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Heaven has six Qi (vital energies): Yin, Yang, Wind, Rain, Obscurity (darkness), and Clarity (light). If these six Qi become excessive, they cause disease, manifesting as Cold diseases, Heat diseases, Extremity diseases (disorders of the limbs), Abdominal diseases, Confusion diseases (disorders of mental clarity), and Heart diseases. The flow and circulation of Qi and Blood in the human body follow specific paths: there is circulation, meridians, arrival points, convergence points, passing points, pathways, and destinations. Additionally, there are 305 Silk Collaterals (fine network vessels) and 647 Tunnel Acupoints (acupuncture points).

Medicine is not so superficial that the learning of ordinary people can exhaust its secrets. Today, there are many who speak of medicine among us, yet where can one find someone who shares a tacit understanding with the Great and Small aspects of Yin and Yang, and who can clearly discern the circulating changes of the Six Pulses and Two Meridians, to discuss with them the appropriateness of prescriptions and herbs from the *Suwen* (Plain Questions) and other classics, the effects of attacking and tonifying methods, the transformations of deficiency and excess, and the techniques of acupuncture and moxibustion? I have often thought that such persons are hard to come by; those known for their medical skills are numerous, but those renowned as famous physicians are few.

*Yixue Zhengzhuan* (Correct Transmission of Medicine) was authored by Elder Hengde, the great-uncle of Yu Gong Shuzu of Dongya, who served as an Imperial Censor. By observing this book, one can understand the author. Mr. Dongya proofread the book, and Jiang Gong of Zhitian, also an Imperial Censor, wrote the preface. I delighted in reading this book, believing I had found a worthy person. However, after reading it for a long time, I felt it was not solely authored by Elder Hengde. His ambition was to attach himself to the lineage of famous masters; thus, his work is a compilation of the achievements of various schools, integrated into one. Affairs in the world can generally be used to test one's ability, but medicine cannot be practiced relying solely on personal cleverness. From Fuxi and Shennong until now, thousands of generations and countless hands have contributed, yet only through mutual respect, narration, transmission, and practice did these texts achieve widespread circulation. There were hardly any who relied solely on their own abilities to promote themselves. Hence it is said: "If a physician does not represent three generations of tradition, do not take his medicine." Regarding this book, if it were entirely the product of Elder Hengde's mind, expressing ideas from memory and holding personal views on decoctions, I would dare not consider it entirely satisfactory. Only by referencing the secrets of various schools and judging them with true wisdom can he grasp the mechanisms of vital Qi, assist Yin and Yang, and unblock meridians, all of which have received transmission. Thus, his words, left for posterity, can undoubtedly be transmitted alongside the classic texts. I certainly delight in *Yixue Zhengzhuan* for its broad scholarship and precise selection. Broad scholarship provides a basis; precise selection yields insight. With a basis, prescriptions and herbs will surely be appropriate; with insight, therapeutic attacks will surely be effective. Diseases under heaven generally do not fall outside this scope. Those in the world who study this book and transmit its formulas will surely achieve perfect efficacy. Therefore, this book can be transmitted. Dongya requested my words, so I have written this summary to present to today's renowned physicians.

Recorded by Shi Wu of Putian, on an auspicious day of mid-spring in the Xinmao year of the Jiajing reign of the Ming Dynasty.

*Yixue Zhengzhuan* is a book composed by Elder Hengde, inheriting the legacy of Master Danxi. Mr. Yixi trusted and cherished it greatly, so I, as his disciple, lectured and read it to him. Errors in characters and strokes were corrected by consulting books. Omissions and deletions in the text were supplemented by comparing several editions. Still ashamed of the many omissions and errors, I hope that future scholars interested in medicine will revise it. This would be most fortunate.

On the full moon day of the ninth month, autumn, in the year Jiachen (9th year of Keichō), Enjuu Gensaku.