A user programmable control mechanism is coupled to the drug pump and is effective to selectively control movement of {HEAD ~ the valves} between {TAIL ~ the open and closed positions} 
between
A user programmable control mechanism is coupled to the drug pump and is effective to selectively control movement of { HEAD ~ the valves } between { TAIL ~ the open and closed positions }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL