舌乃心苗，肾窍通其本，脾脉络其下。时疫舌燥，由火炎土燥，中宫堵截，肾水不能上交心火，须察其苔之有
无，与色之深浅施治。白苔而燥，疫邪在表，痰已结于膈上，吴氏达原饮加石膏、川贝、蒌仁、大黄。此吴氏名白
砂苔，热极不变黄色，下之即黄，不可缓也。黄苔而燥，疫邪传胃，小承气、小陷胸、大柴胡选用。酱色苔而燥，
疫邪入胃，深及中、下二焦，调胃承气汤。黑苔而燥，疫邪入胃至深，伤及下焦，大承气汤。燥成块裂，或生芒
刺，热更甚也，大承气倍其分两，大黄须两许方妙。各燥苔，下之渐减，不即尽净，为药已中病，力未到耳，当再
下之，有下至三、五次、十余次而后愈者。若屡下而燥苔愈长，不可更下，当察其腹中。若揉按作响者，痰水结于
中焦，脾胃受困，津液不能上潮，改用平胃、二陈温燥之剂即愈。又肾阴竭涸，愈下愈亡其阴，燥苔不回，目无
神，耳聋，心悸，腰萎，再下必死，宜六味地黄汤合生脉散。至无苔而燥，须辨其色。正赤或深紫，热归心包，血
分热极，石膏、知母、黄连、犀角、羚羊角、牛黄为主。
鲜红亡阴，二冬、生地、元参、知母、阿胶、人参为主。大抵舌无苔则胃无物，可清润，不可攻下。
（附舌萎）
时疫舌本强硬，为热而兼痰，宜清下无疑，须加清痰之药。兼白苔者，膈间未经煎熬，其痰尚湿，佐以半夏，
大柴胡汤是也。兼黄苔者，已经煎熬，其痰渐燥，佐以川贝、栝蒌，小陷胸汤是也。兼黑苔者，热极，痰亦为火，
佐以牛黄方效。若无痰，舌色正赤、深紫裂燥而强者，热毒蕴于心包也，三黄石膏汤加犀角、牛黄，急清其热。
舌强虽与舌燥相类，而燥属胃，主热；强属心，主痰。又舌萎软而枯小与舌强硬而不缩有异，乃虚脱已极，
大补及滋润或百救一、二。若屡经汗、下、清热消痰，而舌强者，又当与舌萎同治。
The tongue is the sprout of the Heart (Xin, 心), its orifice connects to the root of the Kidney (Shen, 肾), and the collaterals of the Spleen (Pi, 脾) link to its lower aspect. In epidemic febrile diseases, a dry tongue results from flaming fire causing dryness in the Earth element, blocking the middle Jiao (Middle Burner, 中焦), thereby preventing Kidney Water from ascending to balance Heart Fire. Treatment must be based on observing the presence or absence of tongue coating and the depth of its color. If the coating is white and dry, the epidemic pathogen remains at the exterior, and phlegm has already congealed above the diaphragm; use Wu's Da Yuan Yin (Great Origin Reaching Decoction, 达原饮) with added Shi Gao (Gypsum Fibrosum, 石膏), Chuan Bei Mu (Fritillariae Cirrhosae Bulbus, 川贝母), Gua Lou Ren (Trichosanthis Semen, 瓜蒌仁), and Da Huang (Rhei Radix et Rhizoma, 大黄). This is what Wu Kecheng termed "white sand coating"; when heat is extreme but does not turn yellow, it turns yellow only after purgation, so treatment must not be delayed. If the coating is yellow and dry, the epidemic pathogen has transmitted to the Stomach; select Xiao Cheng Qi Tang (Minor Order the Qi Decoction, 小承气汤), Xiao Xian Xiong Tang (Minor Chest-Piercing Decoction, 小陷胸汤), or Da Chai Hu Tang (Greater Bupleurum Decoction, 大柴胡汤). If the coating is sauce-colored and dry, the epidemic pathogen has entered the Stomach, deeply affecting the Middle and Lower Jiao; use Tiao Wei Cheng Qi Tang (Regulate the Stomach and Order the Qi Decoction, 调胃承气汤). If the coating is black and dry, the epidemic pathogen has penetrated deeply into the Stomach, injuring the Lower Jiao; use Da Cheng Qi Tang (Greater Order the Qi Decoction, 大承气汤). If the dryness forms cracks or prickles, the heat is even more severe; double the dosage of Da Cheng Qi Tang, using approximately one tael of Da Huang for optimal effect. For various dry coatings, purgation will gradually reduce them. If they do not clear immediately, it means the medicine has hit the disease but the force has not yet fully reached; repeat purgation. Some patients recover after three to five, or even ten-plus purgations. If repeated purgation causes the dry coating to grow longer, stop purging and examine the abdomen. If pressing the abdomen produces sound, phlegm and water are congealed in the Middle Jiao, the Spleen and Stomach are constrained, and body fluids cannot moisten the tongue; switch to warm-drying agents like Ping Wei San (Calm the Stomach Powder, 平胃散) or Er Chen Tang (Two-Cured Decoction, 二陈汤) for recovery. Furthermore, if Kidney Yin is exhausted, further purgation destroys Yin, the dry coating does not return, and symptoms include spiritless eyes, deafness, palpitations, and flaccid loins; another purge will certainly cause death. Use Liu Wei Di Huang Wan (Six-Ingredient Rehmannia Pill, 六味地黄丸) combined with Sheng Mai San (Generate the Pulse Powder, 生脉散). Regarding tongues without coating but dry, distinguish the tongue body color. If bright red or deep purple, heat has returned to the Pericardium (Bao Gong, 包宫), indicating extreme heat in the Blood level; use Shi Gao, Zhi Mu (Anemarrhenae Rhizoma, 知母), Huang Lian (Coptidis Rhizoma, 黄连), Xi Jiao (Rhino Ceratoss, 犀角), Ling Yang Jiao (Saiga Tataricae Cornu, 羚羊角), and Niu Huang (Calculus Bovis, 牛黄) as main herbs. If the tongue body is fresh red, indicating Yin exhaustion, use Dong Gua (Tian Dong, Asparagi Radix, 天冬), Mai Dong (Ophiopogonis Radix, 麦冬), Sheng Di Huang (Rehmanniae Radix, 生地), Yuan Shen (Scrophulariae Radix, 元参), Zhi Mu, E Jiao (Colla Corii Asini, 阿胶), and Ren Shen (Ginseng Radix, 人参) as main herbs. Generally, a tongue without coating indicates no accumulation in the Stomach; clear and moisten, do not purge.
(Attachment: Tongue Flaccidity)
In epidemic febrile diseases, a stiff and rigid tongue is caused by heat combined with phlegm; clearing and purging is undoubtedly indicated, along with adding phlegm-resolving herbs. If accompanied by a white coating, the phlegm in the diaphragm has not been simmered by heat and remains damp; add Ban Xia (Pinelliae Rhizoma, 半夏), using Da Chai Hu Tang. If accompanied by a yellow coating, the phlegm has been simmered and is becoming dry; add Chuan Bei Mu and Gua Lou, using Xiao Xian Xiong Tang. If accompanied by a black coating, heat is extreme, and phlegm has transformed into fire; add Niu Huang for efficacy. If there is no phlegm, but the tongue is bright red, deep purple, cracked, dry, and rigid, this is heat-toxin accumulating in the Pericardium; use San Huang Shi Gao Tang (Three-Yellow Gypsum Decoction, 三黄石膏汤) with added Xi Jiao and Niu Huang to urgently clear the heat. Although tongue stiffness resembles tongue dryness, dryness belongs to the Stomach and is primarily due to heat; stiffness belongs to the Heart and is primarily due to phlegm. Additionally, a flaccid, shriveled, and small tongue differs from a stiff tongue that does not retract; the latter indicates extreme collapse, where major tonification and moistening might save one or two percent. If tongue stiffness persists after repeated sweating, purging, clearing heat, and resolving phlegm, treat it similarly to tongue flaccidity.