Engaging in the treatment of Shanghan (Cold Damage) with specialized expertise is indeed a heavy responsibility. Judging life and death is as easy as turning one's hand; do not seek profit recklessly. For miscellaneous diseases, one may slowly select prescriptions, but for Shanghan, one must rely on flexible and adaptive methods.

Originally, there were texts on Shanghan such as *Huoren Shu* (Book of Living People), *Mingli Lun* (Theory Clarification), *Zhizhang Tu* (Palm-Guiding Diagram), and *Shanghan Lun* (Treatise on Cold Damage). Among these, some have discussions but lack formulas, some have formulas but lack discussions, some have pulse descriptions but lack symptom records, and some have symptoms but lack treatment methods; none of these constitute Zhang Zhongjing's complete work. Due to the long passage of years, much has been lost. Wang Shuhe supplemented formulas and wrote discussions based on fragmented bamboo slips, and Cheng Wuji annotated the text according to its flow to compile a complete book; thus, the resulting errors and harms persist to this day.

Compare this with how mediocre physicians today treat Shanghan: within one or two days, without distinguishing between deficiency (Xu) and excess (Shi) patterns, they immediately use sweating methods like Mahuang Tang (Ephedra Decoction) or Guizhi Tang (Cinnamon Twig Decoction); within three or four days, without determining whether the pathogen is in the meridians (Jing) or fu organs, they immediately use harmonizing methods like Xiaochaihu Tang (Minor Bupleurum Decoction); within five or six days, without assessing whether the pathogen is in the exterior (Biao) or interior (Li), they immediately use purgative methods like Chengqi Tang (Gut-Clearing Decoction). This leads to both interior and exterior depletion, causing a swarm of complicated changes (Bian Zheng). Generally, patients differ in their exterior-interior and deficiency-excess states, and the transmission of pathogens varies; how can one rely solely on the number of days?

Generally, wind-cold invasion has no fixed pattern; it may enter Yin meridians or Yang meridians. The situation lacks a fixed form, contradicting the simplistic theory that it always starts in Taiyang and ends in Jueyin. Some cases start in Taiyang, transmitting one meridian per day, reaching Jueyin by the sixth day, where the pathogen weakens and stops transmitting, leading to recovery. Others may transmit repeatedly after stopping, transmit immediately, skip meridians, stop after transmitting to two or three meridians, remain confined to one meridian throughout, or transmit across meridians irregularly. Some enter Shaoyin directly from Taiyang without generating stagnant heat, becoming true Yin-cold syndromes. Some strike the Yin meridians directly causing cold syndromes. Symptoms may change, pulses may change, some rely only on symptoms ignoring pulses, others only on pulses ignoring symptoms. Because the classics lack explicit rules, later practitioners have made reckless treatment errors. Moreover, deviations in earlier established laws have harmed many later generations.

Mahuang Tang and Guizhi Tang were established by Zhang Zhongjing specifically for treating "Zheng Shanghan" (True Cold Damage) occurring in winter. Today, people mistakenly use them universally for non-seasonal sudden cold, warm diseases, and summerheat. Furthermore, conflating transmitted Yin syndromes with direct-strike Yin syndromes in theoretical discussions is unwise. Non-seasonal cold, warm diseases, and summerheat require distinct formulas; direct strikes and transmissions into Yin require flexible methods, yet these are now forgotten and unverified. Ancient books guide successors, but books cannot fully express meaning, nor words fully express intent; they provide general outlines. While being knowledgeable about the past and present is good, true mastery lies in receiving the authentic transmission and applying it dynamically.

