The open end of {TAIL ~ the water swellable agent chamber} contains a semipermeable membrane and the open end of the active agent chamber contains a back diffusion regulating {HEAD ~ outlet} 
The open end of { TAIL ~ the water swellable agent chamber } contains a semipermeable membrane and the open end of the active agent chamber contains a back diffusion regulating { HEAD ~ outlet }
OTH OTH OTH OTH TAIL TAIL 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 HEAD HEAD HEAD HEAD HEAD