伤寒咳者。何以明之。咳者声咳之咳。俗谓之嗽者是也。肺主气。形寒饮冷则伤之。
使气上而不下。逆而不收。冲击膈咽。令喉中淫淫如痒。习习如梗。是令咳也。甚者
续续不已。连连不止。坐卧不安。语言不竟。动引百骸。声闻四近矣。咳之由来。有肺
寒而咳者。有停饮而咳者。有邪气在半表半里而咳者。虽同曰咳。而治各不同也。
内经曰。肺之令人咳。何也。皮毛者肺之合也。皮毛先受寒气。寒气以从其合也。其
寒饮食入胃。从肺脉上至于肺。肺寒则外内合邪。因而客之。则为咳嗽者。是肺寒
而咳也。伤寒表不解。心下有水气。干呕发热而咳。小青龙汤主之。少阴病腹痛。小
便不利。四肢沉重疼痛。自下利者。此为有水气。其人或咳者真武汤加五味子细
辛干姜主之。二者是停饮而咳者也。虽皆为水饮所作。而小青龙场所主。为水饮
与表寒相合而咳者。真武汤所主。为水饮与里寒相合而咳者。又不可不知也。伤
寒中风。往来寒热。胸胁苦满。默默不欲饮食。心烦喜呕或咳者。小柴胡汤去人参
大枣生姜。加干姜五味子主之。少阴病四逆。其人或咳者四逆散加干姜五味子
主之。二者是邪气自表传里而咳者。虽皆为邪气传里。而小柴胡汤所主。为阳邪
传里。动肺而咳者。四逆散所主。为阴邪传里。动肺而咳者。又不可不识也。表、寒也。里、寒也。挟水饮则必动肺。
以形寒寒饮则伤肺故也。阳、邪也。阴、邪也。自表传里。则
必动肺。以脏真高于肺故也。咳为肺疾。治之必发散而可矣。而又有不可发汗者。
经曰。咳而小便利者。不可发汗。发汗则四肢厥逆冷。又曰。咳而发汗。蜷而苦满。腹
中复坚。兹虽逆也。又脉散者。为心火刑于肺金。鬼贼相刑必死。临病之侧。可不察
之。
伤寒咳嗽，该如何阐明呢？这里的“咳”，是指有声无痰的咳嗽。世俗称之为“嗽”（有痰无声）的，其实与此不同。肺主司气机运行。如果形体受寒或饮用冷食，就会损伤肺气。
这会导致气机上逆而不能下行，气机紊乱而不能收敛，冲击膈膜和咽喉，使得喉咙中感到阵阵瘙痒，如有异物梗塞感。这就导致了咳嗽。严重的患者会连续不断，连连不止，坐卧不安，说话不能说完，身体动作牵动全身，声音甚至能传到四周。
咳嗽的成因，有的是因肺寒所致，有的是因停饮（水液停滞）所致，有的是因邪气在半表半里之间所致。虽然都称为咳嗽，但治疗方法各不相同。
《内经》说：“肺为什么会让人咳嗽呢？”因为皮毛是肺的外合部位。皮毛先受到寒气侵袭，寒气便顺着其内合关系传入体内。如果此时又有寒凉饮食进入胃中，寒气会沿着肺脉上行至肺。肺脏既受外寒又受内寒，内外之邪相合，从而客居于肺，导致咳嗽。这就是肺寒而咳的情况。
在伤寒病中，如果表证未解，心下有水气，出现干呕、发热且咳嗽的症状，用小青龙汤主治。少阴病出现腹痛、小便不利、四肢沉重疼痛、自发性腹泻的情况，这是体内有水气。如果患者伴有咳嗽，用真武汤加五味子、细辛、干姜主治。这两种情况属于停饮而咳。虽然都是水饮作祟，但小青龙汤所主治的是水饮与表寒相合导致的咳嗽；真武汤所主治的是水饮与里寒相合导致的咳嗽。这一点不可不知道。
伤寒中风，出现往来寒热、胸胁部苦闷胀满、神情沉默不欲饮食、心烦喜呕，或者伴有咳嗽的情况，用小柴胡汤去掉人参、大枣、生姜，加入干姜、五味子主治。少阴病出现四肢厥逆，如果患者伴有咳嗽，用四逆散加干姜、五味子主治。这两种情况属于邪气从表传里导致的咳嗽。虽然都是邪气传里，但小柴胡汤所主治的是阳邪传里，扰动肺气导致的咳嗽；四逆散所主治的是阴邪传里，扰动肺气导致的咳嗽。这一点也不可不知晓。
表，指的是寒邪；里，也指寒邪。如果夹杂水饮，必然会扰动肺脏，因为形体受寒和寒凉饮食会损伤肺脏。阳，指的是阳邪；阴，指的是阴邪。邪气从表传里，必然会扰动肺脏，因为五脏的真气以肺为最高（肺为华盖）。咳嗽是肺部的疾病，治疗时必须通过发散的方法才能奏效。但是，又有不可以发汗的情况。
经书说：“咳嗽且小便通利的，不可发汗。”如果发汗，会导致四肢厥冷逆乱。又说：“咳嗽而误用发汗法，会导致身体蜷缩、苦于胀满，腹部再次变得坚硬。”这些都属于误治后的逆证。另外，如果脉象散乱，这是心火克制肺金，即“鬼贼相刑”（五行相克中的反侮），必然导致死亡。面对疾病时，怎能不仔细审察呢？
Cough in Cold Damage: How should this be elucidated? The term "cough" (Ke) here refers to a cough with sound but no phlegm. What the common people call "sou" (Soo), which typically implies phlegm without prominent sound, is distinct from this. The Lung governs Qi. When the body is exposed to cold or when cold drinks are ingested, the Lung is injured.
This causes Qi to ascend rather than descend, and becomes chaotic rather than convergent. It impacts the diaphragm and throat, causing a tingling itchiness in the throat, as if there were an obstruction. This results in coughing. In severe cases, it continues incessantly, preventing rest in any position, interrupting speech, involving the whole body in movement, and the sound can be heard by those nearby.
The origins of cough vary: some arise from Lung cold, some from retained fluid (Stagnant Fluid), and some from pathogenic factors situated between the exterior and interior. Although all are termed cough, their treatments differ.
The *Neijing* states: "Why does the Lung cause cough?" Because the skin and hair are the external correspondence of the Lung. If the skin and hair first receive cold pathogens, the cold follows its internal connection into the body. If cold food and drink enter the stomach, the cold travels up along the Lung meridian to the Lung. The Lung suffers from both external and internal cold; these combined evils lodge within, resulting in cough. This constitutes cough due to Lung cold.
In Cold Damage, if the exterior syndrome is not resolved and there is fluid retention below the heart, accompanied by dry retching, fever, and cough, Xiao Qing Long Tang (Minor Blue Dragon Decoction) is the primary treatment. In Shaoyin disease, if there is abdominal pain, difficulty in urination, heaviness and pain in the four limbs, and spontaneous diarrhea, this indicates the presence of fluid retention. If the patient also has a cough, Zhen Wu Tang (True Warrior Decoction) added with Wuweizi (Schisandra Fruit), Xixin (Asarum), and Jiangjiang (Dried Ginger) is used. These two cases represent cough due to retained fluid. Although both are caused by fluid retention, Xiao Qing Long Tang treats cough where fluid retention combines with exterior cold, whereas Zhen Yu Tang treats cough where fluid retention combines with interior cold. This distinction must be understood.
In Cold Damage Wind Strike, presenting with alternating chills and fever, fullness and distress in the chest and hypochondrium, silence with loss of appetite, irritability, frequent vomiting, or cough, Xiao Chai Hu Tang (Minor Bupleurum Decoction) with Ren Shen (Ginseng), Da Zao (Jujube), and Sheng Jiang (Fresh Ginger) removed, and replaced with Gan Jiang (Dried Ginger) and Wu Wei Zi (Schisandra Fruit), is indicated. In Shaoyin disease presenting with cold extremities (Si Ni), if the patient has a cough, Si Ni San (Four Reversal Powder) added with Gan Jiang (Dried Ginger) and Wu Wei Zi (Schisandra Fruit) is indicated. These two cases represent cough caused by pathogenic factors transmitting from the exterior to the interior. Although both involve transmission to the interior, Xiao Chai Hu Tang treats cough where Yang pathogenic factors transmit inward and disturb the Lung, while Si Ni San treats cough where Yin pathogenic factors transmit inward and disturb the Lung. This distinction must also be recognized.
"Exterior" refers to cold pathogens; "Interior" also refers to cold pathogens. If accompanied by fluid retention, the Lung will inevitably be disturbed, because physical cold and cold drinks injure the Lung. "Yang" refers to Yang pathogens; "Yin" refers to Yin pathogens. When pathogens transmit from the exterior to the interior, they inevitably disturb the Lung, because the Zhen Qi (True Qi) of the viscera is highest in the Lung (the Lung is considered the canopy of the viscera). Cough is a disease of the Lung, and treatment must employ dispersing methods to be effective. However, there are situations where sweating methods are contraindicated.
The Classics state: "If there is cough with free urination, do not induce sweating." Inducing sweating will lead to cold reversal of the four limbs. It also states: "If cough is treated with sweating, it leads to curling up, distress from fullness, and hardness in the abdomen." These are adverse reactions due to mismanagement. Furthermore, if the pulse is scattered, this indicates Heart Fire punishing Lung Metal (a pathological interaction known as 'Ghost Thief Punishment' in Five Phase theory), which is fatal. When facing illness, how can one fail to examine these details carefully?