闻之津液渗泄之所曰腠。纹理缝会之中曰理。腠者是三焦通会元真之处。理者是皮肤脏腑之纹理也。
字书谓肤肉之间为腠理。以其有脉理焉。三说合观。体用备矣。考之内经。则曰开、曰阖、曰粗、曰细。曰疏、曰
密。有因天者。有因人者。有因腑而异者。有因病而异者。因天者何。热则人气在外。皮肤缓。腠理开。汗大泄。
血气减。皮淖泽。寒则人气在中。皮肤致。腠理闭。汗不出。血气强。肉坚涩。此腠理之开闭。因天之寒暑也。因
人者何。膏者其肉淖。而粗理者身寒。细理者身热。脂者其肉坚。细理者热。粗理者寒。此腠理之粗细。因人
之脂膏也。何谓因腑而异。三焦膀胱者。腠理毫毛其应。密理浓皮者。三焦膀胱浓。粗理薄皮者。三焦膀胱
薄。疏腠理者。三焦膀胱缓。皮急而无毫毛者。三焦膀胱急。毫毛美而疏者。三焦膀胱直。稀毫毛者。三焦膀
胱结。此腠理之疏密。因腑而异者也。何谓因病而异。阳胜则身热。腠理闭。喘粗为之俯仰。汗不出而热。齿
干以烦冤。腹满死。能冬不能夏。阴胜则身寒。汗出身常清。数栗而寒。寒则厥。厥则腹满死。能夏不能冬。此
阴阳更胜之变。病之形能也。然阳病亦有汗出者。阴病亦有不汗出者。其开也卫气虚。其闭也卫气实。是
又因证而异。可与诊汗之法参观也。要之。开则有汗。闭则无汗。察腠理之开闭。视汗液之有无一也。此腠
理之开闭。因病而异者也。盖观粗细与疏密者。欲明其体。而观开阖之常变者。欲达其用也。且夫腠理之
开阖。非腠理之自为开阖也。有温分肉。充皮肤。肥腠理。司开阖者焉。盖卫气也。卫气者。下焦之所出。太阴
主其内。太阳主其外者也。阴平阳秘。卫气和矣。卫气和。则分肉解利。皮肤调柔。腠理致密矣。如是而云开
阖。则似开非开。似阖非阖。然非不开也。非不阖也。有时而开。有时而阖。或因寒暑。或因冷暖。或因动静。非
病也。常也。时开则开。时阖则阖者也。设或不当开而开。不当阖而阖。岂得谓之无病哉。合汗而诊之。因时
而验之。参证而辨之。知其开阖之常。即知其开阖之变矣。经曰。谨察卫气。为百病母。腠理之开阖。卫气之
虚实也。开阖虚实。盖可以忽乎哉。
听说津液渗透排泄的地方叫做“腠”。纹理和缝隙交汇的地方叫做“理”。“腠”是三焦通会元气真气的地方。“理”是皮肤和脏腑的纹理。
字书（字典）称肌肉之间为“腠理”，因为那里有脉理存在。综合这三种说法，其体（本体结构）与用（功能作用）就完备了。考察《内经》中的记载，则有关于“开”、“阖”、“粗”、“细”、“疏”、“密”的描述。有的因天气而异，有的因人身体质而异，有的因腑脏不同而异，有的因病证不同而异。
什么叫因天气而异？天热时，人气行于体表，皮肤松弛，腠理开放，汗液大量排出，血气减少，皮肤湿润光泽；天冷时，人气行于体内，皮肤致密，腠理闭合，汗液不出，血气强盛，肌肉坚实涩滞。这就是腠理的开闭，受天气寒暑的影响。
什么叫因人身体质而异？膏型体质的人，肌肉柔润，如果纹理粗糙则身体怕冷，纹理细腻则身体怕热；脂型体质的人，肌肉坚实，纹理细腻则身体怕热，纹理粗糙则身体怕冷。这就是腠理的粗细，取决于人的脂膏体质。
什么叫因腑脏不同而异？三焦和膀胱，对应于腠理和毫毛。纹理紧密、皮肤厚实的人，三焦和膀胱的功能浓厚；纹理粗糙、皮肤薄的人，三焦和膀胱的功能薄弱；腠理疏松的人，三焦和膀胱的功能弛缓；皮肤紧绷且无毫毛的人，三焦和膀胱的功能拘急；毫毛美观且稀疏的人，三焦和膀胱的功能正直；毫毛稀少的人，三焦和膀胱的功能郁结。这就是腠理的疏密，因腑脏状态不同而异。
什么叫因病证不同而异？阳胜则身体发热，腠理闭合，呼吸急促粗重，身体随之起伏，汗不出而身热，牙齿干燥且心中烦闷痛苦，若出现腹部胀满则死，这种病能耐受冬天而不能耐受夏天。阴胜则身体寒冷，出汗后身体常感清冷，频繁战栗发冷，冷极则四肢厥逆，厥逆若导致腹部胀满则死，这种病能耐受夏天而不能耐受冬天。这是阴阳交替胜复的变化，是病证的形态表现。然而阳病也有出汗的，阴病也有不出汗的。腠理开放是因为卫气虚弱，腠理闭合是因为卫气充实。这又是因证候不同而异，可以与诊察汗液的方法参照观看。总之，开放则有汗，闭合则无汗。观察腠理的开闭，与查看汗液的有无是一致的。这就是腠理的开闭，因病证不同而异。
大略来说，观察粗细与疏密，是为了明白其本体结构；而观察开阖的常态与变化，是为了通达其功能作用。况且腠理的开阖，并非腠理自身主动开阖，而是有负责温煦分肉、充养皮肤、肥厚腠理、主管开阖功能的，那就是卫气。卫气，是从下焦发出的，由太阴经主司于内，太阳经主司于外。阴气平和，阳气固秘，卫气就调和了。卫气调和，则分肉滑利，皮肤柔润，腠理致密。像这样所谓的开阖，则是似开非开、似阖非阖的状态，但并非完全不开或不阖，而是有时开放，有时闭合。或因寒暑，或因冷暖，或因动静，这不是病，而是常态。该开放时开放，该闭合时闭合。假如不该开放却开放，不该闭合却闭合，怎么能说没有病呢？结合汗液来诊察，根据时间验证，参合证候来辨析，知道了开阖的常态，也就知道了开阖的变态了。《经》说：谨慎地审察卫气，它是百病的根源。腠理的开阖，反映的是卫气的虚实。开阖的虚实，难道可以忽视吗？
It is heard that the place where body fluids (Jinye, 津液) seep and excrete is called "Cou" (Cou, 腠). The place where textures and seams meet is called "Li" (Li, 理). "Cou" is the place where the Sanjiao (Triple Burner, 三焦) connects and gathers Yuanzhen (Original True Qi, 元真). "Li" refers to the textures of the skin and Zang-Fu organs.
Dictionaries define the space between skin and flesh as "Coul i" (Couli, 腠理), because there are vein textures therein. Observing these three explanations together, both its substance (Ti, 体) and function (Yong, 用) are complete. Examining the *Neijing* (Inner Canon, 《内经》), it mentions "opening" (Kai, 开), "closing" (He, 阖), "coarse" (Cu, 粗), "fine" (Xi, 细), "sparse" (Shu, 疏), and "dense" (Mi, 密). Some vary due to heaven (environmental climate), some due to human constitution, some differ by Fu organs, and some differ by disease patterns.
What does it mean to vary due to heaven? When hot, human qi moves outward; the skin relaxes, Couli opens, sweat pours out profusely, blood and qi diminish, and the skin becomes moist and lustrous. When cold, human qi stays inward; the skin becomes dense, Couli closes, sweat does not exit, blood and qi become strong, and muscles become firm and stiff. This is how the opening and closing of Couli vary with the cold and heat of heaven.
What does it mean to vary due to human constitution? Those with a "Gao" (Pasty/Fatty, 膏) constitution have soft flesh; if their texture is coarse, they feel cold; if fine, they feel hot. Those with a "Zhi" (Lean/Firm, 脂) constitution have firm flesh; if their texture is fine, they feel hot; if coarse, they feel cold. This is how the coarseness and fineness of Couli depend on one's fatty or lean constitution.
What does it mean to differ by Fu organs? The Sanjiao (Triple Burner, 三焦) and Bladder (Pangguang, 膀胱) correspond to Couli and body hair. Those with dense textures and thick skin have robust Sanjiao and Bladder functions; those with coarse textures and thin skin have weak Sanjiao and Bladder functions. Those with sparse Couli have relaxed Sanjiao and Bladder functions; those with tight skin lacking body hair have constrained Sanjiao and Bladder functions; those with beautiful and sparse body hair have upright Sanjiao and Bladder functions; those with scarce body hair have knotted/stagnant Sanjiao and Bladder functions. This is how the sparsity and density of Couli differ according to the state of the Fu organs.
What does it mean to differ by disease patterns? Yang excess leads to body heat, closed Couli, rapid and rough breathing causing the body to heave, no sweat but fever, dry teeth, and vexation/oppression. If abdominal fullness occurs, death ensues; such patients can tolerate winter but not summer. Yin excess leads to body cold, sweating with constant chilliness, frequent shivering and cold, cold extremities leading to Jue (Cold Reversal, 厥), and if abdominal fullness accompanies Jue, death ensues; such patients can tolerate summer but not winter. These are variations in the alternating dominance of Yin and Yang, representing the form and capacity of diseases. However, Yang diseases may also present with sweating, and Yin diseases may present without sweating. Opening occurs when Wei Qi (Defensive Qi, 卫气) is deficient; closing occurs when Wei Qi is solid. This again varies by syndrome and can be observed alongside methods for diagnosing sweat. In summary, opening implies sweat; closing implies no sweat. Observing the opening and closing of Couli is equivalent to viewing the presence or absence of sweat. This is how the opening and closing of Couli differ by disease.
Generally, observing coarseness and fineness aims to understand its substance, while observing the normality and variation of opening and closing aims to grasp its function. Moreover, the opening and closing of Couli do not occur autonomously by Couli itself, but are governed by something that warms the muscle intervals, nourishes the skin, plumps the Couli, and controls opening and closing—namely, Wei Qi (Defensive Qi, 卫气). Wei Qi originates from the Lower Jiao (Lower Burner, 下焦), is primarily managed internally by the Taiyin (Taiyin Lung/Spleen channel, 太阴), and externally by the Taiyang (Taiyang Bladder/Large Intestine channel, 太阳). When Yin is peaceful and Yang is secure, Wei Qi is harmonious. When Wei Qi is harmonious, muscle intervals are smooth, skin is supple, and Couli is dense. In such a state, what is called opening and closing is neither truly open nor truly closed, yet it is not entirely unopen or unclosed; rather, it opens at times and closes at times. This may be due to cold/heat, warmth/chill, or movement/stillness. This is not disease, but normalcy: opening when it should, closing when it should. If it opens when it should not, or closes when it should not, how can one say there is no disease? By combining sweat diagnosis, verifying by time, and differentiating by symptoms, knowing the normal pattern of opening and closing allows one to know its variations. The Classics state: "Carefully observe Wei Qi, for it is the mother of all diseases." The opening and closing of Couli reflect the deficiency and excess of Wei Qi. Can the deficiency and excess of opening and closing be ignored?