朱 曰。养生至宝书云。近秽气。触真气。近死气。乱生气。深有旨哉。孙真人云。乘马远行。
至暮。当沐浴更衣。方可近婴见处所。若感其气。则为急惊风搐。又曰。步践粪秽之履。勿使近
婴儿。若感其气。则为天吊。伤寒大汗将出。当以艾灸席隅。以避其气。不然。感其汗气。则传染
矣。所以多染侍奉劳役之人者。由其神虚气怯。易为扰乱故也。如剥死马者。感其毒瓦斯。而为马气
之疾。其理同焉。（以上汗气传染）或曰。伤寒只传足经。不传手经。何也。曰。伤寒之邪。多于
足经。而其病甚。少于手经。而其病微。故不特言手经。但寄于足经而已。（手足经辨）外有风寒
暑湿。内有饥饱劳逸。或曰。劳役。非也。劳、倦也。逸、闲逸也。西山记曰。久劳则安闲以保极
力之处。久逸则导引以行积滞之气。（内外伤辨）
夫寒者。天地杀厉之气也。秋之雾露。冬之霜雪。
皆寒邪也。是以辛苦之徒。起居不节。饮食不时。感雾露之气。则邪浅。感霜雪之气。则邪深。
感而即病。名曰伤寒。不即病者。寒邪藏于肌肉之间。伏于荣卫之内。至春因温暖之气而发。名温
病。至夏因暑热之气而作。名热病。一理而已。若疫疠。稍有不同者。盖因春宜温而反凉。夏宜热
而反冷。秋宜凉而反热。冬宜寒而反温。四时不正之气也。感春夏不正之气为温疫。感秋冬不正之
气为寒疫。其经络传受。表里受症。与伤寒同。俗云时气病。经总之曰伤寒。所以谓大病者。害人
甚速也。轩岐后。得其治法之秘者。仲景一人。守真先生。
不遵桂枝发表之法。自制双解通圣辛凉之剂。非不同也。时有异也。五运六气有所更。世态居民有
所变。天以常静。人以常动。动属阳。静属阴。清平之世。同水化也。虽有辛热之药。不生他症。
扰攘之世。同火化也。若用辛热。则发黄出斑。成坏病矣。盖人内火既动。外火又侵。所以辛热发
汗。不如辛温。辛温发汗。不如辛凉。以辛热发汗。轻者必危。重者必死。可不慎哉。（理伤寒
总论）
朱氏说：《养生至宝书》记载：“亲近污秽之气，会触犯人体真气；亲近死气，会扰乱生机。”这其中的深意是很重大的。孙思邈真人说：“骑马远行，到了傍晚，应当沐浴并更换衣服，然后才能接近有婴儿的地方。如果感染了这种气息，就会引发急惊风抽搐。”又说：“穿着踩过粪便污秽的鞋子，不要让它们靠近婴儿。如果感染了这种气息，就会导致天吊（一种惊风病症）。”伤寒患者大汗将要发出时，应当用艾草灸烧床席的角落，以避开邪气。否则，感染了汗气，就会发生传染。所以，侍奉病人或从事劳役的人容易感染此病，是因为他们的精神虚弱、正气怯弱，容易被邪气扰乱。就像剥死马的人，感染了毒瓦斯，从而患上马气之疾，其道理是相同的。（以上论述汗气传染）
有人问：“伤寒只传变足经，不传变手经，为什么呢？”回答说：“伤寒的邪气，多在足经，且病情严重；在手经较少，且病情轻微。所以特别不提及手经，只是依附于足经来论述罢了。”（手足经辨）
外界有风寒暑湿等邪气，内部有饥饱劳逸等因素。有人说“劳役”不对。这里的“劳”，是指疲倦；“逸”，是指闲适安逸。西山记中说：“长久劳累后，应通过安闲静养来保养极度疲劳的身体部位；长久安逸后，应通过导引运动来运行积滞的气机。”（内外伤辨）
寒，是天地间肃杀厉烈的邪气。秋天的雾露，冬天的霜雪，都属于寒邪。因此，那些辛勤劳作的人，起居没有节制，饮食没有定时，如果感染了雾露之气，邪气就浅；如果感染了霜雪之气，邪气就深。感染后立即发病的，名叫伤寒；没有立即发病的，寒邪潜伏在肌肉之间，隐藏在营卫之内，到了春天因为温暖的气候而发作，名叫温病；到了夏天因为暑热的气候而发作，名叫热病。其原理是一样的。至于疫病，则稍有不同，大概是因为春天本该温暖却反而凉冷，夏天本该炎热却反而寒冷，秋天本该凉冷却反而炎热，冬天本该寒冷却反而温暖。这是四时不正之气。感染春夏季的不正之气称为温疫，感染秋冬季的不正之气称为寒疫。其经络传变规律、表里症状表现，与伤寒相同。俗称为时气病，经典总括为伤寒。之所以称之为大病，是因为它害人非常迅速。
自从黄帝、岐伯之后，掌握治疗秘诀的只有张仲景一人。刘守真先生，不遵循桂枝汤发表的方法，自己创制了双解散和通圣散这类辛凉的方剂。这并不是理论不同，而是时代背景不同。五运六气有所变化，社会环境和居民体质也有所改变。天道通常保持静止，人道通常处于运动之中。运动属于阳，静止属于阴。太平清平的时代，如同水化生，即使使用辛热性质的药物，也不会产生其他病变；动荡扰攘的时代，如同火化生，如果使用辛热药物，就会导致发黄、出斑疹，形成坏病。这是因为人体内部之火已经发动，外部之火又加以侵袭。所以，用辛热药发汗，不如用辛温药；用辛温药发汗，不如用辛凉药。如果用辛热药发汗，轻症必定危险，重症必定死亡。能不谨慎吗？（理伤寒总论）
Zhu stated: The *Book of Supreme Treasures for Health Preservation* records, "Approaching foul odors will touch and disturb the body's true Qi; approaching death qi will disrupt vital energy." The profound significance of this is great. Sun Simiao said, "After traveling far on horseback, when evening arrives, one should bathe and change clothes before approaching areas where infants are present. If one contracts this qi, it will cause acute convulsive wind (Ji Jing Feng Chu)." He also said, "Do not allow shoes that have stepped in feces or filth to approach infants. If they contract this qi, it will result in Tian Diao (a type of convulsive disorder)." When a patient with Shanghan has profuse sweating about to occur, moxibustion should be applied to the corners of the mat to avoid the pathogenic qi. Otherwise, contracting the sweat qi will lead to transmission. Therefore, those who serve patients or engage in laborious work are easily infected because their spirit is deficient and their Qi is timid, making them susceptible to disturbance. Just as those who skin dead horses contract toxic vapors and suffer from diseases related to horse qi, the principle is the same. (Regarding the transmission via sweat qi)
Someone asked, "Shanghan transmits only through the Foot meridians and not the Hand meridians. Why is this?" The answer is: The pathogen of Shanghan is more prevalent in the Foot meridians, and the disease is severe; it is less prevalent in the Hand meridians, and the disease is mild. Thus, the Hand meridians are not specifically mentioned, but are merely implied within the discussion of the Foot meridians. (Differentiation of Hand and Foot Meridians)
