虚实者，亦脉学之纲领也。三部九候，力量有余，皆可谓之实；三部九候，力量不及，
皆可谓之虚。则凡言实者，可该弦劲洪紧诸脉；而凡言虚者，可该微弱迟软诸脉。初非专以
虚之与实，指定一种形象之名称。而昔人每以浮而无力为虚，欲以别于沉而无力之弱脉；以
沉而有力为实，欲以别于浮而有力之革脉。细分畛域，虽亦不为无理。寿颐窃谓虚实二字之
本义，不当如是。岂中候沉候之无力者，必不可以言虚，而浮按中按之有力者，必不可以言
实耶。顾名思义，当亦恍然。所以诊得实脉，苟非体质之壮盛，必其病势之有余。然坚实太
过，搏指不挠，则邪势方张，已失冲和之性。诊得虚脉，或为禀赋之素弱，无非元气之不充
，而虚弱已甚，指下无神，则根本欲漓，几等尸居余气。故肿疡脉虚虽曰病有余而脉不及，
然苟非大证，而其人形神未馁，则微见虚软，未必遽为大害。惟疡患甚巨，而脉来虚弱已甚
者，是为脉证相反，必多不治。而肿疡脉实，虽曰病是实邪，脉证相合，然果坚劲异常，则
大毒盘踞，蒂固根深，宁不可虑。溃疡脉虚，是为气血乍泄，于法为顺。然必风波大定，余
浪不兴，清养扶持，始登彼岸。如其恶腐未脱，毒焰未衰，而脉已虚软不起，惟恐正气难扶
，同归于尽。若溃疡脉实，必其余毒尚盛，气血未和，如脓泄太多，脉反坚实者，必难善后
也。
虚实，也是脉学中的纲领性概念。寸、关、尺三部以及浮、中、沉九候，如果搏动力量有余，都可以称为实；如果搏动力量不足，都可以称为虚。因此，凡是说“实”的，可以涵盖弦脉（脉象端直而长，如按琴弦）、劲脉（强劲有力）、洪脉（脉来大而有力，来盛去衰）、紧脉（脉来绷急，状如牵绳转索）等脉象；而凡是说“虚”的，可以涵盖微脉（极细极软，似有似无）、弱脉（沉细而软）、迟脉（一息不足四至）、软脉（即濡脉，浮细而软）等脉象。这原本并不是专门用“虚”或“实”来指定某一种特定形象的名称。
然而，古人常常将“浮取无力”定义为虚，试图以此区别于“沉取无力”的弱脉；将“沉取有力”定义为实，试图以此区别于“浮取有力”的革脉（浮而搏指，中空外坚）。虽然对界限进行细致划分，并非没有道理，但我（张山雷，字寿颐）私下认为，“虚”和“实”这两个字的本义，不应当是这样理解的。难道中取、沉取时无力的，就一定不能称为虚吗？难道浮取、中取时有力的，就一定不能称为实吗？顾名思义，应当对此恍然大悟。
所以，诊察到实脉，如果不是因为患者体质壮盛，那一定是病势有余。但是，如果脉象坚实太过，搏击手指且不屈不挠，说明邪气势力正盛，已经失去了冲和之性。诊察到虚脉，或者是由于先天禀赋素来虚弱，无非是元气不充；而如果虚弱到了极点，指下感觉无神，那就意味着根本动摇，几乎等同于尸体中残存的余气。
因此，在肿疡阶段，如果脉象虚，虽然说是病邪有余而脉象不及（脉证不符），但如果不是大病，且患者的形体和精神尚未衰竭，那么稍微出现虚软的脉象，未必立刻造成大害。只有当溃疡病情非常严重，而脉象却极其虚弱时，这才是脉证相反，大多属于不治之症。而在肿疡阶段，如果脉象实，虽然说是病邪为实，脉证相合，但如果脉象确实坚硬强劲异常，则说明大毒盘踞，根基牢固深厚，难道不值得忧虑吗？
在溃疡阶段，脉象虚，是因为气血刚刚耗泄，按照医理算是顺证。但必须等到风波平息，余浪不起，通过清淡滋养和扶持调理，才能最终痊愈。如果恶肉腐脓尚未脱落，毒火之势未减，而脉象已经虚软无力，那就只恐怕正气难以扶持，导致正气与邪气同归于尽。如果是溃疡阶段出现实脉，必定是余毒仍然旺盛，气血尚未调和；例如脓液排泄过多，脉象反而变得坚实，这就很难善后了。
Deficiency and Excess (Xu-Shi) are also the guiding principles of pulse diagnosis. When the force is sufficient in all three positions (Cun, Guan, Chi) and nine examinations (Superficial, Middle, Deep at each position), it can be termed Excess; when the force is insufficient in all three positions and nine examinations, it can be termed Deficiency. Thus, whenever "Excess" is mentioned, it encompasses pulses such as Xian (Wiry), Jin (Forceful), Hong (Surging), and Jin (Taut); whereas whenever "Deficiency" is mentioned, it encompasses pulses such as Wei (Minute), Ruo (Weak), Chi (Slow), and Ruan (Soft). Originally, this was not intended to designate a specific morphological name exclusively for either Deficiency or Excess.
However, ancient practitioners often defined "floating with insufficient force" as Deficiency, attempting to distinguish it from the Ruo pulse characterized by "deep with insufficient force"; and they defined "deep with sufficient force" as Excess, attempting to distinguish it from the Ge pulse characterized by "floating with sufficient force". Although subdividing these domains is not without logical basis, I (Zhang Shanlei, courtesy name Shouyi) privately believe that the original meaning of the terms "Deficiency" and "Excess" should not be understood in this manner. Could it be that those lacking force at the middle and deep levels cannot be called Deficient, while those possessing force at the superficial and middle levels cannot be called Excessive? By considering the names and their meanings, one should gain sudden enlightenment.
Therefore, when an Excess pulse is diagnosed, unless it is due to robust physical constitution, it must indicate that the pathogenic process is excessive. However, if the pulse is excessively firm and hard, beating against the fingers without yielding, it signifies that the pathogenic force is rising vigorously, having lost its harmonious nature. When a Deficiency pulse is diagnosed, it may be due to innate constitutional weakness, reflecting merely an insufficiency of Yuan Qi (Original Qi); but if the deficiency is extreme, and the pulse feels spiritless under the fingers, it indicates that the root is deteriorating, resembling only the residual breath remaining in a corpse.
Consequently, in the case of a swelling ulcer (Zhong Yang), if the pulse is Deficient, although it suggests that the disease pathology is Excess while the pulse response is Deficient (a mismatch), if it is not a major condition and the patient's form and spirit have not yet collapsed, a slight appearance of Deficient and soft pulse does not necessarily lead to immediate grave harm. Only when the ulcerative condition is extremely severe, yet the pulse comes forth extremely weak, is this considered a contradiction between pulse and symptoms, which usually indicates untreatability. In the case of a swelling ulcer, if the pulse is Excess, although it suggests that the pathogen is Excess and the pulse matches the symptoms, if the pulse is indeed abnormally firm and wiry, it implies that a great toxin is entrenched with deep roots, which surely warrants concern.
In the case of an open ulcer (Kui Yang), a Deficient pulse indicates that Qi and Blood have recently been depleted, which is considered a favorable progression according to medical principles. However, recovery requires that the storm has passed and residual waves have subsided, followed by clear nourishment and support, to finally reach safety. If foul necrotic tissue has not yet detached and the flame of toxicity has not diminished, yet the pulse has already become weak and limp, one must fear that the Healthy Qi (Zheng Qi) will be unable to sustain itself, leading to mutual destruction. If an Excess pulse appears during the open ulcer stage, it must imply that residual toxins are still abundant and Qi and Blood are not yet harmonized; for instance, if too much pus has been discharged, yet the pulse remains firm and solid, it will be difficult to manage the aftermath successfully.