{HEAD ~ An impermeable reservoir} is divided into a water swellable agent chamber and {TAIL ~ an active agent formulation chamber} 
is divided into
{ HEAD ~ An impermeable reservoir } is divided into a water swellable agent chamber and { TAIL ~ an active agent formulation chamber }
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL