perineurium

from WordNet (r) 3.0 (2006)

perineurium
    n 1: the sheath of connective tissue that covers a bundle of
         nerve fibers

from The Collaborative International Dictionary of English v.0.48

Perineurium \Per`i*neu"ri*um\, n. [NL., fr. Gr. peri` about +
   ney^ron a nerve.] (Anat.)
   The connective tissue sheath which surrounds a bundle of
   nerve fibers. See {Epineurium}, and {Neurilemma}.
   [1913 Webster]