素问·太阴阳明论 Discourse on Greater Yin and Yang Brightness
黄帝问曰：太阴阳明为表里，脾胃脉也，生病而异者何也。歧伯对曰：阴阳异位，更虚更实，更逆更从，或从内，或从外，所从不同，故病异名也。帝曰：愿闻其异状也。歧伯曰：阳者，天气也，主外；阴者，地气也，主内。故阳道实，阴道虚。故犯贼风虚邪者，阳受之；食饮不节起居不时者，阴受之。阳受之，则入六府，阴受之，则入五藏。入六府，则身热不时卧，上为喘呼；入五藏则䐜满闭塞，下为飱泄，久为肠澼。故喉主天气，咽主地气。故阳受风气，阴受湿气。故阴气从足上行至头，而下行循臂至指端；阳气从手上行至头，而下行至足。故曰：阳病者，上行极而下，阴病者，下行极而上。故伤于风者，上先受之；伤于湿者，下先受之。
帝曰：脾病而四支不用，何也。歧伯曰：四支皆禀气于胃，而不得至经，必因于脾，乃得禀也。今脾病不能为胃行其津液，四支不得禀水谷气，气日以衰，脉道不利，筋骨肌肉，皆无气以生，故不用焉。
帝曰：脾不主时，何也。歧伯曰：脾者土也，治中央，常以四时长四藏，各十八日寄治，不得独主于时也。脾藏者，常著胃土之精也，土者，生万物而法天地，故上下至头足，不得主时也。
帝曰：脾与胃以膜相连耳，而能为之行其津液，何也。歧伯曰：足太阴者三阴也，其脉贯胃属脾络嗌，故太阴为之行气于三阴。阳明者，表也，五藏六府之海也，亦为之行气于三阳。藏府各因其经而受气于阳明，故为胃行其津液。四支不得禀水谷气，日以益衰，阴道不利，筋骨肌肉无气以生，故不用焉。
Huangdi asked: Greater Yin and Yang Brightness stand in exterior-interior relation, being the vessels of the spleen and stomach; why then do the diseases they generate differ? Qibo replied: Yin and yang occupy different positions; they alternate between deficiency and excess, between rebellion and compliance; some diseases follow from within, others from without — since what they follow differs, the diseases bear different names. Huangdi said: I wish to hear of these differing manifestations. Qibo said: Yang is the qi of Heaven and governs the exterior; yin is the qi of Earth and governs the interior. Hence the way of yang is excess, the way of yin is deficient. Thus when one is struck by marauding wind and depleting evil, yang receives it; when eating and drinking are without moderation and rising and resting are without regularity, yin receives it. When yang receives it, the evil enters the six bowels; when yin receives it, the evil enters the five viscera. Entering the six bowels, the body becomes hot, one cannot rest at proper times, and above there is panting and gasping; entering the five viscera, there is distension, fullness, and blockage, and below there is undigested diarrhea, which in time becomes intestinal flux. Thus the throat governs the qi of Heaven, while the gullet governs the qi of Earth. Hence yang receives the qi of wind, yin receives the qi of dampness. Thus the yin qi travels upward from the feet to the head, then downward along the arms to the fingertips; the yang qi travels upward from the hands to the head, then downward to the feet. Hence it is said: in diseases of yang, the qi ascends to its limit and then descends; in diseases of yin, the qi descends to its limit and then ascends. Thus one injured by wind is affected first above; one injured by dampness is affected first below.
Huangdi said: When the spleen is diseased, the four limbs lose their function — why is this? Qibo said: The four limbs all receive their qi from the stomach, yet this qi cannot reach the channels directly; it must depend upon the spleen in order to be received. Now if the spleen is diseased and cannot circulate the fluids on behalf of the stomach, the four limbs cannot receive the qi of water and grain; the qi daily grows more depleted, the pathways of the vessels become unfree, and the sinews, bones, muscles, and flesh all lack the qi to be nourished and grow — hence they lose their function.
Huangdi said: Why does the spleen not govern a season of its own? Qibo said: The spleen belongs to earth and governs the center; it constantly nourishes the other four viscera throughout the four seasons, being entrusted with governance for eighteen days at the close of each season, and thus cannot alone preside over a single season. The spleen viscus constantly manifests the essence of the stomach's earth qi. Earth gives birth to the myriad things and takes its model from Heaven and Earth; hence its influence reaches upward and downward, to the head and to the feet, and it cannot be confined to governing one season alone.
Huangdi said: The spleen and stomach are joined only by a membrane, yet the spleen is able to circulate the stomach's fluids on its behalf — how is this? Qibo said: The Foot Greater Yin is one of the three yin; its vessel penetrates the stomach, belongs to the spleen, and connects with the gullet — hence Greater Yin circulates qi to the three yin on the stomach's behalf. Yang Brightness constitutes the exterior and is the sea of the five viscera and six bowels; it likewise circulates qi to the three yang. The viscera and bowels each receive qi from Yang Brightness by way of their respective channels; hence the spleen is able to circulate the stomach's fluids on its behalf. Should this fail, the four limbs cannot receive the qi of water and grain, growing daily more depleted; the pathways of yin become unfree, and the sinews, bones, muscles, and flesh lack the qi to be nourished and grow — hence they lose their function.