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