基於身體觀的不同，同一部位的古今命名與所指範圍可能有別。在複雜的人體系統中，下肢的層次分明，編碼詳細，複雜度高，反映現象多，與其他部位相較，是觀察身體認知的好窗口。本文以宋代檢驗書《洗冤集錄》為起點，因該書是成系統、有次第、有根據地細載人體各部位，詳細勾勒古人心中的人體圖像。該書的下肢詞編碼充分展現認知的運作，如下肢與上肢、軀幹發生隱喻；下肢可轉喻骨骼；下肢出現模糊指稱。其下肢系統的價值是：1.展現歷史詞與新興詞、通語與方言詞揉雜的多元局面。2.紀錄眾多脚類與足類詞，以茲辨析異同，留下競爭軌跡。3.「四縫屍首」被宋代驗狀、後代尸帳與屍圖承襲，為檢驗的藍圖，後代據此再明示須細檢的部位。

Due to differences of views on body, the names and parts of the same person's body parts in ancient and modern times can vary. In a complicated human body system, the lower extremity shows specific levels, detailed codes, and high complexity, which reflect an overall phenomenon. In comparison to other parts, it is a proper medium to observe physical cognition. This study focuses on ＂Xi Yuan Ji Lu＂, which is an inspection book in the Song Dynasty, because the book is systematic, organized, and properly recorded the parts of the human body and pictured ancient people's human body images in great detail. We found that codes of lower extremity in ＂Xi Yuan Ji Lu＂ fully demonstrate the operation of cognition, such as metaphors among the lower extremity, upper extremity and body; the terms for the lower extremity are metonymy of bones, while they also show ambiguous names. The value of the lower extremity system in the book is shown as follows: (1) It reveals diversity with a combination between historic and new terms, and general language and dialect. (2) It records numerous terms of leg and foot to analyze the difference and similarity as traces of competition. (3) The human body term ＂four parts of body＂ is followed by an inspection paper in the Song Dynasty and a body record and body picture in a later period. It is a blueprint for inspection. Based on this blueprint, the follow-up generations indicate lower extremity parts, which require further examination.