{HEAD ~ an elastic membrane} covering {TAIL ~ an opening arrangement} formed in a wall of said passage to communicate a first side of said membrane with pressure in said passage 
covering
{ HEAD ~ an elastic membrane } covering { TAIL ~ an opening arrangement } formed in a wall of said passage to communicate a first side of said membrane with pressure in said passage
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH