Thus, there can be an acceptable degree of lapse in {HEAD ~ the rotational relationship} between {TAIL ~ the valve disc} and the stem 
Thus , there can be an acceptable degree of lapse in { HEAD ~ the rotational relationship } between { TAIL ~ the valve disc } and the stem
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH