体象 细直而软累累萦萦；状如丝线，较显于微。
小也，细也，状如丝也。比之于微，指下犹尚易见，未至于举按模糊也。
主病 细主气衰，诸虚劳损。左寸细者，怔忡不寐。细在左关，肝血枯竭。左尺得细，泄痢遗精。
右寸细者，呕吐气怯。细在右关，胃虚胀满。右尺得细。下元冷惫。
细脉、微脉俱为阳气衰残之候。夫气主 之，非行温补，何以复其散失之元乎？常见虚损之人，脉已细
而身常热，医者不究其元，而以凉剂投之，何异于恶醉而强酒？遂使真阳散败，饮食不进，上呕下泄，是
速之使毙耳。《素问·阴阳别论》云∶“壮火食气，少火生气。”人非少火，无以营运三焦，熟腐五谷。未彻
乎此者，安足以操司命之权哉！然虚劳之脉，细数不可并见，并见者必死。细则气衰，数则血败，气血交
穷，短期将至。叔和云∶“细为血少，亦主气衰。有此证则顺，无此证则逆。”故吐利失血，得沉细者生。忧劳
过度之人，脉亦多细，为自戕其气血也。春夏之令，少壮之人，俱忌细脉。谓其不与时合，不与形合也。秋
冬之际，老弱之人，不在禁忌之例。
按丝之质最柔，丝之形最细，故以形容细脉。王启玄曰∶“状如莠蓬。”正于柔细之态，善摩巧拟，恍在目
前。伪诀失其柔软之意，而但云极细则可移于微脉，而岂能独标细脉之体象乎！微、细二脉，或有单指
阳衰，或有单指阴竭，或有兼阴阳而主病，则非画一之论矣。大都浮而细者属之阳分，则见自汗、气急
等证；沉而细者属之阴分，则见下血、血痢等证。
[Body Image]
The body image of the Xi (Thready) pulse is straight yet soft, continuous and unbroken; its shape resembles a silk thread, appearing more distinct than the Wei (Minute) pulse.
It is called Xiao (Small) or Xi (Thready), with a shape like silk. Compared to the Wei (Minute) pulse, it is still easily perceptible under the fingers and has not reached the state where lifting and pressing feel vague or indistinct.
[Chief Pathology]
The Xi (Thready) pulse primarily indicates Qi deficiency and decline, as well as various deficiency and consumptive disorders.
A Xi (Thready) pulse at the Left Cun position indicates Zhengchong (palpitations with restlessness) and insomnia.
A Xi (Thready) pulse at the Left Guan position indicates exhaustion of Liver Blood.
A Xi (Thready) pulse at the Left Chi position indicates diarrhea, dysentery, and spermatorrhea.
A Xi (Thready) pulse at the Right Cun position indicates vomiting and Qi timidity.
A Xi (Thready) pulse at the Right Guan position indicates Stomach deficiency and abdominal distension/fullness.
A Xi (Thready) pulse at the Right Chi position indicates coldness and fatigue of the Lower Yuan (Kidney Yang).
Both the Xi (Thready) pulse and the Wei (Minute) pulse are signs of residual decline of Yang Qi. Since Qi possesses warming functions, without warm-tonifying treatment, how can one restore the scattered original essence? It is commonly seen that patients with deficiency and consumption have a Thready pulse but often present with body heat. If physicians do not investigate the root cause (deficiency of Yuan Qi) and instead administer cooling formulas, what difference is there from hating drunkenness yet forcing oneself to drink? This results in the scattering and collapse of True Yang, loss of appetite, upper vomiting, and lower diarrhea, thereby hastening death. The *Suwen: Yin Yang Bie Lun* states: "Strong fire consumes Qi, while mild fire generates Qi." Without the warming influence of mild fire, humans cannot circulate the Sanjiao (Triple Burner) nor ripen and rot five grains. Those who have not thoroughly comprehended this principle are unfit to wield the authority of life and death! However, in the pulses of consumptive diseases, the Xi (Thready) pulse and the Shuo (Rapid) pulse should not appear together; if they do, death is certain. A Thready pulse indicates Qi decline, while a Rapid pulse indicates Blood deterioration. When both Qi and Blood are exhausted, a short lifespan approaches. Wang Shuhe stated: "The Thready pulse indicates blood deficiency and also Qi decline. Having this symptom with this pulse is favorable; having this symptom without this pulse is unfavorable." Therefore, in cases of vomiting, diarrhea, or blood loss, if the pulse is Deep and Thready, survival is possible. People suffering from excessive worry and labor often have a Thready pulse because they have harmed their own Qi and Blood. During the seasons of Spring and Summer, young and vigorous people should avoid the appearance of a Thready pulse, as it does not accord with the seasonal timing or the physical constitution. In Autumn and Winter, for the elderly and weak, this is not considered a contraindication.
[Commentary]
Silk has the softest texture and the finest form, hence it is used to describe the Xi (Thready) pulse. Wang Qixuan said: "Its shape resembles youpeng (a type of weed)." This is an apt and skillful analogy for its soft and fine nature, vividly presenting itself before the eyes. The spurious prescriptions lost the meaning of softness, merely stating that extremely thready pulses could be transferred to the Wei (Minute) pulse category, which fails to uniquely identify the body image of the Xi (Thready) pulse! The Wei (Minute) and Xi (Thready) pulses may singly indicate Yang decline, singly indicate Yin exhaustion, or jointly indicate pathology involving both Yin and Yang; thus, it is not a uniform theory. Generally, a Floating and Thready pulse belongs to the Yang aspect, manifesting symptoms such as spontaneous sweating and rapid breathing; a Sinking and Thready pulse belongs to the Yin aspect, manifesting symptoms such as lower bleeding and bloody dysentery.