NB: Look tube shape not opening shape.
Zone B: Cavity central side.
Canal: Pore modified by skeletal structure thikening or by lintels streching. Canal length is greater than perforation diameter.
Lintel: Skeletal structure separating and bounding adjacent pores/canals.
Carcass: Part of wall on intervallum side.
IW: Inner wall.
Constitution of carcass canal system (IW) | |_ Shape of carcass canals tubes zone B (IW)