冬月伤寒，邪由皮毛而入，从表入里，初见三阳经证，如太阳病，则头项强痛而恶寒之类。三阳不解，渐
次传入三阴。其中有留于三阳，而不入三阴者∶有结于胃腑，而不涉他经者；亦有不必假道三阳，而直中三阴
者。凡此伤寒之症，初起悉系寒邪见象。迨发作之后，渐次化热内传，始有热象。故初起治法，必以通阳祛寒
为主。及化热之后，始有泄热之法。此伤寒病之大较也。若夫温病，乃冬时寒邪，伏于少阴。迨春夏阳气内动
，伏邪化而为热，由少阴而外出。如邪出太阳，亦见太阳经证，其头项强痛等象，亦与伤寒同。但伤寒里无郁
热，故恶寒不渴，溲清无内热。温邪则标见于外，而热郁于内，虽外有表证，而里热先盛；口渴溲黄、尺肤热
、骨节疼，种种内热之象，皆非伤寒所有。其见阳明、少阳，见证亦然。初起治法，即以清泄里热，导邪外达
为主。与伤寒用药，一温一凉，却为对待。盖感寒随时即发，则为伤寒，其病由表而渐传入里，寒邪郁久，化
热而发，则为温病，其病由里而郁蒸外达。伤寒初起，决无里热见证∶温邪初起，无不见里热之证。此伤寒、
温病分证用药之大关键。临证时能从此推想，自然头头是道矣。
冬时伏邪，郁伏至春夏，阳气内动，化热外达，此伏气所发之温病也。内经云∶冬伤于寒，春必病温。又
云∶凡病伤寒而成温者，先夏至日为病温，后夏至日为病暑。难经云伤寒有五，有温病，有热病。伤寒论云∶
太阳病，发热而渴，不恶寒者为温病。凡此皆指伏邪所发之温病言也。另有一种风温之邪，当春夏间感受温风
，邪郁于肺，咳嗽发热，甚则发为痧疹。内经所谓风淫于内治以辛凉，叶氏温热论所谓温邪上受首先犯肺者，
皆指此一种暴感风温而言也。伏气由内而发，治之者以清泄里热为主；其见证至繁且杂，须兼视六经形证，乃
可随机立法。暴感风温，其邪专在于肺，以辛凉清散为主；热重者，兼用甘寒清化。其病与伏温病之表里出入
，路径各殊；其治法之轻重深浅，亦属迥异。近人专宗叶氏，将伏气发温之病，置而不讲。每遇温邪，无论暴
感伏气，概用叶氏辛凉轻浅之法，银翘、桑菊，随手立方；医家病家，取其简便，无不乐从。设有以伏气之说
进者，彼且视为异说，茫然不知伏气为何病。嗟乎！伏温是外感中常有之病，南方尤多，非怪证也。其病载在
内经、难经、伤寒论诸书，非异说也。临证者，竟至茫然莫辨，门径全无，医事尚堪问哉！
冬季感受寒邪，病邪从皮毛侵入，由表入里，起初出现三阳经的病证，例如太阳病（太阳经受邪所致的病证），表现为头项强痛且恶寒等症状。如果三阳经的病证未解，病邪会依次传入三阴经。其中有的病邪停留在三阳经，而不传入三阴经；有的结聚在胃腑，而不涉及其他经络；也有不需要经过三阳经，而直接中伤三阴经的情况。所有这些伤寒病症，初起时都表现为寒邪的特征。等到发作之后，病邪逐渐化热并向内传变，才出现热象。因此，初起的治疗原则，必须以通阳散寒为主。等到化热之后，才有清热泄火的治疗方法。这是伤寒病的大致情况。
至于温病，是由于冬季寒邪潜伏于少阴（肾脏及其相关经络）。等到春夏季节阳气在内发动，潜伏的邪气化为热邪，从少阴向外透发。如果邪气出于太阳经，也会出现太阳经的病证，其头项强痛等表现，也与伤寒相同。但是，伤寒体内没有郁积的热邪，所以恶寒且不口渴，小便清长，没有内热。温邪则是标症显现于外，而热邪郁积于内，虽然外表有表证，但体内的热势先盛；出现口渴、小便黄赤、尺部皮肤发热、骨节疼痛等种种内热的症状，这些都是伤寒所不具备的。当病邪见到阳明经（阳明经受邪所致的病证）或少阳经（少阳经受邪所致的病证）时，见证也是如此。初起的治疗原则，即以清泄里热、引导邪气向外透达为主。这与治疗伤寒的药物，一温一凉，正好相对。因为感寒后随即发病的，称为伤寒，其病情由表逐渐传入里；寒邪郁积日久，化热而发的，称为温病，其病情由内部郁蒸而向外透达。伤寒初起，绝对没有里热的见证；温邪初起，无不伴有里热的证候。这是区分伤寒和温病进行辨证用药的关键所在。临证时若能由此推想，自然就能条理清晰了。
