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