闻之舌以舒卷为用。口以开阖为用。各一其阴阳也。且口者脾之窍。心之外户也。难经七冲门。谓唇为飞
门。齿为户门。以其开阖运动。声音从口出。饮食从口入。四通五达。为脏腑之冲要也。察之之法。盖有十焉。
曰张、曰噤、曰撮、曰僻、曰振、曰动、曰颏落、曰口啮。由是分其燥湿。辨其寒热。其为病亦可见矣。何言之。张则
开而不闭。噤则闭而难开。撮则上下有蹙聚之形。僻则左右有缓急之状。振者寒栗鼓颔。急急摇振。动者
开阖其口。频频运动。颏落者似张。而颏不能阖。口啮者似动。而啮不频开。燥由津液之干。湿属唾涎之滑。
是故张主虚。噤主实。撮为邪正交争。正气衰而邪气胜。僻是经筋相引。急为正而缓为邪。振乃阳明之虚。
动缘胃气之绝。颏落者。颊车不收。病在阳明之脉。口啮者。肾脏将败。病达胃腑之经。是皆口之形容也。然
形容虽有燥湿之分。燥湿亦有虚实之辨。故燥虽属热。湿虽属寒。而上下表里不同。脏腑阴阳亦异。苟不
合之四诊。参之五官。则知其燥而不知其所以燥。知其湿而不知其所以湿。将治热而热不除。疗寒而寒
不退。其不倒行逆施也者几希。若夫口之五色着于唇。口之五味详于问。又当参伍相证焉。庶乎体益明
而用益达矣。他如浸淫疮。从口流向四肢者可治。从四肢流来入口者不可治。推而论之。即痘疮广疮。及
诸痛疮疡。其顺逆亦犹是也。
听说舌头的功能在于舒展和卷曲。嘴巴的功能在于张开和闭合。它们各自体现了阴阳的特性。况且，口是脾的窍穴，也是心的外门。《难经》中的七冲门理论指出，嘴唇称为飞门，牙齿称为户门。因为通过开合运动，声音从口中发出，饮食从口中进入。它是四通八达、连接脏腑的重要通道。观察口部形态的方法，大概有十种。分别是：张、噤、撮、僻、振、动、颏落、口啮。由此可以分辨燥湿，辨别寒热，疾病的情况也就显而易见了。为什么呢？“张”表现为张开而不能闭合；“噤”表现为闭合而难以张开；“撮”表现为上下唇有紧缩聚拢的形状；“僻”表现为左右两侧有松弛与拘急的不同状态；“振”表现为因寒冷战栗而鼓动下巴，急速摇动颤抖；“动”表现为频繁地开合嘴巴并运动；“颏落”表现为类似“张”，但下巴无法闭合；“口啮”表现为类似“动”，但伴有咬嚼动作而不频繁开合。燥是由于津液干枯所致，湿属于唾涎滑腻的表现。因此，“张”主虚证，“噤”主实证，“撮”表示邪气与正气交争，正气衰弱而邪气盛胜；“僻”是经筋相互牵引，拘急为正气表现，松弛为邪气表现；“振”乃是阳明经虚弱所致；“动”源于胃气的断绝；“颏落”表现为颊车穴部位肌肉不收摄，病在阳明经脉；“口啮”表示肾脏即将败坏，病情波及胃腑的经脉。这些都是口部的形态表现。然而，形态虽然分为燥湿两类，燥湿也有虚实之分。所以，燥虽然属于热证，湿虽然属于寒证，但上下的表里不同，脏腑的阴阳也各异。如果不结合四诊（望、闻、问、切），参考五官的变化，就只知道其燥却不知道为什么会燥，知道其湿却不知道为什么会湿。这样治疗热证则热不能去除，治疗寒证则寒不能消退，这几乎就是倒行逆施了。至于口唇呈现的五种颜色，以及口中滋味的详细询问，又应当综合参验来辨证。这样才能使体悟更加明确，运用更加通达。其他如浸淫疮，从口部流向四肢的可以治愈，从四肢流入口部的则不可治愈。推论开来，即使是痘疮、广疮以及各种痛疮疡，其顺逆预后也是如此。
It is said that the tongue functions through extension and curling. The mouth functions through opening and closing. Each embodies its own yin and yang characteristics. Moreover, the mouth is the orifice of the Spleen (P) and the outer gate of the Heart (H). The *Nan Jing* (Classic of Difficult Issues), in its theory of the Seven Chong Gates, refers to the lips as the "Fei Men" (Flying Gate) and the teeth as the "Hu Men" (Household Gate). Through the movement of opening and closing, sounds emerge from the mouth, and food and drink enter through it. It serves as a crucial thoroughfare connecting the Zang-Fu organs. The methods for observing the morphology of the mouth are approximately tenfold: namely Zhang (Opening), Jin (Gritting/Closed), Cuo (Puckering), Pi (Deviation), Zhen (Trembling/Shivering), Dong (Moving/Flapping), He Luo (Chin Dropping), and Kou Nie (Teeth Gnashing). From these, one can distinguish between dryness and dampness, differentiate cold and heat, and thus discern the nature of the disease. Why is this so? "Zhang" manifests as opening without the ability to close; "Jin" manifests as closing with difficulty in opening; "Cuo" presents a shape of puckering and gathering of the upper and lower lips; "Pi" shows a state of laxity on one side and tension on the other; "Zhen" refers to shivering due to cold chills, with rapid trembling of the chin; "Dong" involves frequent opening and closing movements of the mouth; "He Luo" resembles "Zhang," but the chin fails to close; "Kou Nie" resembles "Dong," but involves gnashing rather than frequent opening. Dryness arises from the depletion of body fluids (Jin-Ye); dampness belongs to the slickness of saliva and phlegm. Therefore, "Zhang" indicates deficiency; "Jin" indicates excess; "Cuo" signifies the struggle between pathogenic factors and healthy qi, where healthy qi is declining and pathogenic factors are prevailing; "Pi" results from the traction of sinews and tendons, where tension represents healthy qi and laxity represents pathogenic factors; "Zhen" stems from deficiency of the Yangming channel; "Dong" originates from the exhaustion of Stomach Qi; "He Luo" indicates flaccidity of the muscles around the Jiache acupoint, indicating pathology in the Yangming meridian; "Kou Nie" suggests impending failure of the Kidney (K) system, with the disease extending to the meridians of the Stomach (S). These are all morphological manifestations of the mouth. However, although morphology is divided into dryness and dampness, both dryness and dampness have distinctions of deficiency and excess. Thus, while dryness generally pertains to heat and dampness to cold, the patterns differ according to interior/exterior and upper/lower locations, and the yin-yang states of the Zang-Fu organs vary. If one does not integrate the Four Diagnostic Methods (Inspection, Auscultation-Olfaction, Inquiry, Palpation) and reference the Five Orifices, one may know there is dryness but not why it exists, or know there is dampness but not its cause. Consequently, treating heat will not eliminate it, and treating cold will not resolve it; such an approach would be little short of acting contrary to reason. Regarding the five colors appearing on the lips and the detailed inquiry into tastes in the mouth, these must also be cross-referenced and verified together. Only then can understanding become clearer and application more effective. Furthermore, regarding impetigo-like sores (Jinyin Chuang), those flowing from the mouth to the limbs are treatable, whereas those flowing from the limbs into the mouth are untreatable. By analogy, this principle applies to smallpox, syphilis-like sores (Guang Chuang), and various painful ulcers and abscesses; their favorable or unfavorable progression follows similar principles.