valve means for selectively permitting and terminating {HEAD ~ a flow} of said contents from said {TAIL ~ reservoir} 
valve means for selectively permitting and terminating { HEAD ~ a flow } of said contents from said { TAIL ~ reservoir }
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL