(Chapter 39) Footnote 25:
First attested in TLG as an adjective (perio/steoj xitw/n) in Rufus Ephesius (1-2 c. AD) De corporis humani appellationibus 130.1; similarly in Galen De anat. adm. 2.591.18, Pseudo-Galen Definitiones medicae 19.367.10 Perio/steoi u(me/nej ei)si\n ei)lu/mata lepta\. Its evolution into a neuter noun is apparently post-classical. Following his program of Latinization, Vesalius deletes the Greek in the 1555 edition and substitutes “which we call circumossalis.” But no English form of this word is cited by OED or the medical dictionaries.