ClipArt ETC
"a, axis cylinder; b, inner border of white substance; c, c, outer border of same; d, d, tubular membrane; B, tubular fibres; e, in natural state; f, under pressure; g, varicose fibres." — Richardson, 1906

Nerves

"a, axis cylinder; b, inner border of white substance; c, c, outer border of same; d, d, tubular membrane;…