太阳为六经之纲领其经行身之背其气主一身之皮毛故病则脉浮头项强痛而恶寒缘邪在本经但病其经脉所行之部分而
不及于他经也在经失解自此而内传二阳里入三阴腑热作则脉浮大脏寒作则脉沉细寒热郁发诸病丛生太阳之脉证然后变耳
若其初感腑热未作脏寒未动之时太阳之病情未改证状犹存则只有脉浮头项强痛恶寒而已即合病于别经别经病见而太阳未
罢亦必见太阳之脉证也揣太阳之脉证而分太阳之风寒何至淆乱于别经亡羊于歧路也仲景提太阳之纲只此一语而太阳之情
状了了所谓握片言而居要也
太阳之为病脉浮头项强痛而恶寒
太阳在表故脉浮其经行身之背起于睛明（在目内 足太阳经之穴名）自头下行而走足病则经气上郁壅塞不降故强痛
也风寒闭其营卫气郁不能透泄则外见恶寒寒者太阳之令气也
病有发热恶寒者发于阳也无热恶寒者发于阴也发于阳者七日愈发于阴者六日愈以阳数七阴数六也
此中风伤寒之总纲也卫气为阳风伤卫气是发于阳也卫伤则遏闭营血而生内热营血为阴寒伤营血是发于阴也营伤则束
闭卫气而生外寒故中风之初先见发热伤寒之初先见恶寒中风内热而营血不宣亦外见恶寒伤寒外寒而卫气不达乃续见发热
中风非无外寒究竟内热多而外寒少伤寒非无内热究竟内热少而外寒多营司于肝木木升则火化木火同情故肝血常温卫司于
肺金金降则水生金水同性故肺气常凉肝藏营血而脾为生血之本中风营病脏阴衰者多传阳明而为热肺藏卫气而胃乃化气之
源伤寒卫病腑阳弱者多传太阴而为寒风伤卫者营郁里热若经中阴旺则营气不至内蒸故七日经尽而自愈寒伤营者卫郁表寒
若经中阳旺则卫气不至内陷故六日经尽而自愈此风寒之顺证在经而不入于脏腑者也若中风阳盛而入于腑伤寒阴盛而入于
脏则营卫方忧其内陷非补泄以救其偏不能应期而愈也六日七日水火之成数大衍之数天一生水地六成之地二生火天七成之
火阳也故数七水阴也故数六满其成数是以病愈也
太阳经是六经的纲领，其经脉循行于身体背部，其气主管全身的皮毛。因此患病时会出现脉浮、头项强痛以及恶寒的症状。这是因为邪气仅在太阳本经，只影响其经脉所循行的部位，而不波及他经。如果在太阳经未能及时解除病邪，就会由此向内传入阳明（二阳），深入三阴；若传入腑则表现为热证，出现脉浮大；若传入脏则表现为寒证，出现脉沉细。寒热郁结发作，各种病症丛生，太阳经的脉象和证候才会发生变化。
如果在初感邪气时，腑中热象尚未产生，脏中寒象尚未发动，此时太阳病的病情未改，证状依然存留，那么就只有脉浮、头项强痛、恶寒这些表现。即使同时合并其他经络的病证，只要太阳病未罢，也必然会出现太阳经的脉象和证候。通过揣测太阳经的脉象和证候来区分太阳中风与伤寒，怎么会与其他经络的病证混淆，在歧路上迷失方向呢？张仲景提出太阳病的提纲，仅用这一句话，就使太阳病的状况清晰明了，可谓掌握片言只语而居于关键地位。
太阳主表，所以脉象浮。其经脉循行于身体背部，起于睛明穴（位于目内眦，足太阳膀胱经的穴位），从头向下行至足。患病时，经气上郁壅塞，不能下降，所以出现头项强痛。风寒闭塞营卫，气机郁滞不能透发宣泄，所以在外表现为恶寒。恶寒是太阳经的本令之气。
疾病有发热且恶寒的，属于发于阳经；无发热而仅恶寒的，属于发于阴经。发于阳经者，七日左右痊愈；发于阴经者，六日左右痊愈，这是依据阳数七、阴数六的原理。
这是中风与伤寒的总纲。卫气属阳，风邪伤及卫气，称为发于阳。卫气受伤则遏闭营血，从而产生内热。营血属阴，寒邪伤及营血，称为发于阴。营血受伤则束闭卫气，从而产生外寒。因此，中风之初先见发热，伤寒之初先见恶寒。中风虽有内热，但营血不宣，也会在外见到恶寒；伤寒虽有外寒，但卫气不达，随后会见到发热。中风并非没有外寒，终究是内热多而外寒少；伤寒并非没有内热，终究是内热少而外寒多。
营血由肝木所司，木气升发则化火，木火同源，所以肝血常保持温暖。卫气由肺金所司，金气肃降则生水，金水同源，所以肺气常保持清凉。肝藏营血，脾为生血之本，中风导致营分病变，多为脏阴衰退，容易传变为阳明热证。肺藏卫气，胃乃化气之源，伤寒导致卫分病变，多为腑阳虚弱，容易传变为太阴寒证。
风邪伤卫，导致营气郁滞而生里热，如果经脉中阴气旺盛，营气不至内蒸，故七日经气运行完毕即可自愈。寒邪伤营，导致卫气郁滞而生表寒，如果经脉中阳气旺盛，卫气不至内陷，故六日经气运行完毕即可自愈。这是风寒之邪顺证，停留在经脉而不进入脏腑的情况。如果中风导致阳盛而入腑，或伤寒导致阴盛而入脏，那么营卫正气正担忧内陷，如果不通过补益或泻下以纠正偏颇，就不能如期痊愈。
六日和七日分别是水和火的成数。根据大衍之数，“天一生水，地六成之”，“地二生火，天七成之”。阳数故为七，水阴数故为六。补足其成数，疾病因此痊愈。
Taiyang (Greater Yang) is the guiding principle of the Six Channels. Its meridian runs along the back of the body, and its Qi governs the skin and hair of the whole body. Therefore, when diseased, it presents with a floating pulse (Mai Fu), stiffness and pain in the head and neck (Tou Xiang Qiang Tong), and aversion to cold (E Han). This is because the pathogenic factor is confined to the Taiyang channel itself, affecting only the parts traversed by this meridian without involving other channels. If the pathogen is not resolved within the channel, it will subsequently transmit inward to Yangming (the Second Yang) or enter the Three Yin channels. If it enters the Fu organs, it manifests as heat syndrome with a floating and large pulse; if it enters the Zang organs, it manifests as cold syndrome with a deep and fine pulse. As cold and heat stagnate and erupt, various diseases arise, and the pulse and syndromes of Taiyang change accordingly.
If at the initial stage of infection, heat in the Fu organs has not yet arisen and cold in the Zang organs has not yet moved, the condition of Taiyang remains unchanged and symptoms persist. In this case, there are only a floating pulse, stiffness and pain in the head and neck, and aversion to cold. Even if there is a concurrent disease in another channel, as long as the Taiyang condition has not ceased, the pulse and syndromes of Taiyang must still be present. By analyzing the pulse and syndromes of Taiyang to distinguish between Wind-stroke (Zhong Feng) and Cold-injury (Shang Han), one avoids confusion with other channels and prevents getting lost on divergent paths. Zhang Zhongjing’s summary of the Taiyang guideline consists of only this sentence, making the characteristics of Taiyang clear, demonstrating how concise words can capture the essence.
The defining features of Taiyang disease are: floating pulse, stiffness and pain in the head and neck, and aversion to cold.
Since Taiyang governs the exterior, the pulse is floating. Its meridian runs along the back, originating from Jingming (Jingming, an acupoint of the Foot-Taiyang Bladder Meridian located at the inner canthus of the eye), descending from the head to the foot. When diseased, the meridian Qi becomes stagnant and obstructed upward, failing to descend, resulting in stiffness and pain. Wind and cold close off Ying (Nutritive) and Wei (Defensive) Qi, causing Qi stagnation that cannot penetrate and dissipate, thus manifesting externally as aversion to cold. Aversion to cold is the characteristic Qi of the Taiyang channel.
Diseases presenting with fever and aversion to cold originate in the Yang; those without fever but with aversion to cold originate in the Yin. Diseases originating in Yang typically resolve around the seventh day; those originating in Yin typically resolve around the sixth day, based on the numerical attributes of Yang being seven and Yin being six.
This is the general principle for Wind-stroke and Cold-injury. Wei Qi belongs to Yang; Wind injuring Wei Qi is termed "originating in Yang." Injury to Wei Qi obstructs Ying Blood, generating internal heat. Ying Blood belongs to Yin; Cold injuring Ying Blood is termed "originating in Yin." Injury to Ying Blood constricts Wei Qi, generating external cold. Therefore, Wind-stroke initially presents with fever, while Cold-injury initially presents with aversion to cold. Although Wind-stroke involves internal heat, if Ying Blood is not unblocked, external aversion to cold may also appear. Although Cold-injury involves external cold, if Wei Qi fails to reach the surface, fever may subsequently appear. Wind-stroke is not devoid of external cold, but ultimately internal heat predominates over external cold. Cold-injury is not devoid of internal heat, but ultimately external cold predominates over internal heat.
Ying Blood is governed by Liver Wood; as Wood ascends, it transforms into Fire. Wood and Fire share the same nature, so Liver Blood remains warm. Wei Qi is governed by Lung Metal; as Metal descends, it generates Water. Metal and Water share the same nature, so Lung Qi remains cool. The Liver stores Ying Blood, and the Spleen is the root of blood generation. Wind-stroke affecting Ying often leads to decline of Zang Yin, frequently transmitting to Yangming as heat. The Lung stores Wei Qi, and the Stomach is the source of Qi transformation. Cold-injury affecting Wei often leads to weakness of Fu Yang, frequently transmitting to Taiyin as cold.
Wind injuring Wei causes Ying stagnation and interior heat; if Yin within the channel is vigorous, Ying Qi does not steam internally, allowing self-resolution after seven days as the channel cycle completes. Cold injuring Ying causes Wei stagnation and exterior cold; if Yang within the channel is vigorous, Wei Qi does not sink internally, allowing self-resolution after six days as the channel cycle completes. These are favorable courses where Wind-Cold remains in the channels without entering the Zang-Fu organs. However, if Wind-stroke leads to excess Yang entering the Fu organs, or Cold-injury leads to excess Yin entering the Zang organs, Ying and Wei Qi fear internal sinking. Without tonification or purgation to correct the imbalance, timely resolution cannot occur.
Six and seven are the completion numbers of Water and Fire, respectively. According to the Great Expansion Numbers: "Heaven generates One, Earth completes Six" (Water); "Earth generates Two, Heaven completes Seven" (Fire). Thus, Seven is the number of Yang, and Six is the number of Yin. Completing these numbers leads to recovery from illness.