{HEAD ~ The rear wall} of {TAIL ~ the third case} in communication with one of the side walls of each of the first case and the second case 
of
{ HEAD ~ The rear wall } of { TAIL ~ the third case } in communication with one of the side walls of each of the first case and the second case
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL 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