李杲曰。四逆者。四肢不温也。厥者。手足逆冷也。伤寒邪在三阳。则手足必热。传到太阴。
则手足不热而温。至少阴。则邪热之入里渐深。故四肢逆而不温。及至厥阴。则又手足厥冷。更甚
于逆矣。其四逆散。以凉药而治四肢不温。其四逆汤。以热药而治寒极而成逆厥者也。四肢通冷。
比之手足独冷。则有间。夫死者。以四逆言之。可治者。以厥冷言之。则亦可见四逆与手足厥冷之
有轻重矣。盖四肢通冷。其病为重。手足独冷。其病为轻也。四肢与手足。却有所分。以
四字加于逆字之上。是通指手足臂胫以上言也。以手足二字加于厥逆厥冷之上。是独指手足言也。盖
以四逆为四肢通冷。而厥为手足独冷也。
陶华曰。阴阳二厥。治之一瘥。生死立判。夫阳厥者。先自三阳经气分。因感寒邪。于头疼发
热恶寒以后。传进三阴血分。变出四肢厥冷乍温。大便燥实。谵语发渴。扬手掷足。不恶寒反怕热。
脉沉有力。此见传经热症。谓之阳厥。阳极发厥者。即阳症似阴。外虽有厥冷。内有热邪耳。盖因
大便结实失下。使血气不通。故手足乍冷乍温也。如火炼金。热极金反化水。水寒极而成冰。反能
载物。厥微热亦微。四逆散。厥深热亦深。大承气汤。正谓亢则害其物。承乃制其极也。若误为阴
症。便进热药。如抱薪救火矣。夫阴厥者。因三阴经血分自受寒邪。初病。无身热。无头疼。就使
恶寒。四肢厥冷。直至臂胫以上。过乎肘膝。不温。引衣蜷卧。不渴。兼或腹满吐泻。或战栗。面
如刀刮。口吐涎沫。脉沉迟无力。此为阴经直中真阴寒症。不从阳经传入。谓之阴厥也。轻则理中
汤。重则四逆汤温之。勿令误也。又曰。人之手足。乃胃土之末。凡脾胃有热。手足必热。脾胃有
寒。手足必冷。理之常也。惟伤寒乃有厥深热亦深。厥微热亦微之论。何耶。曰。此为极则变。火
气亢极。反兼水化。故有此象耳。阴阳反复。病之逆从。未可以常理论也。凡言厥逆厥寒厥冷手足
寒冷。皆变文耳。不必分轻重。若言四肢。则有异也。亦未可纯为寒症。若厥冷直至臂胫以上。则为
真寒无疑。急用姜附等温之。少缓便难治。谓其冷上过乎肘。下过乎膝。非内有真寒。达于四肢而
何。然更当以脉与症参之。庶乎无误。凡看伤寒。不可以厥逆。便断为寒。必参脉与兼症。方知端的。
如手足厥冷。兼之腹痛腹满。泄利清白。小便亦清。口不渴。恶寒战栗。面如刀刮。皆寒症也。
若腹痛后重。泄利稠粘。小便赤涩。渴而好饮。皆热症也。宜详审之。
Li Gao stated: "Si Ni" (Four Reversals) refers to the limbs being not warm; "Jue" (Reversal/Cold Extremities) refers to the hands and feet being reversely cold. When pathogenic factors of Shanghan (Cold Damage) are in the Taiyang, Yangming, and Shaoyang (Three Yang) meridians, the hands and feet must be hot. When transmitted to the Taiyin meridian, the hands and feet become not hot but warm. When reaching the Shaoyin meridian, the pathogenic heat enters deeper into the interior, thus causing the four limbs to be reversely cold and not warm. Upon reaching the Jueyin meridian, there is again cold extremities of the hands and feet, which is even more severe than "Ni". Si Ni San (Four Reversals Powder) uses cooling herbs to treat the non-warmness of the four limbs. Si Ni Tang (Four Reversals Decoction) uses warming herbs to treat the reversal cold extremities caused by extreme cold. Generalized coldness of the four limbs differs from isolated coldness of the hands and feet. For deceased patients, "Si Ni" is used to describe the condition; for those who can be treated, "Jue Leng" (Cold Extremities) is used. This shows the difference in severity between "Si Ni" and "Shou Zu Jue Leng" (Cold Hands and Feet). Generally, generalized coldness of the four limbs indicates a heavier disease, while isolated coldness of the hands and feet indicates a lighter disease. There is a distinction between "Si Zhi" (four limbs) and "Shou Zu" (hands and feet). Adding the character "Si" (four) before "Ni" (reversal) generally refers to the entire limbs including arms, forearms, legs, and calves. Adding "Shou Zu" (hands and feet) before "Jue Ni" or "Jue Leng" specifically refers only to the hands and feet. Thus, "Si Ni" is understood as generalized coldness of the four limbs, while "Jue" is understood as isolated coldness of the hands and feet.
Tao Hua stated: The treatment of Yin Jue (Yin Reversal) and Yang Jue (Yang Reversal), if slightly mistaken, leads to immediate life or death outcomes. Yang Jue originates from the Qi level of the Three Yang meridians due to cold pathogen invasion. After symptoms such as headache, fever, and aversion to cold, it transmits to the Blood level of the Three Yin meridians, manifesting as cold extremities that occasionally become warm, dry and solid stool, delirium, thirst, waving hands and kicking feet, aversion to heat rather than cold, and a deep and forceful pulse. This presents as a heat syndrome transmitted through meridians, termed Yang Jue. Extreme Yang leading to Jue is essentially a Yang syndrome resembling Yin; although there is external coldness, there is internal heat pathogen. This occurs because dry stool was not purged in time, causing stagnation of Qi and Blood, resulting in alternating cold and warmth of the hands and feet. It is like fire refining metal; when heat is extreme, metal transforms into water. When water is extremely cold, it becomes ice, yet can still bear weight. Mild Jue implies mild heat, treated with Si Ni San (Four Reversals Powder); deep Jue implies deep heat, treated with Da Cheng Qi Tang (Major Order the Qi Decoction). This means that when亢盛 (hyperactivity/excess) causes harm, one must follow the principle to control its extremity. If mistakenly treated as a Yin syndrome with warming herbs, it is like adding firewood to save a fire. Yin Jue occurs when the Blood level of the Three Yin meridians directly suffers from cold pathogens. Initially, there is no body heat or headache. Even if there is aversion to cold, the limbs are cold, extending up to the arms and calves above the elbows and knees, remaining unwarmed. The patient prefers curling up, has no thirst, and may have abdominal fullness, vomiting, diarrhea, shivering, a face pale as if scraped by a knife, spitting saliva, and a deep, slow, and forceless pulse. This is a true Yin-cold syndrome directly attacking the Yin meridians, not transmitted from the Yang meridians, termed Yin Jue. Mild cases are treated with Li Zhong Tang (Regulate the Middle Decoction), severe cases with Si Ni Tang (Four Reversals Decoction) to warm them; do not make mistakes. Furthermore, the hands and feet are the extremities of the Stomach Earth. Generally, if the Spleen and Stomach have heat, the hands and feet are hot; if they have cold, the hands and feet are cold. This is the normal rule. Only in Shanghan is there the theory that "deep Jue implies deep heat, mild Jue implies mild heat." Why? This is a transformation at the extreme limit; when Fire Qi is excessively hyperactive, it assumes the characteristics of Water, hence this appearance. Yin and Yang reverse each other; the deviation and compliance of diseases cannot be judged by normal rules. Terms like Jue Ni, Jue Han, Jue Leng, and Shou Zu Leng are merely rhetorical variations and need not distinguish severity. However, mentioning "Si Zhi" (four limbs) is different and cannot be purely considered a cold syndrome. If coldness extends up to the arms and calves, it is undoubtedly true cold, requiring urgent use of warming herbs like Ginger (Sheng Jiang / Gan Jiang) and Aconite (Fu Zi). Delay makes it difficult to treat. If the cold exceeds the elbows and goes below the knees, unless there is true cold inside reaching the four limbs, what else could it be? However, one must further correlate the pulse and symptoms to avoid errors. In diagnosing Shanghan, one cannot conclude it is a cold syndrome solely based on Jue Ni; one must combine the pulse and accompanying symptoms to know the truth. For example, cold extremities accompanied by abdominal pain and fullness, clear white diarrhea, clear urine, no thirst, aversion to cold, shivering, and a face pale as if scraped by a knife are all cold syndromes. If abdominal pain is accompanied by tenesmus, thick and sticky diarrhea, red and scanty urine, thirst with desire to drink, these are heat syndromes. One should examine carefully.