中央黄色。入通于脾。开窍于口。胃脉挟口环唇。大肠脉还出挟口。厥阴脉
下颊里环唇内。又皆统之于脾矣。独其邪之所侵。火热则赤。木乘则青。气
虚则白。火极似水则焦黑。水极似火则裂坼。一寒一热。判若天渊。胃热脉
洪。责于心火。内炽脾虚。脉弱本于阴寒上逼。清胃凉膈。所以彻热。附子理
中。所以温里。今人一见唇焦。便指为热。不知中气虚寒。饮食不进。中焦失
守。无根之火。逼而上浮。若以寒凉投之。则火愈不归。而食愈不进。惟人参
理中。温其中气。火奠厥位。而唇口坼裂。如久旱逢霖。立时润泽矣。至乃舌
为心苗。脾之络。连舌本。散舌下。肾之脉。亦系舌本。伤寒家验舌苔。以焦黑
为胃热。为水枯。则本此。若别口味之辛甘咸苦酸。以察五脏之热。尤其显
白者。则各以其脏治之。斯善耳。要之二阳之病发心脾。火土子母相关。岂浅鲜哉。
一口病实热。脉洪数有力者。用清胃汤。
一口病饮食不进。脉微细软弱者。用人参理中汤。或归脾汤加炮姜。
一谋虑不决。上为口糜。用逍遥散。或升阳散火汤。大肠移热。用秦艽升麻汤。
清胃伤 治胃火血燥唇裂。或为茧唇。或牙龈溃烂作痛。
黄连（炒） 生地黄 升麻（各一钱） 当归（一钱二分） 牡丹皮（八分）
水煎。
中央对应黄色，其气通于脾脏。口窍开泄于外，与脾胃关系密切。足阳明胃经的脉气挟持口唇环绕；手阳明大肠经的脉气回转出来，也挟持口唇；足厥阴肝经的脉气下行至颊里，环绕唇内。这些经脉的气血运行都统摄于脾脏。
然而，邪气侵袭口唇的表现各不相同：火热之邪侵袭则嘴唇发红；木（肝）气乘克则嘴唇发青；气虚则嘴唇苍白；火极似水（真寒假热或阴盛格阳）则嘴唇焦黑；水极似火（真热假寒或阳盛格阴）则嘴唇干裂坼破。一寒一热，差别如同天渊之别。
如果是胃热导致的脉象洪大，责任在于心火内炽；如果是脾虚导致的脉象微弱，根本原因在于阴寒之气上逼。使用清胃凉膈的方法，是为了彻底清除热邪；使用附子理中汤，是为了温补里寒。
现在的人一见嘴唇焦黑，就断定是热证，却不知道这是中气虚寒，导致饮食不进，中焦失守，无根之火逼迫而上浮。如果此时用寒凉药物投治，那么火气更加不能回归本位，饮食也更加无法进入。只有用人参理中汤温补其中气，使火气安归其位，那么嘴唇口角的干裂坼破，就像久旱逢甘霖一样，立刻就能得到润泽。
至于舌头，它是心之苗窍，脾的络脉连接舌根，散布在舌下；肾的脉气也系连舌根。伤寒家通过验看舌苔，认为焦黑代表胃热或津液枯竭，这个观点就是基于上述经络理论。另外，通过辨别口味的辛、甘、咸、苦、酸，来观察五脏是否有热，尤其明显者，分别针对各脏进行治疗，这才是高明的做法。总之，“二阳之病发心脾”，火与土（心与脾/胃）之间母子相生关系密切，这其中的道理难道浅显吗？
1. 口病属于实热证，脉象洪数有力的，使用清胃汤。
2. 口病表现为饮食不进，脉象微细软弱的，使用人参理中汤。或者使用归脾汤加炮姜。
3. 谋虑不决，上行导致口糜（口腔黏膜溃烂），使用逍遥散。或者使用升阳散火汤。如果是大肠移热所致，使用秦艽升麻汤。
【方剂】清胃伤（注：原文此处标题可能有误，通常指清胃散类方，但依原文列出）
主治：胃火血燥导致的嘴唇干裂。或者形成茧唇（唇部赘生物），或者牙龈溃烂疼痛。
组成：黄连（炒）、生地黄、升麻（各一钱），当归（一钱二分），牡丹皮（八分）。
用法：水煎服。
The center corresponds to the color yellow, and its qi communicates with the Spleen (Pi, 脾). The orifice of the mouth opens externally, closely related to the Stomach and Spleen. The meridian of Foot-Yangming Stomach (Zu Yangming Wei Jing, 足阳明胃经) runs alongside the lips and encircles them; the meridian of Hand-Yangming Large Intestine (Shou Yangming Da Chang Jing, 手阳明大肠经) returns and also runs alongside the lips; the meridian of Foot-Jueyin Liver (Zu Jueyin Gan Jing, 足厥阴肝经) descends into the cheek interior and encircles the inner lips. The qi and blood flow of these meridians are all governed by the Spleen.
However, manifestations of pathogenic invasion on the lips vary: invasion by Fire-Heat (Re, 热) causes redness; Wood (Liver) overacting causes blueness; Qi deficiency causes pallor; extreme Fire resembling Water (True Cold, False Heat) causes charring/blackening; extreme Water resembling Fire (True Heat, False Cold) causes cracking/fissuring. One is cold, one is heat, differing as vastly as heaven and earth.
If the pulse is surging (Hong, 洪) due to Stomach Heat, the responsibility lies in the internal blazing of Heart Fire (Xin Huo, 心火); if the pulse is weak due to Spleen Deficiency, the root cause is the upward coercion of Yin-Cold (Yin Han, 阴寒). Using methods to clear the Stomach and cool the Diaphragm aims to thoroughly eliminate Heat; using Fuzi Lizhong Tang (Aconite Decoction for Regulating the Middle) aims to warm the Interior.
Modern practitioners, upon seeing charred lips, immediately diagnose it as Heat, unaware that this may be Deficient-Cold of the Middle Qi, leading to loss of appetite, failure of the Middle Jiao to maintain control, and Rootless Fire being coerced upward. If cold-natured drugs are administered at this time, the Fire will fail to return to its proper position, and food intake will further decrease. Only by using Renshen Lizhong Tang (Ginseng Decoction for Regulating the Middle) to warm the Middle Qi can the Fire be settled in its proper place. Consequently, the cracking and fissuring of the lips and mouth will be instantly moistened and healed, like rain falling after a long drought.
Regarding the tongue, it is the sprout of the Heart, the collaterals of the Spleen connect to the root of the tongue and scatter beneath it, and the meridian of the Kidney also ties to the root of the tongue. Practitioners of Shanghan (Cold Damage) examine the tongue coating, considering blackening to indicate Stomach Heat or exhaustion of Body Fluids (Jin Ye, 津液), based on these theories. Furthermore, by distinguishing tastes such as pungent, sweet, salty, bitter, and sour to observe Heat in the Five Zang Organs, and treating each organ accordingly when signs are prominent, one demonstrates superior skill. In summary, "Diseases of the Two Yangs originate from the Heart and Spleen"; the mother-child relationship between Fire and Earth (Heart and Spleen/Stomach) is significant, and its principles are not trivial.
1. For mouth diseases characterized by Excess-Heat, with a surging, rapid, and forceful pulse, use Qingwei Tang (Clear the Stomach Decoction).
2. For mouth diseases presenting with loss of appetite and a faint, thin, soft, and weak pulse, use Renshen Lizhong Tang (Ginseng Decoction for Regulating the Middle). Alternatively, use Guipi Tang (Restore the Spleen Decoction) with roasted Sheng Jiang (Prepared Ginger).
3. For indecisive planning leading to oral ulcers (Kou Mi, 口糜) ascending from above, use Xiaoyao San (Free and Easy Wanderer Powder). Or use Shengyang Sanhuo Tang (Raise Yang and Disperse Fire Decoction). If caused by Heat transferring from the Large Intestine, use Qinjiao Shengma Tang (Gentian and Cimicifuga Decoction).
[Formula] Qingwei Shang (Clear Stomach Injury - *Note: Text likely refers to a variation of Qingwei San*)
Indications: Lip fissures due to Stomach Fire and Blood Dryness. Or formation of callosous lips (Jian Chun, 茧唇), or ulceration and pain of the gums.
Ingredients: Huang Lian (Stir-fried Coptidis Rhizoma), Sheng Di Huang (Rehmanniae Radix Preparata), Sheng Ma (Cimicifugae Rhizoma) (each 1 qian), Dang Gui (Angelicae Sinensis Radix) (1.2 qian), Mu Dan Pi (Moutan Cortex) (0.8 qian).
Administration: Decoct in water and drink.