尝谓虞书记时以鸟兽。月令占候于虫鱼。是因天之物以验天也。内经诊病于水液。后世辨证以痰涎。是
因人之物以验人也。盖天道远。人道迩。远取诸物。近取诸身。其事虽异。其理则同。而况痰因病生。病以痰
着。又事理之至明且显者乎。间尝考之于书。以为痰形稠而浊。饮色稀而清。寒痰青。湿痰白。火痰黑。热痰
黄。老痰胶。其滑而易出者。湿痰属脾。燥而难出者。燥痰属肺。清而多泡者。风痰属肝。坚而成块者。热痰属
心。有黑点而多稀者。寒痰属肾。病新而轻者。清白稀薄。病久而重者。黄浊稠粘。多唾者胃寒。流涎者脾冷。
舌难言。口吐沫者。邪入于脏。腹时痛。口吐涎者。蛔乱于中。咳唾涎沫。口张气短者。肺痿之证。咳唾脓血。口
干胸痛者。肺痈之征。其吐如米粥。吐而腥臭者。皆肺痈之候。形如败絮。色如煤 者。悉老痰之容。此诸书
因痰涎之形色。诊病之浅深也。或谓痰声相应为轻。不相应为重。由稀而稠者。病日退。由稠而稀者。病日
进。因痰嗽而吐血者。多起于外感。因吐血而痰嗽者。多属乎内伤。亦可因证以相参也。会而观之。析而论
之。则稀者为饮。稠者为痰。清者形气不足。浊者病气有余。青白者少热气。黄赤者多热气。而凡痰形之变。
痰色之殊。胥于是乎推。亦于是乎断矣。
我曾说过，虞书记在记载时令时以鸟兽为象，月令在占候时以虫鱼为验。这是借助自然界的事物来验证天道。《内经》通过诊察水液来诊断疾病，后世通过辨证痰涎来判断病情。这是借助人体自身的事物来验证人道。大概天道遥远，人道切近。远取法于万物，近取法于自身。虽然所取的对象不同，但其中的道理是相同的。更何况痰是由病产生的，而病症又因痰的存在而明确，这更是事理中极其明显且显著的情况啊。
我偶尔考察古籍，认为痰的形状稠厚而浑浊，饮的颜色稀薄而清亮。寒痰呈青色，湿痰呈白色，火痰呈黑色，热痰呈黄色，老痰胶结难化。那些滑利而易于咳出的，属于脾虚生湿的湿痰；干燥而难以咳出的，属于肺燥的燥痰；清澈且多泡沫的，属于肝风内动的风痰；坚硬而成块的，属于心火的实热痰；带有黑点且质地较稀的，属于肾寒的寒痰。
疾病新起且轻浅的，痰色清白、质地稀薄；病程长久且严重的，痰色黄浊、质地粘稠。唾液多的，多为胃寒；流口水的，多为脾冷。舌体僵硬难以言语，口中吐沫的，是邪气侵入脏腑的表现；腹部时常疼痛，口中吐涎的，是蛔虫扰乱体内的表现。咳嗽并吐出涎沫，张口呼吸且气短的，是肺痿的症状；咳嗽并吐出脓血，口干且胸痛的，是肺痈的征象。呕吐物像米粥一样，且气味腥臭的，都是肺痈的征兆。痰形如败絮，颜色如煤炭般的，全是老痰的表现。这些书籍正是根据痰和涎的形态颜色，来诊断疾病的深浅程度。
有人曾说，痰声与症状相应者为轻证，不相应者为重证。由稀变稠的，说明病情日渐好转；由稠变稀的，说明病情日渐加重。因剧烈咳嗽导致吐血的，多起因于外感；因吐血导致咳嗽有痰的，多属于内伤。也可以结合证候相互参照判断。
综合观察，分析论述，可知：稀薄的为饮，稠厚的为痰；清稀的反映正气不足，浑浊的反映病邪有余；青白色的痰表明热气较少，黄赤色的痰表明热气较多。凡是痰形态的变化、颜色的差异，都可以通过此法进行推演和判断了。
I have said that Yu Shuji (a historical figure/author) used birds and beasts to record seasonal changes, and the *Yueling* (Monthly Ordinances) used insects and fish for divination. This is using natural phenomena to verify the Heavenly Dao. The *Neijing* (Inner Canon) diagnoses diseases by examining bodily fluids, while later generations differentiate syndromes by analyzing phlegm and saliva. This is using human physiological substances to verify the Human Way. Generally, the Heavenly Dao is distant, while the Human Way is proximate. One draws analogies from things far away and from one's own body. Although the objects of observation differ, the underlying principles are identical. Moreover, phlegm arises from disease, and the disease becomes manifest through phlegm; this is a matter of principle that is extremely clear and obvious.
Occasionally consulting ancient texts, I hold that phlegm (*Tan*) is thick and turbid, whereas fluid retention (*Yin*) is thin and clear. Cold-phlegm is greenish, damp-phlegm is white, fire-phlegm is black, heat-phlegm is yellow, and old-phlegm (*Lao Tan*) is gelatinous and sticky. Phlegm that is slippery and easy to expectorate belongs to Spleen-dampness (*Shi Tan*). Phlegm that is dry and difficult to expectorate belongs to Lung-dryness (*Zao Tan*). Phlegm that is clear and foamy belongs to Liver-wind (*Feng Tan*). Phlegm that is hard and forms clumps belongs to Heart-heat (*Re Tan*). Phlegm with black spots and a thinner consistency belongs to Kidney-cold (*Han Tan*). In new and mild diseases, the phlegm is white/clear and thin. In long-standing and severe diseases, the phlegm is yellow/turbid and sticky/copious. Excessive salivation indicates Stomach-cold. Drooling indicates Spleen-cold. Difficulty in speaking with froth spitting from the mouth indicates pathogenic factors invading the Zang organs. Abdominal pain occurring intermittently with drool spitting indicates intestinal roundworms (*Hui Chong*) disturbing the interior. Coughing up saliva and froth, with an open mouth and shortness of breath, are signs of Lung萎 (*Fei Fei*, Lung Flaccidity). Coughing up pus and blood, with dry mouth and chest pain, are signs of Lung Abscess (*Fei Yong*). Vomiting material resembling rice porridge with a fishy and foul odor are all indications of Lung Abscess. Phlegm resembling rotten cotton wool or coal dust represents the appearance of Old-phlegm. These texts diagnose the depth of disease based on the form and color of phlegm and saliva.
Some argue that when the sound of phlegm corresponds with symptoms, the condition is mild; when they do not correspond, it is severe. A change from thin to thick indicates the disease is receding daily; a change from thick to thin indicates the disease is advancing daily. Hemoptysis caused by violent coughing often originates from external contraction. Coughing with phlegm caused by hemoptysis often belongs to internal injury. These can also be cross-referenced with other symptoms. Synthesizing these observations and analyzing them discursively: thin substances are Fluid Retention (*Yin*), thick substances are Phlegm (*Tan*). Clear substances indicate deficiency of Qi and Form (Zheng Qi), while turbid substances indicate excess of Pathogenic Qi. Greenish-white phlegm suggests little Heat, while yellow-red phlegm suggests abundant Heat. Thus, variations in the form and differences in the color of phlegm can all be deduced and judged through this method.