{HEAD ~ a first opening} in surface portions thereof adjacent said free extremity and in {TAIL ~ communication} with said passageway, 
{ HEAD ~ a first opening } in surface portions thereof adjacent said free extremity and in { TAIL ~ communication } with said passageway ,
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH