问曰∶下利清谷，何以是直中寒证？答曰∶寒邪内侵，真阳衰少，无以营运三焦，腐化
水谷，经曰∶食下即化腐臭而出是有火也，食下不化，完谷而出是有寒也。又曰天寒则水清
天热则水浊。今见下利清谷，即是直中寒证，若传经热证，则下利肠垢而不下利清谷矣。
又问∶书云邪热不杀谷，何谓也？答曰∶邪热不杀谷者，乃火性急速，不及变化而出，然必
杂于肠垢之中，不比直中寒邪，谷和清水，形如鸭溏也。
问曰∶但欲寐，何以是直中寒证？答曰∶寒邪属阴，阴主静，静则多眠；若传经热证，
则属阳，阳主动，则令人烦躁不眠也。又问曰∶表证多眠者，何也？答曰∶表证多眠，是寒
邪外束，阳气不舒，必见头痛发热诸证。若直中多眠，则见下利清谷，手足厥冷诸证，与表
邪自是不同。至于传经里证，则心烦恶热，揭去衣被，甚则谵语发狂，安得多眠？又问曰∶
热证亦有昏昏而睡者，何也？答曰∶此热邪传入心胞，令人神昏不语，或睡中独语一二句，
与之以水则咽，不与则不思，此乃热甚神昏，非欲寐也。又风温证，风热相搏，亦令神气昏
愦，其证鼻鼾，语言难出，与直中寒邪，厥逆清谷诸证，迥然大异矣。
问曰∶蜷卧何以是直中寒证？答曰∶热则手足舒伸，寒则手足敛束，譬如春夏则万物
发舒，秋冬则万物收藏，此定理也。又问曰∶表证亦蜷卧，何也？答曰∶表证有蜷卧
者，表受寒侵，经络因而敛束，法当温散。至于直中蜷卧，必有厥逆清谷诸证相兼，须
温中为主也。又问曰∶热证亦蜷卧，何也？答曰∶此热邪消烁津液，不能荣养于筋，致有
挛急之象，乃肝脏将绝，名曰搐搦，不得与蜷卧同语矣。
问：下利清谷（腹泻且排出未消化的食物），为什么这是寒邪直中脏腑的证候？答：寒邪侵入体内，导致真阳（人体根本的阳气）衰弱，无法推动三焦的气化功能，也不能腐熟消化水谷。医经说：“食物吃下去后能迅速消化、产生臭味并排出，说明体内有火；食物吃下去后不能消化，原样排出，说明体内有寒。”又说：“天气寒冷时水清澈，天气炎热时水浑浊。”现在见到下利清谷，就是寒邪直中脏腑的证候；如果是传经而来的热证，则会下利肠垢（黏液脓血便）而不会下利清谷。
又问：书上说“邪热不杀谷”，这是什么意思？答：“邪热不杀谷”是指火热之性急迫急速，食物来不及被完全转化就排出了，但必然混杂在肠垢之中；这与寒邪直中不同，寒邪直中时，食物与清水混合，形状像鸭粪一样稀薄。
问：但欲寐（总是想睡觉，精神萎靡），为什么这是寒邪直中脏腑的证候？答：寒邪属于阴，阴主静，静则多眠；如果是传经而来的热证，则属于阳，阳主动，会导致人烦躁不眠。又问：表证（外感病初期）也多见嗜睡，为什么呢？答：表证的嗜睡，是因为寒邪束缚体表，阳气不得舒展，必定伴有头痛、发热等症状。如果是寒邪直中脏腑导致的嗜睡，则伴有下利清谷、手足厥冷等症状，这与表邪显然不同。至于传经入里的热证，会出现心烦、恶热、掀开衣被，甚至胡言乱语、发狂，怎么会有嗜睡的表现呢？又问：热证也有昏昏欲睡的情况，为什么呢？答：这是热邪传入心包络，导致神志昏迷、不语，或者在睡眠中独自说一两句梦话，给水喝就能咽下，不给就不想吃，这是热盛导致的神志昏蒙，并不是所谓的“但欲寐”。另外，风温证是风热相搏，也会导致神气昏愦，症状包括鼻鼾、语言困难，这与寒邪直中引起的四肢厥逆、下利清谷等症状截然不同。
问：蜷卧（身体蜷缩而卧），为什么这是寒邪直中脏腑的证候？答：热证时手足舒展伸展，寒证时手足收敛拘束，就像春夏季节万物发散舒展，秋冬季节万物收藏收敛，这是自然的定理。又问：表证也有蜷卧的情况，为什么呢？答：表证中的蜷卧，是因为体表受寒邪侵袭，经络因此收缩拘紧，治疗应当用温散的方法。至于寒邪直中脏腑引起的蜷卧，必定伴有四肢厥逆、下利清谷等症状，治疗必须以温补中焦为主。又问：热证也有蜷卧的情况，为什么呢？答：这是热邪消耗灼伤津液，不能濡养筋脉，导致出现抽搐拘挛的现象，这是肝脏功能即将衰竭的表现，称为搐搦，不能与蜷卧混为一谈。
Q: Why is "diarrhea with undigested food" (xià lì qīng gǔ) considered a syndrome of cold pathogen directly invading the interior? A: When cold pathogen invades internally, it causes a deficiency of True Yang (Zhēn Yáng, the root Yang qi of the body), rendering it unable to facilitate the Qi transformation of the Sanjiao (Triple Burner) and unable to rot and ripen water and grain. The Classics state: "If food digests quickly after ingestion, produces foul odor, and is excreted, it indicates Fire; if food is not digested and is excreted intact, it indicates Cold." It also states: "When heaven is cold, water is clear; when heaven is hot, water is turbid." Now, seeing diarrhea with undigested food indicates a syndrome of cold pathogen directly invading the interior. If it were a heat syndrome transmitted via meridians, there would be diarrhea with intestinal mucus/pus/blood (cháng gǒu) rather than diarrhea with undigested food.
Another question: The books say "pathogenic heat does not kill/ripen grain," what does this mean? A: "Pathogenic heat does not ripen grain" means that due to the rapid nature of Fire, food is expelled before it can be fully transformed, but it must be mixed with intestinal mucus. This differs from cold pathogen directly invading the interior, where food mixes with clear fluids, resembling duck feces in consistency.
Q: Why is "constant desire to sleep" (dàn yù mèi, characterized by lethargy and drowsiness) considered a syndrome of cold pathogen directly invading the interior? A: Cold pathogen belongs to Yin, and Yin governs stillness; stillness leads to much sleep. If it were a heat syndrome transmitted via meridians, it would belong to Yang, and Yang governs movement, causing irritability and insomnia. Another question: Why do exterior syndromes (biǎo zhèng) often present with drowsiness? A: Drowsiness in exterior syndromes occurs because cold pathogen binds the exterior, preventing the free flow of Yang Qi, and must be accompanied by symptoms such as headache and fever. If drowsiness is caused by cold pathogen directly invading the interior, it will be accompanied by diarrhea with undigested food and cold extremities (jué nì), which is distinctly different from exterior pathogens. As for interior heat syndromes transmitted via meridians, they present with vexation, aversion to heat, pushing off clothes and blankets, and even delirium or mania; how could there be drowsiness? Another question: Heat syndromes also present with drowsiness/confusion, why? A: This is when heat pathogen enters the Pericardium (Xīn Bāo), causing spirit confusion and muteness, or speaking alone during sleep, swallowing water when offered but refusing it otherwise. This is spirit confusion due to extreme heat, not "constant desire to sleep." Furthermore, Wind-Warmth syndrome involves the struggle between wind and heat, leading to confused spirit and mental obtundation, with symptoms such as snoring and difficulty speaking. This is vastly different from the symptoms of cold pathogen directly invading the interior, such as cold extremities and diarrhea with undigested food.
Q: Why is "curling up while lying down" (quán wò) considered a syndrome of cold pathogen directly invading the interior? A: In heat syndromes, hands and feet extend and stretch out; in cold syndromes, hands and feet contract and curl up. This is like how all things expand and flourish in spring and summer, and store and conserve in autumn and winter; this is a fixed principle. Another question: Exterior syndromes also present with curling up, why? A: Curling up in exterior syndromes occurs because the exterior is invaded by cold, causing the collaterals to contract; the treatment method should be warming and dispersing. However, curling up caused by cold pathogen directly invading the interior must be accompanied by symptoms such as cold extremities and diarrhea with undigested food, requiring warming the Middle Jiao as the primary treatment. Another question: Heat syndromes also present with curling up, why? A: This is when heat pathogen consumes and scorches body fluids, failing to nourish the sinews, resulting in spasms and convulsions. This is a sign of impending failure of the Liver, termed twitching and convulsion (chū nuò), and cannot be equated with curling up.