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。
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.