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The Fifty-Eighth Difficulty of the *Nan Jing* (Classic of Difficult Issues) states: How many types are there in Shanghan (Cold Damage diseases)? Do their pulses change? The answer is: There are five types of Shanghan: there is Zhongfeng (Wind Strike), there is Shanghan, there is Shiwen (Damp-Warmth), there is Rebing (Heat Disease), and there is Wenbing (Warm Disease). The suffering associated with each is different.

Xu Huixi stated: "Shanghan" is a general term. The following five categories are differentiated syndromes of Shanghan.

I (Liu Baozhi) comment: Zhongfeng (Wind Strike) and Shanghan refer to the syndromes listed in Zhang Zhongjing's treatise; these are conditions that manifest immediately upon pathogenic invasion. However, if Cold Evil remains latent and suppressed within the body before manifesting, then when triggered by warm winds, it is named Fengwen (Wind-Warmth); when triggered by summer heat, it is named Rebing (Heat Disease), which refers to Summerheat disease after the Summer Solstice; when triggered by dampness, it is named Shiwen (Damp-Warmth). Although they bear different names due to varying seasons and etiologies, since they all originate from cold exposure, they are all referred to as Shanghan.

I further comment: "The suffering differs" means that the pathological manifestations of these five conditions vary. The *Shanghan Lun* (Treatise on Cold Damage) states: In Taiyang disease (Taiyang Channel Syndrome), if there is fever, sweating, aversion to wind, and a slow pulse, it is named Zhongfeng (Wind Strike). In Taiyang disease, whether fever has already appeared or not, there must be aversion to cold; accompanied by body pain, vomiting, and a tight pulse at both yin and yang positions, it is named Shanghan. In Taiyang disease, if there is joint pain and irritability, with a deep and thin pulse, this is Shibi (Damp Bi syndrome). Taiyang Zhongre (Summerheat affecting Taiyang) refers to Ye (Heatstroke); the patient sweats, feels aversion to cold, has body heat, and thirst. In Taiyang disease, if there is fever and thirst without aversion to cold, it is Wenbing (Warm Disease). These five clauses describe the distinct sufferings and clinical presentations of the five diseases listed in the treatise. The first two clauses refer to conditions where cold pathogen induces immediate illness; the latter three refer to cold latent internally, complicated by other pathogens inducing illness. Zhang Zhongjing classified all five under the *Shanghan Lun*, demonstrating that all five syndromes stem from cold, and thus can all be termed Shanghan.

The pulse of Zhongfeng (Wind Strike) is floating and slippery at the yang position (superficial/cun), and soggy and weak at the yin position (deep/chǐ). The pulse of Shanghan is full and tight-rough at both yin and yang positions. The pulse of Shiwen (Damp-Warmth) is soggy and weak at the yang position, and small and rapid at the yin position. The pulse of Rebing (Heat Disease) is floating at both yin and yang positions; superficially it is slippery, deeply it is scattered and rough. The pulse of Wenbing (Warm Disease) moves through various meridians; one does not know which meridian is affected, so diagnosis should follow the location of the affected meridian.

I (Liu Baozhi) comment: Here, "yin and yang" refer to pulse characteristics. Generally, cun is yang, chǐ is yin; right is yang, left is yin; superficial is yang, deep is yin. Regarding this specific section, it is most appropriate to distinguish yin and yang by the cun and chǠ positions. Wind is a yang pathogen, hence the yang pulse is floating and slippery. Cold evil causes contraction, hence the pulse is tight and rough. Dampness is a yin pathogen that damages yang, hence the yang pulse is soggy and the yin pulse is rapid. Rebing (Heat Disease) is a yang pathogen that damages yin fluids, hence superficially floating and slippery, but deeply scattered and rough. Rebing (Heat Disease) represents Warm Evil that has transformed into heat and is moving outward; prior to heat transformation, it is called Wenbing (Warm Disease). The pathogen lies latent in Shaoyin (Lesser Yin), moves with qi, and circulates through various meridians. It may erupt when meridian qi is deficient, or it may erupt carrying newly acquired external pathogens. Its eruption may exit via the Three Yang channels or emerge from the Lung and Stomach. The most severe cases involve heat failing to exit externally and sinking inward into the Hand and Foot Jueyin (Pericardium/Liver) channels; or Kidney qi being deficient, unable to expel the pathogen, causing it to blaze and knot in Shaoyin. Thus, the movement of Warm Evil follows diverse paths and can erupt anywhere; initially, one cannot specify which meridian will be affected, nor can one rigidly predict the pulse manifestation.

I further comment: Latent Warmth disease erupts along the meridians; this teaching is clear and beyond doubt. However, Zhang Shiwang claimed that Warm Evil eruption must originate from Shaoyang (Lesser Yang). Lu Jiuzhi asserted that Warm-Heat disease must erupt in Yangming (Bright Yang). Chen Pingbo considered the Lung and Stomach as the inevitable sites of Warm Evil attack. Wu Keyou argued that the Mouyuan (Miao Yuan/Sea of Origin) is the residence of latent pathogens in Warm Epidemics. Although each school offers unique insights, they only highlight one aspect of Warm Disease and cannot represent its entirety. Furthermore, Wu Jutong, in his *Wenbing Tiaobian* (Systematic Differentiation of Warm Diseases), horizontally divided the pathology into the Triple Burner (San Jiao), asserting that all Warm Diseases begin in the Upper Burner, specifically the Hand Taiyin Lung channel. Consequently, he categorized contemporary seasonal warm wind patterns as diseases caused by latent qi erupting. This conflation is particularly erroneous. Scholars must carefully study this scriptural passage to firmly understand that Warm Disease eruption follows the meridians, thereby gaining true insight during clinical practice and avoiding misleading interpretations.

In Shanghan, some recover through sweating but die after purgation; others die after sweating but recover after purgation. Why? The answer is: In deficiency of Yang and excess of Yin, sweating leads to recovery, while purgation leads to death. In excess of Yang and deficiency of Yin, sweating leads to death, while purgation leads to recovery.

Slip Shou, in his commentary, cited the *Waitai Miyao* (Essential Prescriptions Worth a Thousand Gold for Emergencies): "Surface disease with harmonious interior constitutes Deficiency of Yang and Excess of Yin." When the pathogen is at the surface, diaphoresis (sweating method) is indicated; if purgation is mistakenly used, it draws the pathogen inward and attacks healthy qi unnecessarily, leading to death. "Interior disease with harmonious surface constitutes Excess of Yang and Deficiency of Yin." When the pathogen has entered the interior, urgent purgation is indicated; if diaphoresis is mistakenly used, it further depletes the surface qi, leading to death. The *Shanghan Li* also contains text stating: "Excess of Yang and Deficiency of Yin: sweating causes death, purgation causes recovery; Deficiency of Yang and Excess of Yin: sweating causes recovery, purgation causes death." Various commentators offer differing explanations. Cheng Wuji noted that Yang pathogen entering the fu organs due to deficiency constitutes Excess of Yang and Deficiency of Yin; pathogen invading Ying and Wei due to surface deficiency constitutes Deficiency of Yang and Excess of Yin. The *Waitai Miyao* and Liu Hejian’s *Shanghan Zhige* defined "non-diseased" as excess and "diseased" as deficiency. The *Huo Ren Shu* defined internal and external heat as Excess of Yang and Deficiency of Yin; internal and external cold as Deficiency of Yang and Excess of Yin. Only Wang Andao in his *Suhui Ji* stated that external Cold Evil indicates Excess of Yin suitable for sweating; internal blazing Heat Evil indicates Excess of Yang suitable for purgation. This explanation is the most sound. The theory that "non-diseased is excess, diseased is deficiency" aligns closely with "surface disease/interior harmony" and "interior disease/surface harmony," yet the terms "excess" and "deficiency" remain semantically imprecise in this context.

I (Liu Baozhi) comment: Upon initial invasion of Cold Evil, before heat transformation, Wei Yang is obstructed, resulting in Deficiency of Yang and Excess of Yin; this is acute Shanghan. Using acrid-warm herbs to assist yang and induce sweating resolves the pathogen. If purgation is applied prematurely before the pathogen enters the fu organs and transforms into heat, the interior qi is damaged and the exterior pathogen sinks inward, leading to death. If the pathogen remains suppressed for a long time and transforms into heat, consuming yin fluids, it results in Excess of Yang and Deficiency of Yin; this is latent Qi Wenbing (Warm Disease). Once interior heat is abundant, urgent purgation is required to preserve yin fluids for survival. If acrid-warm herbs are mistakenly used to induce sweating, yin fluids are further depleted and complications arise rapidly. Therefore, at the onset of illness, the pathogen is always cold, justifying the use of Shanghan as the overarching framework. This section comprises two layers, interpreted by contrasting Shanghan and Wenbing, which is highly appropriate. The previously cited scholarly opinions seem less direct than this explanation.