寒者、冬月严寒杀厉之气也，然有冒、有伤、有中之不同。冒者、皮肤受寒，鼻寒眼胀，洒淅寒热，微觉拘
倦者是也。伤者、即下文传经之症也。中者、因体虚腠理?豁，寒邪直入三阴之经，不从表传，其症四
肢厥冷，脐腹绞痛，脉沈迟无力者是也。盖自霜降后至春分前，乃天令严寒，水冰地冻，而成杀厉之
气，人触犯之，实时而病者，名为正伤寒。其不即病，寒毒藏于肌肤，至春而发者，为温病。至夏而发者，
为热病。古人均为之伤寒也。然伤寒从表入里，必次第而传，如发于一二日间，便觉头项痛，腰脊强，
发热恶寒，尺寸俱浮，乃太阳经受病也，若以次传经，必传于胃。如发于二三日间，便觉目疼鼻干不
得眠，日晡潮热，不恶寒，反恶热，尺寸俱长，乃阳明经受病也，若以次传经，必传于胆。如发于三四日
间，便觉胸?痛而耳聋，寒热呕而口苦，尺寸俱弦，乃少阳经受病也，若以次传经，必传于脾。如发于
四五日间，便觉腹满嗌干，自利不渴，尺寸沈细，乃太阴经受病也，若以次传经，必传于肾。如发于五
六日间，便觉口燥舌干而渴，尺寸俱沈，乃少阴经受病也，若以次传经，必传于肝。如发于六七日间，
便觉烦渴囊缩，尺寸微缓，乃厥阴经受病也。则六经之形症已明矣。然六经既明，未可便视为一定
不易之序，有始于太阳，以次传入阴经，而终于厥阴者，或太阳不传于阳明、少阳，而及传于少阴者，
或不由阳经而直入阴经者，或始终只在一经而不传者，或二阳三阳同受而为合病者，或太阳阳
明先后而为并病者，缘经无明文，后人妄治，蒙害者多矣。
寒邪，是冬季严寒肃杀之气。然而，人体受寒有“冒”、“伤”、“中”三种不同情况。“冒”，是指皮肤感受寒邪，出现鼻部寒冷、眼部胀满、阵阵恶寒发热、轻微感到拘急疲倦的症状。“伤”，即指下文所述的传经病症。“中”，是因为体质虚弱、腠理疏松，寒邪直接侵入三阴经，不从体表传入，其症状表现为四肢厥冷、脐腹绞痛、脉象沉迟无力。大概从霜降之后到春分之前，正值天气严寒，水结冰地冻，形成肃杀之气，人若触犯此气，随即发病的，称为“正伤寒”。如果不立即发病，寒毒潜伏在肌肤之中，到了春季发作的，称为“温病”。到了夏季发作的，称为“热病”。古人统称之为“伤寒”。
然而，伤寒病由表入里，必须按次序传变。例如，发病在一两天内，便觉得头项疼痛、腰脊僵硬、发热恶寒、寸关尺三部脉象均浮，这是太阳经受病；如果依次传经，必定传给胃（阳明经）。例如，发病在两三天内，便觉得眼睛痛、鼻子干、无法入睡，下午定时发热，不恶寒反而恶热，寸关尺三部脉象均长，这是阳明经受病；如果依次传经，必定传给胆（少阳经）。例如，发病在三四天内，便觉得胸胁疼痛且耳聋，忽冷忽热、呕吐且口苦，寸关尺三部脉象均弦，这是少阳经受病；如果依次传经，必定传给脾（太阴经）。例如，发病在四五天内，便觉得腹部胀满、咽喉干燥，自发性腹泻且不口渴，寸关尺三部脉象沉细，这是太阴经受病；如果依次传经，必定传给肾（少阴经）。例如，发病在五到六天内，便觉得口干舌燥而渴，寸关尺三部脉象均沉，这是少阴经受病；如果依次传经，必定传给肝（厥阴经）。例如，发病在六七天时，便觉得烦躁口渴、阴囊收缩，寸关尺三部脉象微缓，这是厥阴经受病。这样，六经的形态和症状就明确了。
然而，既然明确了六经，也不能就将其视为固定不变的顺序。有的始于太阳经，依次传入阴经，最终到达厥阴经；有的太阳经不传给阳明、少阳，而直接传给少阴经；有的不由阳经直接陷入阴经；有的始终只停留在一经而不传变；有的两阳或三阳同时受邪而成为“合病”；有的太阳与阳明先后受邪而成为“并病”。由于经典原文中没有明确记载这些复杂情况，后人胡乱治疗，蒙受危害的人很多了。
Cold pathogen refers to the severe, killing cold air of winter. However, there are differences in "mào" (encountering), "shāng" (injuring), and "zhōng" (striking). "Mào" refers to the skin receiving cold, manifesting as coldness in the nose, distension in the eyes, alternating chills and fever, and a slight feeling of stiffness and fatigue. "Shāng" refers to the syndrome of transmission between meridians described below. "Zhōng" occurs due to weak constitution and loose interstices (pores/skin texture), allowing cold pathogen to directly enter the Three Yin meridians without transmitting from the exterior; its symptoms include cold limbs, colicky pain in the umbilical and abdominal regions, and a deep, slow, and forceless pulse. Generally, from after Frost's Descent until before Spring Equinox, the heavenly mandate is severely cold, with water freezing and ground hardening, forming killing qi. If humans encounter this and fall ill immediately, it is named "Zhèng Shānghán" (True Cold Damage). If it does not cause immediate illness but cold toxin hides in the skin and muscles, erupting in spring, it is called "Wēnbìng" (Warm Disease). If it erupts in summer, it is called "Rèbìng" (Heat Disease). The ancients collectively referred to these as Shānghán.
However, Shānghán enters from the exterior to the interior and must transmit sequentially. For instance, if occurring within one or two days, accompanied by headache and stiff neck, back and spine stiffness, fever, aversion to cold, and floating pulses at all three positions (cun, guan, chi), it is a disease of the Taiyang Meridian (Greater Yang Meridian). If transmitted sequentially, it will inevitably transmit to the Stomach (Yangming Meridian). If occurring within two or three days, accompanied by eye pain, dry nose, insomnia, tidal fever in the afternoon, aversion to heat rather than cold, and long pulses at all three positions, it is a disease of the Yangming Meridian (Yang Brightness Meridian). If transmitted sequentially, it will inevitably transmit to the Gallbladder (Shaoyang Meridian). If occurring within three or four days, accompanied by chest and hypochondriac pain, deafness, alternating chills and fever, vomiting, and bitter taste in the mouth, with wiry pulses at all three positions, it is a disease of the Shaoyang Meridian (Lesser Yang Meridian). If transmitted sequentially, it will inevitably transmit to the Spleen (Taiyin Meridian). If occurring within four or five days, accompanied by abdominal fullness, dry throat, spontaneous diarrhea without thirst, and deep, fine pulses at all three positions, it is a disease of the Taiyin Meridian (Greater Yin Meridian). If transmitted sequentially, it will inevitably transmit to the Kidney (Shaoyin Meridian). If occurring within five or six days, accompanied by dry mouth and tongue with thirst, and deep pulses at all three positions, it is a disease of the Shaoyin Meridian (Lesser Yin Meridian). If transmitted sequentially, it will inevitably transmit to the Liver (Jueyin Meridian). If occurring within six or seven days, accompanied by irritability, thirst, and contraction of the scrotum, with slightly relaxed pulses at all three positions, it is a disease of the Jueyin Meridian (Terminal Yin Meridian). Thus, the manifestations and symptoms of the Six Meridians are clarified.
However, even though the Six Meridians are clarified, they should not be viewed as a fixed and unchangeable sequence. Some begin in the Taiyang meridian and transmit sequentially into the Yin meridians, ending in Jueyin. Some do not transmit from Taiyang to Yangming or Shaoyang, but instead transmit to Shaoyin. Some do not enter through the Yang meridians but directly invade the Yin meridians. Some remain in one meridian throughout without transmitting. Some involve simultaneous affliction of two or three Yang meridians, known as Hébing (Combined Disease). Some involve sequential affliction of Taiyang and Yangming, known as Bìngbìng (Concurrent Disease). Due to the lack of explicit text in the classics regarding these complexities, later practitioners have treated them recklessly, causing much harm.