体象 虚合四形，浮大迟软；及乎寻按，几不可见。
主病 虚主血虚，又主伤暑。左寸心亏，惊悸怔忡。右寸肺亏，自汗气怯。左关肝伤，血不营筋。
右关脾寒，食不消化。左尺水衰，腰膝痿痹。右尺火衰，寒症蜂起。
【按】虚之为义，中空不足之象也，专以软而无力得名也。叔和云∶“虚脉迟大而软，按之豁豁
然空”，此言最为合义。虽不言浮字，而曰按之豁豁然空，则浮字之义已包含具足矣。崔紫虚以为形大力薄，
其虚可知，但欠迟字之义耳。伪诀云∶“寻之不足，举之有余”，是浮脉而非虚脉矣。浮以有力得名，虚以
无力取象。有余二字，安可施之虚脉乎！杨仁斋曰∶“状为柳絮，散漫而迟。”滑氏曰∶“散大而软。”二
家之言，俱是散脉而非虚脉矣。夫虚脉按之虽软，犹可见也。散脉按之绝无，不可见也。
虚之异于濡者，虚则迟大而无力，濡则细小而无力也。虚之异于芤者，虚则愈按而愈软，芤则重按而仍见也。
王叔和曰∶“血虚脉虚”，而独不言气虚者，何也？气为阳，主浮分，血为阴，主沉分；今浮分大而沉分空，
故独主血虚耳。
夫虚脉兼迟，迟为寒象，大凡症之虚极者必挟寒，理势然也。故虚脉行指下，则益火之原，以消阴翳，可
划然决矣。更有浮取之而且大且软，重按之而豁然似无，此名内真寒、外假热，古人以附子理中汤冰冷与
服，治以内真热而外假寒之剂也。
[Pulse Morphology] The Xu (Deficiency) pulse possesses four characteristics: upon superficial palpation, it is floating, large, slow, and soft; when pressed deeply to search for it, the pulse image is almost invisible.
[Indications] The Xu pulse primarily indicates Blood Deficiency and also indicates Summerheat Injury. A Xu pulse at the Left Cun position indicates Heart Qi and Blood deficiency, manifesting as palpitations and severe heart palpitations (Zhengchong). A Xu pulse at the Right Cun position indicates Lung Qi deficiency, manifesting as spontaneous sweating and shortness of breath with timidity. A Xu pulse at the Left Guan position indicates Liver blood damage, where blood fails to nourish the sinews. A Xu pulse at the Right Guan position indicates Spleen cold, resulting in indigestion. A Xu pulse at the Left Chi position indicates decline of Kidney Water (Kidney Yin), manifesting as soreness, weakness, and numbness of the lower back and knees. A Xu pulse at the Right Chi position indicates decline of Mingmen Fire, leading to a proliferation of Cold syndromes.
[Commentary] The meaning of the Xu pulse refers to the image of hollowness in the middle and insufficiency of Zheng Qi (Upright Qi); it derives its name specifically from being soft and forceless. Wang Shuhe stated: "The Xu pulse is slow, large, and soft; upon pressing, it feels hollow and empty." This statement best conforms to the true meaning of the Xu pulse. Although he did not explicitly use the word "floating," by stating that it feels hollow and empty upon pressing, the meaning of "floating" is fully contained therein. Cui Zixu believed that the Xu pulse has a large form but thin strength, indicating deficiency, but this lacks the meaning of "slow." The Pseudo-Canon states: "Upon light palpation it feels insufficient, upon heavy lifting it feels abundant." This describes the Fu (Floating) pulse, not the Xu pulse. The Fu pulse is named for having strength, whereas the Xu pulse takes its image from lacking strength. How can the term "abundant" be applied to the Xu pulse? Yang Renzhai said: "Its shape is like willow catkins, scattered and slow." Hua Shi said: "Scattered, large, and soft." The descriptions of these two masters refer to the San (Scattered) pulse, not the Xu pulse. The Xu pulse, although soft upon deep pressure, is still visible; the San pulse completely disappears upon deep pressure and is invisible.
The difference between the Xu pulse and the Ru (Soggy) pulse is that the Xu pulse is slow, large, and forceless, while the Ru pulse is fine, small, and forceless. The difference between the Xu pulse and the Kou (Choppy/Hollow) pulse is that the Xu pulse becomes softer the more it is pressed, whereas the Kou pulse remains palpable even under heavy pressure. Wang Shuhe said: "Blood deficiency leads to a Xu pulse," yet he did not mention Qi deficiency alone. Why? Qi belongs to Yang and primarily manifests in the Floating layer (superficial); Blood belongs to Yin and primarily manifests in the Sunken layer (deep). Now, since the superficial layer is large and the deep layer is empty, it exclusively indicates Blood Deficiency.
The Xu pulse combines with the Chi (Slow) pulse; the Chi pulse is an image of Cold. Generally, syndromes that are extremely deficient must be accompanied by Cold; this follows logical necessity. Therefore, when the Xu pulse is felt under the fingers, the treatment principle is to tonify the source of Fire to eliminate Yin shadows (Yin pathogenic factors), which can be clearly determined. Furthermore, if the pulse is large and soft upon superficial palpation, and feels hollowly absent upon deep palpation, this is named Internal True Cold and External False Heat. The ancients administered Fuzi Lizhong Tang (Aconite and Magnolia Root Decoction), a warming formula, cooled down, to treat cases of Internal True Heat and External False Cold (Note: The original text contains a logical contradiction regarding the indication of Fuzi Lizhong Tang and the method of cold administration, which typically applies to treating internal heat with cold herbs served hot, or internal cold with warm herbs served cold as a counter-sense method. Here translated faithfully to the source text's assertion).