凡病伤寒者，本由寒气所伤，而风即寒之帅也。第以风寒分气令，则风主春而东，寒主冬而北
；以风寒分微甚，则风属阳而浅，寒属阴而深。然风送寒来，寒随风入，透骨侵肌，本为同气，故
凡寒之浅者，即为伤风，风之深者，即为伤寒；而不浅不深，半正半邪之间者，即为疟疾∶其有留
于经络，而肢体疼痛者，则为风痹。然则伤风也，伤寒也，疟疾、风痹也，皆风寒之所为也。观《灵
枢·九宫八风篇》及岁露论所载，俱甚言虚邪贼风之为害，口问篇言风成为寒热，此皆指风为寒邪
也。即如冬伤于寒者，宜乎其为伤寒也，若春夏秋三时之感冒，则孰非因寒，亦孰非因风而入之。
故仲景曰∶凡伤寒之病，多从风寒得之，始因表中风寒，入里则
不消矣，未有温覆而当，不消散者，岂非风寒本为同气乎。《内经》曰∶谨候虚风而避之。故圣人
日避虚邪之道，如避矢石然，邪弗能害，此之谓也，此杜渐防微之道也。
夫伤寒为病，盖由冬令严寒，以水冰地裂之时，最多杀厉之气，人触犯之而实时病者，是为正
伤寒，此即阴寒直中之证也。然惟流离穷困之世多有之，若时当治平，民安饱暖，则直中之病少见，
此伤寒之一也。其有冬时感寒，不即病者，寒毒藏于营卫之间，至春夏时，又遇风寒，则邪气应时
而动，故在春则为温病，在夏则为暑病。是以辛苦之人，春夏多温热病者，皆由冬时触寒所伤，故
随气传变，本非即病正伤寒之属，所当因其寒热而随证调治之，此伤寒之二也。又有时行之气者，
如春时应暖而反寒，夏时应热而反凉，秋时应凉而反热，冬时应寒而反温，此非其时而有其气，是
以一岁之中，长幼之病多相似者，是实时行之病，感冒虚风不正之气，随感随发，凡禀弱而不慎起
居多劳倦者多犯之，此伤寒之三也。凡此三者，皆伤寒之属，第其病有不同，治有深浅，苟不能辨
，则必致误人。
凡是患伤寒病的人，原本都是由寒气伤害所致，而风就是寒气的先导。只是从风寒对应的气令来看，风主春季而在东方，寒主冬季而在北方；从风寒的轻重深浅来看，风属于阳而病位浅，寒属于阴而病位深。然而风携带寒邪而来，寒随风顺而入，穿透骨骼侵袭肌肉，本质上同属一气，所以凡寒气较浅的，就是伤风；风气较深的，就是伤寒；不浅不深、处于半正半邪之间的，就是疟疾；有留滞于经络，导致肢体疼痛的，就是风痹。既然这样，那么伤风、伤寒、疟疾、风痹，都是风寒所导致的。观察《灵枢·九宫八风篇》及岁露论中的记载，都极力强调虚邪贼风的危害，《口问篇》说“风成为寒热”，这都是指风即为寒邪。就像冬天受寒，理应称为伤寒，至于春夏秋三个季节的感冒，难道不是因寒而起，也不是因风而入的吗？所以张仲景说：“大凡伤寒的病，多从风寒得来，起初是表中风寒，如果入里则不能自行消散了，只要保暖得当，没有不消散的，这难道不是风寒本为同气吗？”《内经》说：“谨慎地观察并避开虚风。”所以圣人说要躲避虚邪之道，就像躲避箭石一样，邪气就不能伤害人体，这就是所说的防微杜渐的道理。
所谓伤寒病，大概是由于冬季严寒，在水冰地裂的时候，最多存在杀厉之气，人触犯它而立即发病的，这叫正伤寒，这就是阴寒直中的证候。然而只有在流离失所、穷困潦倒的时代才多有发生，如果时世太平，百姓安居乐业、吃饱穿暖，那么直中的病就很少见，这是伤寒的第一种情况。有的人在冬季感受寒邪，当时没有立即发病，寒毒潜伏在营卫之间，到了春夏季节，又遇到风寒，那么邪气就会应时而动，所以在春季就发为温病，在夏季就发为暑病。因此，那些辛勤劳作的人，在春夏季节多发温热病，都是因为冬季触犯了寒邪所致，所以随着气机传变，本来就不是立即发病的正伤寒一类，应当根据他们的寒热症状随证调理治疗，这是伤寒的第二种情况。又有的是时行之气，比如春季应该温暖却反而寒冷，夏季应该炎热却反而凉爽，秋季应该凉快却反而炎热，冬季应该寒冷却反而温暖，这不是应有的时节却有相应的气候，因此一年之中，老人和小孩得的病大多相似，这就是实时的时行病，是感冒了虚风不正之气，感邪即发，凡是禀赋虚弱且不谨慎起居、经常劳累疲倦的人容易犯此病，这是伤寒的第三种情况。大凡这三种情况，都属于伤寒的范畴，只是它们的病症有所不同，治疗的深浅程度也不同，如果不能辨别清楚，就一定会导致误治害人。
In all cases of Shaoyang disease (diseases caused by cold pathogens), the root cause is injury by cold qi, with wind acting as the commander of cold. However, when distinguishing wind and cold by their seasonal commands, wind governs spring and the east, while cold governs winter and the north; when distinguishing them by severity and depth, wind belongs to Yang and is superficial, whereas cold belongs to Yin and is deep. Nevertheless, wind brings cold along, and cold enters following wind, penetrating bones and invading muscles, essentially sharing the same nature. Therefore, shallow cold constitutes Shangfeng (Wind Injury); deep wind constitutes Shanghan (Cold Damage); neither shallow nor deep, existing in a state between upright and pathogenic, constitutes Nueji (Malaria); if it remains in the meridians causing limb pain, it becomes Fengbi (Wind Bi). Thus, Shangfeng, Shanghan, Nueji, and Fengbi are all caused by wind and cold. Observing the *Lingshu · Jiugong Bafeng Chapter* and the *Suilu Lun*, both emphasize the harm of Xuexi Zeifeng (Empty Evil and Robber Wind). The *Kouwen Chapter* states that "wind becomes cold-heat," referring