{HEAD ~ The nontransparent hollow tube} has {TAIL ~ inner and outer surfaces} that define a wall of the hollow tube 
{ HEAD ~ The nontransparent hollow tube } has { TAIL ~ inner and outer surfaces } that define a wall of the hollow tube
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH