古之论疾多取像取类使人易晓以脏腑稀散为鸭溏或为 溏(野鸭谓之 )谓其生于水中屎
常稀
散故也以遇夜目昏不见物为雀目雀遇昏晚目不见物故也以肾气奔冲为奔豚为能奔逸而不能远
也以时气声嗄咽干欲睡复不安眠为狐惑以狐多疑惑也以大便艰难为野鸡痔谓欲便而复止故也
野狼漏始发于颈肿无头有根起于阙盆之上连延耳根肿大谓其疾来暴猛如野狼故也其源缘忧恚气上
不得下蛴螬漏始发于颈下无头尾如枣核块累移在皮中谓其无头尾状若蛴螬故也
治病之法莫不以寒疗热以热疗寒通则塞之塞则通之益所不胜损其所胜气平邪服病乃良已
然疾
势有小大药力有重轻圣贤制方论必求其所因以伏其所主譬犹火也人间之火遇草而 得木而燔
可以湿伏可以水灭疾之小者似之而疾之大者则若神龙之火得湿则焰遇水则燔寒与热相拒热与
寒相违不可以常法治也故经有热因寒用寒因热用塞因塞用通
因通用之法可使气调可使必已治热者以豆豉浸酒此因热用寒者也治寒者以蜜煎乌头此因寒用
热者也久痢通滑必当先去其积中满实塞必当峻补其下经云寒积内凝久痢泄溏愈而复发连历岁
时以热下之结散痢止此因通治之法也下虚中满之病补虚则满甚于中宣导则转虚其下故当疏
启其中峻补其下此因塞治之法也(同上)
古代论述疾病时，多采用取象比类的方法，使道理浅显易懂。例如，将脏腑之气稀散导致的腹泻称为“鸭溏”或“鹜溏”，因为野鸭（谓之鹜）生活在水中，其粪便常呈稀散状，以此比喻病机；将夜间视力模糊、看不见物体的症状称为“雀目”，因为麻雀在黄昏夜晚看不清物体，以此类比；将肾气上冲奔突的症状称为“奔豚”，因为豚（小猪）善于奔跑但不能远行，以此形容气逆之状；将因时行疫气导致的声音嘶哑、咽喉干燥、想睡却又无法安眠的症状称为“狐惑”，因为狐狸生性多疑疑惑，以此描述患者心神不宁的状态；将大便排便困难、欲解又止的症状称为“野鸡痔”，以此比喻排便不畅；将“野狼漏”初发于颈部，肿块无头但有根，起始于缺盆之上并蔓延至耳根肿大，因其发病暴猛如野狼而得名，其病因源于忧怒导致气机上逆不得下行；将“蛴螬漏”初发于颈下，无头无尾，如枣核大小的块状物在皮中移动，因其形状无头尾且似蛴螬（金龟子幼虫）而得名。
治疗疾病的方法，没有不是用寒凉药治疗热证，用温热药治疗寒证的。通则塞之，塞则通之，补益所不胜的脏气，损害所胜的脏气，使气血平和，邪气服从，疾病才能痊愈。然而，病情有轻重大小之分，药力有轻重之别。圣贤制定方剂、论述医理，必定探求疾病的成因，以制服主要病邪。这就好比人间的火，遇到草就燃烧，遇到木头就猛烈燃烧，可以用湿气压制，可以用水扑灭；但病情轻微者类似于此，而病情严重者则如同神龙之火，遇湿则火势更旺，遇水则燃烧更烈。此时寒与热相互抗拒，热与寒相互违背，不能用常规方法治疗。因此，《内经》中有“热因寒用”、“寒因热用”、“塞因塞用”、“通因通用”的治疗方法，可以使气血调和，疾病必愈。例如，治疗热证用豆豉浸泡的酒，这是“因热用寒”的方法；治疗寒证用蜜煎制的乌头，这是“因寒用热”的方法。对于久痢导致肠道滑脱不禁的，必须先去除积滞；对于中焦痞满实塞的，必须峻补下焦。《内经》说：“寒积内凝，久痢泄泻，愈后复发，连年不断，用热药攻下，结散痢止。”这是“因通治之法”。对于下虚中满的病证，补虚则中满更甚，宣导则下焦更虚，所以应当疏通其中焦，峻补其下焦。这是“因塞治之法”。（同上）
In ancient discussions of diseases, the method of taking images and drawing analogies was often employed to make the principles easy to understand. For instance, diarrhea caused by the dispersion of Qi in the Zang-Fu organs is referred to as "duck stool" (Ya Tang) or "wild duck stool" (Wu Tang), because wild ducks live in water and their excrement is often loose and scattered, thus metaphorically describing the pathological mechanism; the symptom of blurred vision at night and inability to see objects is called "sparrow eye" (Que Mu), because sparrows cannot see clearly at dusk and night, serving as an analogy; the symptom of Kidney Qi rushing upward is termed "running piglet" (Ben Tun), because a piglet is capable of running but cannot travel far, describing the sensation of rebellious Qi; the symptoms of hoarseness, dry throat, drowsiness yet inability to sleep soundly, caused by seasonal epidemic pathogens, are called "fox bewitchment" (Hu Huo), because foxes are characterized by suspicion and confusion, describing the patient's restless state of mind; difficulty in defecation, where one desires to pass stool but stops, is called "wild chicken hemorrhoid" (Ye Ji Zhi), illustrating the obstruction; "wild wolf fistula" (Ye Lang Lou) initially appears on the neck, with a swelling that has no head but has a root, starting above the Quepen area and extending to the ear, named for its sudden and fierce onset like a wild wolf, originating from emotional distress causing Qi to rise and fail to descend; "earthworm fistula" (Qi Cao Lou) initially appears below the neck, without head or tail, resembling a date pit-sized mass moving within the skin, named for its headless and tailless shape resembling the larva of a scarab beetle (Qi Cao).
The methods of treating disease invariably involve using cold to treat heat and heat to treat cold. Where there is free flow, there may be blockage; where there is blockage, there must be free flow. One tonifies the organ that overcomes the diseased organ and reduces the organ that is overcome by it. When Qi becomes balanced and pathogenic factors submit, the disease is cured. However, diseases vary in severity, and medicinal potency varies in strength. The sages formulated prescriptions and discussed medical principles by seeking the etiology to subdue the primary pathology. This is akin to fire among humans: it burns when encountering grass and flares up when encountering wood; it can be subdued by dampness and extinguished by water. Diseases of minor severity resemble this, but severe diseases are like the fire of divine dragons: they flare up when encountering dampness and burn fiercely when encountering water. In such cases, cold and heat repel each other, and heat and cold contradict each other, so they cannot be treated with conventional methods. Therefore, the Classics mention methods such as "treating heat with cold administration," "treating cold with heat administration," "treating blockage with blockage-inducing methods," and "treating free flow with free-flow-inducing methods." These can harmonize Qi and ensure cure. For example, treating heat conditions with wine infused with fermented soybean (Dou Chi) is a method of "using cold due to heat"; treating cold conditions with honey-fried Aconite Root (Wutou) is a method of "using heat due to cold." For chronic dysentery leading to intestinal slipping and incontinence, one must first remove the accumulation; for middle-jiao fullness and solid blockage, one must strongly tonify the lower jiao. The Classics state: "Cold accumulation congeals internally, causing chronic dysentery and loose stools that recur after remission for years; using hot purgatives disperses the knot and stops the dysentery." This is the method of "treating free flow via free flow." For diseases of lower deficiency and middle fullness, tonifying deficiency exacerbates the middle fullness, while promoting movement further depletes the lower jiao. Therefore, one should unblock the middle and strongly tonify the lower. This is the method of "treating blockage via blockage." (Ibid.)