河间曰∶咳谓无痰而有声，肺气伤而不清也；嗽是无声而有痰，脾湿动而为痰也；咳嗽
谓有痰而有声，盖因伤于肺气，动于脾湿，咳而为嗽也。脾湿者，秋伤于湿，积于脾也。故
经曰∶秋伤于湿，冬必咳嗽。大抵素秋之气宜清肃，而反动之，气必上冲为咳嗽，甚则动于
湿而为痰也。假令湿在肝经，谓之风痰；湿在心经，谓之热痰；湿在脾经，谓之湿痰；湿在
肾经，谓之寒痰，宜随证而治之。若咳而无痰者，以辛甘润其肺，如蜜煎生姜汤，蜜煎橘皮
汤之属是也。若咳而嗽者，当以治痰为先，治痰者，必以顺气为主，是以南星、半夏胜其痰
，而咳嗽自愈，枳壳、陈皮利其气，而痰自下。痰而能食者，大承气汤微下之；痰而不能食
者，浓朴汤疏导之，此治法之大体也。
愚观河间此说，谓治嗽当先治痰，因以南星、半夏之属为主，似得治嗽之法矣。此其意
谓嗽必因痰，故胜其痰而嗽自愈，则理有不然也。盖外感之嗽，必因风寒，风寒在肺，则肺
气不清，所以动嗽，动嗽然后动痰，此风邪痰嗽之本，本于外感，非外感本于痰也。又如内
伤之嗽，必因阴虚，阴虚则水涸金枯，所以动嗽，脾虚肾败，所以化痰，此阴虚痰嗽之本，
本于内伤，非内伤本于痰也。今曰治嗽当先治痰，岂求本之道乎？然治外感之嗽者，诚惟二
陈之属为最效，又何故也？盖南星、半夏、生姜、陈皮、枳壳之类，其味皆辛，辛能入肺，
辛能散寒，寒邪散则痰嗽自愈，此正所以治本，而实非所以治痰也。若内伤阴虚之嗽，则大
忌辛燥，此辈岂堪轻用哉。经曰∶肺欲辛，以辛泻之，此肺实者之宜辛也。又曰∶辛走气，
气病无多食辛，此肺虚者之忌辛也。气味宜否之理，《内经》妙用如此，河间何以不察，而
谓南星、半夏之属但能治痰，岂果治痰之标便能治嗽之本乎。
刘河间说：咳嗽中，“咳”是指没有痰但有声，这是肺气受损而不清肃的表现；“嗽”是指有痰但无声，这是脾湿扰动而生痰的结果；“咳嗽”则是指既有痰又有声，这是因为肺气受伤、脾湿内动，导致先咳后嗽。所谓脾湿，是因为秋季感受了湿邪，湿气积聚在脾脏所致。所以医经上说：“秋季伤于湿，到了冬天必定会咳嗽。”大抵初秋的气候应当清肃，如果这种气候被反常之气所扰动，气机必然上冲引发咳嗽，严重时还会因湿邪而动生痰液。假如湿邪停留在肝经，就称为风痰；湿邪停留于心经，就称为热痰；湿邪停留在脾经，就称为湿痰；湿邪停留在肾经，就称为寒痰，治疗应当根据具体证候来施治。如果是干咳无痰的，应当用辛甘之品滋润肺脏，比如蜜煎生姜汤、蜜煎橘皮汤这类方剂。如果是既咳又嗽（有痰）的，应当以治疗痰为先，治疗痰饮的关键在于顺调气机，因此使用天南星、半夏来消除痰浊，咳嗽自然痊愈；使用枳壳、陈皮来疏通气机，痰液自然下行。如果患者有痰且能进食，可用大承气汤轻微攻下；如果患者有痰而不能进食，则用浓朴汤疏导气机，这是治疗的大致原则。
我认为刘河间的这一说法，主张治疗嗽症应当先治痰，并以天南星、半夏等药物为主，似乎掌握了治疗嗽症的方法。但他的观点认为嗽症必然由痰引起，所以消除了痰嗽症就会自愈，这个道理其实是不对的。大概外感引起的嗽症，必然因为风寒之邪，风寒侵袭肺脏，导致肺气不清，从而引发咳嗽，咳嗽久了才带动痰液生成，这是风邪痰嗽的根本，根本在于外感，而不是外感源于痰。又如内伤引起的嗽症，必然因为阴虚，阴虚导致津液枯竭、肺金干燥，从而引发咳嗽；脾虚肾败，从而产生痰液，这是阴虚痰嗽的根本，根本在于内伤，而不是内伤源于痰。现在他说治疗嗽症应当先治痰，这难道是探求病本之道吗？然而，治疗外感引起的嗽症，确实以二陈汤之类的方剂最为有效，这是什么原因呢？原来天南星、半夏、生姜、陈皮、枳壳等药物，味道都是辛的，辛味能入肺，辛能发散寒邪，寒邪散去则痰嗽自然痊愈，这才是真正在治疗根本，实际上并不是单纯在治疗痰。如果是内伤阴虚引起的嗽症，则非常忌讳辛燥之品，这些药物怎么可以轻易使用呢？医经上说：“肺喜辛，用辛味来泻肺”，这是针对肺实证适宜用辛味的情况。又说：“辛味走气，气病时不要多吃辛味”，这是针对肺虚证忌讳辛味的情况。关于气味是否适宜的机理，《黄帝内经》的运用如此精妙，刘河间为什么不仔细考察，而认为天南星、半夏之类仅仅能治痰，难道治疗痰的标症就能治好嗽症的本源吗？
Liu Hejian stated: "Ke" (cough with sound but no phlegm) refers to the impairment of Lung Qi resulting in a lack of clarity; "Sou" (phlegm production without sound) refers to Spleen dampness stirring up and generating phlegm; "Ke Sou" (cough with both sound and phlegm) occurs due to injury to Lung Qi and agitation by Spleen dampness, where coughing leads to phlegm production. The so-called Spleen dampness arises from dampness injured in autumn, accumulating in the Spleen. Thus, the classics state: "Injury to dampness in autumn leads to Ke Sou in winter." Generally, the qi of early autumn should be clear and肃 (descending/clearing); if this is disturbed, the qi must rush upward causing Ke Sou, and severely, it moves dampness to generate phlegm. If dampness resides in the Liver channel, it is called Wind Phlegm; if in the Heart channel, Heat Phlegm; if in the Spleen channel, Damp Phlegm; if in the Kidney channel, Cold Phlegm. Treatment should follow the specific syndrome. For dry cough without phlegm, one should moisten the Lung with acrid-sweet substances, such as Honey-fried Ginger Decoction or Honey-fried Tangerine Peel Decoction. For cough accompanied by