伤寒传经次第，先太阳，次阳明，次少阳，次太阴，次少阴，次厥阴，此其常也。然而
风寒
之邪，亦有径中阳明者。仲景云∶阳明中风，口苦，咽干，腹满，微喘，发热，恶寒，脉浮
而紧。又少阳中风，两耳无所闻，目赤，胸中满而烦者是也。不独阳明、少阳为然，即三阴
亦有之。云少阴病始得之，反发热、脉沉者，少阴初受寒邪之症也。太阴中风，四肢烦疼，
阳微阴涩而长者，太阴初受风邪之症也。厥阴中风，脉微浮为欲愈，不浮为未愈，此厥阴初
受风邪之脉也。此三者，又与三阴直中不同。直中者，病在脏，此则病在经也。是以六经皆
能自受风寒，何必尽从太阳传入；即从太阳传入，亦不必循经递进。海藏言之最详，兹不重
述。
伤寒传足不传手者，寒邪中人，先着皮肤，而足太阳膀胱之脉，在最外一层，故先入之
；稍
深则去皮肤而入肌肉，肌肉为足阳阴之分，故次入之；又稍深则在躯壳之内，脏腑之外？而
足少阳之脉，正当半表半里之间，故又次入之。迨去表而之里，离阳而入阴，则三阴者，太
阴为开，厥阴为阖，少阴为枢，故邪气入之，先太阴，次少阴，次厥阴也。合而言之，阳主
表而阴主里，表为腑而里五脏，故邪气在表，则足三阳受之，在里则足三阴受之也。手之三
阳，虽亦主表，而太阳小肠、少阳三焦、阳明大肠，并从手至于头，位偏而脉短，不若足经
之自下行上，纲维一身也。手之三阴，虽亦主里，然太阴肺、少阴心、厥阴胞络，并处上焦
，不若肝、脾、肾之实居阴位也。是故手三阳经虽阳，而脉绌于表，惟足三阳为独主阳之表
；手三阴脏虽阴，而位不处阴，惟足三阴为独主阴之里。伤寒之邪，所以恒在足而不在手欤
！发明所谓伤寒止伤西北，而不伤东南，亦穿凿之语。夫邪气侵淫，自足及手者有之。如《
玉机》所谓足经实，手经虚，故能冤热。洁古所谓壬病传丙、丙病传丁者是也。然非汗下差
误，或七情劳倦之故，焉有传及手经者哉？
伤寒病传变的次序，通常是先太阳经，再阳明经，接着少阳经，然后太阴经，随后少阴经，最后厥阴经，这是正常的规律。然而风寒之邪，也有直接侵犯阳明经的。张仲景说：阳明中风，出现口苦、咽干、腹部胀满、轻微气喘、发热、恶寒、脉象浮而紧的症状。还有少阳中风，出现两耳听不见、眼睛发红、胸中胀满且烦躁的症状，就是这种情况。不仅阳明、少阳是这样，即使是三阴经也有这种情况。如说少阴病刚开始时，反而出现发热、脉沉的现象，这是少阴初受寒邪的症状。太阴中风，出现四肢烦扰疼痛，脉象寸部微、尺部涩且长的现象，这是太阴初受风邪的症状。厥阴中风，脉象微浮表示将要痊愈，不浮表示未愈，这是厥阴初受风邪的脉象。这三种情况，又与三阴直中不同。直中是指病在脏，这里则是病在经。因此六经都能直接感受风寒，何必一定要从太阳传入；即使是从太阳传入，也不必按照经络顺序依次递进。张元素（海藏）对此论述得最详细，这里不再重复叙述。
认为伤寒只传足经不传手经的说法，是因为寒邪侵入人体，先附着于皮肤，而足太阳膀胱经的经脉位于最外层，所以先受到侵袭；稍微深入则离开皮肤进入肌肉，肌肉属于足阳明胃经的分野，所以其次受到侵袭；再稍微深入则在躯壳之内、脏腑之外，而足少阳胆经的经脉正当半表半里之间，所以再次受到侵袭。等到离开表证进入里证，离开阳经进入阴经，那么三阴经中，太阴为开，厥阴为阖，少阴为枢，所以邪气进入，先入太阴，次入少阴，再入厥阴。综合来说，阳主表而阴主里，表对应腑而里对应五脏，所以邪气在表，则由足三阳经受邪，在里则由足三阴经受邪。手之三阳经虽然也主表，但手太阳小肠经、手少阳三焦经、手阳明大肠经，都是从手走向头，位置偏上且脉道较短，不如足经自下而上运行，能纲维全身。手之三阴经虽然也主里，但手太阴肺经、手少阴心经、手厥阴心包络，都处在上焦，不如肝、脾、肾实居阴位。因此手三阳经虽然是阳经，但脉气绌缩于表，只有足三阳经独自主宰阳之表；手三阴脏虽然是阴脏，但位置不处于阴位，只有足三阴经独自主宰阴之里。伤寒的病邪，所以常常在足经而不在手经吧！所谓伤寒只伤害西北方人而不伤害东南方人的说法，也是穿凿附会的言论。邪气侵淫，由足及手的确实有这种情况。如《素问·玉机真脏论》所说足经实证、手经虚证，所以能产生冤热（郁热）。洁古（张元素）所说的壬病传丙、丙病传丁的情况就是这样。然而如果不是发汗或攻下治疗失误，或者七情劳倦的原因，怎么会有传及手经的呢？
The sequence of transmission in Shanghan (Cold Damage) disease typically proceeds from the Taiyang channel, then to Yangming, Shaoyang, Taiyin, Shaoyin, and finally Jueyin; this is the normal pattern. However, Wind-Cold pathogens may also directly invade the Yangming channel. Zhang Zhongjing stated: In Yangming Wind-strike, symptoms include bitter taste in the mouth, dry throat, abdominal fullness, slight wheezing, fever, aversion to cold, and a floating and tight pulse. Similarly, in Shaoyang Wind-strike, symptoms include hearing loss in both ears, red eyes, chest fullness with irritability. This applies not only to Yangming and Shaoyang but also to the Three Yin channels. For instance, when Shaoyin disease first occurs, the presence of fever and a deep pulse indicates that Shaoyin has initially been affected by Cold pathogens. In Taiyin Wind-strike, painful and uncomfortable limbs with a pulse that is faint at the Cun position, choppy at the Chi position, and long indicate that Taiyin has initially been affected by Wind pathogens. In Jueyin Wind-stroke, a slightly floating pulse suggests impending recovery, while a non-floating pulse indicates no recovery; this is the pulse manifestation when Jueyin is initially affected by Wind pathogens. These three scenarios differ from "Direct Invasion" (Zhi Zhong) of the Three Yin channels. Direct invasion implies pathology within the Zang organs, whereas here the pathology is within the Channels. Therefore, all Six Channels can independently contract Wind-Cold; it is not necessary for the pathogen to transmit exclusively from Taiyang. Even if transmitted from Taiyang, it does not necessarily follow a sequential order through the channels. Zhang Yuansu (Hanghai) discussed this in detail, so it will not be repeated here.
The notion that Shanghan transmits only to the Foot channels and not the Hand channels arises because Cold pathogens first attach to the skin. The Foot-Taiyang Bladder channel is located on the outermost layer, thus receiving the pathogen first. As the pathogen penetrates deeper, moving from skin into muscle, it affects the Foot-Yangming Stomach channel, which governs the muscle layer. Further penetration places the pathogen inside the body shell but outside the Zang-Fu organs, where the Foot-Shaoyang Gallbladder channel resides in the half-exterior half-interior region, thus being affected next. When the pathogen moves from exterior to interior, leaving the Yang channels to enter the Yin channels, the dynamics are governed by Taiyin as the opening, Jueyin as the closing, and Shaoyin as the pivot. Consequently, the pathogen enters Taiyin first, then Shaoyin, and finally Jueyin. Generally speaking, Yang governs the exterior and Yin governs the interior; the exterior corresponds to the Fu organs and the interior to the Zang organs. Thus, when the pathogen is in the exterior, the Foot-Yang channels are affected; when in the interior, the Foot-Yin channels are affected. Although the Hand-Yang channels also govern the exterior, the Hand-Taiyang Small Intestine, Hand-Shaoyang Sanjiao, and Hand-Yangming Large Intestine channels run from hand to head, occupying higher positions with shorter vessel paths, unlike the Foot channels which ascend from below to above and support the entire body. Although the Hand-Yin channels also govern the interior, the Hand-Taiyin Lung, Hand-Shaoyin Heart, and Hand-Jueyin Pericardium are located in the Upper Jiao, unlike the Liver, Spleen, and Kidney which reside firmly in the Yin positions. Therefore, although the Hand-Yang channels are Yang, their Qi is constrained relative to the exterior, making the Foot-Yang channels the sole governors of the Yang exterior; although the Hand-Yin Zang organs are Yin, their location is not purely Yin, making the Foot-Yin channels the sole governors of the Yin interior. Hence, why do Shanghan pathogens often affect the Foot channels rather than the Hand channels? The claim that Shanghan affects only people in the Northwest and not the Southeast is an arbitrary interpretation. It is true that pathogens may spread from Foot to Hand channels. As mentioned in the *Yu Ji* chapter, when Foot channels are excess and Hand channels are deficient, "Yuan Re" (stagnant heat) can occur. This aligns with Zhang Yuansu's (Jiegou) theory of Ren transmitting to Bing, and Bing transmitting to Ding. However, unless there are errors in sweating or purging therapies, or causes related to Seven Emotions and fatigue/overwork, how could the pathogen transmit to the Hand channels?