一、白为阴，为寒，为湿。
二、黄为胃中有热，深黄为热极胃火，黄浓苔为湿热。
三、赤而带血，为胃火，更必兼阴亏。赤如猪腰子，表面有极薄绉白衣，为肾脏本色上泛，难治。鲜红如血，心
胃热炽。满舌光红，心营涸竭。正红色，白净苔，不腻亦不干，是为平人正色舌。
四、黑而多津，为水克火，宜参附四逆。
五、黄而起刺，黑而起刺，宜三承气急下存阴。红而起刺如杨梅，宜神犀丹。均以脉证合参决之。
六、舌底糙，上面粘着如碎饭粒，玉女煎主之；轻则桂苓甘露饮。虚劳见舌糜，为大忌。
七、不青不紫不黑，亦青亦紫亦黑，名死现舌，主肝胃绝，必败无疑。
仲景立方之祖，医中之圣。所着《伤寒》、《金匮》诸书，打开屯蒙，学人当奉为金科玉律，后起诸贤不可相
提并论。所谓四大家者，乃刘河间、张子和、李东垣、朱丹溪也。就四家而论，刘张二家，善攻善散，即邪去则
正安之义。但用药太峻，虽有独到处，亦未免有偏胜处。学人用其长而化其偏，斯为得之。李朱两家，一补
阳，一补阴，即正胜则邪退之义，各有灼见，卓然成家。无如后之学人，宗东垣则诋丹溪，宗丹溪则呵东垣，
入主出奴，胶执成见，为可叹也。殊不知相反实以相成，前贤并非翻新立异。即发热一症而论，仲景谓凡
热病者，皆伤寒之类也，故有麻黄、桂枝等汤，以治外感之发热。至内伤之症，东垣则以甘温治阳虚之发
热；丹溪则以苦寒治阴虚之发热，各出手眼，补前人所未备。本随症治症，未尝混施。乃宗东垣者，虽遇阴
虚发热，亦治以甘温，参、 不已，甚而附、桂。宗丹溪者，虽遇阳虚发热，亦治以苦寒，地、冬不已，甚而知、柏。
此尚何异于操刃乎！非东垣、丹溪误人，乃不善学东垣、丹溪，自误以误人也。吾愿世之学人，于各家之异处
以求其同处，则辨症施治，悉化成心，要归一是矣。
二、舌苔发黄，表示胃中有热；深黄色表示热势极盛、胃火旺盛；黄而厚腻的舌苔表示湿热内蕴。
三、舌色红且带有血点，是胃火炽盛的表现，必定兼有阴液亏损。舌色红如猪腰子表面，覆盖着极薄的皱缩白色膜，这是肾脏本色上泛于舌面，属于难治之症。舌色鲜红如血色，是心胃热毒炽盛。满舌光红无苔，是心营枯竭的表现。舌色正红，舌面洁净且有薄白苔，不腻也不干燥，这是健康人的正常舌色。
四、舌苔黑而多津液，是水气克制心火（肾水凌心）的表现，适宜使用人参、附子及四逆汤治疗。
五、舌苔黄而起刺，或舌苔黑而起刺，适宜用三承气汤急下以保存阴液。舌色红而起刺，状如杨梅，适宜使用神犀丹。以上情况均需结合脉象和症状综合判断决定。
六、舌底粗糙，舌面上粘附着像碎饭粒一样的物质，应用玉女煎主治；病情较轻者，可用桂苓甘露饮。虚劳病患者出现舌面糜烂，是大忌。
七、舌色既不单纯是青色、紫色或黑色，又混杂着青、紫、黑三色，称为“死现舌”，主肝胃之气绝灭，必然败亡无疑。
张仲景是创立方剂的始祖，医学中的圣人。他所著的《伤寒论》、《金匮要略》等书籍，开启了蒙昧学者的智慧，后学者应当将其奉为金科玉律，后世其他贤才不可与之相提并论。所谓的“金元四大家”，是指刘河间、张子和、李东垣、朱丹溪这四位医家。就这四家而言，刘河间和张子和两家，擅长攻邪和发散，体现了“邪气去除则正气安宁”的道理。但是他们的用药过于峻猛，虽然有其独到之处，也难免有偏颇过胜的地方。学习者若能利用他们的长处而化解其偏颇，这才是得法。李东垣和朱丹溪两家，一家补阳，一家补阴，体现了“正气强盛则邪气退却”的道理，他们各有真知灼见，卓然成家。无奈后来的学习者，尊崇李东垣的就贬低朱丹溪，尊崇朱丹溪的就呵斥李东垣，门户之见深重，固执成见，实在令人叹息。殊不知相反的理论实际上可以相互成就，前贤并非为了标新立异。就以发热这一症状而论，张仲景认为凡是热病，都属于伤寒的范畴，所以有麻黄汤、桂枝汤等方剂，用来治疗外感引起的发热。至于内伤疾病，李东垣则用甘温药物来治疗阳气虚弱引起的发热；朱丹溪则用苦寒药物来治疗阴液亏虚引起的发热，各自展现独特的医术见解，补充了前人未备的内容。本应随病症施治，未曾混淆乱用。然而尊崇李东垣的人，即使遇到阴虚发热，也用甘温药物治疗，用到人参、黄芪还不够，甚至用到附子、肉桂。尊崇朱丹溪的人，即使遇到阳虚发热，也用苦寒药物治疗，用到地黄、麦冬还不够，甚至用到知母、黄柏。这与拿着刀胡乱砍杀有什么区别呢！这不是李东垣、朱丹溪误人，而是后人不善学习李东垣、朱丹溪，自己误解从而误导他人。我希望世间的学习者，在各家的不同之处中寻找共同点，那么辨证施治就能完全出于内心自然，最终归于同一真理。
1. A white tongue coating indicates Yin patterns, manifesting as Cold or Dampness.
2. A yellow tongue coating indicates Heat in the Stomach; a deep yellow color signifies extreme Heat and vigorous Stomach Fire; a thick and greasy yellow coating indicates Damp-Heat accumulation.
3. A red tongue with blood spots indicates vigorous Stomach Fire and must be accompanied by Yin deficiency. A tongue red like the surface of a pig kidney, covered with an extremely thin, wrinkled white membrane, indicates the true color of the Kidney floating up to the tongue surface, which is difficult to treat. A bright red tongue like fresh blood indicates blazing Heart and Stomach Heat. A completely red tongue without coating indicates exhaustion of the Heart Ying (Nutritive Level). A normal red tongue with a clean, thin white coating that is neither greasy nor dry is the normal tongue color of a healthy person.
4. A black tongue coating with abundant saliva indicates Water overcoming Fire (Kidney Water flooding the Heart), for which Ren Shen (Ginseng Root) and Fu Zi (Aconite Lateral Root) combined in Si Ni Tang (Frigid Extremities Decoction) are appropriate.
5. A yellow tongue coating with prickles, or a black tongue coating with prickles, requires urgent purgation using one of the San Cheng Qi Tangs (Three Inherited Qi-Decreasing Decoctions) to preserve Yin. A red tongue with prickles resembling a mulberry fruit requires Shen Xi Dan (Divine Calming Pill). These cases must be decided by integrating pulse diagnosis and symptom analysis.
6. A rough tongue base with material adhering to the surface resembling crushed rice grains should be treated with Yu Nu Jian (Jade Woman Decoction); for milder cases, Gui Ling Gan Lu Yin (Cinnamon Twig, Poria, Sweet Dew Drink) is used. The appearance of tongue ulceration/maceration in patients with Xu Lao (Consumptive Disease) is strictly contraindicated.
7. A tongue that is not purely green, purple, or black, but rather a mixture of these three colors, is called "Si Xian She" (Dead Manifestation Tongue). It indicates the exhaustion of Liver and Stomach Qi and inevitably leads to defeat and death.
Zhang Zhongjing is the ancestor of formula creation and a sage in medicine. His works, such as Shang Han Lun (Treatise on Cold Damage) and Jin Gui Yao Lue (Essential Prescriptions from the Golden Cabinet), enlightened beginners. Students should regard them as golden rules; later sages cannot be compared to him. The so-called "Four Great Masters" refer to Liu Wansu (Liu Hejian), Zhang Congzheng (Zhang Zizi), Li Dongyuan, and Zhu Danxi. Regarding these four masters: Liu and Zhang excelled in attacking pathogens and dispersing evils, embodying the principle that "when evil is expelled, Zheng Qi (Upright Qi) becomes peaceful." However, their medications were too harsh; although they had unique strengths, they inevitably had biases. Learners who utilize their strengths while neutralizing their biases will succeed. Li and Zhu focused on tonifying Yang and tonifying Yin respectively, embodying the principle that "when Zheng Qi prevails, evil retreats." Both had profound insights and established distinct schools. Regrettably, later learners who followed Li Dongyuan disparaged Zhu Danxi, and those following Zhu Danxi criticized Li Dongyuan, falling into sectarian prejudice and rigid dogmatism, which is lamentable. One should not realize that opposing theories actually complement each other; the ancients did not innovate merely for novelty's sake. Taking fever as an example, Zhang Zhongjing stated that all heat diseases belong to the category of cold damage, hence he used formulas like Ma Huang Tang (Ephedra Decoction) and Gui Zhi Tang (Cinnamon Twig Decoction) to treat fevers caused by external contraction. For internal injuries, Li Dongyuan used sweet-warm methods to treat fevers due to Yang deficiency, while Zhu Danxi used bitter-cold methods to treat fevers due to Yin deficiency. Each demonstrated unique expertise, supplementing what predecessors lacked. Treatment was tailored to specific symptoms, never mixed indiscriminately. Yet, followers of Li Dongyuan, even when encountering Yin-deficiency fever, used sweet-warm treatments, escalating from Ren Shen (Ginseng Root) and Huang Qi (Astragalus Root) to Fu Zi (Aconite Lateral Root) and Gui Zhi (Cinnamon Twig). Followers of Zhu Danxi, even when encountering Yang-deficiency fever, used bitter-cold treatments, escalating from Di Gu Pi (Lycium Bark) and Mai Dong (Ophiopogon Tuber) to Zhi Mu (Anemarrhena Rhizome) and Huang Bo (Phellodendron Bark). This is no different from wielding a blade blindly! It is not that Li Dongyuan or Zhu Danxi misled people, but that later learners failed to study them properly, leading themselves astray and misleading others. I hope future learners seek commonalities within the differences of various schools, so that syndrome differentiation and treatment will flow naturally from the heart, ultimately converging on one truth.