晦庵朱子跋郭长阳医书云∶“予尝谓古人之于脉，其察之固非一道矣。然今世通行，惟寸、关、尺之法为
最要，且其说具于《难经》之首篇，则亦非凭空结撰也。故郭公此书，备载其悟，而并取丁德用密排三指之法
以释之。夫《难经》蔓
乎尚已，至于丁德用之法则，余窃意诊者之指有肥瘠，病者之臂有长短，以是相求，或未为定论也。盖尝考经
之所以分尺寸者，皆自关而前却是。则所谓关者，必有一定之处，亦若鱼际，尺泽之可以外见而先识也。然考
诸书，皆无的论，惟《千金方》内，以为寸口之处，其骨自高，而关尺由是而却取焉。则其言之先后，位之进
退，若与经文相合。独俗间所传《脉诀》，五七韵语，其词浅陋，非叔和本书明甚，乃能直指高骨为关，而分
其前后，以为尺寸阴阳之位，似得《难经》本旨。余非精于道者，不能有以正也，姑附于此，以俟明者而折衷
焉。”按《内经》十八卷，即三坟古书，既未经孔子删定，复未经朱子集注，医喙争鸣，互相排诋，分门别户，
莫知适从。独指高骨为关，以定尺寸，得朱子之跋，而脉之部位始得其准。
高骨为关，从关至鱼际得一寸（脉浮九分），而寸以名；从关至尺泽得一尺（脉见一寸），而尺以名。
以关为间隔，而尺寸不得混为一家。合寸、关、尺为三部，其解最为直捷，不得曲为分晰。
Zhu Xi (Hui'an) wrote a postscript for Guo Changyang's medical book, stating: "I have often said that the ancients employed various methods to examine the pulse. However, among those currently in common use, the method of locating Cun (Inch), Guan (Bar), and Chi (Cubit) is the most important. Furthermore, this theory is presented in the first chapter of the *Nan Jing* (Classic of Difficult Issues), so it was not fabricated out of thin air. Therefore, Mr. Guo's book comprehensively records his insights and adopts Ding Deyong's method of closely arranging three fingers to explain it. The *Nan Jing* has been transmitted for a long time. Regarding Ding Deyong's method, I privately speculate that since the examiner's fingers vary in thickness and the patient's arms differ in length, using these variables to seek correspondence may not constitute a definitive conclusion. I have examined the classics regarding the distinction between Cun and Chi; both are calculated forward from the Guan position. Thus, the 'Guan' must have a fixed location, similar to how Yuji (LU10) and Chize (LU5) can be visually identified externally beforehand. However, consulting various texts reveals no definitive discussion. Only within the *Qian Jin Fang* (Essential Prescriptions Worth a Thousand Gold) is it stated that at the Cun Kou (Radial Pulse) site, the bone is naturally higher, and the Guan and Chi positions are determined backward from there. This sequence of description and the advancement/retreat of positions seem to align with the classic text. Uniquely, the popularly circulated *Mai Jue* (Pulse Rhymes), consisting of five- or seven-character verses, contains shallow and vulgar language, clearly not Wang Shuhe's original work, yet it directly points to the high bone as the Guan, dividing the anterior and posterior into Cun and Chi yin-yang positions. This seems to capture the original intent of the *Nan Jing*. As I am not an expert in this Dao, I cannot correct it, but I attach it here to await judgment by those more enlightened." According to the eighteen volumes of the *Nei Jing* (Inner Canon), which are ancient books akin to the San Fen, having neither been edited by Confucius nor annotated by Zhu Xi, physicians argue and clash, mutually disparaging each other, forming separate schools, leaving people unsure whom to follow. Only by identifying the high bone as the Guan to determine the Cun and Chi positions, corroborated by Zhu Xi's postscript, did the pulse locations finally find accuracy.
From the Guan to Yuji (LU10) measures one Cun (pulse superficially taken at nine fen), hence named 'Cun'; from the Guan to Chize (LU5) measures one Chi (pulse visible at one Cun), hence named 'Chi'. With Guan serving as the separator, Cun and Chi are prevented from being conflated. Combining Cun, Guan, and Chi into three sections offers the most direct explanation, precluding need for convoluted analysis.