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