凡用药处方，最宜通变，不可执滞。观仲景以麻黄汤治太阳经发热头痛，脉浮无汗之伤寒，而
阳明病脉浮无汗而喘者亦用之；太阳与阳明合病，喘而胸满者亦用之，此麻黄汤之通变也。又如桂
枝汤，本治太阳经发热
汗出之中风，而阳明病如疟状，日晡发热，脉浮虚，宜发汗者亦用之；太阳病外证未解，脉浮弱，
当以汗解者亦用之；太阴病，脉浮，可发汗者亦用之；厥阴证下痢，腹胀满，身疼痛，宜攻表者亦
用之，此桂枝汤之通变也。又如小柴胡汤，本治少阳经胁痛干呕，往来寒热之伤寒，而阳明病潮热
胸胁满者亦用之；阳明中风，脉弦浮大，腹满胁痛，不得汗，身面悉黄，潮热等证亦用之；妇人中
风，续得寒热，经水适断，热入血室，如疟状者亦用之，此小柴胡之通变也。由此观之，可见仲景
之意，初未尝逐经执方，而立方之意，多有言不能悉者，正神不可以言传也。所以有此法，未必有
此证，有此证，未必有此方。即仲景再生，而欲尽踵其成法，吾知其未必皆相合，即仲景复言，而
欲尽吐其新方，吾知其未必无短长。于戏！方乌足以尽变，变胡可以定方，但使学人能会仲景之意
，则亦今之仲景也，又何必以仲景之方为拘泥哉。余故曰∶用药处方，最宜通变，不当执滞也。虽
然，此通变二字，盖为不能通变者设，而不知斯道之理，又自有一定不易之要焉。苟不知要，而强
借通变为谈柄，则胡猜乱道，何匪经权，反大失通变之旨矣。
凡是用药处方，最适宜灵活变通，不可固执拘泥。看张仲景用麻黄汤治疗太阳经受邪所致的发热头痛、脉浮无汗的伤寒证，而阳明病出现脉浮无汗且喘息的，也使用它；太阳经与阳明经同时发病，出现喘息且胸部胀满的，也使用它，这就是麻黄汤的灵活变通。又如桂枝汤，原本用于治疗太阳经受邪所致发热汗出的中风证，而阳明病症状像疟疾一样，下午申时发热，脉象浮虚，应当发汗的，也使用它；太阳病表证未解，脉象浮弱，应当通过发汗来解除的，也使用它；太阴病，脉象浮，可以发汗的，也使用它；厥阴证出现下痢，腹部胀满，身体疼痛，适宜攻逐表邪的，也使用它，这就是桂枝汤的灵活变通。又如小柴胡汤，原本用于治疗少阳经受邪所致胁痛干呕、忽冷忽热的伤寒证，而阳明病出现定时发热、胸胁胀满的，也使用它；阳明中风，脉象弦浮大，腹部胀满胁痛，无法出汗，全身及面部都发黄，定时发热等症状，也使用它；妇女患中风，持续出现忽冷忽热，月经恰好中断，热邪侵入血室，症状像疟疾一样的，也使用它，这就是小柴胡汤的灵活变通。由此看来，可见张仲景的本意，起初从未拘泥于某一经而固定使用某一方，他创立方剂的本意，有很多言语无法完全表达的，这正是神妙的医理无法仅靠言语传授的缘故。所以有这种治法，未必对应这种病症；有这种病症，未必对应这种方剂。即使张仲景再生，想要完全遵循他已有的成法，我知道那未必都能契合病情；即使张仲景复生，想要完全发表他新的方论，我知道那也未必没有长短优劣之分。唉！方剂怎么能够穷尽变化？变化又怎么能被固定的方剂所限定？只要学习的人能领会张仲景的本意，那么也就是当今的张仲景了，又何必拘泥于张仲景的方剂呢。所以我常说：用药处方，最适宜灵活变通，不应当固执拘泥。虽然如此，这“通变”二字，是给那些不能灵活变通的人设立的，然而不知道医学道理中，自有一定不变的要旨。如果不知道这个要旨，却强行借用“通变”作为谈论的资本，那就是胡乱猜测、违背正道，哪里还算得上是经权之变，反而大大失去了灵活变通的宗旨了。
In prescribing medication, one must be most adept at flexibility and adaptation, avoiding rigidity. Consider Zhang Zhongjing using Mahuang Tang (Ephedra Decoction) to treat Taiyang disease (disease of the Taiyang channel characterized by exterior syndrome) with fever, headache, floating pulse, and absence of sweating. Yet, he also employed it for Yangming disease presenting with a floating pulse, absence of sweating, and wheezing; and for concurrent Taiyang and Yangming diseases manifesting as wheezing and chest fullness. This illustrates the flexible application of Mahuang Tang. Similarly, Guizhi Tang (Cinnamon Twig Decoction), originally intended for Wind-strike (Zhongfeng) in the Taiyang channel featuring fever and sweating, was also used for Yangming disease resembling malaria with afternoon fever (occurring around 3-5 PM), a floating and deficient pulse requiring diaphoresis; for Taiyang disease where exterior signs remained unresolved with a floating and weak pulse requiring release via sweating; for Taoyin disease with a floating pulse amenable to diaphoresis; and for Jueyin disease presenting with dysentery, abdominal distension, and body pain, where attacking the exterior was indicated. This demonstrates the flexible application of Guizhi Tang. Furthermore, Xiaochaihu Tang (Minor Bupleurum Decoction), originally designed for Shaoyang disease involving hypochondriac pain, dry retching, and alternating chills and fever, was also applied to Yangming disease with tidal fever and chest/hypochondriac fullness; to Yangming wind-strike with wiry, floating, and large pulses, abdominal distension, hypochondriac pain, inability to sweat, generalized jaundice, and tidal fever; and to women suffering from wind-strike with persistent alternating chills and fever, whose menstruation had just ceased, indicating heat entering the Blood Chamber (Xueshi) with malaria-like symptoms. This exemplifies the flexible application of Xiaochaihu Tang. From this, we see that Zhang Zhongjing’s intent was never to rigidly adhere to specific channels or fixed formulas. The rationale behind his prescriptions often transcends verbal description, reflecting a profound medical wisdom that cannot be fully conveyed through words. Thus, a method may exist without a corresponding specific symptom pattern; a symptom pattern may exist without a corresponding specific formula. Even if Zhang Zhongjing were reborn and sought to strictly follow his established methods, I believe they would not always fit every case perfectly. Even if he spoke anew regarding new formulas, I believe there would still be aspects of strength and weakness. Alas! How can formulas exhaust all variations? How can variations be confined by fixed formulas? If practitioners can grasp Zhang Zhongjing’s underlying intent, they become Zhang Zhongjing of their own time. Why then should they be bound by his specific formulas? Therefore, I say: Prescribing requires utmost flexibility and adaptation, avoiding rigidity. However, these two characters "flexibility and adaptation" are set forth for those who lack such ability. One must understand that within this art lies an unchanging essential principle. If one ignores this essence and uses "flexibility" merely as a talking point, it leads to wild speculation and deviation from the correct path, fundamentally missing the true spirit of adaptation.