内经论五脏之痿。谆谆以肺热为主。而治痿则独取阳明阳明与太阴相表里为五脏六腑之
海。主
润宗筋束骨而利机关合冲带督三脉而又为阴阳之总会。故人身有真阳升降营运。强健不息精
神气血性情魂魄。无委靡不振之。患咸得其阖辟。动静之。常者也。夫痿者痿弱不劲。举动
不力也。盖金不能生水致肾。失作强之用痿斯见矣。肺主皮毛心主血脉。脾主肌肉。肝主筋
膜。肾主骨髓。肺为诸脏之长为心之盖。痿则内叶焦而皮毛不荣金为火燥水难卫母。热气留着。
必
及于筋脉骨肉。则病生痿 也。心痿脉上逆而下虚。枢析挈胫。纵不任地。为脉痿。肝痿则
胆
泄口苦。筋膜干而挛急为筋痿。脾痿则胃干而渴。肌肉不仁。为肉痿肾痿则腰脊不举。骨枯
髓减。为骨痿此经之言诸痿也。仲景金匮有谓肺痿者。以热在上焦。因咳而为痿。得之或从
汗出。或从呕吐。或从消渴小便利数。或从便难。或被快药下利。重亡津液。故寸口脉数而
虚。口中反有浊唾涎沫。原其意从内经痿条推展。在脏气虚不得布荣卫行津液。反冤郁为
热
蕴结涎沫浊唾而后咳。故附方或用炙甘草汤。或用生姜人参大枣汤。所治大意似之矣。又谓
肺痿吐涎沫而不咳。其人不渴。必遗尿水便数。亦以上虚不能制下故也。此为肺冷咳多涎唾
。
甘草生姜汤以温之。若服汤已渴属消渴。则此所治。便与前条上焦热者不同矣。上焦热则冤
郁而肺之玄府燥涩。气不利则咳。津不布则渴。此云肺中冷者非形寒饮冷之邪在其中。由上
焦无阳。故曰冷。阳气不足则不成热。不热则不咳亦不渴唯气虚而不能约制其水道之行也。
肺
与肾连。肺虚则肾亦虚。故水入咽直达于肾。肾亦不能以水精四布于五脏。而径出于溺矣。
此仲景之为肺冷咳也。大都肺焦而迫于热。良由肾水衰。不能制火。此为真藏之患。当与诸
藏热痿从壮水之剂。而治其右肾火衰。致巳土失资。而肺金寡卫。冒触外邪。不渴而咳。唾
涎沫背成龟胸者。特以下虚而不能奉上也。虽曰不热不咳。此为因寒致逆。不得以热论治宜
益火之源。或巳土自虚。不能生子。皮毛日瘁。或咳或唾。从中亏论。至仲景
所云冷痿者。则宜升举其阳而温存之。若形寒饮冷而痿者。则须温散其寒。资养化源。刘河
涧亦论气血者人之神。若气血或郁结。或衰虚不能宣通。则神无所用。而不遂其机。故劣弱
也。当随其虚实补泻之。使气血宣行则神自清。利而应机。能为用矣。东垣有谓暑月痿厥者
。乃独举四肢痿软热厥。及冲脉气逆而论。治以清燥去湿热之药。或生脉饮。合四苓散加黄
柏知母不知。此乃湿热成痿不足中有余之病也。故宜渗泄。若夫精血枯涸。筋脉衰弛。肌肉
日削而成痿。此不足中之复不足也。全须峻补之剂。法大异耳。察诸书又以痿痹不仁。每每
混同立论。此为因内经脾痿中肌肉不仁。安得执以合痿痹为一病。盖痛则为痹。不痛则为痿
。痹实痿虚。痹为风寒湿所成。气滞不行。而痿则血少气虚。此甚悬绝。亦有误作风治湿治
者。病之似同而实异者以此。经又尝举其端。所谓肾风而不能食善惊惊已心气痿者死。又太
阴司天湿气下临肾气上从阴痿气太衰而不起。此从所司之内症而论也。若仲景更明肺藏所生
气之虚实者又如此。则肝脾二脏。虽无明文。观此亦可例举矣。愚以为内经诸痿。则真痿症
也。仲景从而推明之。又有谓为冷痿者。东垣有谓湿热痿者。又有从火衰而致者。土虚而得
者。饮冷而得者。此非真痿。乃如痿也。如痿真痿不可不详辨也。
《内经》论述五脏之痿，反复强调以肺热为主要病机。而治疗痿证则主张独取阳明经。阳明与太阴相表里，是五脏六腑气血汇聚的大海，主要滋润宗筋（聚于前阴的筋脉），约束骨骼并利于关节运动，同时合会冲脉、带脉、督脉，又是阴阳经脉的总会。因此，人体有真阳之气升降营运，强健不息，精神、气血、性情、魂魄等，没有萎靡不振的隐患，都能得到开阖动静的正常规律。所谓痿证，就是肢体痿弱无力，举动不强劲。大概是因为金（肺）不能生水（肾），导致肾失去作强（精力充沛、动作矫健）的功能，于是出现痿证。肺主皮毛，心主血脉，脾主肌肉，肝主筋膜，肾主骨髓。肺为诸脏之长，是心的覆盖物。发生痿证时，肺叶焦枯，皮毛不得荣润；金被火燥，水难卫护母脏，热气留滞，必然波及筋脉骨肉，从而产生痿病。心痿则脉气上逆而下部虚弱，枢节断裂、小腿纵弛，足不能着地，称为脉痿。肝痿则胆气泄溢、口苦，筋膜干枯而挛急，称为筋痿。脾痿则胃干而口渴，肌肉麻木不仁，称为肉痿。肾痿则腰脊不能挺举，骨骼枯槁、髓液减少，称为骨痿。这是《内经》关于各类痿证的论述。
张仲景在《金匮要略》中提到肺痿，认为是热在上焦，因咳嗽而导致肺叶枯萎。其成因或是发汗过多，或是呕吐，或是消渴症小便频数，或是大便困难，或是被峻下药攻下导致腹泻，严重耗伤津液。所以寸口脉象数而虚，口中反而有浑浊的唾沫涎液。推究其意，是从《内经》痿证的条文推演而来，在于脏气虚弱，不能布散营卫、运行津液，反而冤郁化为热，蕴结为涎沫浊唾，进而引发咳嗽。所以附方中或用炙甘草汤，或用生姜人参大枣汤，所治的大致意思相似。又说肺痿吐涎沫但不咳嗽，患者不口渴，必定伴有遗尿、小便频数，这也是因为上焦虚寒不能制约下焦的缘故。这属于肺冷，咳嗽多涎唾，用甘草生姜汤来温补。如果服药后感到口渴，属于消渴症，那么此处所治的情况，就与前条上焦热者不同了。上焦热则冤郁，肺之玄府（毛孔及气机出入之门户）燥涩，气机不利则咳，津液不布则渴。这里说的肺中冷，并非有形寒饮冷之邪在其中，而是由于上焦无阳气，所以叫冷。阳气不足则不能化热，不热则不咳也不渴，只有气虚而不能约制水道的运行。肺与肾相连，肺虚则肾亦虚，所以水入咽直达于肾，肾也不能将水精四布于五脏，而径直从溺道排出。这就是仲景所说的肺冷咳。
大抵肺焦迫于热，良由肾水衰败，不能制约火势，这是真脏受损的祸患。应当配合各种脏腑热痿，使用壮水之剂，并治疗右肾火衰，导致脾土失于资助，肺金缺乏护卫，冒犯外邪，不渴而咳，唾涎沫背部形成龟胸者，特因为是下虚而不能奉养上焦。虽然说不热不咳，但这是因寒导致的气逆，不能用热证论治，宜益火之源。或者脾土自虚，不能生肺金，皮毛日渐憔悴，或咳或唾，从中焦亏虚论治。至于仲景所说的冷痿，则宜升举阳气而温存它。如果是形寒饮冷导致的痿证，则须温散其寒，资养化源。刘河涧也论述过，气血是人的神志基础，如果气血或郁结，或衰虚，不能宣通，则神无所用，不能遂其机能，所以显得劣弱。应当随其虚实进行补泻，使气血宣行，则神自然清利而应机，能发挥作用了。李东垣曾提到暑月发生的痿厥，乃单独列举四肢痿软、热厥，以及冲脉气逆等情况，治疗用清燥去湿热之药，或生脉饮合四苓散加黄柏、知母。不知此乃是湿热成痿，属于不足中有余的病证。所以宜用渗泄法。至于精血枯涸，筋脉衰弛，肌肉日渐消瘦而成痿，这是不足中的复不足，全须用峻补之剂，方法大不相同。考察诸书，又将痿痹不仁每每混同立论，这是因为依据《内经》脾痿中提到的“肌肉不仁”，便固执地认为痿痹是一病。其实痛则为痹，不痛则为痿。痹实痿虚，痹由风寒湿所致，气滞不行；而痿则是血少气虚，二者相差甚远。也有误作风湿论治的，病状看似相同实则不同，原因就在这里。《内经》又曾提及一端，所谓肾风而不能食，善惊，惊已心气痿者死。还有太阴司天，湿气下临，肾气上从，阴痿气太衰而不起，这是从所司之内症而论。若仲景更明确肺藏所生气之虚实者又如此，那么肝脾二脏，虽然没有明文，观此亦可类推了。我认为《内经》所言诸痿，则是真正的痿症。张仲景从而推明之，又有说是冷痿的，李东垣说有湿热痿的，又有从火衰而致的，土虚而得的，饮冷而得的，这些不是真痿，乃是如痿（像痿证但不是真痿）。如痿与真痿不可不详加辨别。
The *Neijing* (Classic of Internal Medicine) discusses the five Zang organ flaccidity syndromes, repeatedly emphasizing lung heat as the primary pathogenesis. However, in treating flaccidity syndromes, it advocates exclusively selecting the Yangming channel. The Yangming and Taiyin are exteriorly-interiorly related; they serve as the sea of Qi and Blood for the five Zang and six Fu organs, primarily moistening the Zongjin (tendons gathered at the anterior yin), binding the bones, and facilitating joint movement. They also converge with the Chong, Dai, and Du vessels and act as the general assembly of Yin and Yang meridians. Therefore, the human body possesses True Yang Qi that ascends and descends, circulating and operating, remaining vigorous and unceasing. Spirit, Qi, Blood, temperament, nature, Hun, and Po do not suffer from languor and depression; rather, they all adhere to the normal patterns of opening/closing and movement/stillness. Flaccidity syndrome refers to limbs that are weak and lacking strength, unable to move vigorously. Generally, this occurs because Metal (Lung) fails to generate Water (Kidney), causing the Kidney to lose its function of "Zuoqiang" (physical vigor and robustness), thereby manifesting as flaccidity. The Lung governs the skin and hair, the Heart governs the blood vessels, the Spleen governs the muscles, the Liver governs the sinews/fascia, and the Kidney governs the bone marrow. The Lung is the chief of all Zang organs and serves as a cover for the Heart. When flaccidity occurs, the lung leaves become scorched and dry, and the skin and hair lose their nourishment; Metal is parched by Fire, making it difficult for Water to protect the Mother organ. Heat qi lingers and stagnates, inevitably affecting the sinews, vessels, bones, and flesh, thus generating the disease of flaccidity. In Heart flaccidity, vessel Qi rebels upward while the lower part is deficient; the joints break, the shins hang loose, and the feet cannot bear weight, termed Mai Fei (Vessel Flaccidity). In Liver flaccidity, Gallbladder Qi leaks, causing bitter taste in the mouth; the fascia becomes dry and contracts, termed Jin Fei (Sinew Flaccidity). In Spleen flaccidity, the Stomach becomes dry with thirst, and the muscles feel numb and insensible, termed Rou Fei (Flesh Flaccidity). In Kidney flaccidity, the waist and spine cannot be held upright, the bones become withered, and the marrow decreases, termed Gu Fei (Bone Flaccidity). This constitutes the Neijing's discussion on various flaccidity syndromes.
Zhang Zhongjing, in the *Jingui Yaolue* (Essential Prescriptions of the Golden Cabinet), mentions Fei Fei (Lung Flaccidity), attributing it to heat in the Upper Jiao, leading to lung withering due to coughing. Its causes include excessive sweating, vomiting, Xiao Ke (Wasting-Thirst) with frequent urination, difficulty in defecation, or severe fluid depletion caused by harsh purgatives inducing diarrhea. Consequently, the Cun Kou pulse is rapid yet empty, and the mouth produces turbid saliva and froth. Tracing its logic, this expands upon the flaccidity clauses in the Neijing: when Zang Qi is deficient and cannot distribute Ying-Wei (Nutritive and Defensive Qi) or transport Body Fluids, oppression transforms into heat, which accumulates to form saliva and froth, subsequently triggering coughing. Thus, supplementary formulas such as Zhigancao Tang (Honey-Fried Licorice Decoction) or Shengjiang Renshen Dazao Tang (Fresh Ginger, Ginseng, and Jujube Decoction) are used, sharing similar therapeutic principles. It is further stated that in Lung Flaccidity, one may expect spitting of saliva and froth without coughing, and the patient feels no thirst but suffers from enuresis and frequent urination. This is due to upper deficiency failing to control the lower. This condition represents Cold Lung, characterized by coughing with abundant saliva and froth, treated with Gancao Shengjiang Tang (Licorice and Fresh Ginger Decoction) to warm the interior. If thirst arises after taking the decoction, it indicates Xiao Ke (Wasting-Thirst); thus, the treatment here differs from the previously mentioned Upper Jiao Heat pattern. Upper Jiao Heat causes oppression, drying the Xuanfu (pores and Qi gates) of the Lung; obstructed Qi leads to coughing, and unspread fluids lead to thirst. The "Cold Lung" described here does not imply the presence of exogenous cold or cold drinks, but rather the absence of Yang Qi in the Upper Jiao, hence termed "cold." Insufficient Yang Qi fails to generate heat; without heat, there is no cough or thirst. Only Qi deficiency prevents the regulation of water passage flow. The Lung and Kidney are connected; Lung deficiency leads to Kidney deficiency. Therefore, ingested water flows directly to the Kidney, which, being unable to distribute essence throughout the five Zang organs, discharges it directly via urine. This explains Zhang Zhongjing's concept of Cold Lung Cough.
