F11: A higher power view of a rat sciatic (I think) nerve. No epineurium is seen here, but the perineurium is nicely stained. The cross-sectional appearance of myelinated axons is obvious. Note how well the perineurium surrounds ("insulates") the nerve bundle, but does not penetrate it. This is a key criterion for distinguishing peripheral nerve bundles from smooth muscle bundles under the light microscope.