伤寒渴者。何以明之。渴者里有热也。伤寒之邪。自表传至里。则必有名证。随其邪
浅深而见焉。虽曰一日在皮。二日在肤。三日在肌。四日在胸。五日在腹。六日入胃。
其传经者。又有证形焉。太阳主气。而先受邪。当一二日发。头项痛而腰脊强者是
矣。太阳传阳明。则二三日发。身热目疼。鼻干不得卧也。阳明传少阳。则三四日发。
胸胁痛而耳聋。此三阳皆受病。为邪在表。而犹未作热。故不言渴。至四五日。少阳
传太阴经。邪气渐入里。寒邪渐成热。当是时也。津液耗少。故腹满而嗌干。至五六
日。太阴传少阴。是里热又渐深也。当此之时。则津液为热所搏。渐耗而干。故口燥
舌干而渴。及至六七日。则少阴之邪。传于厥阴。厥阴之为病。消渴。为里热已极矣。
所谓消渴者。饮水多而小便少者是矣。谓其热能消水也。所以伤寒病至六七日。
而渴欲饮水。为欲愈之候。以其传经尽故也。是以厥阴病云。渴欲饮水。少少与之。
愈者是也。邪气初传入里。热气散漫。未收敛成热。熏蒸焦膈。搏耗津液。遂成渴也。
病患虽渴。欲得饮水。又不可多与之。若饮水过多。热少不能消。故复为停饮诸疾。
经曰。凡得时气病至五六日。而渴欲饮水。饮不能多。勿多与也。何者。以腹中热尚
少。不能消之。使更与人作病也。若大渴欲饮水。犹当根据证与之。与之常令不足。勿
极意也。言能饮一斗与五升。又曰渴欲饮水。少少与之。但以法救之。渴者宜五苓
散。至于大渴欲饮水数升者。白虎加人参汤主之。皆欲润其燥而生津液也。凡得
病反能饮水。此为欲愈之病。其不晓病者。但闻病饮水自瘥。小渴者乃强与饮之。
因成大祸。不可复救。然则悸、动也。支、结也。喘咳噎哕。干呕肿满。下利小便不利。数
者皆是饮水过伤。而诊病之工。当须识此。勿令误也。
伤寒病出现口渴症状，该如何阐明其机理？口渴是因为体内有热邪。伤寒的邪气，从体表传入体内，必然会有相应的证候表现，随着邪气侵入的深浅不同而显现出来。虽然说第一天邪气在皮毛，第二天在肌肤，第三天在肌肉，第四天在胸中，第五天在腹部，第六天进入胃腑。但如果是循经传变的，又有不同的证状表现。太阳经主一身之气，最先受邪，通常在发病后一两天内出现，表现为头痛、项强以及腰脊僵硬。太阳经邪气传入阳明经，则在发病后两三天内出现，表现为身体发热、眼睛疼痛、鼻干且无法安卧。阳明经邪气传入少阳经，则在发病后三到四天内出现，表现为胸胁部疼痛和耳聋。这三阳经都受到病邪侵袭，属于邪气在表，尚未化热成实，所以不提及口渴。到了第四五天，少阳经邪气传入太阴经，邪气逐渐深入体内，寒邪逐渐转化为热邪。在这个时候，津液消耗减少，所以出现腹部胀满和咽喉干燥。到了第五六天，太阴经邪气传入少阴经，这是体内的热邪进一步加深。在这个时候，津液被热邪煎熬，逐渐消耗而变得干枯，所以出现口燥、舌干并且口渴。等到第六七天，少阴经的邪气传入厥阴经。厥阴经受病的表现是消渴（极度口渴，饮水不解），这是因为体内的热邪已经极盛。所谓消渴，就是喝很多水但小便很少，因为热邪能消耗水分。所以伤寒病发展到第六七天，如果患者想喝水，这是病情将要痊愈的征兆，因为邪气已经传遍所有经络。因此《伤寒论》中说厥阴病篇提到：“如果患者想喝水，少量给予饮用，病就会好。”当邪气刚刚传入体内，热气散漫，尚未收敛聚集成实热，熏蒸膈膜，煎熬耗损津液，于是形成口渴。病人虽然口渴想要喝水，但又不能大量给予。如果饮水过多，少量的热邪无法消化这些水，反而会导致停饮等病症。医经说：“凡是患时气病到了第五六天，想要喝水，可以喝但不能多喝，不要给太多。”为什么呢？因为腹中的热邪还比较少，无法消化过多的水，再给水喝反而会制造新的病患。如果患者极度口渴想要大量饮水，仍然应当根据证候给予相应治疗。给予饮水时要让患者感到稍不足，不要让他喝得太饱。意思是如果能喝一斗水，只给他五升。又说：“如果患者想喝水，少量给予。”只要按照法则救治即可。对于口渴的患者，适宜使用五苓散。至于那些极度口渴、想要喝几升水的患者，应当用白虎加人参汤主治。这些都是为了滋润燥热并生津液。凡是患病后反而能喝水，这是病情将要痊愈的表现。那些不懂医术的人，只是听说病人喝水就能自愈，对于轻微口渴的病人就强行让他们大量饮水，结果造成大祸，不可挽救。那么，“悸”是指心跳不安，“动”是指肢体颤动，“支”是指胸胁支撑感，“结”是指气机郁结。喘咳、呃逆、干呕、肿胀、腹满、腹泻、小便不利，这几种情况都是由于饮水过量损伤身体所致。诊治疾病的医生，必须认识这一点，不要犯错误。
In cases of Taiyang cold damage (Shanghan) presenting with thirst, how should this be elucidated? Thirst indicates the presence of heat within the interior. The pathogenic factor of cold damage, transmitting from the exterior to the interior, will inevitably manifest specific syndromes, appearing according to the depth of the pathogen's invasion. Although it is said that on the first day the pathogen is in the skin, on the second day in the flesh, on the third day in the muscles, on the fourth day in the chest, on the fifth day in the abdomen, and on the sixth day in the stomach, those undergoing meridian transmission exhibit different clinical manifestations.
The Taiyang meridian governs the body's defensive Qi and is the first to receive the pathogen; symptoms typically appear within one or two days, characterized by headache, stiffness of the neck and occiput, and rigidity of the lower back and spine. When the Taiyang pathogen transmits to the Yangming meridian, symptoms appear within two or three days, characterized by fever, eye pain, dry nose, and inability to lie down comfortably. When the Yangming pathogen transmits to the Shaoyang meridian, symptoms appear within three or four days, characterized by hypochondriac pain and deafness. These three Yang meridians are all affected by the pathogen, which remains at the exterior level and has not yet transformed into full heat; therefore, thirst is not mentioned.
By the fourth or fifth day, the Shaoyang pathogen transmits to the Taiyin meridian, and the pathogen gradually enters the interior, with cold transforming into heat. At this time, body fluids are consumed and diminished, leading to abdominal fullness and dryness of the throat. By the fifth or sixth day, the Taiyin pathogen transmits to the Shaoyin meridian, indicating that the interior heat has deepened further. At this stage, body fluids are constrained and depleted by the heat, becoming dry; thus, dry mouth, dry tongue, and thirst occur. By the sixth or seventh day, the Shaoyin pathogen transmits to the Jueyin meridian. The disease manifestation of Jueyin is Xiao Ke (wasting-thirst syndrome), indicating that interior heat has reached its extreme. "Xiao Ke" refers to a condition where the patient drinks large amounts of water but produces little urine, because the heat consumes the water. Therefore, when cold damage progresses to the sixth or seventh day and the patient desires water, it is a sign that the disease is about to resolve, as the transmission through the meridians is complete. Hence, the Jueyin chapter states: "If the patient desires water, give them small amounts to drink, and they will recover."
When the pathogen initially transmits to the interior, the heat is diffuse and has not yet condensed into solid heat. It steams and scorches the diaphragm, constraining and depleting body fluids, thereby causing thirst. Although the patient is thirsty and desires water, it must not be given in large quantities. If too much water is drunk, the slight remaining heat cannot transform it, leading to conditions of retained fluid. The Classics state: "For those suffering from seasonal pathogens, by the fifth or sixth day, if they desire water, they may drink, but do not drink excessively; do not provide too much." Why? Because the heat in the abdomen is still insufficient to transform large volumes of water; providing more would create new pathology. If the patient is extremely thirsty and desires copious drinking, treatment should still follow the syndrome differentiation. Water should be given such that the patient feels slightly unsatisfied, avoiding excessive intake. This means if they can drink one dou, give only five sheng. It is also stated: "If the patient desires water, give small amounts." Rescue should be conducted according to proper principles. For patients with thirst, Wu Ling San (Five-Ingredient Powder with Poria) is appropriate. For those with extreme thirst desiring several sheng of water, Bai Hu Jia Ren Shen Tang (White Tiger Decoction plus Ginseng) is the primary formula. Both aim to moisten dryness and generate body fluids.
Generally, if a patient who has fallen ill can drink water, it indicates the disease is resolving. Those unfamiliar with pathology hear that drinking water cures the illness and, for patients with mild thirst, force-feed them water, resulting in severe disaster that cannot be rescued. Thus, "Ji" refers to palpitations, "Dong" refers to tremors, "Zhi" refers to a sensation of support or distension, and "Jie" refers to knotting or stagnation. Wheezing, coughing, hiccups, dry retching, edema, abdominal fullness, diarrhea, and difficulty urinating are all caused by injury from excessive water intake. Physicians diagnosing diseases must recognize this to avoid errors.