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In my youth, I studied the *Analects of Confucius* (Lunyu). When I reached the passage "Retire into obscurity to preserve one's principles, and practice righteousness to realize one's Way," I resolved in my heart, saying: "Should not a gentleman act thus? I wish to compare myself with such men."

I studied diligently for over twenty years but suffered repeated failures in the imperial examinations. Suddenly reflecting on myself, I realized that my talents were as useless as wild trees (Chuli), originally unfit to be pillars of the state. Why should I still exhaust my hair studying the classics, only to end up taking the童zi examinations?! Thus, I devoted myself to researching the *Ling Shu* (Spiritual Pivot) and *Su Wen* (Basic Questions)—the foundational texts of Traditional Chinese Medicine (TCM)—and set my mind on following Qi Bo and Huang Di (mythical founders of TCM). Although medicine is considered a minor art, it is sufficient to allow me to exercise my skills.

I perused the thirteen medical specialties as well as the works of the Hundred Schools of Thought, exploring the subtleties of each. However, regarding the category of *Shanghan* (Cold Damage Diseases), Zhang Zhongjing (Zhang Ji) regarded it as an acute and critical condition. He noted that a slight error in syndrome differentiation could lead to premature death. He documented 397 treatment methods and 113 formulas to benefit the world and future generations; his intention can be described as profoundly benevolent.

As for *Yizhen* (Plague Rash), its prevalence and severity are a hundred times greater than that of *Shanghan*. How could I bear to neglect it without discussion? Examining the historical context, perhaps there were no plagues at that time? Or perhaps Zhang Zhongjing’s original work consisted of sixteen volumes, but only ten volumes have been transmitted to the present day, meaning the section on plague rash was among those lost? Consequently, later physicians纷纷 established their own theories, following and modeling after previous authorities, all basing their arguments on *Shanghan*. Regarding the syndrome of *Reyi* (Heat Plague), they often neglected to discuss it. Therefore, practitioners recited and transmitted endless pages of text, all concerning *Shanghan*. Yet when facing clinical cases, they treated them solely using the methods for *Shanghan*, unaware that it was actually a plague. This malpractice penetrated deeply into society, becoming universal practice where ten thousand people used the same method. Ultimately, the dead did not know what disease killed them, and the living did not know what medicine could save them. Reflecting on the past, how can one express the depth of this sigh!

In the Jia Shen year of the Qianlong reign (1764 AD), while residing in Zhongzhou (Henan), my father contracted a seasonal plague. He was misdiagnosed and mistreated by a group of physicians. Upon returning home for the funeral, I examined their prescriptions and found they all adhered to only three methods. Filled with lifelong regret and boundless sorrow, I pondered: there must be a way to save lives from this syndrome. I decided to publish my findings to the world, also to alleviate my own inner distress.

Having read the Materia Medica (*Bencao*), I learned that Shi Gao (Gypsum Fibrosum) has a cold nature, capable of clearing stomach heat intensely; its flavor is light and thin, enabling it to release heat from the muscle layer; its texture is heavy and descending, allowing it to purge excess heat. I suddenly had a great enlightenment: without Shi Gao, it would be insufficient to treat Heat Plague. Whenever I encountered such syndromes, I administered it, achieving desired results effortlessly. For thirty years, I have been confident in this approach. The number of people I have saved whom others deemed incurable cannot be fully recorded in writing.

I privately reflect that one person’s capacity to heal is limited, but teaching others to heal is infinite. Therefore, presumptuously combining the theories of Si Tian (Heavenly Stems influencing climate), Da Yun (Great Movement), Zhu Qi (Principal Qi), and Xiao Yun (Minor Movement)—concepts from the Five Movements and Six Qi theory—I composed the book *Yi Zhen Yi De* (One Gain from Plague Rash). I offer these humble insights to the public, hoping that those in the world suffering from this plague may rise from death to life and all attain longevity, so that my heart might find some peace. Did I dare to write this book and establish theories merely to boast of my abilities?

Preface written by Yu Lin, styled Shiyu, of Tongxi, in the third month of spring, in the Jia Yin year of the 59th year of the Qianlong reign (1794 AD).