Wang Kentang: Shaoyin, Jueyin, and Taiyin diseases (Three Yin diseases) involve pathogenic factors transmitted via meridians and those caused by internal infection. Transmission via meridians refers to the progression from the Taiyang meridian. Internal infection refers to direct invasion of the Three Yin meridians, not sequentially spreading from the Yang meridians. This is caused by damage to the Stomach Qi due to exposure to cold and consumption of cold drinks or food. The pulse and symptoms are somewhat similar to those of external contraction in Shanghan (Cold Damage), but careful differentiation reveals significant differences. However, these belong to the category of miscellaneous diseases (Zabing) and are not the cold-induced heat diseases described in the *Shanghan Lun*.

Pathogens arise either from Yin or from Yang. Those arising from Yang result from wind, rain, cold, and summer-heat. Those arising from Yin result from improper diet and lifestyle, as well as emotional fluctuations (joy, anger, etc.). Zhang Zhongjing stated: "Fever with aversion to cold indicates onset in the Yang; absence of fever with aversion to cold indicates onset in the Yin." In cases of internal infection of the Three Yin, there is typically no fever throughout the course. If fever does occur, it is what Zhang Zhongjing termed "counter fever" (Fan Re). Examining the phrase "at the beginning" clarifies this. Internal infection remains confined to one meridian without further transmission. Why does it not transmit? Because Yang is dynamic and Yin is static; thus, Yang meridians transmit while Yin meridians do not. If discussed in terms of the Six Meridians of Shanghan, only the exterior-interior meridians are involved. Moreover, when Wind-Cold and the Six Qi pathogens attack humans, they may strike Yang meridians or enter Yin collaterals. Who comes first, who comes second? How can one exclusively regard the Taiyang meridian as the starting point of pathogenic invasion? Therefore, all meridians can be affected. However, invasions starting from Taiyang are more common than others. Generally, even if heat arises within the Three Yin, it will eventually transmit to the Yangming before subsiding. Cold invasion of the Three Yin never transmits further. This is why there are no combined diseases in the Three Yin.

Wang Kentang: I once read Zhang Zhongjing's *Shanghan Lun*. Regarding the Taiyin chapter, it states: "Spontaneous diarrhea without thirst belongs to Taiyin because the zang organs have cold; therefore, it should be warmed, and formulas like Sini Tang (Four Reversal Decoction) are appropriate." Regarding the Shaoyin chapter, it states: "In Shaoyin disease, after one or two days, if the mouth feels normal but there is aversion to cold on the back, moxibustion should be applied, and Fuzi Tang (Aconite Decoction) should be used." "Shaoyin disease with body pain, cold hands and feet, bone and joint pain, and a deep pulse is treated with Fuzi Tang." "Shaoyin disease with diarrhea is treated with Baitong Tang (White Onion Decoction)." "In Shaoyin disease, if diarrhea is accompanied by a faint pulse, give Baitong Tang; if diarrhea persists, leading to cold limbs, absent pulse, dry vomiting, and irritability, use Baitong Tang plus Porcine Gallbladder Juice." "Shaoyin disease with clear undigested stool in diarrhea, interior cold with exterior heat, cold limbs, and a pulse faint and near extinction, yet the body is not averse to cold, and the face is red, or there is abdominal pain, dry vomiting, sore throat, or cessation of diarrhea with an unpalpable pulse, is treated with Tongmai Sini Tang (Pulse-Recovering Four Reversal Decoction)." "Shaoyin disease with a deep pulse requires urgent warming with Sini Tang." Regarding the Jueyin chapter, it states: "Cold limbs and a pulse fine and near extinction are treated with Danggui Sini Tang (Angelica Decoction for Warming the Extremities)." "Profuse sweating or severe diarrhea leading to cold limbs is treated with Sini Tang." Observing these discussions by Zhang Zhongjing, it is evident that Three Yin diseases in Shanghan must present with cold syndromes suitable for warm-hot formulas.

However, upon reading Liu Shouzhen's (Liu Wansu's) works, he stated: "Shanghan pathogenic heat in the exterior and fu organ diseases are Yang pathogens; heat in the interior and zang organ diseases are Yin pathogens. It is a vulgar misconception to believe there are distinct cold and hot Yin-Yang syndromes, which has misled people for a long time. Cold diseases exist, but they do not refer to sweat-inducing diseases (external febrile diseases). Cold diseases are limited to miscellaneous diseases and cannot constitute external febrile diseases. Furthermore, the qi that generates bodily fluids is Yang-heat qi, not something produced by Yin-cold. Although Zhang Zhongjing mentions Sini Tang syndrome, it treats cases where exterior heat was present with interior harmony, but cold herbs were used to purge too early, causing exterior heat to enter the interior and resulting in persistent diarrhea; or cases of exterior heat with interior cold causing spontaneous diarrhea, where Sini Tang is urgently used to warm the interior. Once diarrhea stops and interior harmony is restored, the exterior is then resolved. Thus, after Sini Tang, Chengqi Tang (Gardenia and Rhubarb Decoction) may be used for purging. Consequently, the classics explicitly discuss Shanghan as heat diseases, not cold diseases. When the classics mention Three Yin syndromes, it is because pathogenic heat is in the zang and interior (which are Yin), requiring purging of the heat. The *Suwen* has two chapters on Shanghan heat diseases titled 'Re Bing' (Heat Disease), containing no mention of 'cold'. Combining the *Suwen* and *Lingshu*, and deducing from the principles of Yungu (Six Qi transformation), these are indeed heat diseases, certainly not cold. Based on Liu Shouzhen's argument, whether Shanghan is in the exterior or interior, and regardless of the Three Yang or Three Yin, it is uniformly heat, with absolutely no cold."

These two theories differ, and their correctness must be determined. I repeatedly scrutinized and investigated the meaning, unable to reach a conclusion for a long time, exhausting my spirit and energy without giving up, believing this to be the general principle of Shanghan. Without understanding this principle, thousands of words are insufficient for students, and the harm to human life would be endless. I assumed Cheng Wuji's commentary must have some insights, so I sought them there, but he merely explained the text superficially without clearly stating why it is heat or why it is cold. This was not because he didn't want to say, but because he believed Shanghan involves only meridian transmission, suspecting that all six meridians transmit heat, and since heat does not transform into cold, he dared not distinguish otherwise. If it were intrinsic cold of the zang, how could one see only cold and no heat when heat pathogens transmit deeply into the interior? Would warm-hot medicines not aid the transmitting heat? If it were external cold, wouldn't it already be heat in the Three Yang? How could it become cold upon reaching the Three Yin? If Cheng had pondered this, he would have understood. Since Zhang Zhongjing wrote the *Shanghan Lun*, it has been revered without omission. But with the rise of debates on similarities and differences, proponents of different views have gone their separate ways (like fishermen seeking fish in abysses and woodcutters in mountains). No wonder later generations could not decide between plausible and implausible interpretations. Some claim true Shanghan does not exist today; others say modern diseases are all internal injuries; ignorant people even claim that all warm medicines in the *Shanghan Lun* are used for transmitting heat because the Three Yin are Yin. The most absurd view is that any character 'cold' in the text should be read as 'heat'. Alas, the degeneration of scholarship has reached this point!

I cleared my mind and contemplated deeply. Suddenly, it became clear as if I had realized something, though I dare not assert its absolute correctness. I present it here for correction by those knowledgeable in the Way.

Regarding Three Yang diseases, when cold pathogens are in the Taiyang meridian, cold stagnates Yang Qi, causing obstruction and generating heat. Although Yang Qi is righteous Qi in the body, once obstructed, it becomes pathogenic. Using Mahuang Tang (Ephedra Decoction) to release the exterior expels cold, opening the pores and venting stagnant heat, leading to recovery through sweating. If sweating does not occur and heat is not resolved, it cannot escape outward and must enter the interior, transmitting to Yangming or Shaoyang, or entering the Fu organs.

Why are Three Yin diseases sometimes cold and sometimes heat? Generally, cold pathogens attacking humans may: 1) cause heat stagnation in Taiyang first, then transmit sequentially to Yin meridians; 2) skip Yangming and Shaoyang from Taiyang and directly transmit to the Three Yin; 3) bypass Yang meridians entirely and directly injure Yin meridians; 4) start in Taiyang but transmit to Shaoyin before heat stagnation occurs, showing only Shaoyin symptoms; 5) start in Taiyang and enter Shaoyin immediately, while Taiyang remains slightly injured; 6) directly injure and enter, transforming from cold to heat, or starting as cold and ending as heat. Cases involving heat stagnation transmitting to Yin or cold transforming to heat result in heat syndromes. Cases of direct Yin injury or immediate entry from Taiyang to Shaoyin result in cold syndromes. If Taiyang is not completely uninjured, Shaoyin pulse/symptoms may combine with Taiyang marker signs. If starting as cold and transforming to heat, cold signs appear first, followed by heat signs. This explains why Three Yin diseases vary between cold and heat. By carefully studying the clauses in the Three Yin chapters, the principles can be derived.

Why do some transmit, some suffer direct injury, some enter immediately, and some go from cold to heat? Because pathogens strike suddenly without fixed patterns, and transmission is irregular. As the classics state: "Pathogens attacking humans have no constancy; some strike Yang, some strike Yin."

Liu Shouzhen was an extraordinary scholar. Did he prefer heretical views to shock people? No. He likely equated Warmth and Summer-heat diseases with Shanghan. Since Zhang Zhongjing's formulas did not specifically address Warmth/Summer-heat, he omitted warm-hot formulas and generally used cold-cool ones. He categorized all Shanghan as heat without cold, thus claiming Zhang's Sini Tang was a cold formula mistakenly used for exterior heat with interior harmony, or for exterior heat with interior cold diarrhea, establishing methods to warm the interior, stop diarrhea, and urgently resolve the exterior. He also claimed cold diseases are only miscellaneous diseases. Alas! Zhang Zhongjing's *Shanghan Lun* was written specifically for Shanghan contracted immediately upon cold exposure, not for non-immediate Warmth/Summer-heat diseases. Therefore, Three Yin cold syndromes exist, and warm-hot formulas are used because the disease is cold and the season is cold; their use is appropriate. Later generations, misunderstanding this, search further away and make increasingly rigid interpretations. Understanding this is like Cook Ding carving an ox—moving precisely at the joints.

Although cold herbs mistakenly purging leading to interior cold is undeniable, can we say interior cold arising spontaneously without such mistake is impossible? We must realize that cold syndromes in Yin meridians often arise because cold pathogens directly injure these meridians without passing through Yang, or pass through Taiyang but enter before heat stagnation occurs. Cases due to mistaken purging are rare. Were Zhang's warm-hot formulas established solely for mistaken purging? Did exterior heat with interior cold always require urgent exterior resolution? The syndrome of interior cold with exterior heat is caused by cold pathogens invading internally, forcing Yang Qi outward, or by deficient Yang Qi manifesting as false exterior heat, not true heat pathogens. Zhang Zhongjing treated interior cold with warm medicines without addressing the exterior heat in such cases, revealing his intent. If urgent exterior resolution were necessary, would he not have specified it after interior harmony was restored?

If Three Yin cold diseases are merely miscellaneous diseases, why are they recorded in the *Shanghan Lun* to confuse later generations? Why do the Jueyin chapter clauses begin with the word "Shanghan"? The *Neijing* describes Three Yin diseases as uniformly heat, representing the norm. Zhang Zhongjing describes them as mixed heat and cold, representing variations. Both coexist without contradiction. To claim Shanghan has no cold syndromes is to know the norm but ignore variation.

Ironically, those who strictly follow the Bureau Formulary and favor warm-hot formulas often succeed in treating cold syndromes. This is because, although their theory is biased, recognizing that Three Yin inherently has cold syndromes allows one to understand Zhang Zhongjing's original intent and resist other theories.

Someone asks: "Shanghan must transmit from Yang meridian heat stagnation to Three Yin. You claim direct injury to Yin meridians causes cold syndromes. What is your evidence?" I answer: Zhang Zhongjing. He said: "Disease with fever and aversion to cold originates in Yang; disease without fever and with aversion to cold originates in Yin. Yang-originating diseases heal in seven days; Yin-originating in six." "Without fever and with aversion to cold" proves it is not Yang heat stagnation. "Originating in Yin" proves it did not transmit from Yang. "Healing in six days" proves it did not start in Taiyang but began counting from the day of Yin meridian onset. Zhang Zhongjing also said: "Shanghan, from day one or two to four or five, if there is cold extremities (Jue), there must be fever. If Jue lasts five days, fever lasts five days. If on the sixth day Jue returns, the disease progresses; if it does not return, it heals. If Jue lasts four days, fever three days, then Jue five days, the disease worsens." Can cold extremities appearing before fever in Shanghan be attributed to deep-transmitted heat pathogens? Today, many patients present with cold syndromes from the onset without any heat. These are cases of direct Yin injury and immediate entry. If one fails to grasp Zhang Zhongjing's heart and clings to "all cold injuries result in heat diseases," few will avoid premature death.