Numerous configurations are within the scope of the present invention, including elongate chambers, {HEAD ~ some} of which can be formed of {TAIL ~ a long, relatively narrow pipe} 
formed of
Numerous configurations are within the scope of the present invention , including elongate chambers , { HEAD ~ some } of which can be formed of { TAIL ~ a long , relatively narrow pipe }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL