两感者，表里双传也，一日太阳与少阴同病，二日阳明与太阴同病，三日少阳与厥阴同
病，如在太阳，则发热头痛；在少阴，则咽干口燥；在阳明，则目痛鼻干；在太阴，则腹满
自利；在少阳，则耳聋胁痛；在厥阴，则烦满囊缩。表里并传，为祸最速，此论传经之两感
也。又如仲景所谓少阴证反发热，用麻黄附子细辛汤者，此论直中之两感也。传经两感，以
解表为主而清里佐之；直中两感以温中为主而发表次之。此治两感之大法也。或问曰∶太阳
初得病，尚未传经，何以即有少阴热证也？答曰∶此温热之候多有之，本有积热在内，而外
为风寒鼓之，故表里并见，阴阳双传也，其病至暴，倘治失其宜，去生远矣。
伤寒兼症者，非传经六经之正病，亦非直中三阴之正病，而实为伤寒所恒有之症，故皆
以兼症名之。其间有见于手经者，有因误治而变症者，有病中调摄失宜而变症者，有病气相
传染而变症者，临症之工，按法取之，曲尽其情，则伤寒无余蕴矣。
咳嗽者，肺寒也。经云∶形寒饮冷则伤肺是也。肺主皮毛，寒邪侵于皮毛，连及于肺，
故令人咳。宜用止嗽散，加荆芥、防风、紫苏子主之。或问曰∶少阳证与直中证，水气证，
皆令咳嗽，何也？答曰∶少阳证兼咳嗽者，以其肺有寒也，仲景用小柴胡去参、枣加干姜者
所以温肺散寒也。直中证兼咳嗽者，亦寒气上束于肺也，但温其中而咳自止。水气证兼咳
嗽者，以寒水上射于肺也，宜分表里水气治之∶表有水气而发热，用小青龙汤发散以行水；
里有水气而下利，则用本方去麻黄，加荛花，以攻之；轻则用小半夏加茯苓汤，以疏之，俾
水饮流通，而咳自止矣。以上三证，皆感寒水之气而咳，故谓咳为肺寒也。又问曰∶俗称热
伤风咳嗽者，何也？答曰∶热伤风者，如冬温之候、天应寒而反温，自人受之，则为头痛喉
肿，咽干咳嗽之属，与正风寒之咳稍异。又或其人素有郁热，而外为风寒束之，热在内而寒
在外，谚云寒包火是也。又问曰∶咳嗽有不兼风寒，而专属火者，何也？答曰∶此杂证嗽也
或夏令暑热之火，或饮食辛辣之火，或脾肺气虚之火，或龙雷 上之火，皆令咳嗽，各有
兼证，与伤寒鼻塞声重，头痛发热恶寒之状，自是不同，并与热伤风之咳迥别，宜于本门求
之，不得与伤寒同日语矣。
两感病，是指表里两经同时受邪。第一天是太阳经与少阴经同病，第二天是阳明经与太阴经同病，第三天是少阳经与厥阴经同病。如果病在太阳经，则出现发热、头痛；病在少阴经，则出现咽干、口燥；病在阳明经，则出现目痛、鼻干；病在太阴经，则出现腹部胀满、自发性腹泻；病在少阳经，则出现耳聋、胁肋疼痛；病在厥阴经，则出现心烦、胸中满闷、阴囊收缩。表里两经同时传变，危害最为迅速，这是指循经传变的“两感”病。又比如张仲景所说的少阴病反而发热，使用麻黄附子细辛汤治疗的情况，这是指寒邪直中的“两感”病。对于循经传变的两感病，治疗以解表为主，兼清里热为辅；对于寒邪直中的两感病，治疗以温中为主，兼解表次之。这是治疗两感病的总原则。有人问：太阳病初起，尚未传经，为什么立刻就有少阴经的热证呢？回答说：这种情况在温热病候中多有发生，患者体内本有积热，又被外部的风寒所激发，所以表里症状同时出现，阴阳两经同时受邪，病情非常急暴，如果治疗不当，离生存就远矣。
伤寒兼症，不是六经正病的传变，也不是三阴经直中的正病，而是伤寒病中经常出现的症状，所以都称为兼症。其中有的见于手经（肺、心包、三焦），有的是因误治而变生的症状，有的是因病中调摄失宜而变生的症状，有的是因病气相互传染而变生的症状。临证医生若能按照法则选取治疗方法，详尽探究其情状，那么对伤寒病的认识就没有遗漏了。
咳嗽，多属肺寒。医经说：“形体受寒、饮食生冷就会损伤肺脏。”肺主皮毛，寒邪侵袭皮毛，进而连及于肺，所以使人咳嗽。适宜使用止嗽散，加入荆芥、防风、紫苏子来主治。有人问：少阳病证、寒邪直中证、水气证，都会导致咳嗽，为什么呢？回答说：少阳病兼见咳嗽的，是因为肺中有寒，张仲景用小柴胡汤去掉人参、大枣，加入干姜，是为了温肺散寒。寒邪直中证兼见咳嗽的，也是寒气上束于肺所致，只要温补中焦，咳嗽自然停止。水气证兼见咳嗽的，是因为寒水上射于肺，应当分表里水气进行治疗：表有水气且伴有发热的，用小青龙汤发散以行水；里有水气且伴有下利的，则用本方（小青龙汤）去掉麻黄，加入荛花，以攻逐水饮；病情较轻的，用小半夏加茯苓汤，以疏利水道，使水饮流通，咳嗽自然停止。以上三种证候，都是感受寒水之气而致咳，所以说咳嗽属于肺寒。又问：俗称的“热伤风”咳嗽是怎么回事？回答说：所谓热伤风，如冬温时节，天气本该寒冷却反常温暖，人受此邪气，就会出现头痛、喉肿、咽干、咳嗽等症状，这与普通风寒引起的咳嗽稍有不同。或者是其人素有郁热，又被外部风寒束缚，热在内而寒在外，谚语所说的“寒包火”就是这种情况。又问：咳嗽有不兼风寒，而专门属于火邪的，是怎么回事？回答说：这是杂病引起的咳嗽，或是夏令暑热之火，或是饮食辛辣之火，或是脾肺气虚之火，或是龙雷之火上炎，都会导致咳嗽，各有兼夹症状，与普通伤寒鼻塞声重、头痛发热恶寒的症状自然不同，也与热伤风的咳嗽截然不同，应当在杂病门类中寻求治法，不能与伤寒同日而语。
