三虚者。阴也。指下寻之不足。举之亦然。曰虚。主少力多惊。心中恍惚。小儿
惊风。
虚者。阴也。离之象也。离中虚。在天为火。在人为心。心主血脉。血实则脉
实。血虚则脉虚。今指下寻之不足。举之亦然。则心血虚矣。心血虚则神
无所倚。故少力多惊。心中恍惚。易曰。日昃之离。何可久也。若小儿见此
虚脉。则易于成惊。何也。小儿乃方长之气。脉当有力。今反见虚脉。则为
先天不足。或脾胃虚弱。风火易乘。故主惊风之证也。治之者。宜益其元
气。培其脾土。气血充足。而风木不得以乘之。惊风之患。庶可免矣。张世
贤释谓治以湿青丸。加减小柴胡汤。则虚虚之祸。其能免乎。
按脉经云。虚脉迟大而软。按之不足。隐指豁豁然空。
恍惚心中多悸惊。三关定息脉难成。血虚脏腑生烦热。补益三焦便得宁。
心主血脉。心中恍惚而多惊悸。血虚可知矣。及候其脉。则寸关尺部三
关之内。寻按俱虚。而不成息数。自非一脏一腑之虚。乃三焦之虚也。夫
三焦。五脏六腑之本也。三焦之血虚。则脏腑之烦热生矣。治之者。当补
益其三焦。夫心血虚。而曰补益其三焦者。何也。正以心火也。三焦亦火
也。补益三焦。即大易所云。明而作离。大人以继明之义也。不然。则为日
昃之离。安可久也。
按脉经云。尺脉虚小者。足胫寒痿痹脚疼。
三虚脉，属于阴脉。指下重按感觉力量不足，轻取同样感觉不足，这种脉象称为虚脉。它主要主病元气虚弱、容易受惊，心中恍惚不定，以及小儿惊风。
虚脉，属于阴脉，也是离卦的象征。离卦中间是空的（离中虚），在天对应火，在人对应心。心主管血脉，血液充实则脉象充实，血液虚弱则脉象虚弱。现在指下重按感觉不足，轻取也同样不足，这说明心血虚弱了。心血虚弱则神志没有依托，所以会出现精力不足、容易受惊、心中恍惚不定的症状。《易经》说：“太阳偏西的离火，怎么能长久呢？”如果小儿出现这种虚脉，就容易发展成惊风。为什么呢？小儿正处于生长发育阶段，脉象应当有力。现在反而见到虚脉，说明先天禀赋不足，或者是脾胃虚弱，导致风邪和火邪容易侵袭。所以主治惊风这类病症。治疗时，应该补益元气，培补脾土，使气血充足，那么风木之邪就不能乘虚侵袭，惊风的祸患或许就可以避免了。张世贤解释说要使用湿青丸，加减小柴胡汤来治疗，这样岂不是犯了“虚虚”（使虚者更虚）的错误，灾祸怎能避免呢？
据《脉经》记载：虚脉迟慢、大而柔软，按压时感觉不足，手指下有一种豁然空虚的感觉。
心中恍惚多悸动受惊，寸关尺三部脉在定息间难以成形。血虚导致脏腑产生烦热，补益三焦就能安宁。
心主管血脉，心中恍惚且多惊悸，可知是血虚。等到诊察脉象，则在寸、关、尺三部之内，寻按都感到虚弱，而且脉搏节律不成息数。这不仅仅是一脏一腑的虚损，而是三焦整体的虚损。夫三焦，是五脏六腑的根本。三焦的血虚，就会导致脏腑产生烦热。治疗时，应当补益三焦。既然说是心血虚，为什么又说补益三焦呢？正因为心属火，三焦也属相火。补益三焦，就是《易经》所说的“光明而成为离卦，君子效法此义以连续光明”的道理。否则，就像太阳偏西的离火，怎么能够长久呢？
Sanxu pulse (Three-Deficiency Pulse) is a Yin pulse. Under the fingers, deep pressure reveals insufficiency, and light pressure similarly reveals insufficiency; this pulse image is called Deficiency Pulse (Xu Mai). It primarily indicates insufficient vitality and susceptibility to fright, mental vagueness (huang hu), and infantile convulsions (Jing Feng).
The Deficiency Pulse is a Yin pulse and represents the Li trigram. The center of Li is empty (Li zhong xu); in Heaven it corresponds to Fire, and in Humans it corresponds to the Heart. The Heart governs the blood vessels. When blood is substantial, the pulse is substantial; when blood is deficient, the pulse is deficient. Now, since deep pressure reveals insufficiency and light pressure similarly reveals insufficiency, this indicates a deficiency of Heart Blood. When Heart Blood is deficient, the Spirit (Shen) has no foundation, thus resulting in lack of strength, susceptibility to fright, and mental vagueness. The *I Ching* states: "The Li fire at sunset, how can it last long?" If an infant presents with this Deficiency Pulse, they are prone to developing convulsions. Why? Infants are in a phase of vigorous growth, and their pulse should be forceful. To now see a Deficiency Pulse indicates congenital insufficiency or Spleen-Stomach weakness, allowing Wind-Fire pathogens to easily invade. Therefore, it primarily governs conditions of convulsions. In treatment, one should tonify Yuan Qi (Primordial Qi) and cultivate the Spleen Earth, so that when Qi and Blood are sufficient, the Wood pathogen cannot take advantage of the deficiency, and the disaster of convulsions may hopefully be avoided. Zhang Shixian's interpretation suggests treating with Shi Qing Wan (Moist Green Pill) and modified Xiao Chai Hu Tang (Minor Bupleurum Decoction); would this not cause the disaster of "deficientifying the deficient" (making the deficient even more deficient), and how could disaster be avoided?
According to the *Mai Jing* (Pulse Classic): The Deficiency Pulse is slow, large, and soft; upon pressing, there is a sense of insufficiency, and under the finger, it feels hollow and empty.
Mental vagueness, palpitations, and frequent fright; within the three positions (Cun, Guan, Chi) fixed by breath, the pulse is difficult to form. Blood deficiency causes organs and bowels to generate vexatious heat; tonifying the San Jiao brings peace.
The Heart governs the blood vessels. Mental vagueness accompanied by frequent palpitations and fright indicates blood deficiency. Upon examining the pulse, within the Cun, Guan, and Chi positions, both searching and pressing reveal deficiency, and the pulse rhythm does not conform to normal breath counts. This is not merely the deficiency of one Zang or Fu organ, but the deficiency of the entire San Jiao (Triple Burner). The San Jiao is the root of the five Zang and six Fu organs. When the blood of the San Jiao is deficient, vexatious heat arises in the organs and bowels. In treatment, one should tonify and benefit the San Jiao. Since it is stated as Heart Blood deficiency, why speak of tonifying the San Jiao? Precisely because the Heart belongs to Fire, and the San Jiao also belongs to Ministerial Fire. Tonifying the San Jiao aligns with the meaning in the *I Ching*: "Bright and becoming Li, the superior person continues the brightness." Otherwise, like the Li fire at sunset, how can it last long?
According to the *Mai Jing*: If the Chi position pulse is deficient and small, it leads to coldness, flaccidity, bi-syndrome (painful obstruction), and pain in the lower legs and feet.