八卦之中，离为 物。五行之中，火能焚物。六气之中，火能消物。故火之为用，燔木
则消
而为炭，焚土则消而为砖，炼金则消而为汗，煨石则消而为灰，煮水则消而为汤，煎海则消
而为盐，炼汞则消而为粉，熬锡则消而为丹。故泽中之潦，涸于炎晖。鼎中之水，涸于壮火
。盖五脏心为君火正化，肾为君火对化，三焦为相火正化，胆为相火对化，得其平，则烹炼
饮食，糟粕去焉。不得其平，则燔灼脏腑，而津液竭焉。故入水之物，无物不长。入火之物
，无物不消。无一身之心火，甚于上为膈膜之消，甚于中为肠胃之消，甚于下为膏液之消，
甚于外为肌肉之消。上甚不已，则消及于肺；中甚不已，则消及于脾；下甚不已，则消及于
肝肾；外甚不已，则消及于筋骨。四脏皆消尽，则心始自焚而死矣。故《素问》有消瘅、消
中、消渴、风消、膈消、肺消之说。消之证不同，归之于火则一也。故消瘅者，众消之总名
；消中者，善饥之通称；消渴者，善饮之通谓，惟风消、膈消、肺消三说，不可不分。风消
者，二阳之疾，多风邪所鼓。格拒贲门，消铄肠胃，水不能咽，口干善渴。经曰；二阳结，
为之消，善食而瘦者，名曰食 是也。膈消者，金受火邪，善饮数溲，变为水肿。经曰∶心
移热于肺，为膈消是也。肺消者，肺外为寒邪所搏，阳气不施，内为火所燥，元极水复，故
皮肤索泽而 着，溲溺积湿而频下，上饮半升，下行十合。经曰∶心移寒于肺为肺消，饮一
溲二死，不治是也。膈消不为寒所薄，阳气得以散于外，为可治。肺消为寒所薄，阳气自溃
于中，为不可治。夫消者必渴，渴亦有别。膏粱之人，多肥甘之渴，与药石之渴；藜藿之人
，则惟燥热之渴而已。故火在上者，善渴，火在中者善饥。火在下者善渴。多饮而数溲，火
在中下者不渴而溲白液；火遍上中下者，饮多而数溲，此其判也。后人断消为肾虚，水不胜
火之故，其用药则又非是，何也？以八味丸治消水不能生，而火反助也，惟河间制言立法，
甚得《内经》之旨，而世俗不知。故消渴一证，调之而不下，则水润少濡，不能杀炎上之势
，下之而不调，亦旋饮旋消，不能沃膈膜之干。下之调之，而不戒嗜欲，不节喜怒，不减滋
味，则病已而复作。能知此者，消渴不足忧也。
在八卦之中，离卦象征火。在五行之中，火能够焚烧物体。在六气之中，火能够消蚀物体。所以火的作用，是燃烧木头使其消解成为炭，焚烧泥土使其消解成为砖，熔炼金属使其消解成为汗液（比喻熔化状态），煅烧石头使其消解成为灰，煮水使其消解成为汤，煎煮海水使其消解成为盐，提炼汞使其消解成为粉，熬制锡使其消解成为丹砂。因此，沼泽中的积水，会在烈日下干涸；鼎锅中的水，会在猛火下干涸。
五脏之中，心属于君火的正化，肾属于君火的对化，三焦属于相火的正化，胆属于相火的对化。如果保持平衡，就能烹煮消化饮食，排出糟粕。如果不平衡，就会燔灼脏腑，导致津液枯竭。所以进入水中的物体，没有不生长的；进入火中的物体，没有不消解的。人体中心火过旺，在上部表现为膈膜部位的消渴，在中部表现为肠胃部位的消渴，在下部表现为膏脂津液的消渴，在外表表现为肌肉的消削。上部症状严重不止，则消损波及到肺；中部症状严重不止，则消损波及到脾；下部症状严重不止，则消损波及到肝肾；外表症状严重不止，则消损波及到筋骨。当其他四脏都被消损殆尽时，心脏才会因自焚而死亡。所以《素问》中有消瘅、消中、消渴、风消、膈消、肺消的说法。消渴的症状虽然不同，但归结于火邪这一病因是一致的。
所谓消瘅，是各种消证的总称；消中，是容易饥饿的通称；消渴，是多饮的通称。只有风消、膈消、肺消这三种说法，不可不加以区分。风消，是二阳经（胃与大肠）的疾病，多由风邪鼓动所致。邪气格拒于贲门，消烁肠胃，导致水不能咽下，口干且喜欢喝水。经文说：“二阳结，为之消”，容易进食却身体消瘦，名叫食ite（注：原文此处可能有缺字或异体字，通常指“食亦”）。膈消，是金（肺）受到火邪侵袭，喜欢饮水且小便频繁，进而变为水肿。经文说：“心移热于肺，为膈消”。肺消，是肺外部被寒邪所迫，阳气不能布散，内部被火邪燥伤，元气极度亏损，津液复竭，所以皮肤干枯无光泽且紧贴骨骼，小便积聚湿气而频数下行，喝下半升水，下行排出十合水。经文说：“心移寒于肺为肺消”，喝一溲二，属死证，难以治疗。膈消不被寒邪逼迫，阳气得以散发于外，属于可治之症。肺消被寒邪逼迫，阳气在中焦自行溃败，属于不可治之症。
凡是消证必然口渴，但口渴也有区别。吃精细食物的人，多有因肥甘厚味引起的口渴，以及药物引起的口渴；吃粗劣食物的人，则只有因燥热引起的口渴。所以火邪在上部的，喜欢口渴；火邪在中部的，喜欢饥饿；火邪在下部的，喜欢口渴。如果多喝且小便频繁，是火邪在中下部的表现，此时不口渴而小便排出白色液体；如果火邪遍布上中下三部，则饮水多且小便频繁，这是它们的区别所在。后人将消证断定为肾虚，认为是不胜火邪的缘故，他们的用药方法却是错误的。为什么呢？用八味丸治疗消证，水不能生发，反而助长火势。只有刘河间制定的言论和立法，很符合《内经》的宗旨，但世俗之人并不知晓。所以消渴这一病症，只调理而不攻下，则肾水滋润不足，不能遏制炎上的势头；只攻下而不调理，也是边喝边消，不能滋润膈膜的干燥。如果既攻下又调理，但不戒除嗜欲，不节制喜怒，不减少滋腻美味的食物，那么病好了又会复发。能懂得这些道理，消渴病就不值得担忧了。
In the Eight Trigrams, Li (Fire) represents fire. In the Five Elements, fire can burn objects. In the Six Qi, fire can consume objects. Therefore, the function of fire is to burn wood until it is consumed and turns into charcoal, to burn earth until it is consumed and turns into bricks, to smelt metal until it is consumed and becomes like sweat (metaphor for molten state), to calcine stone until it is consumed and turns into ash, to boil water until it is consumed and becomes soup, to boil seawater until it is consumed and becomes salt, to refine mercury until it is consumed and becomes powder, to distill tin until it is consumed and becomes cinnabar. Thus, the water in marshes dries up under the scorching sun; the water in cauldrons dries up under fierce fire.
Among the Five Zang organs, the Heart belongs to the orthodox transformation of Sovereign Fire (Jun Huo), the Kidney belongs to the counter-transformation of Sovereign Fire, the Sanjiao (Triple Burner) belongs to the orthodox transformation of Ministerial Fire (Xiang Huo), and the Gallbladder belongs to the counter-transformation of Ministerial Fire. If balance is maintained, food and drink are cooked and digested, and waste products are expelled. If balance is not maintained, organs and tissues are scorched, and body fluids (Jin Ye) are exhausted. Therefore, objects entering water grow without exception; objects entering fire are consumed without exception. If Heart Fire in the body is excessive, it manifests as Xiao Ke (Wasting-Thirst) in the diaphragm region above, in the stomach and intestines in the middle, in the essence and fluids below, and causes muscle wasting on the exterior. If the upper symptoms are severe and uncontrolled, the wasting affects the Lungs; if the middle symptoms are severe and uncontrolled, the wasting affects the Spleen; if the lower symptoms are severe and uncontrolled, the wasting affects the Liver and Kidneys; if the exterior symptoms are severe and uncontrolled, the wasting affects the sinews and bones. When the other four Zang organs are completely consumed, the Heart itself burns out and death ensues. Therefore, the *Su Wen* (Basic Questions) mentions Xiao Dan (Wasting-Fever), Xiao Zhong (Middle Wasting), Xiao Ke (Wasting-Thirst), Feng Xiao (Wind Wasting), Ge Xiao (Diaphragm Wasting), and Fei Xiao (Lung Wasting). Although the manifestations of Xiao differ, they all归结 to Fire pathogen.
Xiao Dan is the general term for all types of wasting syndromes; Xiao Zhong is the common term for excessive hunger; Xiao Ke is the common term for excessive thirst. Only Feng Xiao, Ge Xiao, and Fei Xiao must be distinguished. Feng Xiao is a disease of the Two Yang meridians (Stomach and Large Intestine), often driven by Wind pathogen. The pathogen obstructs the贲门 (cardia), consumes the stomach and intestines, making it impossible to swallow water, causing dry mouth and excessive thirst. The classic states: "When the Two Yang are knotted, wasting occurs." Eating well but becoming thin is called Shi Yi (Food Wasting). Ge Xiao occurs when Metal (Lung) is invaded by Fire pathogen, leading to excessive drinking and frequent urination, which may transform into edema. The classic states: "Heart transfers heat to the Lung, resulting in Ge Xiao." Fei Xiao occurs when the exterior of the Lung is constrained by Cold pathogen, preventing Yang Qi from distributing, while internally it is dried by Fire, causing extreme depletion of Yuan Qi and exhaustion of fluids. Consequently, the skin becomes dry and shrinks against the bones, and urine accumulates dampness and is passed frequently; half a sheng of liquid drunk results in ten he of liquid excreted. The classic states: "Heart transfers cold to the Lung, resulting in Fei Xiao. Drinking one part and urinating two parts indicates a fatal, incurable condition." Ge Xiao is not constrained by Cold, allowing Yang Qi to dissipate outwardly, making it treatable. Fei Xiao is constrained by Cold, causing Yang Qi to collapse centrally, making it incurable.
All wasting syndromes involve thirst, but there are distinctions. Those who eat rich foods often have thirst due to sweet and fatty foods or medicinal side effects; those who eat coarse foods have thirst only due to dryness-heat. Fire in the upper jiao causes excessive thirst; Fire in the middle jiao causes excessive hunger; Fire in the lower jiao causes excessive thirst. Excessive drinking with frequent urination indicates Fire in the middle and lower jiao, where there is no thirst but white fluid in urine; Fire pervading the upper, middle, and lower jiao causes excessive drinking and frequent urination. These are the differentiating factors. Later physicians diagnosed wasting syndromes as Kidney deficiency failing to control Fire, yet their medication was incorrect. Why? Using Ba Wei Wan (Eight-Ingredient Pill with Rehmannia) to treat wasting fails to generate Water and instead aids Fire. Only Liu Hejian's theories and prescriptions align well with the principles of the *Nei Jing*, though this is unknown to the secular world. Therefore, for Xiao Ke, if one only regulates without purging, Kidney Water will be insufficient to moisten and cannot suppress the flaming-up tendency; if one only purges without regulating, drinking and wasting occur simultaneously, unable to moisten the dry diaphragm. If one purges and regulates but does not abstain from desires, control emotions, or reduce rich foods, the disease will recur after remission. Understanding these principles makes Xiao Ke a matter of little concern.