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