新感温热，邪从上受，必先由气分陷入血分，里症皆表症侵入于内也。伏气温热，邪从里发，必先由血
分转入气分，表症皆里症浮越于外也。新感轻而易治，伏气重而难疗，此
其大要也。
谓予不信，请述陆氏九芝评孟英之言曰∶仲景所论温热是伏气，天士所论温热是外感，故以温邪上受，
首先犯肺，逆传心包十二字揭之篇首，以自别异，果如其说，则所称温热者，即俗所谓小风温、小风热，如目
赤、颐肿、喉梗，牙痛之类，却只须辛凉轻剂，其病立愈。更述薛瘦吟之言曰∶凡病内无伏气，纵感风、寒、
暑、湿之邪，病必不重，重病皆新邪引发伏邪者也。但伏气有二∶伤寒伏气，即春温夏热病也；伤暑伏气，即秋
温冬温病也。邪伏既久，血气必伤，故治法与伤寒、伤暑正法大异；且其气血亦钝而不灵，故灵其气机，清其
血热，为治伏邪第一要义。第其间所伏之邪，有微甚、有浅深，人之性质，有阴阳、有强弱，故就中又有轻重
之分焉。医必识得伏气，方不至见病治病，能握机于病象之先，然非熟于亢害承制之理，亦岂能测未来之病乎？
然非谓司天运气也，雨 寒燠，在在留心，久当自悟耳。
由是观之，同一温热症，而新感之与伏气病所之浅深不同，病情之轻重不同，病机之安危不同，故其疗法
亦因之而不同。
新感温热病，邪气从上部侵入人体，必定先由气分陷入血分，所有的里证都是表证侵入体内所致。伏气温热病，邪气从内部发出，必定先由血分转入气分，所有的表证都是里证浮越于体表所致。新感温热病轻浅且容易治疗，伏气温热病深重且难以治愈，这是它们之间的大致区别要点。
如果你们不相信我的话，请让我引用陆九芝评价王孟英的话说：张仲景所论述的温热病是伏气致病，叶天士所论述的温热病是外感致病，所以用“温邪上受，首先犯肺，逆传心包”这十二个字揭示在篇章开头，以此来表明自己的观点与众不同。果真像他所说的那样，那么所称的温热病，就是世俗所谓的小风温、小风热，比如眼睛发红、腮部肿胀、咽喉梗塞、牙痛这一类病症，却只需要使用辛凉轻剂，病情就会立即痊愈。再引用薛瘦吟的话说：凡是体内没有伏气的疾病，纵然感受了风、寒、暑、湿等邪气，病情一定不严重，严重的疾病都是新近感受的邪气引动了体内潜伏的邪气所致。但是伏气有两种：伤寒伏气，就是春温和夏热病；伤暑伏气，就是秋温和冬温病。邪气潜伏时间既久，气血必定受到损伤，所以治疗方法与伤寒、伤暑的正治法大不相同；而且患者的气血也迟钝而不灵敏，所以调畅其气机，清除其血热，是治疗伏邪的第一要义。只是其中所潜伏的邪气，有轻微和严重之分，有浅表和深入之别；人的体质属性，有阴和阳的区别，有强和弱的不同，所以在中间又有轻和重的区分。医生必须识别出伏气，才不至于见到病症就只治疗病症，能够把握先机于病象显现之前，然而如果不熟悉亢盛克制承袭制约的道理，又怎能预测未来的疾病呢？然而这并不是指司天运气学说，而是对风雨寒冷温暖，处处留心观察，时间久了自然会有领悟罢了。
由此看来，同样是温热病，但新感与伏气在病位的浅深、病情的轻重、病机的安危方面都不同，所以它们的治疗方法也因此而不同。
In new-onset warm-heat disease, the pathogenic factor enters from the upper orifices and must first sink from the Qi level (Qi level: a diagnostic level in warm disease theory indicating functional disturbance) into the Blood level (Blood level: a diagnostic level indicating pathological changes in blood and organs). All interior syndromes are exterior syndromes invading inward. In latent warm-heat disease, the pathogenic factor emerges from within and must first transition from the Blood level to the Qi level. All exterior syndromes are interior syndromes floating outward to the surface. New-onset cases are mild and easy to treat, whereas latent cases are severe and difficult to cure; this constitutes the general principle.
If you do not believe me, let me cite Lu Jiuzhi's commentary on Wang Mengying: Zhang Zhongjing discussed warm-heat diseases as caused by latent pathogens, while Ye Tianshi discussed them as caused by external infections. Therefore, Ye placed the twelve characters "Warm pathogenic factors enter from above, initially attacking the Lung, and if regressing, transmit to the Pericardium" at the beginning of his chapter to distinguish his views. If this is indeed the case, then the so-called warm-heat diseases refer to what is commonly known as minor wind-warmth or minor wind-heat, such as red eyes, swollen parotids, throat obstruction, and toothache. These require only mild acrid-cool formulas, and the illness will resolve immediately. Furthermore, citing Xue Shouyin: For any disease where there is no latent pathogen internally, even if one contracts Wind, Cold, Summer-heat, or Dampness, the illness will certainly not be severe. Severe illnesses are always those where new pathogens trigger latent pathogens. However, there are two types of latent pathogens: Latent pathogens from Cold damage refer to Spring-Warmth and Summer-Heat diseases; latent pathogens from Summer-heat injury refer to Autumn-Warmth and Winter-Warmth diseases. Since the pathogen has been latent for a long time, Qi and Blood must be damaged. Thus, treatment methods differ significantly from the standard treatments for Cold damage and Summer-heat injury. Moreover, the patient's Qi and Blood become dull and unresponsive. Therefore, regulating Qi mechanism and clearing Blood heat are the primary principles in treating latent pathogens. Nevertheless, among these, the latent pathogen varies in intensity and depth; human constitutions vary in Yin-Yang balance and strength/weakness. Consequently, there are distinctions between mild and severe cases. A physician must recognize latent pathogens to avoid merely treating symptoms as they appear, thereby grasping the opportunity before clinical manifestations arise. However, without mastering the principles of excessive restriction and mutual generation/restriction, how can one predict future diseases? This does not refer to the Six Qi transformation theory (Six Qi: Wind, Heat, Fire, Dampness, Dryness, Cold), but rather requires attentiveness to weather changes—rain, cold, warmth—and understanding will come with time.
From this perspective, although both are warm-heat diseases, new-onset and latent cases differ in the depth of the pathological location, the severity of the condition, and the stability of the disease mechanism. Therefore, their therapeutic approaches differ accordingly.