to wind as cold evil. Just as being injured by cold in winter should rightly be called Shanghan, what about cold damage contracted in spring, summer, and autumn? Are they not due to cold, and do they not enter via wind? Thus, Zhang Zhongjing said: "All diseases of Shanghan mostly arise from wind and cold. Initially, wind-cold affects the exterior; if it enters the interior, it will not dissipate on its own. If one keeps warm and covered, there is no case where it does not dissipate. Is this not proof that wind and cold share the same nature?" The *Neijing* states: "Carefully observe and avoid empty wind." Therefore, the sages taught that the way to avoid empty evils is like avoiding arrows and stones, so that evil cannot harm the body. This is referred to as preventing problems before they arise.
The disease of Shanghan arises largely from severe cold in winter. During times when water freezes and earth cracks, there is an abundance of Shaoli qi (killing and harsh qi). When people encounter it and fall ill immediately, this is Zheng Shanghan (True Cold Damage), which is the syndrome of Yin-cold directly striking the interior. However, this occurs mostly in times of displacement and poverty. In times of peace, when people are secure, well-fed, and warm, direct-striking diseases are rare. This is the first type of Shanghan. There are those who contract cold in winter but do not fall ill immediately; the cold toxin hides between Ying (Nutritive) and Wei (Defensive) qi. When spring and summer arrive, encountering wind and cold again causes the pathogenic qi to activate according to the season. Thus, in spring it manifests as Wenbing (Warm Disease), and in summer as Shubing (Summerheat Disease). Therefore, hardworking people often suffer from warm-heat diseases in spring and summer because they were injured by cold in winter. These conditions change with the transmission of qi and do not belong to immediate-onset True Shanghan. Treatment should follow the symptoms of cold and heat. This is the second type of Shanghan. Furthermore, there are Shixing zhiqi (Seasonal Epidemic Qi). For example, spring should be warm but is cold; summer should be hot but is cool; autumn should be cool but is hot; winter should be cold but is warm. Having such qi out of season results in many people, young and old alike, suffering from similar illnesses throughout the year. This is Shixing bing (Seasonal Epidemic Disease), caused by contracting abnormal empty wind. It manifests immediately upon contraction. Those with weak constitution who are careless with daily life and prone to fatigue are easily affected. This is the third type of Shanghan. All three types belong to Shanghan, but their manifestations differ, and treatments vary in depth. Failure to distinguish them will inevitably lead to misdiagnosis and harm to patients.