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