冬季潜伏的邪气，郁伏到春夏季节，阳气在内发动，化为热邪向外透达，这是伏气所引发的温病。《内经》说：冬季受寒，春天必定发生温病。又说：凡是患伤寒而转化为温病的，在夏至日之前发病的叫作温病，在夏至日之后发病的叫作暑病。《难经》说伤寒有五种，其中有温病，有热病。《伤寒论》说：太阳病，如果发热且口渴，不恶寒的，称为温病。以上这些论述，都是指伏邪所引发的温病而言。另外还有一种风温之邪，在春夏之间感受温风，邪气郁积在肺脏，导致咳嗽发热，严重时发展为痧疹。《内经》所说的“风淫于内，治以辛凉”，叶天士《温热论》所说的“温邪上受，首先犯肺”，都是指这种暴感风温而言。伏气由内部发出，治疗以清泄里热为主；其见证非常繁杂，必须兼看六经（太阳、阳明、少阳、太阴、少阴、厥阴）的形证，才能随机确立治法。暴感风温，其邪气专门在于肺脏，治疗以辛凉清散为主；热势重的，兼用甘寒清化之法。这种病的表里出入路径，与伏气温病截然不同；其治疗的轻重深浅，也完全不一样。近代医生专门推崇叶天士，将伏气引发温病的病症，搁置不讲。每当遇到温邪，无论是暴感还是伏气，一概使用叶天士辛凉轻浅的方法，银翘散、桑菊饮随手开立方剂；医家和病家，贪图简便，没有不乐意接受的。如果有提出伏气学说的人，他们反而视为异端邪说，茫然不知伏气是什么病。唉！伏温是外感病中常见的疾病，南方尤其多，并非怪病。其病记载在《内经》、《难经》、《伤寒论》等书中，并非异说。临证者竟然茫然无法辨别，毫无门径，医学还能问津吗！
In winter, cold pathogenic factors invade from the skin and hair, moving from the exterior to the interior. Initially, symptoms of the Three Yang meridians appear, such as Taiyang disease (disease syndrome caused by pathogenic invasion of the Taiyang meridian), characterized by stiffness and pain in the head and neck accompanied by aversion to cold. If the disorders of the Three Yang meridians are not resolved, the pathogen gradually transmits into the Three Yin meridians. Among these, some pathogens remain in the Three Yang meridians without entering the Three Yin; some knot in the Fu organs of the Stomach without involving other meridians; and some directly strike the Three Yin meridians without passing through the Three Yang. All these Shanghan (Cold Damage) syndromes initially present with signs of cold pathogenic factors. Only after onset do they gradually transform into heat and transmit inward, revealing heat signs. Therefore, the initial treatment must focus on unblocking Yang and dispelling cold. Only after transformation into heat is there a method to drain heat. This is the general principle of Shanghan disease.
As for Warm diseases (Wenbing), they arise from cold pathogenic factors latent in Shaoyin (the Kidney meridian system) during winter. When Yang Qi moves internally in spring and summer, the latent pathogen transforms into heat and emerges outward from Shaoyin. If the pathogen emerges via the Taiyang meridian, it also presents Taiyang meridian symptoms, such as stiffness and pain in the head and neck, similar to Shanghan. However, Shanghan lacks internal stagnant heat, so there is aversion to cold without thirst, clear urine, and no internal heat. In contrast, Warm pathogens manifest superficially while heat stagnates internally; although exterior symptoms exist, internal heat is already vigorous. Symptoms include thirst, yellow urine, heat in the Chi pulse area (wrist), and joint pain—various signs of internal heat absent in Shanghan. The same applies when symptoms involve Yangming disease (syndrome of the Yangming meridian) or Shaoyang disease (syndrome of the Shaoyang meridian). Initial treatment focuses on clearing and draining internal heat and guiding the pathogen outward. This contrasts with Shanghan treatment, which uses warming versus cooling methods. Cold contracted and immediately manifesting is Shanghan, progressing from exterior to interior; cold pathogen stagnating and transforming into heat manifests as Warm disease, progressing from interior steaming outward. Shanghan initially never shows internal heat signs; Warm disease always presents internal heat signs at onset. This is the key distinction in differentiating Shanghan and Warm diseases for medication. Understanding this allows for clear clinical reasoning.
Latent pathogens from winter, stagnating until spring and summer, activate with internal Yang Qi, transforming into heat and emerging outward; this is Warm disease caused by latent Qi (Fuqi). The *Neijing* states: "Winter injury by cold leads to Warm disease in spring." It also says: "For those whose Shanghan transforms into Warm disease, onset before the Summer Solstice is termed Warm disease, and after the Summer Solstice is termed Heat disease (Shu)." The *Nanjing* states that Shanghan includes five types, among them Warm disease and Heat disease. The *Shanghan Lun* states: "Taiyang disease with fever, thirst, and no aversion to cold is called Warm disease." All these refer to Warm disease caused by latent pathogens.
Another type is Wind-Warmth (Fengwen) pathogen. Contracted during spring and summer from warm winds, the pathogen stagnates in the Lung, causing cough and fever, potentially developing into macules (Shazhen). The *Neijing*'s statement "Wind rampant within, treat with acrid-cool" and Ye Tianshi's *Wenre Lun* statement "Warm pathogens enter from above, first attacking the Lung" both refer to this acute contraction of Wind-Warmth. Latent Qi emerges from within; treatment focuses on clearing and draining internal heat. Its manifestations are complex, requiring observation of Six Meridian (Taiyang, Yangming, Shaoyang, Taiyin, Shaoyin, Jueyin) patterns to establish random legislation. Acute Wind-Warmth targets the Lung specifically; treatment focuses on acrid-cool dispersal. For severe heat, sweet-cool resolving methods are added. The path of interior-exterior interaction differs significantly from latent Warm disease; the depth and weight of treatment are also distinct. Recent physicians exclusively follow Ye Tianshi, ignoring latent Qi-induced Warm disease. Upon encountering Warm pathogens, whether acute or latent, they uniformly apply Ye's light acrid-cool methods, prescribing Yinqiao San (Honeysuckle and Forsythia Decoction) or Sangju Yin (Mulberry Leaf and Chrysanthemum Decoction) casually. Physicians and patients prefer this simplicity. Those proposing latent Qi theories are dismissed as heterodox, ignorant of what latent Qi disease entails. Alas! Latent Warm disease is common among external contractions, especially in the South, not a strange ailment. It is recorded in the *Neijing*, *Nanjing*, and *Shanghan Lun*, not heterodoxy. Clinicians' inability to distinguish it, lacking even basic pathways, renders medical practice questionable!