Leijing 類經

Leijing 類經 "Book of [medical] categories" is a general book on medicine written during the late Ming period 明 (1368-1644) by Zhang Jiebin 張介賓 (1563-1640), courtesy name Jingyue 景岳 or Huiqing 會卿, style Tongyizi 通一子, from Shanyin 山陰 (today part of Shaoxing 紹興, Zhejiang).

As a youth, he travelled with his father, where he pursued his studies and apprenticed under the renowned physician Jin Ying 金英 (also known as Jin Mengshi 金夢石), from whom he thoroughly learned the art of medicine. He devoted several decades to the study and practice of medicine, making it his profession and becoming a famous physician of the time. He also wrote the books Leijing tuyi 類經圖翼, Leijing fuyi 類經附翼 and Zhiyilu 質疑錄. Many of his works are assembled in the collection Jingyue quanshu 景岳全書.

A primary feature of Zhang's medical thought is the development of the idea that medicine and the Classic Yijing 易經 "Book of Changes" share the same origin. In his work Leijing fuyi, he writes that although the principles of Yin and Yang were already fully articulated in the medical classic Huangdi neijing 黃帝內經 "The Yellow Emperor's Inner Canon", no text captures change more profoundly than the Zhouyi 周易 (i.e., the Yijing). Zhang held that every word and phrase in the Yijing holds guidance for medicine; every symbol and line reflects the intent to cherish life. The The Yijing contains the principles of medicine, and medicine gains its application through the Yijing.

Another major contribution is his theory on the Yin-Yang dynamics of the Gate of Life (mingmen 命門). Zhang believed the mingmen is located "between the two kidneys, and is the Taiji 太極 "Supreme Ultimate" of the human body. He drew an analogy to the hexagram Kan ☵坎 in the Yijing: the upper and lower broken lines represent Yin — the two kidneys — while the solid line in the middle represents Yang — the mingmen. The mingmen, he emphasised, is essential to life and transformation, and is the very root of vitality. The fire of the mingmen is referred to as "original ether" (yuanqi 元氣), the "true Yang" (zhenyang 真陽) while the water of the mingmen is known as "original essence" (yuanjing 元精), or "true Yin" (zhenyin 真陰).

In treating illness, one must seek the root cause, and the preservation of true Yin and true Yang must not be compromised. If the Gate of Life is depleted, then "the five viscera and six bowels" (wuzang liufu 五臟六腑) lose their support, and imbalances of Yin and Yang can give rise to all kinds of disorders. On this basis, Zhang established the important therapeutic principle of "nourishing the root with sweet-warm methods" (gan-wen gu ben da fa 甘溫固本大法). He believed that to treat disease, one must focus on the physical body; and to treat the body, one must first replenish essence and blood (fan yu zhi bing zhe, bi xi xingti wei zhu; yu zhi xing zhe, bi yi jingxue wei xian 凡欲治病者，必以形體為主，欲治形者，必以精血為先). In clinical practice, he frequently employed warm-tonifying formulas, which had a significant influence on later generations of physicians.

The Leijing, with a length of 12 juan, was completed in 1624. It is a major work dedicated to the categorized study of the "Inner Canon of the Yellow Emperor" (Huangdi neijing).

Zhang believed that the Neijing was "profound and intricate in its classical language, but truly difficult to study." With the intention of "illuminating the obscure and turning the difficult into the accessible", he adopted a method of "completely breaking from the old structure, rearranging the content, organizing it by category, and then elaborating on the meanings."

He extracted the original texts of the Suwen 素問 and Lingshu 靈樞 parts of the Neijing and reorganized them into twelve thematic categories: health preservation (Shesheng 攝生), Yin-Yang (Yinyang 陰陽), visceral manifestation theory (Zangxiang 臟象), pulse and complexion (Maise 脈色, meridians and collaterals (Jingluo 經絡), root and branch (Biaoben 標本), flavors and "ether" (Qiwei 氣味), therapeutic discussions (Lunzhi 論治), diseases (Jibing 疾病), acupuncture (Zhenci 針刺), movement of ether (Yunqi 運氣), and comprehensive correlations (Huitong 會通). The text consists of over 360 entries grouped by "subject" (lei 類), hence the title Leijing.

The book's structure is well-organized and clearly outlined. In addition to categorizing the Neijing by subject, Zhang also provided commentary and annotations beneath each original passage, offering critiques of earlier interpretations and presenting his own insights. Drawing from clinical practice, he introduced many original ideas, which earned the work high praise from later generations. Moreover, he integrated the two classic texts Lingshu and Suwen, providing comprehensive annotations to both. He used the Lingshu to illuminate the subtleties of the Suwen, and the Suwen to reveal the hidden meanings of the Lingshu, showing how the two texts complement and explain one another. This approach has been of great assistance to students and scholars studying the Neijing, making the Leijing one of the finest and most respected annotated editions among the many commentaries on the Huangdi neijing.

The book was first printed in 1624. The Hongdao Studio 宏道堂 reproduced this print in 1840. The text is also included in the imperial series Siku quanshu 四庫全書.