《痿论》云∶五脏使人痿，而本于肺热叶焦。终之曰∶治痿独取阳明。是痿病原于手太阴一经，以热
相传而成，而治之者，惟取足阳明一经以为要。阳明为五脏六腑之海，总宗筋而束骨以利机关。阳明虚则
宗筋纵，带脉不引，故手足不用而成痿。是痿之来，起于肺经，而治则取于阳明。后人谓独取阳明，此
“取”字有教人补之意。是以丹溪独引越人泻南方、补北方之法，以发明“独取阳明”之旨。究未能尽所
以取阳明之义，而意反有相戾者。夫南方，离火也；北方，坎水也。其言曰∶金体燥而居上，主畏火；土
性湿而居中，主畏木。泻南方，则肺金清而东方不实；补北方，则心火降而西方不虚。此其论似为肺热
叶焦者发明之，而于治痿取阳明之法，反未之悉也。阳明者，胃土也。补火可以生土，而反云泻南；滋水
则能助湿，而反云补北，则与取阳明之义有不合矣。夫足阳明为水谷之海，以为阳明虚而宗筋不用似矣，
何以病痿之人，有两足不任身，而饮食如故，其啖物反有倍于平人者何也？岂阳明之气旺，而水谷入海，
独不能运化精微，以强筋骨乎？何饮啖日盛，形体日肥，而足痿不能用也？则知阳明之虚，非阳明之
本虚，而火邪伏于胃中，但能杀谷，而不能长养血气、生津液，以灌溉百骸，是以饮食倍于平人，而足反为
之不用。此所谓“壮火食气”，而邪热不杀谷也。阳明之邪热，原是肺热中传来，故治痿独取阳明者，非补阳
明也，治阳明之火邪，毋使干于气血之中，则湿热清而筋骨强，筋骨强而足痿以起。张子和尝言痿病皆因客
热而成，断无有寒。丹溪亦云治痿以清热为主，不可作风治用风药。诚得取阳明之义者矣。
《痿论》中说：五脏的功能失调会导致痿证，但其根本原因在于肺热导致肺叶焦枯。文章最后总结道：治疗痿证应当专门取法于足阳明经。这说明痿证的病源起始于手太阴肺经，通过热邪的传变而形成，而治疗方法上，则以调理足阳明经为关键。足阳明胃经是五脏六腑气血的海源，统领宗筋并约束骨骼以利于关节运动。如果阳明经虚弱，就会导致宗筋松弛，带脉失去牵引力，从而出现手足不能随意运动而形成痿证。由此可见，痿证的发生起于肺经，而治疗则侧重于阳明经。后世医家认为“独取阳明”中的“取”字，含有教导人们进行补益的意思。因此，朱丹溪单独引用了扁鹊（越人）提出的“泻南方、补北方”的方法，来阐发“独取阳明”的宗旨。但这终究未能完全阐明为何要取阳明经的道理，其用意反而与原文相悖。所谓南方，对应离卦之火；北方，对应坎卦之水。他们的说法是：肺金性质燥烈且位居上焦，主要畏惧火邪；脾土性质湿润且位居中焦，主要畏惧木邪。泻南方之火，则肺金得以清肃，东方肝木也不会过于亢盛；补北方之水，则心火得以下降，西方肺金也不会虚弱。这种论述看似是为“肺热叶焦”的情况做了阐发，但对于治疗痿证取法阳明经的方法，却并未完全理解。阳明经对应的是胃土。补火可以生土，但他们反而说要泻南方的火；滋水能够助湿，但他们反而说要补北方的水，这就与取阳明经的本义不相符合了。足阳明胃经是水谷之海，如果说因为阳明虚弱导致宗筋功能失常，这似乎有道理，但是为什么患痿证的人，虽然双脚无法支撑身体，但饮食却和常人一样，甚至进食量反而比正常人加倍呢？难道是因为阳明之气旺盛，水谷进入胃中，唯独不能运化精微物质来强壮筋骨吗？为什么饮食摄入日益增加，身体日益肥胖，但双脚却痿废不能使用呢？由此可知，阳明经的虚弱，并非阳明经本身的虚损，而是火邪潜伏在胃中，只能消化食物，却不能生长养血气、生津液，以灌溉全身百骸，所以饮食量超过常人，但双脚反而不能使用。这就是所谓的“壮火食气”，以及邪热不能正常化生谷气。阳明经的邪热，原本是从肺热的传变而来，所以治疗痿证独取阳明经，并不是为了补益阳明经，而是为了清除阳明经的火邪，使其不干扰气血的运行，这样湿热清除后筋骨就会强健，筋骨强健后足痿就能痊愈。张子和曾经说，痿病都是由客热引起的，绝对没有寒证。朱丹溪也说，治疗痿证应以清热为主，不可当作风证治疗而使用风药。这才是真正理解了取阳明经的真义啊。
The *Treatise on Flaccidity* (Wei Lun) states: "Dysfunction of the five zang organs leads to flaccidity syndromes, with the root lying in lung heat causing the lung leaves to become scorched and dry." It concludes by stating: "In treating flaccidity syndromes, one should exclusively focus on the Yangming channel." This indicates that the origin of flaccidity syndrome lies in the Hand-Taiyin Lung channel, developing through the transmission of heat pathogens, while the treatment primarily targets the Foot-Yangming Stomach channel. The Foot-Yangming is the sea of the five zang and six fu organs, governing the Zongjin (major tendons) and binding the bones to facilitate joint movement. If the Yangming is deficient, the Zongjin will relax, and the Dai Mai (Girdle Vessel) will fail to exert its pulling force, resulting in the inability to use the hands and feet, thus forming a flaccidity syndrome. Therefore, the onset of flaccidity originates from the Lung channel, but the treatment focuses on the Yangming channel. Later scholars interpreted the word "qu" (take/focus on) in "exclusively focus on Yangming" as implying instruction to tonify. Consequently, Zhu Danxi solely cited the method of "draining the South and tonifying the North" proposed by Yue Ren (Bian Que) to elucidate the principle of "exclusively