Lianggan (Two-Channel Simultaneous Infection) refers to the simultaneous transmission of pathogens to both the exterior and interior channels. On the first day, the Taiyang Channel (Greater Yang) and Shaoyin Channel (Lesser Yin) are affected simultaneously; on the second day, the Yangming Channel (Bright Yang) and Taiyin Channel (Greater Yin); on the third day, the Shaoyang Channel (Lesser Yang) and Jueyin Channel (Terminal Yin). If the pathogen is in the Taiyang Channel, fever and headache occur; if in the Shaoyin Channel, dryness of the throat and mouth occurs; if in the Yangming Channel, pain in the eyes and dryness of the nose occur; if in the Taiyin Channel, abdominal fullness and spontaneous diarrhea occur; if in the Shaoyang Channel, deafness and hypochondriac pain occur; if in the Jueyin Channel, irritability, chest fullness, and contraction of the genitalia occur. The simultaneous transmission of exterior and interior channels causes the most rapid deterioration. This discusses Lianggan resulting from sequential channel transmission. Furthermore, as mentioned by Zhang Zhongjing regarding Shaoyin syndrome presenting with fever, treated with Mahuang Fuzi Xixin Tang (Ephedra, Aconite, and Asarum Decoction), this discusses Lianggan resulting from direct invasion by cold pathogens. For Lianggan via sequential transmission, treatment prioritizes releasing the exterior, assisted by clearing the interior. For Lianggan via direct invasion, treatment prioritizes warming the interior, with releasing the exterior as secondary. This is the general principle for treating Lianggan. One might ask: When Taiyang disease is just acquired, before it has transmitted to other channels, why are there immediately Shaoyin heat symptoms? The answer is: Such conditions frequently occur in warm-heat patterns. The patient inherently has accumulated heat within, which is stirred up by external wind-cold, resulting in simultaneous exterior and interior manifestations and dual transmission of Yin and Yang. The disease is extremely acute; if treated improperly, survival becomes distant.
