《难经》立望闻问切四者以治病，而望而知之谓之神。《内经》辨望色之理多端，而不及舌。近世医者，
看舌色，矮人看场，而不明其理，惟《张氏医通》有《伤寒舌鉴》，列图、论方，而其法亦简略不备，且伤
寒之外，杂症未暇论及也。叶香岩先生《温热论》中兼及舌色，最为独出手眼，冠绝千古，而细筋入骨，切中
病机，比之张石顽所列图论，相去天渊。张石顽《舌鉴》，凡白者一小柴胡，黄者一大柴胡，灰者一凉膈，
黑者一承气，灰黑虚寒入阴者，理中四逆，此层殊不细。理非不是，而舌色之理，不明不备。且舌黑而言入足
三阴，用温药，殊足误人。香岩先生看舌色，别有神悟，历练而知，所谓不传其妙也。其论温邪，初起舌白而
燥者，肺阴亡也。宜麦冬、花粉、元参等。白虎汤。舌中心绛干者，心胃火燔也。玉女煎及梨蔗、藕汁。舌
白如粉者，热据上焦也。栀豉汤，及枳、杏、蒌、桔、蒡等。舌黄浓者，热据中焦也。承气汤。舌尖红绛者，
心营暗炽也。宜犀角、羚羊角、鲜石斛、鲜生地等。舌中心焦黑者，肾阴涸，心胃火炽也。犀角地黄汤、
牛黄丸、至宝丹、紫雪丹，选用。舌浓芒刺，断纹燥裂者，积滞热极也。凉膈散、碧雪丹。舌焦而齿煤，唇血
燥裂者，火炽血涸，欲成风痉也。炙甘草汤加犀角汁。舌干枯而短者，肾气竭也。宜阿胶、鸡蛋黄、地黄等。
舌生大红点者，热极生疳也。宜黄连、金汁方诸水等。无苔而红绛者，热伤血分也。宜丹皮、地黄、麦冬、
元参等。有苔而黄白者，热滞胃脘也。宜枳实、浓朴、明粉、凉膈散。温邪变态最速，舌色一黄，顷刻即变成
灰黑，以其火中挟风，天下至速莫如风火，火就燥，口渴舌干，皆热邪横肆，迷漫三焦也。又有舌灰齿煤干枯
之至，其脉细涩若无，身已不热者，此如火过成炭，只须大剂补阴，宜熟地、洋参、麦冬、阿胶、龟板、鸡蛋
黄。不必寒凉，以其病已无热也，大抵舌有白
苔，丹溪谓丹田有热，胸中有寒，此论大谬。白苔在杂症，是胃中积滞，白苔在温症，亦属积滞，定属热邪，
更无寒邪，一二日间，变成黄黑矣。且舌白而尖渐红，口渐燥，其为热亦何疑，若无苔而舌白兼淡红者，方
是虚寒，亦非温症。所有温症中，舌尖红，唇亦绎，目必赤，面色亦红。烦躁有谵语，即可用犀角至宝丹。舌
灰，断宜犀角至宝丹。舌浓而燥，或黄或灰或黑，急下存阴，舌苔不浓而干，大剂救阴。初起舌白浓，宣通
气分；病久舌黄浓，宣通血分。病久有苔而燥，泻积救阴；病久无苔而干，滋阴养液。有舌白而语谵者，其
舌必干；玉女煎。有舌红绛而语谵者，热入心营。牛黄丸、至宝丹。舌灰舌黑，断无不语谵者，大剂犀角至
宝丹、紫雪等。其不语谵，乃阴证，非温症也。舌色紫，亦热传营分，宜琥珀、丹参、丹皮等。舌干枯，欲救
阴泻火已难，必须大剂，鲜生地、鲜石斛、赤芍、元参、麦冬，俱一两用。若唇焦齿煤，肾水已枯，宜熟地、
阿胶、麦冬、鸡蛋黄。更难得效矣。至若伤寒温症外，舌色，并无古书言及。香岩先生温症舌论，引而不发，
便可触类旁通。如疫症，舌白浓，必须大黄利下，不爽，亦须承气，黄苔不必再言，此吴又可所以专主急下。
至疟痢，舌白浓，必须枳、朴，或白而兼黄，必须枳、朴加芩连。若寒饮停泊，呕吐，唇淡，舌灰有津，必须
桂、附，肥人舌灰，有津亦然。霍乱手足冷，烦躁，舌灰亦然。又有痢疾，舌灰而不甚干，亦属热邪，不得
用桂、附者，或其人素吃鸦片，最易灰黑，乃用芩、连。有久痢已虚，反生浓苔，而舌边糜烂，阴火上冲，
水来克火，或白或黄，终成不治。有舌唇淡白无华，必须温理。有舌色深绛无苔，定属营虚伤血，宜养血，不
宜寒凉，以症非外感也。有杂症，舌中心绛干，须清营热。有杂症，舌中心灰色，有津，须引火归原。有杂
症舌黄，味苦味酸，皆脾经有热，宜芩、连、知母。亦有脾虚，口甜舌淡，宜四君、六君。大抵无苔而淡白者
寒，无苔而红绛者热。淡白而口干者，以桂、附补命火，则津液熏蒸，上朝于肺，不得以口干燥；而用寒凉，
以其干与温症之舌干有别，不过病患自觉干，而视舌者，不知其干也。凡有苔而退者，由舌尖退至中，由中退
至根，若舌本干燥，服药后有津，则苔必
退。亦有舌尖中根渐薄，而一齐退者。舌灰薄者易消。阴症舌灰必薄，热邪舌灰薄者邪轻，舌黑浓者邪重；
舌苔渐退者，邪亦退；舌苔渐进者，邪亦进。妇人胎死腹中，则舌灰舌青，而舌青皆厥阴之病，凡病舌青者
不治。又有重舌、木舌、舌衄，此非舌症，非舌之色也。舌尖主心，主上焦，舌中主胃，主中焦，舌根主下
焦。而舌为心之苗，心为君主，皆宜细细辨明，用药方合病症。非深心领会，乌足入神圣之门哉。
《难经》确立了望、闻、问、切四种诊断方法来治疗疾病，其中通过观察就能知晓病情被称为“神”。《黄帝内经》中辨析面色原理的内容繁多，却没有涉及舌诊。近世的医生，在观察舌色时，如同矮人看戏场，只看到表面而不明白其中的道理。只有《张氏医通》中有《伤寒舌鉴》，列出了图谱和方论，但其中的方法也简略不完备，而且除了伤寒之外，对于其他杂病没有来得及论述。叶天士（字香岩）先生的《温热论》中兼及舌色，最为独具慧眼，冠绝千古，其分析细致入微，切中病机关键，与张石顽所列的图谱和论述相比，相差如天地之远。张石顽的《舌鉴》中，凡是白苔就用小柴胡汤，黄苔就用大柴胡汤，灰苔就用凉膈散，黑苔就用承气汤；如果是灰黑色且属于虚寒入阴证的，就用理中汤或四逆汤，这种分类殊为不细致。道理并非不对，但是关于舌色的原理阐述得不够明确完备。况且舌头变黑却伴有言语不清（提示邪入足三阴），使用温药，足以误导病人。叶香岩先生观察舌色，别有神悟，是通过临床历练而得知的，所谓不传之妙就在于此。他论述温邪，初起时舌苔白而干燥的，是肺阴耗亡。适宜用麦冬、天花粉、玄参等，或者白虎汤。舌中心部位红绛而干燥的，是心胃火盛。适宜用玉女煎以及梨汁、蔗汁、藕汁。舌苔白如粉末状的，是热邪占据上焦。适宜用栀子豉汤，以及枳壳、杏仁、瓜蒌、桔梗、牛蒡子等。舌苔黄而浓厚的，是热邪占据中焦。适宜用承气汤。舌尖红绛的，是心营分暗火炽盛。适宜用水牛角、羚羊角、鲜石斛、鲜生地等。舌中心焦黑的，是肾阴枯竭，心胃火炽盛。适宜选用犀角地黄汤、牛黄丸、至宝丹、紫雪丹。舌苔厚腻且有芒刺、断纹、干燥裂开的，是积滞热极。适宜用凉膈散、碧雪丹。舌焦枯且牙齿发黑，嘴唇干裂出血的，是火炽血枯，将要形成风痉证。适宜用炙甘草汤加水牛角汁。舌干枯且短的，是肾气竭绝。适宜用阿胶、鸡蛋黄、地黄等。舌面生大红点的，是热极生疳。适宜用黄连、金汁、方诸水等。无苔而红绛的，是热伤血分。适宜用牡丹皮、地黄、麦冬、玄参等。有苔而黄白的，是热邪停滞在胃脘。适宜用枳实、厚朴、明矾、凉膈散。温邪变化最快，舌色一旦变黄，顷刻间就会变成灰黑色，因为火中夹带风邪，天下速度最快的莫过于风火，火性就燥，口渴舌干，都是热邪横肆，弥漫三焦所致。又有舌灰、牙齿发黑、干枯到极致的，脉象细涩仿佛没有，身体已经不热的，这就像火烧过变成炭一样，只需要大剂量补阴，适宜用熟地黄、西洋参、麦冬、阿胶、龟板、鸡蛋黄。不需要用寒凉药，因为病已经没有热了。大抵舌上有白苔，朱丹溪说是丹田有热，胸中有寒，这个观点大错特错。白苔在杂病中，是胃中积滞；在白苔在温病中，也属积滞，必定属于热邪，绝无寒邪，一二天内就会变成黄黑色。况且舌苔白而舌尖逐渐变红，口逐渐干燥，其为热邪还有什么可疑呢？如果没有苔而舌白兼淡红色的，才是虚寒证，也不属于温病。所有温病中，舌尖红，嘴唇也会绎动（颤动），眼睛必定红，面色也红。烦躁并有谵语的，就可以用犀角、至宝丹。舌灰的，断然适宜用犀角、至宝丹。舌苔厚而干燥，或者黄、或者灰、或者黑的，急下以存阴液；舌苔不厚而干的，大剂量救阴。初起舌苔白厚，宣通气分；病久舌苔黄厚，宣通血分。病久有苔而干燥，泻积滞救阴液；病久无苔而干燥，滋阴养液。有舌苔白而说胡话的，其舌必干；适宜用玉女煎。有舌红绛而说胡话的，是热入心营。适宜用牛黄丸、至宝丹。舌灰舌黑的，断然不会有不说胡话的，适宜大剂量用犀角、至宝丹、紫雪等。那些不说胡话的，乃是阴证，不是温病。舌色紫的，也是热传入营分，适宜用琥珀、丹参、牡丹皮等。舌干枯，想要救阴泻火已经很难，必须用大剂量，鲜生地、鲜石斛、赤芍、玄参、麦冬，都各用一两。如果嘴唇焦黑、牙齿发黑，肾水已枯，适宜用熟地黄、阿胶、麦冬、鸡蛋黄。更难见效了。至于在伤寒和温病之外，关于舌色的论述，并没有古书提及。叶香岩先生关于温病舌诊的论述，引而不发，便可触类旁通。比如疫病，舌苔白厚，必须用大黄利下，如果不顺畅，也必须用承气汤；黄苔不必再言，这就是吴又可所以专门主张急下的原因。至于疟疾和痢疾，舌苔白厚，必须用枳实、厚朴，或者白苔兼黄苔，必须用枳实、厚朴加上黄芩、黄连。如果是寒饮停聚，呕吐，嘴唇淡，舌灰而有津液，必须用桂枝、附子；肥胖人舌灰而有津液也是如此。霍乱手足冷，烦躁，舌灰也是如此。又有痢疾，舌灰而不甚干燥，也属于热邪，不能用桂枝、附子的，或者是其人平时吃鸦片，最容易舌色灰黑，乃是用黄芩、黄连。有久痢已经虚弱的，反而生厚苔，而舌边糜烂，阴火上冲，水来克火，或者白或者黄，最终成为不治之症。有舌唇淡白无光泽的，必须温里理中。有舌色深绛无苔的，定属营虚伤血，适宜养血，不宜用寒凉药，因为病症不是外感引起的。有杂病，舌中心红绛干燥的，须清营热。有杂病，舌中心灰色，有津液的，须引火归原。有杂病舌苔黄的，味觉苦或酸，都是脾经有热，适宜用黄芩、黄连、知母。也有脾虚，口甜舌淡的，适宜用四君子汤、六君子汤。大抵无苔而淡白色的是寒证，无苔而红绛色的是热证。淡白色而口干的人，用桂枝、附子补命门之火，则津液熏蒸，上朝于肺，不能认为口干燥；而如果用寒凉药，是因为这种干燥与温病的舌干不同，不过是病患自觉干燥，而观察舌象的人，不知道它是干燥的。凡是有苔而消退的，由舌尖退至中部，由中部退至根部，如果舌根干燥，服药后有津液，则苔必然消退。也有舌尖、中部、根部逐渐变薄，而一齐消退的。舌苔灰薄的容易消除。阴证舌苔灰必薄，热邪舌苔灰薄的邪气轻，舌苔黑厚的邪气重；舌苔逐渐消退的，邪气也随之消退；舌苔逐渐增进的，邪气也随之增进。妇人胎死腹中，则舌苔灰舌色青，而舌色青的都是厥阴经的病，凡是病见舌色青的都不治。又有重舌、木舌、舌衄（舌出血），这些不是舌症，也不是舌的颜色。舌尖主心，主上焦；舌中主胃，主中焦；舌根主下焦。而舌为心之苗窍，心为君主之官，都应该细细辨明，用药才符合病症。如果不是深刻领会，怎么能够进入神圣医学的门径呢？
The *Nan Jing* (Classic of Difficult Issues) established four diagnostic methods—inspection, auscultation and olfaction, inquiry, and palpation—to treat diseases, among which knowing the condition through inspection alone is called "divine" (Shen). The *Nei Jing* (Inner Canon) contains much discussion on the principles of inspecting facial complexion but does not mention tongue diagnosis. Physicians in recent times, when observing tongue color, are like short people watching a play from afar, seeing only the surface without understanding the underlying principles. Only the *Zhang Shi Yi Tong* (Comprehensive Medical Records by Master Zhang) features the *Shanghan She Jian* (Tongue Diagnosis in Cold Damage), which lists diagrams and discusses prescriptions, yet its methods are also brief and incomplete, and it fails to address miscellaneous diseases beyond cold damage. Mr. Ye Tianshi (style name Xiangyan) in his *Wenre Lun* (Treatise on Warm Diseases) also covers tongue color, showing unique insight that surpasses all previous works. His analysis is meticulous and hits the pathogenesis accurately, differing vastly from the diagrams and discussions listed by Zhang Shiweng. In Zhang Shiweng's *She Jian*, white coating is associated with Xiao Chai Hu Tang (Minor Bupleurum Decoction), yellow with Da Chai Hu Tang (Major Bupleurum Decoction), gray with Liang Ge San (Cooling the Chest Powder), and black with Cheng Qi Tang (Descending the Qi Decoction); for gray-black coatings indicating deficiency-cold entering the Yin levels, Li Zhong Tang (Regulate the Middle Decoction) or Si Ni Tang (Frigid Extremities Decoction) are used. This classification is particularly imprecise. Although the rationale is not entirely wrong, the principles of tongue color are not clearly or comprehensively explained. Moreover, a black tongue accompanied by speech difficulties suggests pathogen entering the three Yin meridians of the foot; using warming herbs can mislead patients. Mr. Xiangyan’s observation of tongue color possesses divine inspiration, gained through clinical experience, representing an untransmitted subtlety. He discussed warm pathogens: if at onset the tongue is white and dry, it indicates consumption of Lung Yin. Mai Dong (Ophiopogonis Radix), Hua Fen (Trichosanthis Radix), and Yuan Shen (Scrophulariae Radix) are suitable, as well as Bai Hu Tang (White Tiger Decoction). If the center of the tongue is crimson and dry, it indicates blazing Fire in the Heart and Stomach. Yu Nu Jian (Jade Woman Decoction), along with pear juice, sugarcane juice, and lotus root juice, are appropriate. If the coating is white like powder, heat occupies the Upper Jiao. Zhi Chi Tang (Gardenia and Fermented Soybean Decoction), along with Zhi Ke (Aurantii Fructus), Xing Ren (Armeniacae Semen), Gua Lou (Trichosanthis Fructus), Jie Geng (Platycodonis Radix), and Niu Bang Zi (Arctii Fructus) are suitable. If the coating is thick and yellow, heat occupies the Middle Jiao. Cheng Qi Tang is appropriate. If the tongue tip is crimson, latent Fire is blazing in the Ying (Nutrient) level of the Heart. Xi Jiao (Rhinocerotis Cornu, now substituted with Shui Niu Jiao/Bubali Cornu), Ling Yang Jiao (Caprae Cornu), fresh Shi Hu (Dendrobii Caulis), and fresh Sheng Di Huang (Rehmanniae Radix) are suitable. If the center of the tongue is scorched black, Kidney Yin is exhausted while Heart and Stomach Fire is blazing. Xi Jiao Di Huang Tang (Rhino Horn and Rehmannia Decoction), Niu Huang Wan (Calculus Bovis Pill), Zhi Bao Dan (Precious Treasure Pellet), and Zi Xue Dan (Purple Snow Pellet) should be selected. If the coating is thick with prickles, cracks, and dryness, it indicates extreme accumulation of heat. Liang Ge San and Bi Xue Dan are suitable. If the tongue is scorched and teeth are blackened, with lips cracked and bleeding, Fire is blazing and Blood is depleted, potentially leading to wind-spasm. Zhi Gan Cao Tang (Honey-Fried Licorice Decoction) added with Xi Jiao juice is appropriate. If the tongue is dry, shriveled, and short, Kidney Qi is exhausted. E Jiao (Colla Corii Asini), egg yolk, and Di Huang are suitable. If large red spots appear on the tongue, extreme heat generates ulcers (gan). Huang Lian (Coptidis Rhizoma), Jin Zhi (Gold Juice), and Fang Zhu Shui are suitable. If there is no coating and the tongue is crimson, heat has injured the Blood level. Mu Dan Pi (Moutan Cortex), Di Huang, Mai Dong, and Yuan Shen are suitable. If there is a coating that is yellow and white, heat stagnates in the stomach region. Zhi Shi (Aurantii Fructus Immaturus), Hou Po (Magnoliae Officinalis Cortex), Ming Fan (Alumen), and Liang Ge San are suitable. Warm pathogens change most rapidly; once the tongue turns yellow, it may turn gray-black in an instant because fire carries wind. Nothing in the world is faster than wind-fire. Fire follows dryness; thirst and dry tongue indicate rampant heat overflowing the Three Jiao. There are cases where the tongue is gray, teeth are blackened, and extreme dryness occurs, with a fine and choppy pulse seemingly absent, and the body no longer hot. This is like wood burned to charcoal; only large doses of Yin-nourishing herbs are needed, such as Shu Di Huang (Prepared Rehmanniae Radix), Yang Shen (American Ginseng), Mai Dong, E Jiao, Gui Ban (Testudinis Carapax et Plastrum), and egg yolk. Cooling herbs are unnecessary because the heat has resolved. Generally, a white coating was described by Zhu Danxi as heat in the Dantian and cold in the chest, which is a major error. In miscellaneous diseases, a white coating indicates gastric stagnation; in warm diseases, it also indicates stagnation and definitely belongs to heat pathogens, never cold. Within one or two days, it will turn yellow or black. Furthermore, if the tongue coating is white but the tip gradually turns red and the mouth becomes dry, how can it be doubted that it is heat? If there is no coating and the tongue is white with a pale-red hue, it is a deficiency-cold pattern, not a warm disease. In all warm diseases, if the tongue tip is red, the lips may tremble, eyes will be red, and the complexion will be red. Restlessness and delirium warrant the use of Xi Jiao and Zhi Bao Dan. A gray tongue strictly warrants Xi Jiao and Zhi Bao Dan. If the coating is thick and dry, whether yellow, gray, or black, purgation is urgently required to preserve Yin; if the coating is not thick but dry, large doses of Yin-nourishing herbs are needed. At onset, a thick white coating requires venting the Qi level; in prolonged illness, a thick yellow coating requires venting the Blood level. In prolonged illness, a dry coating with accumulation requires purging stagnation to save Yin; in prolonged illness, a dry coating without accumulation requires nourishing Yin and fluids. If the tongue is white with delirium, it must be dry; Yu Nu Jian is suitable. If the tongue is crimson with delirium, heat has entered the Heart Ying level. Niu Huang Wan and Zhi Bao Dan are suitable. Gray or black tongues invariably present with delirium; large doses of Xi Jiao, Zhi Bao Dan, and Zi Xue Dan are appropriate. Those without delirium have Yin patterns, not warm diseases. A purple tongue indicates heat transmitted to the Ying level; Hu Po (Amber), Dan Shen (Salviae Miltiorrhizae Radix et Rhizoma), and Mu Dan Pi are suitable. If the tongue is dry and shriveled, saving Yin and purging fire is difficult; large doses of fresh Sheng Di Huang, fresh Shi Hu, Chi Shao (Paeoniae Radix Rubra), Yuan Shen, and Mai Dong, each one liang, are required. If lips are scorched and teeth are blackened, Kidney Water is exhausted; Shu Di Huang, E Jiao, Mai Dong, and egg yolk are suitable, though efficacy is hard to achieve. Regarding tongue colors outside of Shanghan and warm diseases, ancient texts rarely mention them. Mr. Xiangyan’s treatise on warm disease tongues is suggestive, allowing for analogical reasoning. For example, in epidemic diseases, a thick white coating requires Da Huang (Rhei Radix et Rhizoma) for purgation; if ineffective, Cheng Qi Tang is still necessary. Yellow coatings need no further explanation; this is why Wu Keyi advocated urgent purgation. For malaria and dysentery, a thick white coating requires Zhi Shi and Hou Po; if white mixed with yellow, Zhi Shi and Hou Po plus Huang Qin (Scutellariae Radix) and Huang Lian are needed. If cold-fluid retention causes vomiting, with pale lips and a gray tongue with moisture, Gui Zhi (Cinnamomi Ramulus) and Fu Zi (Aconiti Lateralis Radix Praeparata) are required; this applies similarly to obese individuals with a moist gray tongue. In cholera with cold extremities and restlessness, a gray tongue is also indicated. In dysentery, a gray tongue that is not very dry also indicates heat pathogens, so Gui Zhi and Fu Zi should not be used; however, if the patient habitually uses opium, the tongue easily turns gray-black, requiring Huang Qin and Huang Lian. In chronic dysentery with deficiency, a sudden appearance of thick coating with erosion at the tongue edges indicates flaming-up of ministerial fire, water overcoming fire, turning white or yellow, ultimately becoming incurable. Pale and lusterless tongue and lips require warming and regulating. Deep crimson tongue without coating indicates Ying deficiency and blood injury; blood-nourishing herbs are suitable, avoiding cooling herbs since it is not an exogenous condition. In miscellaneous diseases, a crimson and dry center of the tongue requires clearing Ying heat. In miscellaneous diseases, a gray center of the tongue with moisture requires guiding fire back to its source. Yellow tongue in miscellaneous diseases with bitter or sour taste indicates heat in the Spleen meridian; Huang Qin, Huang Lian, and Zhi Mu (Anemarrhenae Rhizoma) are suitable. Spleen deficiency with sweet taste and pale tongue requires Si Jun Zi Tang (Four Gentlemen Decoction) or Liu Jun Zi Tang (Six Gentlemen Decoction). Generally, no coating with pale-white color indicates cold; no coating with crimson color indicates heat. In pale-white cases with dry mouth, Gui Zhi and Fu Zi tonify Ming Men Fire, steaming fluids to ascend to the Lung; one should not mistake this for dryness. Using cooling herbs is inappropriate because this dryness differs from warm disease tongue dryness; it is merely subjective dryness felt by the patient, not visible dryness upon inspection. When a coated tongue sheds its coating, it recedes from the tip to the center, then to the root. If the root was dry but moisture returns after medication, the coating will shed. Sometimes the tip, center, and root thin out simultaneously. Thin gray coatings are easy to resolve. In Yin patterns, gray coating must be thin; in heat patterns, thin gray coating indicates light pathogen, while thick black coating indicates heavy pathogen. Gradual shedding of coating indicates pathogen retreat; gradual progression indicates pathogen advance. If a fetus dies in the womb, the tongue becomes gray and green. Green tongue always indicates Jueyin disease; any disease presenting with green tongue is untreatable. Heavy tongue, wooden tongue, and tongue bleeding are not tongue disorders nor tongue colors. The tongue tip governs the Heart and Upper Jiao; the center governs the Stomach and Middle Jiao; the root governs the Lower Jiao. Since the tongue is the sprout of the Heart, and the Heart is the Sovereign, careful differentiation is essential for correct prescription. Without deep comprehension, how can one enter the gates of sacred medicine?