The so-called "flexible method" is like a pearl rolling on a plate: if you see Taiyang syndrome, attack Taiyang directly; if you see Shaoyin syndrome, attack Shaoyin directly. This is flexibility. Zhang Zhongjing also stated: Even if many days have passed, if exterior signs exist and the pulse is floating, sweating is particularly appropriate. Even if few days have passed, if interior signs exist and the pulse is deep, purging is particularly appropriate. This is the definitive view of former sages. One must not rigidly adhere to releasing the exterior on days 1-2, harmonizing on days 3-4, and purging on days 5-6. This is the dead-handed approach of mediocre doctors. One must carefully examine pulses and verify symptoms, distinguish names, and determine meridians with absolute clarity before acting. Truly knowing it is an exterior pathogen, use sweating; truly knowing it is an interior pathogen, use purging; truly knowing it is a direct strike, use warming. Thus sweating, thus purging, thus warming: Guizhi Tang and Chengqi Tang will be applied without error; Jiangfu Tang (Ginger and Aconite Decoction) and Lizhong Tang (Regulate the Middle Decoction) will yield certain efficacy. A slight deviation in dosage leads immediately to fatal syndromes; can one fail to think deeply and consider thoroughly?

Zhang Zhongjing was very strict in selecting formulas and establishing principles, using terms like "can be warmed," "can be sweated," "give sparingly," and "urgently purge." He also discussed warming the interior first then attacking the exterior, or releasing the exterior first then attacking the interior. Those who grasp the outline find it easy. It becomes like an echo following a sound, or a shadow following a form; seeing a patient brings immediate understanding, and consulting colleagues brings ease. Those lacking true transmission find it difficult. Seeing a patient, they are at a loss; facing colleagues, they blush and remain silent. This is like embroidering a qilin—having nominal prestige but lacking substantive virtue. Alas, using standard methods for common diseases is known by everyone. However, consider those who mistake non-seasonal sudden cold for True Shanghan; those who mistake labor-induced cold for True Shanghan; those who treat miscellaneous diseases resembling Wind-Cold as Shanghan; those who mistake direct-strike Yin-cold syndromes for transmitted Heat syndromes; those who treat Warm Diseases as True Shanghan; those who treat Summerheat as Shanghan; those who mistake agitation resembling madness for actual mania; those who mistake blood-related jaundice for Damp-Heat jaundice; those who mistake mosquito bites for macules; those who mistake Yin-blood disturbance for epistaxis; those who mistake delirium for manic speech; those who mistake solitary muttering for confused speech (Zheng Sheng); those who mistake post-coital relapse (Nu Lao Fu) for Yin-Yang exchange; those who mistake shortness of breath for panting; those who mistake fullness/stuffiness for chest binding (Jie Xiong); those who mistake lower abdominal hardness with pure watery diarrhea (colloquially called "leaky bottom") for other conditions; those who mistake hiccups for dry heaving; those who mistake concurrent diseases (Bing Bing) for combined diseases (He Bing); those who mistake Yangming Fu organ disease for Yangming Meridian disease; those who see no pulse in Taiyang syndrome and declare it fatal; those who mistake interior aversion to cold for exterior aversion; those who mistake exterior heat for interior heat; those who mistake Yin-restlessness for Yang syndromes; those who mistake fever in Shaoyin disease for Taiyang syndrome; those who understand neither root nor branch. These cases of lifelong misidentification are commonplace. If one does not clarify symptoms and pulses in mind, and fails to master formula selection, merely joining mediocre practitioners in reckless treatment is killing without a blade. Not only is saving lives a great merit, but the hidden virtue is significant. I am old. My specialization in Shanghan truly captures the essence of Master Zhang Zhongjing. Though not infallible, I save eight or nine out of ten. Having written books previously, I could not pour my heart and soul into them. Now, fearing that successors will lose the transmission and tarnish our reputation due to my advanced age, I record here the insights of my life, family secrets, and techniques such as "Ti Jin" (Lifting Gold) and "Sha Che Chui" (Killing Cart Hammer). I discuss symptoms via theories, theories via pulses, pulses via methods, and methods via formulas. I earnestly instruct my descendants: do not collect random formulas or read scattered theories that lead to confusion without knowing the source. Memorize diligently; over time, precision will come naturally. Do not associate with mediocre doctors; avoid ridicule by contemporary practitioners. Treasure and transmit this carefully, with caution and diligence, never neglecting it. This is my warning.