Shanghan Jianzheng (Complications of Cold Damage) are not the primary diseases of the six-channel transmission nor the primary diseases of direct invasion into the three Yin channels, but rather symptoms constantly present in Shanghan, hence named "complications." Some appear in the Hand Channels (Lung, Pericardium, Sanjiao), some arise from mismanagement, some from improper care during illness, and some from contagion of pathogenic factors. Clinicians who apply methods according to principles and thoroughly understand these conditions will have exhausted the knowledge of Shanghan.
Ke Sou (Cough) is primarily due to Lung Cold. The Classics state: "Exposure to cold and consumption of cold drinks injure the Lung." The Lung governs the skin and hair. When cold pathogens invade the skin and hair, they extend to the Lung, causing cough. Zhisou San (Stop Cough Powder) added with Jingjie (Schizonepetae Spica), Fangfeng (Saposhnikoviae Radix), and Zisuzi (Perillae Fructus) is appropriate. One might ask: Shaoyang syndrome, direct invasion syndrome, and Shuiqi Syndrome (Water-Qi Syndrome) all cause cough. Why? The answer is: Shaoyang syndrome with cough is due to cold in the Lung; Zhang Zhongjing uses Xiaochaihu Tang (Minor Bupleurum Decoction), removing Renshen (Ginseng Radix et Rhizoma) and Dazao (Jujubae Fructus), adding Ganjiang (Zingiberis Rhizoma) to warm the Lung and disperse cold. Direct invasion syndrome with cough is also due to cold qi binding upward to the Lung; warming the middle jiao stops the cough naturally. Shuiqi Syndrome with cough is due to cold water flooding upward to the Lung. Treatment should distinguish between exterior and interior water-qis: If there is exterior water-qis with fever, use Xiao Qinglong Tang (Minor Green Dragon Decoction) to release the exterior and promote water metabolism; if there is interior water-qis with diarrhea, use the same formula minus Mahuang (Ephedrae Herba), adding Wanghua (Adenophorae Radix), to attack the pathogen; for mild cases, use Banxia Houpo Tang variant or specifically Xiaobanxia Jia Fuling Tang (Minor Pinellia plus Poria Decoction) to dredge the pathways, allowing water-drink to circulate freely, stopping the cough. These three syndromes all result from contracting cold-water qi, hence cough is attributed to Lung Cold. Another question: What is commonly called "Heat Wind-Cold" cough? Answer: Heat Wind-Cold, such as in Winter-Warmth seasons where weather is abnormally warm instead of cold, affects humans causing headache, sore throat, dry throat, and cough, differing slightly from standard wind-cold cough. Or, if a person has inherent stagnant heat bound by external wind-cold, with heat inside and cold outside, known colloquially as "Cold Wrapping Fire." Another question: What about coughs not associated with wind-cold but exclusively due to Fire? Answer: These are miscellaneous disease coughs, caused by summer heat-fire, spicy food-fire, Spleen-Lung Qi deficiency fire, or Dragon-Lei Fire rising. Each has accompanying symptoms, distinct from Shanghan symptoms like nasal congestion, heavy voice, headache, fever, and aversion to cold, and clearly different from Heat Wind-Cold cough. These should be sought in their respective categories and cannot be discussed alongside Shanghan.