也。
【脉象特征】疾脉表现为急促急迫，是数脉的极致状态；一息跳动七到八次，脉搏流动急迫有力。
一息六次以上，脉象有两种称呼，或者称为“疾”，或者称为“极”。这总是呈现急速的形态，是数脉中最为严重的情况。
【主病分析】疾脉代表阳极状态，阴气即将枯竭。脉象被称为“离经”（偏离正常常度的脉象），虚弱的魂气即将断绝。病情逐渐加重且脉象越来越快，生命将在早晚之间终结。无论寸口或尺部出现此脉，短命的期限已经注定。
如果阴阳平衡，脉象到达时停匀均匀。如果脉象过快而达到疾脉的程度，只有阳没有阴，人怎么能生存呢！这种情况只有在伤寒热邪极盛时才会出现，不是其他疾病经常有的。如果是劳瘵（慢性消耗性疾病）身体极度虚弱的人，也可能出现这种脉象，这时阴精髓液在下部枯竭，阳气在上部亢盛，可以据此判断其寿命短暂。患有阴阳易病（大病初愈因房事复发的疾病）的人，脉象常常七八至，被称为离经之脉，这已经是接近死亡的人了。至于孕妇临产时，也会出现离经之脉，但这并不是因为脉跳七八下而得名。比如昨天浮今天沉，昨天大今天小，昨天迟今天数，昨天滑今天涩，只要偏离了平时正常的脉象，就称为离经。心肺的各种病症，总之都是真阴消亡枯竭的征兆。譬如繁密的弦乐和急促的管乐，音乐演奏即将结束时的情景；又像烈火腾空，柴薪即将烧尽的样子。人一息跳动四次，那么一昼夜大约是一万三千五百息，总计起来应当在全身循环五十周，脉行八百一十丈，这是人身经脉流行的常规度数。如果一息跳动八次，那么一日一夜在全身循环的次数，应当是一百营，而脉就会行走一千六百多丈了，必然导致气喘急促、声音嘶哑，只能在胸中几寸之间呼吸，而不能到达根本之地，这是真阴在下部极度衰竭，孤阳在上部亢盛，而气的短促已经达到极限了。人的生死取决于气，气的聚散取决于血，凡是残喘还能延续的，只凭借这一线未绝的气罢了。一息八次的脉候，说明气已经将要脱失，却还希望依靠草木药物来救治，难怪药力赶不上病情啊。
[Characteristics] The Ji (Rapid) pulse presents as urgent and hurried, representing the extreme of the Shu (Rapid) pulse; it beats seven to eight times per respiration, with blood flow being forceful and rapid.
When there are more than six beats per respiration, the pulse has two names: either "Ji" (Rapid) or "Ji" (Extreme). It always manifests a hurried form, which is the most severe degree of the Rapid pulse.
[Etiology and Pathogenesis] The Ji pulse indicates Extreme Yang, where Yin Qi is on the verge of exhaustion. The pulse is termed "Li Jing" (Departing from the Normal Channel), signifying that the deficient Hun (Ethereal Soul) is about to perish. As the condition progressively worsens and the pulse becomes faster, death may occur within a day or night. Regardless of whether it appears at the Cun (Inch) or Chi (Cubit) position, a short lifespan is determined.
If Yin and Yang are in equilibrium, the pulse arrives evenly. If the pulse is excessively fast, reaching the degree of Ji, there is Yang without Yin; how can life be sustained? This pulse is seen only when Heat is extreme in Shang Han (Cold Damage); it is not commonly found in other diseases. In patients with Lao Zhai (Consumption Disease) who are extremely debilitated, this pulse may also appear, indicating that Yin Essence and Marrow are exhausted below while Yang Fire flares above, allowing for a prognosis of a short life. In cases of Yin-Yang Yi disease (recurrence due to sexual intercourse after recovery from a major illness), the pulse often beats seven to eight times per respiration and is called Li Jing; such patients are essentially on the threshold of death. For pregnant women near delivery, a Li Jing pulse may also appear, but this is not named so because of beating seven to eight times. For instance, if a pulse was floating yesterday and sinking today, large yesterday and small today, slow yesterday and rapid today, slippery yesterday and choppy today—any deviation from the habitual normal pulse is termed Li Jing. Various conditions of the Heart and Lung are, in summary, signs of the depletion of True Yin. It is like complex strings and urgent pipes playing as music is about to end, or like fierce flames soaring into the sky as firewood is about to be consumed. Normally, with four beats per respiration, there are approximately 13,500 respirations in a day and night, circulating fifty times through the body, covering 810 zhang, which is the standard rate of meridian circulation. If there are eight beats per respiration, the circulation would be one hundred Ying (cycles) in a day and night, covering over 1,600 zhang. This inevitably leads to panting, hoarseness, and breathing confined only to a few inches in the chest, unable to reach the root. This represents Extreme Yin deficiency below and solitary Yang hyperactivity above, with Qi depletion reaching its limit. Human life and death depend on Qi, and the gathering and scattering of Qi depend on Blood. Those who survive on residual gasp do so only because a thread of Qi remains unbroken. With a pulse of eight beats per respiration, Qi is about to collapse; hoping to save them with herbal medicine is no wonder why it fails to catch up.