focusing on Yangming." However, this failed to fully explain the rationale behind focusing on the Yangming channel, and its intent was actually contradictory. The South corresponds to the Fire of the Li trigram; the North corresponds to the Water of the Kan trigram. Their argument was: Metal has a dry nature and resides superiorly, primarily fearing Fire; Earth has a damp nature and resides centrally, primarily fearing Wood. Draining the Southern Fire clears the Lung Metal and prevents the Eastern Wood from becoming excessive; tonifying the Northern Water descends the Heart Fire and prevents the Western Metal from becoming deficient. While this discussion seems to elucidate the condition of "lung heat causing scorched lung leaves," it does not fully comprehend the method of focusing on the Yangming channel for treating flaccidity. Yangming corresponds to the Stomach Earth. Tonifying Fire can generate Earth, yet they advocate draining the Southern Fire; nourishing Water can assist Dampness, yet they advocate tonifying the Northern Water. Thus, their approach contradicts the true meaning of focusing on the Yangming channel. The Foot-Yangming is the sea of water and grain. It might seem plausible to attribute the dysfunction of the Zongjin to Yangming deficiency, but why do patients with flaccidity, whose legs cannot support their body weight, have normal appetites and even consume more food than healthy individuals? Is it because the Qi of Yangming is vigorous, allowing food and drink to enter the stomach, yet failing to transform and transport essential nutrients to strengthen the sinews and bones? Why does increased intake lead to increasing obesity while the legs remain flaccid and unusable? This reveals that the deficiency of Yangming is not an intrinsic deficiency of the Yangming itself, but rather fire pathogens lurking within the Stomach. These pathogens can digest food ("kill grain") but cannot generate blood and Qi or produce body fluids to irrigate the entire body. Hence, dietary intake exceeds that of normal people, yet the legs are unusable. This is what is meant by "vigorous fire consumes Qi" and "pathogenic heat fails to properly transform grain." The pathogenic heat in the Yangming channel originally transmits from lung heat. Therefore, "exclusively focusing on the Yangming channel" in treating flaccidity does not mean tonifying the Yangming, but rather clearing the fire pathogens in the Yangming to prevent them from interfering with the blood and Qi. Once the damp-heat is cleared, the sinews and bones will strengthen, and the leg flaccidity will resolve. Zhang Zihe once stated that flaccidity syndromes are caused by exogenous heat and absolutely never by cold. Zhu Danxi also said that treating flaccidity should prioritize clearing heat and should not be treated as wind syndromes using wind-dispelling herbs. This truly captures the essence of focusing on the Yangming channel.