A question was raised: "The hands and feet of a human are the extremities of the Stomach Earth. Whenever the Spleen and Stomach have Heat, the hands and feet must be hot; whenever the Spleen and Stomach have Cold, the hands and feet must be cold. This is the normal principle. Yet in Shanghan (Cold Damage), there is the discussion that 'the deeper the Jue (cold reversal), the deeper the Heat; the more slight the Jue, the more slight the Heat.' Why is this?" The answer is: "Stomach Cold causes cold hands and feet, Stomach Heat causes hot hands and feet; this is the normal state of disease. However, when conditions reach an extreme, they transform, and one cannot be bound by normal principles. When something is excessive, it causes harm; only through subordination can it be controlled. When Fire Qi is excessively hyperactive, it may manifest with Water transformations, thus producing such phenomena. Yin and Yang undergo reversals; the deviation or compliance of diseases cannot be judged by normal theories. All terms in the classics such as Jue Ni (reversal of cold), Jue Leng (cold reversal), Jue Han (cold reversal), and cold hands and feet are rhetorical variations and should not be used to determine the severity of the condition. If referring to the four limbs, the situation differs, and it cannot be purely considered a Cold syndrome. If the coldness extends up to above the elbows and down to below the knees, it is undoubtedly true Cold. One must urgently use drugs like Sheng Jiang (Dried Ginger) and Fu Zi (Prepared Aconite Root) to warm it; if delayed even slightly, it will be difficult to treat. To say that Cold has passed above the elbows and below the knees—what else could it be but true Cold within reaching the four limbs? However, one must also consult the pulse and accompanying symptoms to avoid errors. In treating Shanghan, one cannot diagnose Cold merely upon seeing Jue Ni; one must combine pulse and symptoms to ascertain the truth. For example, if Jue Ni of the hands and feet is accompanied by abdominal pain and fullness, clear watery diarrhea, clear urine, no thirst, aversion to cold with shivering, and a face pale as if scraped by a knife, these are all Cold syndromes. If there is abdominal pain with tenesmus, thick and sticky diarrhea, red and scanty urine, thirst with desire to drink, these are all Heat syndromes. Careful examination is required.

Treating Shanghan by grasping its general principles is not difficult. If one seeks complexity, it becomes fragmented and difficult. What are the principles? They are pulse, symptoms, and theory. I have often treated meticulously using the Floating, Middle, and Deep pulse methods, leaving no aspect of the pathology hidden. Since it is called Shanghan, Cold pathogenic factors enter from the exterior and damage the interior. Their entry has degrees of depth and sequence, moving from the exterior to the interior; deducing from this is not difficult. When Wind-Cold first enters, it must invade the Taiyang Bladder channel, which has Cold as its root and Heat as its manifestation. Thus, symptoms such as aversion to wind and cold, headache, and stiffness of the spine appear. Cold stagnating in the skin and hair constitutes an Exterior syndrome. If it affects other channels, these symptoms would not appear. If the pulse is Floating and Tight with no sweating, it is Shanghan; treat with Mahuang Tang (Ephedra Decoction) to induce sweating for resolution. If the pulse is Floating and Slow with sweating, it is Shangfeng (Wind Strike); treat with Guizhi Tang (Cinnamon Twig Decoction) to disperse pathogens and stop sweating for resolution. If there is no headache or aversion to cold, and the pulse is not Floating, this indicates the Exterior syndrome has resolved and the pathogen is in the Half-Exterior/Half-Interior (Middle). What is the Middle? It is between the Exterior and Interior, specifically the domains of the Yangming Stomach and Shaoyang Gallbladder. The pulse is neither Floating nor Deep, located between the muscles, beneath the skin. There are two possibilities here. If the pulse is slightly Full and Long, it is a Yangming pulse; external symptoms include eye pain, dry nose, and insomnia; treat with Gegen Tang (Kudzu Decoction) to resolve the muscle layer. If the pulse is Wiry and Rapid, it is a Shaoyang pulse; symptoms include chest and hypochondriac pain and deafness. Upon seeing these symptoms and pulse, treat with Xiaochaihu Tang (Minor Bupleurum Decoction) to harmonize. Generally, Yangming and Shaoyang do not follow their root or manifestation but are treated via the Middle. Beyond this stage, pathogens enter the Interior transforming into Excess Heat. The pulse is not Floating but Deep; Deep means pressing with fingers until the bones and sinews. If the pulse comes Deep, Solid, and Forceful, external symptoms show no aversion to wind or cold but rather aversion to heat, delirious speech, severe thirst, and constipation for six or seven days. This clearly indicates Heat entering the Interior causing dryness and excess in the intestines and stomach. Mild cases are treated with Daxiehu Tang (Major Bupleurum Decoction) to purge; severe cases select among the Three Chengqi Decoctions. Once stool passes, the Heat subsides. If the pulse comes Deep, Slow, and Weak, this is a Yin syndrome. One must then examine the external symptoms. Mild cases are treated with Lizhong Tang (Regulate the Middle Decoction); severe cases use Sheng Jiang and Fu Zi combined in Sini Tang (Frigid Extremities Decoction) to warm. The Floating, Middle, and Deep pulses are listed in diagrams below for careful study.

In Shanghan, Large, Floating, Rapid, Agitated, and Slippery pulses are Yang; Deep, Choppy, Weak, Wiry, and Micro pulses are Yin. However, pulse theory is profound, and beginners struggle to discern it. I believe that in Shanghan affecting humans, progressing from shallow to deep, first involving skin and muscles, then intestines, stomach, bones, and sinews, observing via Floating, Middle, and Deep pulses seems to leave no pathology hidden. These are arranged in three diagrams with notes on symptom treatment below, making Yin/Yang and Exterior/Interior easy to see. Let one know symptoms through pulses, understand treatment through symptoms, bridging concepts from coarse to refined, serving as a ladder for beginners. To explore the ultimate depths, one must diligently study the works of Zhang Zhongjing, thereby approaching the Dao."