Externally, there are Wind, Cold, Summer-heat, and Dampness pathogens; internally, there are factors such as hunger, fullness, fatigue, and rest. Some argue that "laborious work" is incorrect. Here, "Labor" refers to fatigue/exhaustion, and "Rest" refers to leisure/idleness. The *Xishan Ji* states, "After long periods of labor, one should maintain tranquility to preserve the areas of extreme physical exertion; after long periods of idleness, one should practice Daoyin (guiding and pulling exercises) to move stagnant Qi." (Differentiation of Internal Injury)
Cold is the killing and fierce qi of Heaven and Earth. Autumn fog and dew, and winter frost and snow, are all Cold pathogens. Therefore, among those who endure hardship, if their daily routine is irregular and meals are untimely, contracting fog and dew qi results in shallow pathogenesis, while contracting frost and snow qi results in deep pathogenesis. If illness occurs immediately upon contraction, it is named Shanghan. If illness does not occur immediately, the Cold pathogen hides between the muscles and lies dormant within Ying and Wei. In spring, triggered by warm qi, it erupts and is named Wenbing (Warm Disease). In summer, triggered by heat qi, it arises and is named Rebing (Heat Disease). The underlying principle is the same. Epidemic diseases differ slightly, generally occurring because spring should be warm but is instead cool, summer should be hot but is instead cold, autumn should be cool but is instead hot, and winter should be cold but is instead warm. These are the abnormal qi of the four seasons. Contracting abnormal qi in spring and summer is called Wenyi (Warm Epidemic); contracting abnormal qi in autumn and winter is called Hanyi (Cold Epidemic). Their meridian transmission patterns and exterior-interior symptom manifestations are the same as Shanghan. Commonly known as Shiqi Bing (Seasonal Qi Disease), the classics summarize it under Shanghan. It is called a major disease because it harms people very rapidly.
Since Huangdi and Qibo, only Zhang Zhongjing mastered the secrets of treatment. Liu Wansu (Mr. Shouzhen) did not follow the method of releasing the exterior with Guizhi Tang (Cinnamon Twig Decoction) but independently created cooling agents like Shuangjie San (Double Resolution Powder) and Tongsheng San (Universal Benefit Powder). This is not due to difference in theory, but difference in times. The Five Movements and Six Qi undergo changes, and social conditions and resident constitutions vary. Heaven remains constantly still, while humans are constantly moving. Movement belongs to Yang, stillness belongs to Yin. In peaceful times, the environment resembles Water transformation; even if acrid-hot medicines are used, no other syndromes arise. In turbulent times, the environment resembles Fire transformation; if acrid-hot medicines are used, jaundice and macules will appear, resulting in complicated diseases. Because internal fire is already active and external fire invades, using acrid-hot medicine to induce sweating is inferior to using acrid-warm medicine; using acrid-warm medicine to induce sweating is inferior to using acrid-cool medicine. Using acrid-hot medicine to induce sweating will endanger mild cases and kill severe cases. Can one not be cautious? (General Discussion on Managing Shanghan)