Generally, lung scorching under heat pressure stems from Kidney Water decline, failing to control Fire, representing a disaster of the True Zang. Treatment should combine agents that tonify Water for various Zang organ heat flaccidities, address Right Kidney Fire decline (which deprives Spleen Earth of support), and manage Lung Metal lacking protection against external pathogens. Cases presenting with non-thirsty coughing, spitting of saliva/froth, and dorsal deformity resembling turtle shell (Guixiong) are specifically due to lower deficiency failing to nourish the upper. Although described as non-hot and non-coughing, this is Qi rebellion induced by cold and should not be treated as a heat syndrome; instead, one should benefit the source of Fire. Alternatively, if Spleen Earth is inherently deficient and fails to generate Lung Metal, causing daily deterioration of skin and hair, or coughing/spitting originating from middle jiao deficiency, it should be treated from the perspective of middle deficiency. Regarding Zhang Zhongjing's "Cold Flaccidity," one should raise Yang and warm gently. If flaccidity results from external cold and cold drinks, one must dispel cold warmly and nourish the transformation source. Liu Wansu also discussed that Qi and Blood are the spirit of humans; if Qi and Blood are stagnant or deficient and cannot circulate freely, the spirit has no utility and fails to perform its functions, resulting in weakness. One should tonify or drain according to deficiency or excess, allowing Qi and Blood to circulate so that the spirit naturally clears and responds appropriately. Li Dongyuan mentioned flaccidity and syncope occurring in summer heat, focusing on four-limb softness, heat syncope, and rebellious Qi in the Chong vessel. He treated these with herbs clearing dryness and removing damp-heat, or combining Shengmai San (Generate Pulse Powder) with Siling San (Four-Ling Powder) plus Huangbai (Phellodendri Cortex) and Zhimu (Anemarrhenae Rhizoma). Unaware that this represents damp-heat-induced flaccidity, a condition of "excess within deficiency," he should have employed draining and leaching methods. Conversely, when Essence and Blood are exhausted, sinews and vessels relax, and muscles waste away daily, this is "deficiency within deficiency," requiring potent tonification, a method vastly different from the former. Reviewing various texts, Fei (Flaccidity) and Bi (Obstruction) insensitivity are often conflated. This error stems from interpreting the "muscle insensitivity" in Spleen Fei from the Neijing as evidence that Fei and Bi are the same disease. Actually, pain characterizes Bi, while lack of pain characterizes Fei. Bi is excess, caused by Wind-Cold-Dampness stagnating Qi; Fei is deficiency, caused by scant Blood and deficient Qi. These are sharply distinct. Some mistakenly treat them as Wind-Damp diseases; although symptoms appear similar, the pathology differs fundamentally. The Neijing also mentions specific endpoints: Ren Feng (Kidney Wind) causing anorexia, frightfulness, and subsequent Heart Qi flaccidity leading to death; or during Taiyin ruling heaven, dampness descends, Kidney Qi follows upward, causing Yin flaccidity and extreme Qi failure to rise. These are internal symptoms based on celestial influences. If Zhang Zhongjing clarified the deficiency/excess of Qi generated by the Lung Zang, then the Liver and Spleen, though lacking explicit text, could be inferred by analogy. I believe the various flaccidities in the Neijing represent true Fei syndromes. Zhang Zhongjing expanded upon them. Others mention Cold Fei, Li Dongyuan mentions Damp-Heat Fei, some attribute it to Fire decline, Spleen deficiency, or cold drink consumption. These are not true Fei but "pseudo-flaccidity" (Ru Fei). True flaccidity and pseudo-flaccidity must be carefully distinguished.