Library

Xu Chang naturally loved medicine. In his youth, during breaks from reading classics, he sought out the writings of famous physicians. He observed that external diseases (Wai Zheng) and pediatric smallpox/rubella conditions (Xiao'er Dou Zheng) could determine life or death in an instant, unlike internal diseases (Nei Zheng), which allowed for delay and waiting for treatment. Hearing that Mr. Zhou Shuxuan from Dongtai was proficient in medical arts, Xu Chang went to study under him. After more than ten years of deep investigation and refined thinking, he grasped the general outline.

Subsequently, he obtained Zheng Xibin's *Dou Zheng Bi Du* (Essential Reading on Smallpox/Rubella). Although it gathered fragments into a whole like collecting armpit fur to make a coat, its categorization was clear, making the content easy to understand at a glance. He also obtained the manuscript of Geng Renzhai's *Ma Ke Ming Jing* (Clear Mirror of Measles) from the previous Ming Dynasty. Regrettably, it was more than half incomplete. Xu Chang added missing parts, deleted redundancies, and divided it into four sections for easier learning. Both books were printed and circulated. However, regarding books on external diseases, there are countless volumes (described as "filling oxen with books and filling cows with manuscripts"), yet many are biased, while few are balanced and accurate.

A colleague named Bi Canglin authored *Wai Ke Zheng Zhi* (Treatment of External Diseases), providing thorough explanations that greatly benefited the field. However, Bi had only completed two volumes before dying at the age of thirty, leaving the manuscript abandoned. Although not particularly intelligent, Xu Chang extensively collected evidentiary studies on external diseases by various masters and sought effective prescriptions. He established simplified guidelines for carbuncles and sores (Yong Ju Jiu Jian) at the beginning of each disease section, distinguishing between Yin and Yang, Zang-Fu organs, and meridians to accurately diagnose and treat.

After more than twenty years of clinical trials, his diagnoses and prescriptions achieved consistent efficacy. Patients came from all directions every day without fail. He further added five categories: Internal Scenery (Nei Jing), External Causes (Wai Yin), Strange Conditions (Qi Zheng), Gu Poison (Gu Zheng), and Poisoning (Zhong Du), attaching verified prescriptions to the end of the book for emergency use, thus completing five volumes. He did not dare to present this to the world, but merely kept it to prevent forgetting.

Xu Chang recorded this himself.

A physician with learning is a physician with experience. In ancient times, surgery had specialized practitioners but no specialized books; thus, experience was particularly crucial. There were over a dozen authors from the Han and Tang dynasties, but most works have been lost. The *Waitai Miyao* (Secret Essentials of the Outer Terrace) is the most detailed. However, its content is profound and complex, difficult to comprehend. Moreover, times and circumstances change; even if prescriptions are recorded, some may be too expensive and suddenly unobtainable, while others are very cheap but their names are unrecognized. Therefore, those who master and apply them are increasingly rare. Since then, sources have diverged, leading to diverse treatments. Most renowned specialists advanced from experience to learning.

The recent book *Wai Ke Zheng Zhi* does not offer high-flown theories but starts with Yin-Yang deficiency and excess. Its methods aim for brevity, and its formulas strive for balance and harmony. It deeply draws from Wang's *Quan Sheng Ji* (Complete Life Collection), deleting redundancy and supplementing deficiencies, nearly achieving clarity and completeness. Reading it reveals the correct approach; using it yields results. Compared to other books that merely dazzle with titles or luxuriously expound ancient meanings without practical daily application, this book stands apart.

Since Cao Jian'an from Wujin published *Yang Yi Ya Yan* (Elegant Words on Surgeon Medicine), the *Qian Jin Fang* (Thousand Gold Formulas) and *Waitai Miyao* can be clarified again in the world. Only the schools after the Song Dynasty are dismissed as inferior (compared to figures below Qin Hui). Now, taking this book as the standard (arrowhead), learning becomes experience, and experience becomes learning. Tracing the stream to its source eliminates regrets. I briefly record the general idea to inform those in the world who are devoted to this path.

Tu Renshou from Xiaogan wrote this in his residence in Chengdu in the winter of the Yichou year of the Tongzhi era.