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Liu Baozhi's commentary: The term "Fu Xie" (latent pathogenic factor) was not mentioned before. Since Jiang Wenzhai wrote the *Yi Lue* (Medical Strategy), thirteen chapters, prominently proposing the name "Fu Xie", the disease of "Fu Wen" (latent warm disease) has finally become clear to the world. Unfortunately, in his chapter on "Fu Xie", although he extensively cited texts from the *Neijing* (Inner Canon) and Zhang Zhongjing, being detailed and complete; he intermingled Wu Keyou's theory about the "Mu Yuan" (seminary/moat origin), claiming that Fu Xie is identical to and closely linked with Wen Yi (warm epidemic). Little did he know that the pathogen of Wen Yi enters through the mouth and nose, absorbing damp-turbid pathogens, which hide in the Mu Yuan, thereby causing symptoms such as alternating chills and fever, chest fullness and stuffiness, nausea, and vomiting. On the other hand, the pathogen of Fu Wen invades internally via the meridians, attacking with wind-cold pathogens, hiding in the Shaoyin (Lesser Yin) meridian, causing symptoms like alternating chills and fever, and body pain. The etiology and manifestations are completely different. Jiang failed to carefully distinguish them, often forcing the theory of Mu Yuan into his discussion of Fu Xie, causing confusion among learners. Therefore, I urgently selected the original text of Jiang's "Fu Xie" chapter to refute it item by item, so that readers may have a clear mind and not confuse Fu Xie with epidemic pathogens. I do not enjoy debating with predecessors; rather, because the mechanism of disease involves life and death, no ambiguity is tolerated.

What is called Fu Xie is winter cold pathogens hiding between the Mu Yuan, transforming into heat and damaging Yin fluids, transmitting simultaneously to the exterior and interior, mostly manifesting as heat syndromes. The basis for this is that upon onset, urine becomes turbid, either yellow or red.
Original note by Lanting states: Urination is governed by the Qi transformation of the Zhou Du (bladder). If the pathogen is at the exterior, it should not affect the interior, so why would the color change and become turbid? This is clearly evidence of pathogens hiding in the middle, transforming into heat and damaging Yin.

Liu Baozhi's commentary: Damp-turbid pathogens absorbed through the mouth and nose hide in the Mu Yuan via the Lung and Stomach. When autumn cool air binds the exterior, it manifests as Fu Shu (latent summerheat). Winter cold pathogens entering through the skin and hair hide in the Shaoyin via the Taiyang (Greater Yang) meridian. When spring warmth reaches the exterior, it manifests as two diseases: Fu Wen (latent warm disease) and Shu Wen (summerheat-warm disease). Their etiologies and manifestations are strictly separate paths. Wu Keyou's discussion on the etiology of warm epidemics belongs entirely to damp-turbid pathogens. Jiang claimed that winter cold hides in the Mu Yuan, mixing Wen (warm) and Shu (summerheat) pathogens into one disease. Since his understanding of the topic is wrong, his theoretical arguments naturally miss the mark.

Manifestations include: At onset, urine is red and turbid; mental restlessness and insomnia; or aversion to cold with shivering; or steaming fever; or only fever without aversion to cold; or fever persisting after sweating; or tidal fever with alternation; or chills and fever resembling malaria; or headache and body pain; or mania and delirium; or thirst or no thirst; or preference for hot drinks despite heat; or sweating or no sweating; or sweating but heat not reaching the lower limbs.

Liu Baozhi's commentary: When latent cold transforms into heat and emerges from the Shaoyin, there are often painful joints and stiffness/pain in the waist and spine, because the Kidney governs bone marrow, and the waist/spine is the territory of the Taiyang meridian. Internal heat steaming upward causes headache. Do not mistake this for an exterior syndrome and force sweating. If the pathogen has transformed into heat but the patient still desires hot drinks, it is due to turbid phlegm obstructing the interior; hot drinks help disperse it. In warm diseases, if sweat occurs but heat does not reach the lower limbs, or feet are cold, this is due to deficiency of healthy Qi leading to stagnant Qi flow, or severe pathogen causing Qi depression. The condition will likely worsen subsequently, requiring careful attention.

Tongue coating may be white, yellow, gray, or black; slippery or rough; with prickles; or conversely, no coating with purple-red tongue body.

Liu Baozhi's commentary: When pathogens involve the Stomach, coating appears on the tongue. Wu Keyou discussed pathogens emerging from the Mu Yuan, hence initially the coating resembles accumulated powder. As pathogens transform into heat and worsen day by day, the coating changes from white to yellow, then gray, then black, worsening progressively. However, if Fu Wen transforms into heat and emerges from the Shaoyin, sometimes it does not involve the Stomach, resulting in a normal tongue color. Whether gray/black coating is absent, even white/yellow coating is not thick. Indeed, heat in the Yin meridians does not invade the Stomach, so turbid Qi in the Stomach cannot ascend to form coating. This is also the distinction between warm and summerheat syndromes; learners should comprehend this carefully.

Stool may be constipated or loose; or discharge foul-smelling water; or resemble spoiled sauce; or contain blood stasis.

Liu Baozhi's commentary: Latent warm-heat pathogens nourish themselves within the interior. Unobstructed bowel movement serves as the exit route for heat pathogens. This contrasts with Shanghan (cold damage) where loose stool indicates pathogen sinking inward, yet the underlying principle is consistent.

If wet-earth season commands,酿成湿温 (brewing damp-warmth), body pain is extreme, urine more turbid. Treat referencing the Dampness chapter. However, dampness transforms from earth, earth has no fixed position, dampness has no specific syndrome. Focus primarily on treating Fu Xie, assisted by warming and unblocking methods for dampness.

Liu Baozhi's commentary: Damp pathogens include external seasonal dampness and internal long-term latent dampness. Body pain may also occur unrelated to dampness. All must be treated separately. Regarding treatment strategy—whether prioritizing dampness or latent warmth—depends on the severity of damp vs. warm pathogens and the urgency of symptoms. One must not hold preconceived notions.

Resolution may occur via battle-sweat, spontaneous sweat, restless sweat, manic sweat, macules, or papules.

Liu Baozhi's commentary: Exterior Qi stagnation can indeed resolve via macules/papules or battle-sweat. But to seek resolution at the exterior, Interior Qi must first flow freely. Thus, purging the bowels is a critical juncture in treating Fu Wen and cannot be overlooked.

Severe cases may present with convulsions, coma resembling drunkenness, black tongue coating with prickles, scorched lips/teeth, soot-like nostrils, cracked tongue, hiccups rushing up from the lower abdomen, head shaking, limb tremors, or急促 breathing with phlegm obstruction.

Liu Baozhi's commentary: These severe symptoms indicate heat溃败 (溃败:溃烂/breakdown) in the Yin levels, blazing to the Stomach organ, or involving the Hand-Foot Jueyin meridians. They must be treated distinctly, not mixed together.

Pulse should avoid tight, choppy, fine, and rapid qualities; instead, prefer harmonious, slippery, and large pulses.

Liu Baozhi's commentary: Warm pathogen pulses are typically string-taut, slippery, rapid, and large. Occasionally, heat constraint causes fine/rapid/unsmooth pulses; healthy Qi deficiency causes weak/fine/non-rapid pulses. Both indicate serious illness; physicians must pay attention.

Treatment methods vary: Some start with modified Wu's Da Yuan Yin (Reach the Origin Decoction), treating from the Middle Jiao, followed by sweating or purging. If Taiyang/Yangming/Jueyin exterior signs appear, add Qiang Huo (Notopterygium Rhizome), Ge Gen (Kudzu Root), Chai Hu (Bupleurum Root). If Yin interior signs appear, add Mang Xiao (Mirabilite), Da Huang (Rhubarb Root). Order may be sweat then purge, or purge then sweat; repeat sweating or purging; or only sweat, or only purge; or nourish Yin to resolve pathogens, combining tonification and draining. Do not be confused by "Jia Yin" (clamped Yin); mistakenly using Gui Zhi Tang (Cinnamon Twig Decoction) or Fu Zi (Aconite Root) will cause death. Observe syndrome and pulse, exterior/interior, deficiency/excess, age/strength, local climate, diet richness/coarseness, and treat comprehensively. Post-illness care should harmonize the Stomach and nourish Yin.

Original note by Lanting says: The term "Jia Yin" is folk tradition without basis. If sexual activity causes disease in men as "Jia Yin", does it mean women have "Jia Yang"? It is laughable. Yin syndromes in the Three Yin meridians occur in children too, unrelated to sexual activity. Moreover, Yin syndromes belong to Zheng Shanghan (True Cold Damage); Fu Xie and Yi Xie (epidemic pathogens) generally do not have Yin syndromes; if any, they are rare.

Liu Baozhi's commentary: When latent cold transforms into warmth and emerges from Yin, the method should assist Yin to push out pathogens. Da Yuan Yin is drying and damaging to Yin; it is suitable only for damp-heat in the Mu Yuan with turbid/greasy tongue coating. Using it for Fu Wen would aggravate heat and consume Yin. Jiang mistakenly identified Wu Keyou's epidemic pathogens as Fu Wen, ignoring the *Neijing* and *Nanjing*.

Further commentary: Wu's listed treatments for exterior syndromes use many drying/harsh agents that injure Yin, unsuitable for latent Qi warming which first damages the Yin level. However, his interior treatments align well with Fu Wen and offer much to learn. Wu observed mostly latent Qi cases; his discussions reflect latent Qi patterns. Due to unclear etiology and imprecise insight, compounded by mixed damp-heat pathogens, he labeled everything as epidemic pathogens even when describing Fu Wen accurately. This shows Wu's rash theorizing.

For no sweat: Jiu Wei Qiang Huo Tang (Nine-Ingredient Notopterygium Decoction), Huo Ren Bai Du San (Life-Saving Toxin-Expelling Powder), Chai Ge Jie Ji Tang (Bupleurum and Kudzu Muscle-Releasing Decoction), Xiao Chai Hu Tang (Minor Bupleurum Decoction), Wu's Da Yuan Yin plus Taiyang/Yangming/Jueyin exterior herbs, or Chai Hu Bai Hu Tang (Bupleurum and White Tiger Decoction) from medical anecdotes. For purging: Da Cheng Qi Tang (Major Order the Qi Decoction), Tiao Wei Cheng Qi Tang (Regulate the Stomach Order the Qi Decoction), Tao Ren Cheng Qi Tang (Peach Kernel Order the Qi Decoction), Da Chai Hu Tang (Major Bupleurum Decoction), Chai Hu Jia Mang Xiao Tang (Bupleurum Plus Mirabilite Decoction), Liang Ge San (Cool the Grid Powder), Ba Cui Xi Jiao Di Huang Tang (Excellence Collection Rhino Horn Rehmannia Decoction), Wu's Da Yuan Yin plus Da Huang, or Zhong Cheng Qi Tang/Lou Bei Er Chen Tang from anecdotes. For nourishing Yin/resolving pathogens: Xi Jiao Di Huang Tang (Rhino Horn Rehmannia Decoction), Chai Hu Sheng Di Tang (Bupleurum and Rehmannia Decoction) from anecdotes. For combined tonification/draining: Tao Shi Huang Long Tang (Tao's Yellow Dragon Decoction), Da Huang Ren Shen Tang (Rhubarb and Ginseng Decoction) from anecdotes, or Ban Xia Xie Xin Tang (Pinellia Drain the Epigastrium Decoction), Shi Wei Wen Dan Tang (Ten-Ingredient Warming Gallbladder Decoction). Post-care: Gui Shao Er Chen Tang plus Gu Ya (Grain Sprout) and Shen Qu (Medicated Leaven) from anecdotes. This is the general outline; divine application depends on the individual.

Liu Baozhi's commentary: Listed formulas are roughly scattered. Learners seeing the gist cannot directly use them for treatment. The sweating agents listed, such as Jiu Wei Qiang Huo and Bai Du/Jie Ji formulas, are harsh and injure Yin, especially unsuitable for warm diseases. Learners must not be misled.

The *Huangdi Neijing Lingshu: Xieqi Zangfu Bingxing Pian* states: When Zheng Xie (regular pathogens) attack humans, it is subtle; first seen in complexion, unnoticed by the body; seeming present yet absent, existing yet vanishing; shapeless, its nature unknown.

The *Wubian Pian* states: At the beginning of all diseases, they must arise from wind, rain, cold, and heat, entering through hair follicles and couli (pores); some return, some remain.

The *Suwen: Shengqi Tongtian Lun* states: Injury by cold in winter leads to warm disease in spring.

The *Bazheng Shenming Lun* states: Zheng Xie attacks subtly when the body exerts effort, pores open from sweat, encountering deficient winds; its nature is unknown, its form unseen.

The *Relun Pian* states: Current heat diseases are all categories of Shanghan (cold damage).

These *Neijing* chapters clearly state that Zheng Xie hides internally, later manifesting as warm disease.

Liu Baozhi's commentary: The above *Neijing* passages discuss Fu Xie in detail. Why does Jiang still mix in the Mu Yuan theory, confusing them?

The *Liuyuan Zhengji Dalun* states: When Si Tian (ruling) Qi brings warmth, grass flourishes. Amidst public health, warm plagues erupt widely; this indicates prior latent pathogens.

The *Nanjing* states: Pulses of warm diseases travel through various meridians, making it hard to identify the active meridian. This implies latent pathogens in the meridians. The *Zhouli* mentions plagues in all four seasons. Deeply hidden pathogens can take a year to manifest.

The *Lüshi Chunqiu* states: The *Liji* defines non-seasonal Qi as plague, i.e., Fu Xie manifesting upon stimulation.

The *Shiji* records: Changxin of Qi's Imperial Guard fell into water in winter, soaking clothes; in spring, he developed fever. This proves latent pathogens transform into heat.

Liu Baozhi's commentary: The *Lüshi Chunqiu* passage conflates plague and Fu Xie, which is Jiang's fundamental error.

The *Jingui Yaolüe* notes: Baihe Bing (Lily Disease) resolves only after sufficient days pass, indicating it is a type of Fu Xie.

The *Shanghan Lun: Pingmai Pian* explicitly names Fu Xie as a disease category.

The *Shanghan Li* states: Cold toxins hide in skin/flesh, becoming warm in spring, summerheat in summer. This bases "winter cold injury leading to spring warm disease" on canonical principles.

The *Taiyang Pian* states: Taiyang disease with fever, thirst, and no aversion to cold is warm disease. No aversion to cold means pathogen is not at the exterior; thirst indicates internal heat, clearly showing latent Qi.

The *Yangming Pian*'s purgative syndromes align with the concept of Fu Xie entering the Stomach.

The *Shaoyin Pian*'s spontaneous diarrhea and epigastric pain, and the *Jueyin Pian*'s "deeper cold, deeper heat," along with purgative syndromes, align with the concept of Fu Xie transforming into heat and damaging Yin.

Liu Baozhi's commentary: After Shanghan transforms into heat, its treatment is largely similar to Fu Wen. The difference lies in the onset: Fu Wen emerges from interior to exterior, opposite to typical Shanghan progression.

The *Taiping Yulan* cites Cao Zhi: Plague afflicts those wearing coarse cloth and eating vegetables, living in thorn-huts; rarely affects palace dwellers and noble families. This shows malnutrition/cold damaging healthy Qi, with pathogens hiding then manifesting. Chao Yuanfang compared plague to seasonal warm-heat, failing to recognize variations in severity based on the same hidden pathogen. The *Tongjian Tang Ji* records: Guanzhong suffered famine; soldiers/civilians were emaciated. When wheat ripened, drunkards appeared in markets, hailed as auspicious. Sudden overeating killed one-fifth. This wasn't wind-cold, but internal activation of latent pathogens. Liu Hejian's *Xuanming Fang* advised against hot drugs for plague; using Bai Hu Tang and Liang Ge San for exterior release confirms internal latent heat.

Li Dongyuan's *Bianhuo Lun* records: During Wang Chen's reign change, Beijing was besieged for half a month. After relief, almost everyone got sick, nearly a million died. Was it all wind-cold? No, it was caused by latent pathogens. The *Danxi Xinfa Fuyu* includes methods for treating Fu Xie excellently; compare with Wu's *Wenyi Lun*.

The *Danxi Xinfa* states: Plague affects everyone similarly. Treatment has three methods: tonify, disperse, descend. Start with Da Huang and Huang Qin to purge the interior, acknowledging internal latent pathogens.

Fang Yuezhi stated: Warm-heat diseases arise from external/internal injuries triggering stagnant fire, emerging from interior to exterior. This explicitly states pathogens hide within. The *Yuan Shi* records Yelu Chucai using Da Huang to treat soldiers' plague, proving pathogens hide in the interior.

Liu Baozhi's commentary: The above passages discuss plague syndromes; Jiang forces them into Fu Xie discussions. Plague syndromes include pure plague cases and those combined with Fu Xie; treat according to symptoms. Conflating them confuses both Fu Xie and plague treatments.

Wang Lv's *Suhui Ji* states: Warm/heat diseases emerge during hot weather, with stifling heat rising from interior to exterior. He noted that mistakenly purging the interior in warm-heat treatment causes little harm, but mistakenly sweating the exterior causes unpredictable changes, proving heat rises from interior to exterior.

Zhang Jingyue considered plague essentially Shanghan, occurring in spring/summer, resolving only after sufficient days with sweat. This aligns with *Jingui*'s Baihe Bing, implying internal latent pathogens. Wu Keyou's *Wenyi Lun* addressed Fu Xie effectively but denied "winter cold leads to spring warm disease." He failed to understand that winter cold is the regular pathogen of winter; its attack is subtle, appearing in complexion, seemingly present/absent, activating upon exertion/sweat/open pores. Thus, regular pathogens can hide and manifest later. This shows the ancient origins of Fu Xie theory.

Liu Baozhi's commentary: *Suhui Ji* correctly discusses latent Qi emergence. Jiang's conflation of Fu Xie and plague is erroneous. Zhang Jingyue's claim that plague is Shanghan is doubly wrong. His insistence on waiting for days to resolve is also inaccurate, as Zhang lacked clarity on Six Exogenous Pathogens.

Wu Keyou focused solely on plague, labeling all contemporary diseases as epidemic pathogens regardless of whether they were Fu Wen or plague. Blaming others for his lack of distinction, he doubted the *Neijing*'s "winter cold" statement. His reasoning was crude and dogmatic. Although Jiang recognized the hidden pathogen as Zheng Xie, surpassing Wu, he still used Da Yuan Yin as the main formula in his chapter, contradicting himself.

Human strength varies; attack and tonification differ. There are three major principles: Attacking pathogens is the best strategy; supporting healthy Qi while expelling pathogens is medium; nourishing Yin and holding fast is the worst. Pathogens hiding within are like internal rebellion; healthy Qi and pathogens clash irreconcilably. If healthy Qi is intact, directly attack pathogens; once pathogens retreat, healthy Qi recovers. If healthy Qi is deficient and cannot withstand attack, temporarily support healthy Qi, fighting and defending simultaneously, outcome uncertain. If healthy Qi is severely depleted, only nourishing Yin remains; hold fast hoping pathogens self-resolve, though this is dangerous. Therefore, if healthy Qi is not deficient, even heavy Fu Xie can be cured properly; only healthy Qi deficiency is feared. Ignorant people consider attacking pathogens too harsh, preferring mild formulas, allowing pathogens to advance daily, healthy Qi to decline, leading to light cases becoming heavy, heavy cases becoming critical, and death. They blame fate, which is absurd.

Liu Baozhi's commentary: Jiang's argument prioritizes attacking pathogens, believing that removing pathogens saves Yin. Wu Juztong's *Wenbing Tiaobian* prioritizes nourishing Yin. Once Yin is replenished, exterior fluid suffices for sweat; interior fluid allows navigation (bowel movement). Abundant Yin resolves heat; nourishing Yin drains heat. I believe these two methods should be applied based on the patient. For Yin deficiency, nourishing Yin to drain heat suits Wu's approach. For severe pathogens, draining heat to preserve Yin suits Jiang's approach. Though seemingly opposite, they complement each other.