phlegm, treating phlegm should be prioritized. Treating phlegm requires regulating Qi as the main principle; thus, using Arisaema Rhizoma (Nanxing) and Pinellia Tuber (Banxia) eliminates phlegm, and Ke Sou heals spontaneously; using Aurantium Fructus (Zhike) and Citrus Reticulatae Pericarpium (Chenpi) benefits Qi flow, and phlegm descends naturally. If phlegm is present but the patient can eat, Da Cheng Qi Tang (Great Conveyer Qi Decoction) should be used for mild purgation; if phlegm is present but the patient cannot eat, Nong Po Tang (Thick Magnolia Bark Decoction) should be used for dredging and guiding. This is the general principle of treatment.
I observe that Liu Hejian's theory advocates treating Sou first by addressing phlegm, primarily using Arisaema Rhizoma and Pinellia Tuber, which seems to grasp the method for treating Sou. His intent implies that Sou must be caused by phlegm, so eliminating phlegm cures Sou. However, this reasoning is not entirely correct. Generally, external contraction-induced Sou is necessarily due to Wind-Cold. When Wind-Cold invades the Lung, Lung Qi becomes unclear, triggering cough; prolonged cough then stirs phlegm. The root of Wind-Phlegm Sou lies in external contraction, not that external contraction originates from phlegm. Similarly, internal injury-induced Sou is necessarily due to Yin Deficiency. Yin Deficiency leads to dried fluids and withered Metal (Lung), triggering cough; Spleen deficiency and Kidney failure generate phlegm. The root of Yin-Deficient Phlegm Sou lies in internal injury, not that internal injury originates from phlegm. To say that treating Sou requires first treating phlegm—is this seeking the root? Yet, for treating external contraction-induced Sou, Er Chen Tang (Two-Aged Decoction) and similar formulas are indeed most effective. Why is this? Because Arisaema Rhizoma, Pinellia Tuber, Fresh Ginger, Citrus Reticulatae Pericarpium, and Aurantium Fructus all have Acrid flavors. Acrid enters the Lung, and Acrid disperses Cold. Once Cold pathogens are dispersed, Phlegm-Sou heals spontaneously. This is truly treating the root, not merely treating phlegm. Conversely, for internal injury Yin-Deficient Sou, Acrid-Dry substances are strictly contraindicated; how can these herbs be lightly used? The classics state: "The Lung desires Acrid; use Acrid to drain it," which applies to Lung Excess patterns suitable for Acrid. It also states: "Acrid moves Qi; do not consume much Acrid when Qi is diseased," which applies to Lung Deficiency patterns contraindicating Acrid. The principles regarding the suitability of flavors and properties are applied so exquisitely in the Huangdi Neijing (Yellow Emperor's Inner Canon). Why did Liu Hejian fail to examine this, claiming that Arisaema Rhizoma and Pinellia Tuber only treat phlegm? Does treating the branch of phlegm truly cure the root of Sou?