素问·皮部论 Treatise on the Regions of the Skin
黄帝问曰：余闻皮有分部，脉有经纪，筋有结络，骨有度量，其所生病各异，别其分部左右上下阴阳所在病之始终，愿闻其道。歧伯对曰：欲知皮部以经脉为纪者，诸经皆然。阳明之阳，名曰害蜚，上下同法，视其部中有浮络者，皆阳明之络也，其色多青则痛，多黑则痹，黄赤则热，多白则寒，五色皆见，则寒热也，络盛则入客于经，阳主外，阴主内。少阳之阳，名曰枢持，上下同法，视其部中有浮络者，皆少阳之络也，络盛则入客于经，故在阳者主内，在阴者主出以渗于内，诸经皆然。太阳之阳，名曰关枢，上下同法，视其部中有浮络者，皆太阳之络也，络盛则入客于经。少阴之阴，名曰枢儒，上下同法，视其部中有浮络者，皆少阴之络也，络盛则入客于经，其入经也，从阳部注于经，其出者，从阴内注于骨。心主之阴，名曰害肩，上下同法，视其部中有浮络者，皆心主之络也，络盛则入客于经。太阴之阴，名曰关蛰，上下同法，视其部中有浮络者，皆太阴之络也，络盛则入客于经。凡十二经络脉者皮之部也。
是故百病之始生也，必先于皮毛，邪中之则腠理开，开则入客于络脉，留而不去，传入于经，留而不去，传入于府，廪于肠胃。邪之始入于皮也，泝然起毫毛，开腠理。其入于络也，则络脉盛色变。其入客于经也，则感虚乃陷下。其留于筋骨之间，寒多则筋挛骨痛，热多则筋弛骨消，肉烁䐃破，毛直而败。帝曰：夫子言皮之十二部，其生病皆何如。歧伯曰：皮者，脉之部也。邪客于皮则腠理开，开则邪入客于络脉，络脉满则注于经脉，经脉满则入舍于府藏也，故皮者有分部，不与，而生大病也。帝曰：善。
Huangdi asked: I have heard that the skin has its divided regions, the vessels their regulating channels, the sinews their knots and links, and the bones their measurements, and that the diseases arising from each differ. I wish to distinguish these regions — left and right, upper and lower, where yin and yang lie — and to understand the beginning and end of disease within them. I wish to hear this principle. Qibo replied: To know the regions of the skin, one takes the channels and vessels as the guide; this holds true for every channel. The yang aspect of yang brightness is called Hai Fei; the rule is the same above and below. Observing the floating connecting vessels within its region — these are all connecting vessels of yang brightness. When their color is predominantly green, there is pain; predominantly black, there is impediment; yellow-red, there is heat; predominantly white, there is cold; and when all five colors appear together, there is cold and heat alternating. When the connecting vessels grow exuberant, the pathogen enters and lodges in the channel; yang governs the exterior, yin governs the interior. The yang aspect of lesser yang is called Shu Chi; the rule is the same above and below. Observing the floating connecting vessels within its region — these are all connecting vessels of lesser yang. When they grow exuberant, the pathogen enters and lodges in the channel; hence when it lies in the yang aspect it tends inward, and when it lies in the yin aspect it tends outward so as to seep inward — this holds true for every channel. The yang aspect of greater yang is called Guan Shu; the rule is the same above and below. Observing the floating connecting vessels within its region — these are all connecting vessels of greater yang. When they grow exuberant, the pathogen enters and lodges in the channel. The yin aspect of lesser yin is called Shu Ru; the rule is the same above and below. Observing the floating connecting vessels within its region — these are all connecting vessels of lesser yin. When they grow exuberant, the pathogen enters and lodges in the channel; upon entering the channel it pours in from the yang region, and upon leaving it pours inward from the yin aspect into the bone. The yin aspect of the pericardium is called Hai Jian; the rule is the same above and below. Observing the floating connecting vessels within its region — these are all connecting vessels of the pericardium. When they grow exuberant, the pathogen enters and lodges in the channel. The yin aspect of greater yin is called Guan Zhe; the rule is the same above and below. Observing the floating connecting vessels within its region — these are all connecting vessels of greater yin. When they grow exuberant, the pathogen enters and lodges in the channel. In sum, the twelve channels and their connecting vessels constitute the regions of the skin.
Therefore, when the hundred diseases first arise, they must begin in the skin and body hair. When a pathogen strikes there, the interstices open; once open, it enters and lodges in the connecting vessels; if it lingers without departing, it is transmitted into the channels; if it lingers there still without departing, it is transmitted into the bowels, where it accumulates in the intestines and stomach. When the pathogen first enters the skin, it produces a shivering that raises the fine hairs and opens the interstices. When it enters the connecting vessels, the connecting vessels grow full and their color changes. When it enters and lodges in the channels, the channels, sensing the deficiency, sink and collapse. When it lingers between sinew and bone, if cold predominates the sinews cramp and the bones ache; if heat predominates the sinews go slack and the bones waste, the flesh melts and the muscle masses break down, and the body hair stands erect and turns lusterless. Huangdi said: You, Master, have spoken of the twelve regions of the skin — how do the diseases arising within them present themselves? Qibo said: The skin is the region of the vessels. When a pathogen lodges in the skin, the interstices open; once open, the pathogen enters and lodges in the connecting vessels; when the connecting vessels become full, it pours into the channel vessels; when the channel vessels become full, it enters and takes up residence in the bowels and viscera. Hence, although the skin has its divided regions, if the disease is not addressed there, it will give rise to grave illness. Huangdi said: Good.