并病者，一经先病未愈，又起一经病者。如先见太阳病未解，又见阳明病，此太阳与阳明并
病。如先见太阳病未解，又见少阳病，此太阳与少阳并病。《伤寒论》言二阳并病两条，一曰
面赤色，不足言，阳气怫郁在表，烦躁不知痛处，但坐以汗出不彻，更发汗则愈。此言宜汗
也，虽不立方，然北方冬月麻黄汤，南方羌活汤跃跃矣。二曰太阳症罢，潮热汗出，大便难
而谵语者，宜大承气汤。此言宜下也。其论太阳少阳并病三条，第一言头项强痛，眩冒如结
胸，心下痞硬，当刺大椎，慎不发汗。脉弦谵语，当刺期门，此言不可汗也。第二言心下
硬，颈项强而眩者，当刺大椎、肺俞、肝俞、此言慎勿下也。第三言反下之，成结胸，下利
不止，水浆不入，其人心烦，此言误下变症也。
汗吐下温针诸法皆用过而病不解，名坏症。又有汗吐下诸法，颠倒误用而病不解，亦名坏
症。言坏症，非言必坏之症，言无经络表里，无汗吐下诸法可治者，故曰坏症。按《伤寒论》
坏症两条，上条言太阳病，汗吐下温针用过，桂枝汤又不中用；下条言太阳病，已吐下发汗，
温针反见谵语，此为坏症。自此详之，则太阳病用不得发表解肌，少阳病用不得柴胡和解，
阳明症用不得葛根汤，即是坏病。总之，此经之病，用不得此经之方法正治者，亦名坏症。
故曰看其脉症，知犯何逆，随症治之，而不立方法。
并病，是指一经的病证尚未痊愈，又出现了另一经的病证。例如，先出现太阳病未解，又出现阳明病，这称为太阳与阳明并病。又如，先出现太阳病未解，又出现少阳病，这称为太阳与少阳并病。《伤寒论》中论述二阳（太阳、阳明）并病的条文有两条：第一条说，面部发红，这是阳气郁滞在体表所致，患者烦躁不安且不知道疼痛的具体部位，只是因为发汗不彻底，再次发汗即可痊愈。这里指出适宜采用发汗法，虽然原文没有列出具体方剂，但北方冬季适用的麻黄汤，南方适用的羌活汤，其意已跃然纸上。第二条说，如果太阳病症候消失，出现定时发热、出汗、大便困难且胡言乱语的情况，适宜使用大承气汤。这里指出适宜采用攻下法。
关于太阳与少阳并病的论述有三条：第一条说，头项强痛，头晕目眩如同结胸证的症状，胃脘部痞塞硬满，应当针刺大椎穴，切忌发汗。若脉象弦细且出现胡言乱语，应当针刺期门穴，这里指出不可发汗。第二条说，胃脘部硬满，颈项强直且头晕的，应当针刺大椎穴、肺俞穴、肝俞穴，这里指出切忌攻下。第三条说，如果误用攻下法，导致变成结胸证，腹泻不止，水浆不能入口，心中烦乱，这里指出是误用攻下法导致的变证。
经过发汗、催吐、攻下、温针等各种治法治疗后，病证仍未解除，称为坏症。又有因发汗、催吐、攻下等治法颠倒误用而导致病证未解除的，也称为坏症。所谓坏症，并非指必然会导致败坏的病证，而是指此时病邪已无明确的经络表里之分，也没有固定的汗、吐、下等常规治法可以应用，所以称为坏症。
查阅《伤寒论》中关于坏症的条文有两条：上一条说太阳病，已经用过发汗、催吐、攻下、温针等法，连桂枝汤也不起作用了；下一条说太阳病，已经用过催吐和攻下，又误用温针，反而出现胡言乱语，这属于坏症。由此详细分析可知，太阳病若不能用发表解肌的正治法，少阳病若不能用柴胡汤和解，阳明病若不能用葛根汤（注：此处原文意指阳明经证或相关解表法失效），即属于坏病。总之，这一经的病证，若不能使用这一经的正治方法，也称为坏症。因此说，要观察患者的脉象和症状，了解医生犯了什么错误（逆治），然后随证进行治疗，而不设立固定的治疗方法。
Bingbing (Concurrent Disease) refers to a condition where the disease in one meridian has not yet resolved, and a disease in another meridian arises. For example, if Taiyang disease (Disease of the Taiyang Meridian) appears first and remains unresolved, followed by Yangming disease (Disease of the Yangming Meridian), this is called Taiyang-Yangming Bingbing. Similarly, if Taiyang disease appears first and remains unresolved, followed by Shaoyang disease (Disease of the Shaoyang Meridian), this is called Taiyang-Shaoyang Bingbing.
The *Shanghan Lun* (Treatise on Cold Pathogenic Diseases) contains two clauses discussing Er Yang (Dual Yang: Taiyang and Yangming) Bingbing. The first states: "Facial redness indicates that Yang Qi is constrained at the exterior. The patient experiences irritability and restlessness without knowing the specific location of pain; this is due to incomplete sweating. Re-administering diaphoresis will lead to recovery." This indicates that diaphoresis (sweating therapy) is appropriate. Although no specific formula is prescribed, the implication points to Mahuang Tang (Ephedra Decoction) for winter in the north, or Qianghuo Tang (Notopterygium Decoction) for the south. The second clause states: "If Taiyang symptoms have ceased, but there is tidal fever, sweating, difficulty in defecation, and delirium, Da Chengqi Tang (Major Order the Qi Decoction) is indicated." This indicates that purgation (downward-draining therapy) is appropriate.
There are three clauses discussing Taiyang-Shaoyang Bingbing. The first states: "Stiffness and pain in the head and neck, dizziness and vertigo resembling Jie Xiong (Chest Binding), and fullness and hardness in the epigastrium indicate need for acupuncture at Dazhui (GV14). Caution against diaphoresis. If the pulse is wiry and delirium occurs, acupuncture at Qimen (LR14) is indicated." This indicates that diaphoresis is contraindicated. The second states: "Fullness and hardness in the epigastrium, stiffness in the neck, and dizziness indicate need for acupuncture at Dazhui (GV14), Feishu (BL13), and Ganshu (BL18)." This indicates that purgation is strictly contraindicated. The third states: "If purgation is mistakenly used, it results in Jie Xiong (Chest Binding), incessant diarrhea, inability to take food or fluids, and mental restlessness." This describes complications arising from erroneous purgation.
When diseases remain unresolved after the use of diaphoresis, emesis, purgation, and warm needle moxibustion, it is termed Huai Zheng (Ruined Disease/Malpractice Sequelae). Similarly, if these methods are applied incorrectly or in the wrong sequence, leading to unresolved disease, it is also termed Huai Zheng. The term "Huai Zheng" does not necessarily mean a disease destined to deteriorate fatally, but rather a state where the disease no longer follows clear meridian exterior-interior patterns, and standard therapies (diaphoresis, emesis, purgation) are ineffective. Hence, it is called Huai Zheng.
Reviewing the two clauses on Huai Zheng in the *Shanghan Lun*: The first describes Taiyang disease where diaphoresis, emesis, purgation, and warm needle moxibustion have been used, and Guizhi Tang (Cinnamon Twig Decoction) is ineffective. The second describes Taiyang disease where emesis and purgation were used, followed by erroneous warm needle moxibustion, resulting in delirium; this constitutes Huai Zheng. From this detailed analysis, we understand that if Taiyang disease cannot be treated with exterior-releasing and muscle-relaxing methods, if Shaoyang disease cannot be treated with Chai Hu (Bupleurum) harmonizing methods, or if Yangming disease cannot be treated with Gegen Tang (Kudzu Decoction) [Note: Contextually referring to appropriate Yangming exterior/interior resolution], it becomes a Huai Bing (Ruined Disease). In summary, when the disease of a specific meridian cannot be treated with the standard correct method for that meridian, it is named Huai Zheng. Therefore, the principle is: "Observe the pulse and symptoms, determine what error was made, and treat according to the current presentation," without establishing fixed treatment protocols.