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