燥者，阳明金气之所化也。在天为燥，在地为金，在人为大肠。阳明以燥金主令，胃土从令而化燥。
太阴以湿土主令，肺金从令而化湿。胃土之燥，子气而非本气。子气不敌本气之旺，故阴盛之家，胃土恒湿
。肺金之湿，母气而非本气。母气不敌木气之旺，
故阳盛之家，肺金恒燥。太阴性湿，阳明性燥，燥湿调停，在乎中气，旺则辛金化气于湿土，而肺不伤燥，
戊土化气于燥金，而胃不伤湿，中气衰则阴阳不交，而燥湿偏见。湿胜其燥，而饮少而食减，溺涩而便滑。
燥胜其湿，则疾饥而善渴，水利而便坚。阴易进，而阳易退。湿胜者，常多；燥胜者，常少；辛金化湿者，
十之八九，戊土化燥者，百不二三。阳明虽燥，病则太阴每胜，而阳明每负，土燥而水亏者，伤寒阳明
承气证外，绝无而仅有，是以仲景垂法，以少阴负趺阳者为顺，缘火胜则土燥，水胜则土湿，燥则克水，
湿则反为水侮。水负则生，土负则死，故少阴宜负，而趺阳宜胜，以土能胜水，则中气不败，未有中气不
败而人死者。燥为寒热之中气，上燥则
化火而为热，下燥则化水而为寒。反胃噎膈之家，便若羊矢，其胃则湿，而肠则燥。湿为阴邪，阴性亲下
，故根起于脾土，而标见于膝踝。燥为阳邪，阳性亲上，故根起于大肠，而标见于
肘腕。所谓阳邪居下，阴邪居上，一定之位也。然上之燥，亦因于下之湿。中风之家，血枯筋缩，其膝踝是
湿，而肘腕未尝非燥，使己土不湿，则木荣血畅，骨弱筋柔，风自何来？医家识燥湿之消长，则仲景堂奥可
阶而升矣。
燥，是阳明金气所化生的。在天为燥，在地为金，在人为大肠。阳明经以燥金为主令，胃土顺从主令而化生燥气。
太阴经以湿土为主令，肺金顺从主令而化生湿气。胃土的燥，是子气而非本气。子气不敌本气的旺盛，所以在阴盛的人家，胃土常常偏湿。
肺金的湿，是母气而非本气。母气不敌木气的旺盛，所以在阳盛的人家，肺金常常偏燥。太阴性质为湿，阳明性质为燥，燥与湿的调和平衡，取决于中气（脾胃之气）。中气旺盛时，辛金（肺）在湿土中化气，从而肺不伤于燥；戊土（胃）在燥金中化气，从而胃不伤于湿。中气衰弱时，阴阳不能交通，导致燥湿偏颇。湿胜过了燥，就会饮水少、食欲减退、小便涩滞而大便滑泄。燥胜过了湿，就会容易饥饿且善于口渴、小便通利而大便干结。阴邪容易进犯，阳邪容易退却。湿胜的情况常见，燥胜的情况少见；辛金化湿的情况，十之八九；戊土化燥的情况，百中不到二三。阳明虽然本性为燥，但发病时往往是太阴常胜而阳明常败。土燥而水亏的情况，除了伤寒阳明承气汤证之外，绝无仅有。因此张仲景立下法则，认为少阴脉弱于趺阳脉为顺证，因为火胜则土燥，水胜则土湿。燥会克制水，湿反而会受水的侮反。水弱则生机存，土弱则死亡。所以少阴宜弱，而趺阳宜强，因为土能胜水，则中气不败，从来没有中气不败而人死亡的。燥是寒热之间的中气，上部的燥会化火而为热，下部的燥会化水而为寒。患有反胃噎膈的人，大便像羊屎一样，其胃是湿的，而肠是燥的。湿属于阴邪，阴的性质亲附于下，所以根源起于脾土，标象见于膝踝。燥属于阳邪，阳的性质亲附于上，所以根源起于大肠，标象见于肘腕。所谓阳邪居下，阴邪居上，这是固定的位置。然而上部的燥，也源于下部的湿。患中风的人，血枯筋缩，其膝踝处是湿，而肘腕处未尝不是燥。如果己土（脾）不湿，那么木气荣盛、血液通畅，骨骼柔弱、筋脉柔和，风邪从何而来？医生若能识别燥湿的消长变化，那么就能逐步登堂入室，掌握张仲景医学的深奥道理了。
Dryness is the transformation of Yangming Metal Qi. In Heaven it is Dryness, in Earth it is Metal, and in Man it is the Large Intestine. The Yangming channel governs with Dryness-Metal, and the Stomach Earth follows this command to transform into Dryness.
The Taiyin channel governs with Damp-Earth, and the Lung Metal follows this command to transform into Dampness. The Dryness of Stomach Earth is the Child Qi rather than its Original Qi. Since Child Qi cannot rival the prosperity of Original Qi, in individuals with Yin excess, Stomach Earth is constantly damp.
The Dampness of Lung Metal is the Mother Qi rather than its Original Qi. Since Mother Qi cannot rival the prosperity of Wood Qi, in individuals with Yang excess, Lung Metal is constantly dry. Taiyin nature is Damp, Yangming nature is Dry. The balance between Dryness and Dampness depends on Middle Qi (Spleen-Stomach Qi). When Middle Qi is prosperous, Xin Metal (Lung) transforms Qi within Wet Earth, so the Lung is not injured by Dryness; Wu Earth (Stomach) transforms Qi within Dry Metal, so the Stomach is not injured by Dampness. When Middle Qi declines, Yin and Yang fail to interact, leading to bias in Dryness and Dampness. If Dampness exceeds Dryness, there will be reduced thirst, decreased appetite, astringent urination, and loose stools. If Dryness exceeds Dampness, there will be frequent hunger and easy thirst, profuse urination, and hard stools. Yin pathogens easily advance, while Yang pathogens easily retreat. Cases of Dampness excess are common; cases of Dryness excess are rare. Cases where Xin Metal transforms Dampness account for eight or nine out of ten; cases where Wu Earth transforms Dryness account for less than two or three out of a hundred. Although Yangming is inherently Dry, in disease, Taiyin often prevails while Yangming often loses. Conditions of Earth Dryness and Water Deficiency, except for the Chengqi Syndrome of Yangming in Cold Damage, are extremely rare. Therefore, Zhang Zhongjing established the principle that it is auspicious if the Shaoyin pulse is weaker than the Fuyang pulse, because Fire excess leads to Earth Dryness, and Water excess leads to Earth Dampness. Dryness conquers Water, but Dampness is insulted by Water. When Water is deficient, life persists; when Earth is deficient, death ensues. Thus, Shaoyin should be weak, and Fuyang should be strong, because Earth can conquer Water, ensuring Middle Qi remains unbroken. There is no case where Middle Qi remains unbroken yet the person dies. Dryness is the intermediary between Cold and Heat. Upper Dryness transforms into Fire and becomes Heat; Lower Dryness transforms into Water and becomes Cold. In patients with regurgitation or dysphagia, stools resemble sheep droppings; their Stomach is Damp, while their Intestines are Dry. Dampness is a Yin pathogen; Yin nature tends downward, so its root originates in Spleen Earth, and its manifestation appears at the knees and ankles. Dryness is a Yang pathogen; Yang nature tends upward, so its root originates in the Large Intestine, and its manifestation appears at the elbows and wrists. This is the fixed position: Yang pathogens reside below, Yin pathogens reside above. However, Upper Dryness also arises from Lower Dampness. In patients with wind-stroke, blood depletion, and tendon contraction, the knees and ankles are Damp, while the elbows and wrists are not necessarily Dry. If Ji Earth (Spleen) were not Damp, Wood would flourish, Blood would flow freely, bones would be weak, and tendons flexible, from where would Wind arise? If physicians can recognize the waxing and waning of Dryness and Dampness, they can ascend step by step to the profound mysteries of Zhang Zhongjing's teachings.