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