舌者，心之窍。凡伤寒症，津液如常，此邪在表而未传里也。见白胎而滑，邪在少阳，
半表半里之间也。见黄胎而干燥，邪已入里，胃腑热甚也，宜下之。见黑胎芒刺，破裂干枯
邪热盛极，肾水枯涸，至重之候也，宜急下之。若舌黑津润，不破裂干燥，此直中寒证也
宜急温之。夫寒证舌黑，本色也。而热症反赤为黄，反黄为黑者，何也？盖热极反兼水化
若燔柴然，火变成炭，至危之候也。凡舌肿胀，或重舌、木舌、舌生芒刺，舌苔黄燥，皆
热甚也。凡舌硬、舌强、舌短缩、舌卷、神气昏乱、语言不清者，皆危症也。又阴阳易病，
吐舌数寸者，危恶已甚也。
大抵病患身轻，自能转侧者，为轻。若身体沉重，不能转侧者，为重。然中湿、风湿、
感寒，皆主身重疼痛，须以兼症辨之。若阴证身重，必厥冷而蜷卧，无热恶寒，闭目不
欲向明，懒见人也。又阴毒身痛如被杖，身重如山而不能转侧也。大抵热则流通，身轻无痛
寒则凝塞，故身重而痛也。若手足抽搐，角弓反张者，痉也。若头重视身，此天柱骨倒而
元气败也。若头摇而不止，发直如妆，头上撺，皆绝证也。凡病中循衣摸床，两手撮空，此
神去而魂乱也。凡病患皮肤润泽者生，枯槁者危。若大肉尽脱，九候虽调，犹难治也。
The tongue is the orifice of the Heart (Xin, 心). In all cases of Shanghan (Cold Damage, 伤寒), if the body fluids are normal, it indicates that the pathogenic factor is in the exterior and has not yet transmitted to the interior. If a white coating is seen and it is slippery, the pathogen is in the Shaoyang (Lesser Yang, 少阳) stage, which is between the exterior and the interior. If a yellow coating is seen and it is dry, the pathogen has entered the interior, indicating excessive heat in the Stomach (Wei, 胃) organ; purgation should be applied. If a black coating with prickles is seen, and the tongue surface is cracked and dry, this indicates extreme excess of pathogenic heat and depletion of Kidney (Shen, 肾) water, a very critical condition; urgent purgation is required. If the tongue is black but moist with saliva, without cracking or dryness, this is a direct attack by cold pathogens; urgent warming treatment is required. The black color of the tongue in cold syndromes is its natural color. Why do heat syndromes turn red then yellow, and then black? This is because extreme heat may assume the transformation of water, similar to burning firewood where fire turns into charcoal, which is a critically dangerous sign. Any swelling of the tongue, or conditions such as double tongue (Chongshe, 重舌), wooden tongue (Mushe, 木舌), prickles on the tongue, and a yellow dry coating, all indicate excessive heat. Any stiffness, rigidity, shortening, or curling of the tongue, along with confused spirit and unclear speech, are all critical symptoms. Furthermore, in Yin-Yang Exchange disease (Yinyang Yi Bing, 阴阳易病), if the tongue protrudes several inches, it is an extremely perilous sign.
Generally, if a patient's body is light and they can turn over independently, the illness is mild. If the body feels heavy and turning over is impossible, the illness is severe. However, dampness invasion, wind-dampness, and cold invasion all cause heaviness and pain in the body; differentiation must be made based on accompanying symptoms. If the heaviness is due to a Yin syndrome, it must be accompanied by cold extremities, a curled-up posture, absence of fever but aversion to cold, eyes closed unwillingly facing brightness, and reluctance to see people. Additionally, in Yin Toxin syndrome (Yindu, 阴毒), body pain feels like being beaten with a staff, and the body is as heavy as a mountain, unable to turn over. Generally, heat allows for free flow, resulting in a light body without pain; cold causes stagnation and blockage, resulting in a heavy and painful body. If there are spasms and convulsions of the hands and feet, and opisthotonos (Jiang, 痉), this is Spasm disease. If the head cannot lift and looks down at the body, this indicates the collapse of the Tianzhu bone (cervical spine) and failure of Yuan Qi (Original Qi, 元气). If the head shakes incessantly, hair stands straight like a wig, and the scalp bulges, these are signs of death. Any patient exhibiting "feeling around clothes and bed" (Xunyimo Chuang, 循衣摸床) and "clutching at empty air" (Liangshuocong, 两手撮空) has lost their Shen Spirit (Shen, 神) and their Hun Soul (Hun, 魂) is chaotic. Patients with moist and lustrous skin have vitality; those with withered and rough skin are in danger. Even if the pulses at the three positions and nine locations are harmonious, if the large muscles are completely wasted away, the condition is difficult to treat.