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Huangdi asked Bo Gao, "The *Mai Du* (Pulse Length) chapter discusses the lengths of the meridians. How are these standards established?" Bo Gao replied, "First, measure the size, width, and length of the bone joints, and then the lengths of the meridians can be determined." Huangdi said, "I wish to hear about the measurements of ordinary people. For a person who is seven chi five cun tall, what are the sizes and lengths of their bone joints?" Bo Gao said, "The circumference of the large bones of the head is two chi six cun. The circumference of the chest is four chi five cun. The circumference of the waist is four chi two cun. From the top of the skull covered by hair to the nape of the neck, the length is one chi two cun. From below the hairline to the chin, the length is one chi. For gentlemen (whose hairline is typically higher), a comprehensive calculation is required. (*Jia Yi Jing* reads 'can zhe', likely because gentlemen's hairlines are higher than average, so the hair-covered part is less than one chi two cun, and the part from below the hairline to the chin is more than one chi, requiring mutual reference for calculation). From the Adam's apple to the center of Quepen (Sudocentral fossa, CV15 area), the length is four cun. From Quepen to Jiwei (CV15, below the xiphoid process), the length is nine cun. If this exceeds the standard, the Lung is large; if it falls short, the Lung is small. From Jiwei to Tianshu (ST25, two cun lateral to the umbilicus), the length is eight cun. If this exceeds the standard, the Stomach is large; if it falls short, the Stomach is small. From Tianshu to Henggu (pubic symphysis upper margin), the length is six chi half cun. If this exceeds the standard, the transverse intestine (small intestine) is wide and long; if it falls short, it is narrow and short. The length of Henggu is six chi half cun. From the upper border of Henggu to the upper border of the inner auxiliary bone (medial epicondyle of femur), the length is one chi eight cun. From the upper border of the inner auxiliary bone to its lower border (lower edge of medial tibial condyle), the length is three chi half cun. From the lower border of the inner auxiliary bone to the medial malleolus, the length is one chi three cun. From the medial malleolus to the ground, the length is three cun. From the knee to the tarsal connection (foot dorsum attachment), the length is one chi six cun. From the tarsal connection to the ground, the length is three cun. Therefore, if the bone circumference is large, it is excessive; if small, it is insufficient. From the armpit (Jiquan area) to the Zhu Gu (C7 spinous process), the length is one chi. The portion running through the axilla that is not visible, the length is four cun. From the armpit to the costal margin (12th rib end), the length is one chi two cun. From the costal margin to the Bi Shu (greater trochanter of femur), the length is six cun. From Bi Shu to the middle of the knee, the length is one chi nine cun. From the knee to the lateral malleolus, the length is one chi six cun. From the lateral malleolus to Jinggu (BL64, prominence of fifth metatarsal bone), the length is three cun. From Jinggu to the ground, the length is one cun. The width behind the ear at Wanggu (mastoid process) is nine cun. The width in front of the ear at Ermen (TE21) is one chi three cun. The distance between the two cheekbones is seven cun. The width between the two nipples is nine chi half cun. The width between the two thighs is six chi half cun. The foot is one chi two cun long and four chi half cun wide. From the shoulder to the elbow, the length is one chi seven cun. From the elbow to the wrist, the length is one chi two chi half cun. From the wrist to the proximal phalanx joint of the middle finger, the length is four cun. From this joint to the fingertip, the length is four chi half cun. From the hairline at the nape to the back bone (Dazhui GV14 area), the length is two chi half cun. From the spinal column (Lu Gu) to the tailbone, there are twenty-one segments, totaling three chi in length. The upper segment measures one and one-quarter cun per segment, with the remaining fraction attributed to the lower segments. Thus, the upper seven segments, up to the spinal column, total nine and seven-tenths cun. (Based on textual logic, the upper sentence should be one and one-quarter cun plus one-tenth, and the lower sentence should be nine and seven-tenths cun. The text is concise and obscure, and the numbers do not perfectly align). These are the bone measurements of ordinary people, which serve as the basis for establishing the lengths of the meridians. Therefore, when observing the meridians in the body: those that appear floating and firm have abundant Qi; those that appear bright and large have abundant Blood; those that are fine and deep have abundant Qi. (Logically, it should be interpreted that floating and firm indicates abundant Qi, bright and large indicates abundant Blood, and fine and deep indicates deficient Qi. However, the original text's meaning is also plausible, so I dare not arbitrarily change it).

This chapter primarily discusses *Mai Du* (Pulse Length), yet the entire text only describes *Gu Du* (Bone Length), with *Mai Du* mentioned only at the beginning and end. The concluding remarks take a sudden turn, appearing disconnected yet continuous with the preceding text, transforming the piled-up data into ephemeral clouds. Every sentence in the passage deals with concrete facts, yet simultaneously evokes an abstract realm. One must keep these firmly in mind and focus intently while reading; this establishes the foundation for understanding *Mai Du*, making every word seem to float in the air.