夫医之为道，民命死生所系，其责不为不重。籍或不经儒术，业擅偏门，懵然不知，正道不反，几于操刃以杀人乎！
粤自神农尝百药，制本草，轩岐着《素问》，越人作《难经》，皆所以发明天地人身阴阳五行之理，卓为万世医家祖，不
可尚已。厥后名医代作，蹑圣门而探玄微者，未易悉举。又若汉·张仲景、唐·孙思邈、金之刘守真、张子和、李东垣
辈，诸贤继作，皆有着述，而神巧之运用，有非常人所可及也。其所以辨内外、异攻补而互相发明者，一皆祖述《素》、
《难》而引伸触类之耳。其授受相承，悉自正学中来也。吾邑丹溪朱彦修先生，初游许文懿公之门，得考亭之余绪。爱
自母病，刻志于医，求师于武林罗太无，而得刘、张、李三家之秘，故其学有源委，术造精微。所着《格致余论》、《局
方发挥》等编，皆所以折衷前哲，尤足以救偏门之弊，伟然百世之宗师也。东阳卢和氏类集丹溪之书为《纂要》，俾医者
出入卷舒之便，其用心亦勤矣，以愚观之，犹未足以尽丹溪之余绪。然丹溪之书，不过发前人所未发，补前人所未备耳，
若不参以诸贤所着，而互合为一，岂医道之大成哉。愚承祖父之家学，私淑丹溪之遗风，其于《素》、《难》，靡不苦志钻
研，然义理玄微，若坐丰 ，迨阅历四纪于兹，始知蹊径。今年七旬有八矣，桑榆景迫，精力日衰，每憾世医，多蹈偏
门，而民命之夭于医者不少矣。是以不揣荒拙，锐意编集，以成全书，一皆根据乎《素》、《难》，综横乎诸说，傍通己意，
而不凿以孟浪之空言，总不离乎正学范围之中，非敢自以为是，而附会以误人也，目之曰∶医学正传，将使后学知所适
从，而不蹈偏门以杀人，盖亦端本澄源之意耳。高明之士，幸毋诮焉。
时正德乙亥正月之望，花溪恒德老人虞抟序。
The Way of Medicine is closely tied to the life and death of the people; its responsibility is indeed heavy. If a practitioner has not undergone Confucian scholarly training but instead specializes in heterodox methods, remaining ignorant and unaware of the orthodox path, would this not be akin to wielding a blade to kill?
Since Shennong tasted hundreds of herbs and compiled the *Bencao* (Compendium of Materia Medica), and since Huangdi (Yellow Emperor) and Qibo authored the *Suwen* (Basic Questions), while Bian Que (Qin Yueren) wrote the *Nanjing* (Classic of Difficult Issues), all were intended to elucidate the principles of Yin-Yang and Five Elements within Heaven, Earth, and the human body. They stood out as the ancestral founders of medical practitioners for ten thousand generations, a status beyond compare. Since then, famous physicians have emerged generation after generation; those who followed the gates of the Sages to explore profound mysteries are too numerous to list completely. Furthermore, figures such as Zhang Zhongjing of the Han Dynasty, Sun Simiao of the Tang Dynasty, and Liu Shouzhen, Zhang Zihe, and Li Dongyuan of the Jin Dynasty, among other sages, succeeded each other in producing writings. The divine and skillful application of their arts was beyond the reach of ordinary people. The reason they could distinguish between internal and external causes, differentiate between attacking (purging) and tonifying methods, and mutually illuminate these concepts, was entirely based on following the *Suwen* and *Nanjing* and extending their principles through analogy. Their transmission and inheritance all originated from orthodox learning.
Mr. Zhu Yanshou (Zhu Danxi) of our county first studied under Mr. Xu Wenyi, inheriting the legacy of the Kaoting (Zhu Xi) school. Loving his mother's illness, he dedicated himself to medicine, seeking instruction from Luo Taiwu in Wulin (Hangzhou), thereby obtaining the secrets of the three schools of Liu, Zhang, and Li. Thus, his learning had clear origins and developments, and his techniques reached subtlety and precision. His works, such as *Gezhi Yulun* (Further Discussions on Investigating Things) and *Jufang Fahui* (Exposition of the Standard Formulary), were intended to reconcile the views of former philosophers and were particularly sufficient to remedy the defects of heterodox methods, making him a grand master revered for a hundred generations. Lu He of Dongyang compiled Zhu Danxi’s books into the *Zuoya*, facilitating convenient reading for practitioners; his diligence was considerable. However, in my opinion, this still does not fully exhaust the remnants of Zhu Danxi’s scholarship. Nevertheless, Zhu Danxi’s writings merely expounded what predecessors had not yet expressed and supplemented what they had not yet prepared. If one does not integrate the works of various sages and merge them into one, how can it be considered the great completion of the medical way?
I inherited the family learning of my ancestors and privately admired the legacy of Zhu Danxi. Regarding the *Suwen* and *Nanjing*, I did not cease from ardent study. However, the principles were profound and subtle; initially, I felt like sitting in abundance yet finding no direction. It was only after forty years of experience that I finally understood the path. Now at seventy-eight years old, with twilight approaching and energy declining daily, I often regret that many contemporary physicians fall into heterodox paths, resulting in many lives lost due to medical errors. Therefore, without presuming upon my own clumsiness, I resolutely compiled this collection to complete the book. Its content is entirely based on the *Suwen* and *Nanjing*, comprehensively integrating various theories, incorporating my own insights, avoiding empty talk, and staying strictly within the scope of orthodox learning. I dare not claim correctness nor attach false interpretations to mislead others. I titled it *Yixue Zhengzhuan* (Orthodox Transmission of Medical Learning), intending to guide later learners to know where to direct themselves, so as not to tread into heterodox paths and cause harm. This is essentially an effort to rectify the root and clarify the source. I hope learned gentlemen will not ridicule me.
On the fifteenth day of the first month of the Yihai year of the Zhengde era, Yu Tun, the Old Man Hengde of Huaxi, wrote the preface.