To prevent {HEAD ~ leakage} of gas from within {TAIL ~ the cell} the substrates have sealing areas 24 at opposite edges to cooperate with the sealing surfaces on the plates 
from within
To prevent { HEAD ~ leakage } of gas from within { TAIL ~ the cell } the substrates have sealing areas 24 at opposite edges to cooperate with the sealing surfaces on the plates
OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH