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The subtlety of medicine is more difficult to master than the civil service examinations. Vulgar scholars busy themselves daily with reciting classics; they begin studying in childhood but remain bewildered until their hair turns white, amounting merely to self-neglect. In contrast, physicians bear the responsibility for life and death. A scholar who fails to read widely, remaining ignorant and silent, may still escape criticism. However, if a physician has limited exposure and lacks internal certainty, it will be extremely difficult to manage patients clinically, let alone achieve therapeutic efficacy! Therefore, those engaged in medicine must strive for mastery.

I (Cheng Zhongling) was prone to illness from childhood and had been confined to bed several times. I thus deferred my pursuit of official rank, spending each day handling medicinal packages, thereby familiarizing myself with drug properties. By perusing ancient and modern medical texts, I grasped their general principles. After participating in the provincial examinations, I traveled north to Yan, where my health improved slightly and my medication decreased, causing my engagement with medical arts to gradually wane. Later, engrossed in administrative paperwork and hurried postal duties, with little food and scarce leisure, I almost forgot what medicine was. Recently returning home from Qinghai, I conversed daily with elders in my hometown. I often heard that families seeking medical help found doctors unable to cure them. Surprised by this, I inquired about their treatments and found that practitioners applied attacking, tonifying, warming, or cooling methods without consistent judgment, treating patients as experiments. This was likely due to a lack of clarity regarding pulse and syndrome differentiation. As I am not a specialist and have not fully penetrated the crux of these issues, I remained silent yet harbored deep concern, hoping to find guidance from a learned gentleman. Within my limited vicinity, my horizons could not expand, so I could only study the works of former sages diligently, striving for understanding, yet still failing to achieve absolute conviction without doubt. This spring, my teacher Master Xi San returned, stating that Mr. Cheng of Guanquan Village in Yanzhen was a renowned scholar-physician. Yearning to meet him, I visited. He was gentle and sincere; we felt like old friends upon meeting. He showed me his two volumes of *Poetry Collection* and three volumes of *Medical Cases*, and allowed me to read his sixteen-volume work, *Yi Shu* (Record of Medicine). Through this, I further recognized his scholarship: drawing extensively from distant sources, extracting essences, broad yet concise, truly capable of revealing the profound mysteries of predecessors and serving as a bridge for future learners. Indeed, the Way of Medicine is great!

Medicine embodies Yin-Yang and the Five Elements, resonating with the *I Ching* (Book of Changes) and texts on human nature and principle; it distinguishes the climates and customs of the five directions, aligning with the *Rites* (*Zhou Li*) and systems of governance; it observes pulse and syndrome manifestations of cold, heat, deficiency, and excess with rigor surpassing that of judicial case reviews; it establishes formulas for attacking, tonifying, harmonizing, and resolving, bearing weight comparable to military campaigns. It is certainly not a subject for those with shallow views and narrow knowledge! Mr. Cheng has synthesized decades of textual research, adhering to and expounding upon ancient methods without being bound by them. Whatever previous authors stated hit the mark precisely, he arranged them systematically, categorized them, and presented them with solemnity and thoroughness. The *Book of Rites* states: "If a physician's lineage does not extend back three generations, do not take their medicine." Here, "three generations" refers to books from the era of the Three Sovereigns. Mr. Cheng traces back to Huangdi (Yellow Emperor) and Qibo, and down through the Han, Tang, Song, and Ming dynasties, integrating all schools of thought into his mind. He speaks originally and faithfully, going far beyond mere "three generations." If he were to apply this approach to the civil service exams, he would undoubtedly have stood out uniquely among his contemporaries long ago. Yet, I foolishly believe that his merit in saving lives and extending longevity through benevolent heart and skill is ultimately greater and more enduring. Respectfully inscribed.

On the third day before the Winter Solstice in the Dinghai year of the Daoguang reign, humble student Zhu Zhong respectfully composed.